[05/10] hwmon: generic-pwm-tachometer: Add generic PWM based tachometer

Message ID 1519196339-9377-6-git-send-email-rrajk@nvidia.com
State Superseded
Headers show
Series
  • Implementation of Tegra Tachometer driver
Related show

Commit Message

Rajkumar Rampelli Feb. 21, 2018, 6:58 a.m.
Add generic PWM based tachometer driver via HWMON interface
to report the RPM of motor. This drivers get the period/duty
cycle from PWM IP which captures the motor PWM output.

This driver implements a simple interface for monitoring the speed of
a fan and exposes it in roatations per minute (RPM) to the user space
by using the hwmon's sysfs interface

Signed-off-by: Rajkumar Rampelli <rrajk@nvidia.com>
---
 Documentation/hwmon/generic-pwm-tachometer |  17 +++++
 drivers/hwmon/Kconfig                      |  10 +++
 drivers/hwmon/Makefile                     |   1 +
 drivers/hwmon/generic-pwm-tachometer.c     | 112 +++++++++++++++++++++++++++++
 4 files changed, 140 insertions(+)
 create mode 100644 Documentation/hwmon/generic-pwm-tachometer
 create mode 100644 drivers/hwmon/generic-pwm-tachometer.c

Comments

Mikko Perttunen Feb. 21, 2018, 7:15 a.m. | #1
AIUI, the PWM framework already exposes a sysfs node with period 
information. We should just use that instead of adding a new driver for 
this.

In any case, we cannot add something like this to device tree since it's 
not a hardware device.

Mikko

On 21.02.2018 08:58, Rajkumar Rampelli wrote:
> Add generic PWM based tachometer driver via HWMON interface
> to report the RPM of motor. This drivers get the period/duty
> cycle from PWM IP which captures the motor PWM output.
>
> This driver implements a simple interface for monitoring the speed of
> a fan and exposes it in roatations per minute (RPM) to the user space
> by using the hwmon's sysfs interface
>
> Signed-off-by: Rajkumar Rampelli <rrajk@nvidia.com>
> ---
>  Documentation/hwmon/generic-pwm-tachometer |  17 +++++
>  drivers/hwmon/Kconfig                      |  10 +++
>  drivers/hwmon/Makefile                     |   1 +
>  drivers/hwmon/generic-pwm-tachometer.c     | 112 +++++++++++++++++++++++++++++
>  4 files changed, 140 insertions(+)
>  create mode 100644 Documentation/hwmon/generic-pwm-tachometer
>  create mode 100644 drivers/hwmon/generic-pwm-tachometer.c
>
> diff --git a/Documentation/hwmon/generic-pwm-tachometer b/Documentation/hwmon/generic-pwm-tachometer
> new file mode 100644
> index 0000000..e0713ee
> --- /dev/null
> +++ b/Documentation/hwmon/generic-pwm-tachometer
> @@ -0,0 +1,17 @@
> +Kernel driver generic-pwm-tachometer
> +====================================
> +
> +This driver enables the use of a PWM module to monitor a fan. It uses the
> +generic PWM interface and can be used on SoCs as along as the SoC supports
> +Tachometer controller that moniors the Fan speed in periods.
> +
> +Author: Rajkumar Rampelli <rrajk@nvidia.com>
> +
> +Description
> +-----------
> +
> +The driver implements a simple interface for monitoring the Fan speed using
> +PWM module and Tachometer controller. It requests period value through PWM
> +capture interface to Tachometer and measures the Rotations per minute using
> +received period value. It exposes the Fan speed in RPM to the user space by
> +using the hwmon's sysfs interface.
> diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
> index ef23553..8912dcb 100644
> --- a/drivers/hwmon/Kconfig
> +++ b/drivers/hwmon/Kconfig
> @@ -1878,6 +1878,16 @@ config SENSORS_XGENE
>  	  If you say yes here you get support for the temperature
>  	  and power sensors for APM X-Gene SoC.
>
> +config GENERIC_PWM_TACHOMETER
> +	tristate "Generic PWM based tachometer driver"
> +	depends on PWM
> +	help
> +	  Enables a driver to use PWM signal from motor to use
> +	  for measuring the motor speed. The RPM is captured by
> +	  PWM modules which has PWM capture capability and this
> +	  drivers reads the captured data from PWM IP to convert
> +	  it to speed in RPM.
> +
>  if ACPI
>
>  comment "ACPI drivers"
> diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
> index f814b4a..9dcc374 100644
> --- a/drivers/hwmon/Makefile
> +++ b/drivers/hwmon/Makefile
> @@ -175,6 +175,7 @@ obj-$(CONFIG_SENSORS_WM8350)	+= wm8350-hwmon.o
>  obj-$(CONFIG_SENSORS_XGENE)	+= xgene-hwmon.o
>
>  obj-$(CONFIG_PMBUS)		+= pmbus/
> +obj-$(CONFIG_GENERIC_PWM_TACHOMETER) += generic-pwm-tachometer.o
>
>  ccflags-$(CONFIG_HWMON_DEBUG_CHIP) := -DDEBUG
>
> diff --git a/drivers/hwmon/generic-pwm-tachometer.c b/drivers/hwmon/generic-pwm-tachometer.c
> new file mode 100644
> index 0000000..9354d43
> --- /dev/null
> +++ b/drivers/hwmon/generic-pwm-tachometer.c
> @@ -0,0 +1,112 @@
> +/*
> + * Copyright (c) 2017-2018, NVIDIA CORPORATION.  All rights reserved.
> + *
> + * This program is free software; you can redistribute it and/or modify it
> + * under the terms and conditions of the GNU General Public License,
> + * version 2, as published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope it will be useful, but WITHOUT
> + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
> + * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
> + * more details.
> + *
> + */
> +
> +#include <linux/module.h>
> +#include <linux/platform_device.h>
> +#include <linux/err.h>
> +#include <linux/pwm.h>
> +#include <linux/hwmon.h>
> +#include <linux/hwmon-sysfs.h>
> +
> +struct pwm_hwmon_tach {
> +	struct device		*dev;
> +	struct pwm_device	*pwm;
> +	struct device		*hwmon;
> +};
> +
> +static ssize_t show_rpm(struct device *dev, struct device_attribute *attr,
> +			char *buf)
> +{
> +	struct pwm_hwmon_tach *ptt = dev_get_drvdata(dev);
> +	struct pwm_device *pwm = ptt->pwm;
> +	struct pwm_capture result;
> +	int err;
> +	unsigned int rpm = 0;
> +
> +	err = pwm_capture(pwm, &result, 0);
> +	if (err < 0) {
> +		dev_err(ptt->dev, "Failed to capture PWM: %d\n", err);
> +		return err;
> +	}
> +
> +	if (result.period)
> +		rpm = DIV_ROUND_CLOSEST_ULL(60ULL * NSEC_PER_SEC,
> +					    result.period);
> +
> +	return sprintf(buf, "%u\n", rpm);
> +}
> +
> +static SENSOR_DEVICE_ATTR(rpm, 0444, show_rpm, NULL, 0);
> +
> +static struct attribute *pwm_tach_attrs[] = {
> +	&sensor_dev_attr_rpm.dev_attr.attr,
> +	NULL,
> +};
> +
> +ATTRIBUTE_GROUPS(pwm_tach);
> +
> +static int pwm_tach_probe(struct platform_device *pdev)
> +{
> +	struct pwm_hwmon_tach *ptt;
> +	int err;
> +
> +	ptt = devm_kzalloc(&pdev->dev, sizeof(*ptt), GFP_KERNEL);
> +	if (!ptt)
> +		return -ENOMEM;
> +
> +	ptt->dev = &pdev->dev;
> +
> +	platform_set_drvdata(pdev, ptt);
> +	dev_set_drvdata(&pdev->dev, ptt);
> +
> +	ptt->pwm = devm_of_pwm_get(&pdev->dev, pdev->dev.of_node, NULL);
> +	if (IS_ERR(ptt->pwm)) {
> +		err = PTR_ERR(ptt->pwm);
> +		dev_err(&pdev->dev, "Failed to get pwm handle, err: %d\n",
> +			err);
> +		return err;
> +	}
> +
> +	ptt->hwmon = devm_hwmon_device_register_with_groups(&pdev->dev,
> +					 "pwm_tach", ptt, pwm_tach_groups);
> +	if (IS_ERR(ptt->hwmon)) {
> +		err = PTR_ERR_OR_ZERO(ptt->hwmon);
> +		dev_err(&pdev->dev, "Failed to register hwmon device: %d\n",
> +			err);
> +		return err;
> +	}
> +
> +	return 0;
> +}
> +
> +static const struct of_device_id pwm_tach_of_match[] = {
> +	{ .compatible = "generic-pwm-tachometer" },
> +	{}
> +};
> +MODULE_DEVICE_TABLE(of, pwm_tach_of_match);
> +
> +static struct platform_driver pwm_tach_driver = {
> +	.driver = {
> +		.name = "generic-pwm-tachometer",
> +		.of_match_table = pwm_tach_of_match,
> +	},
> +	.probe = pwm_tach_probe,
> +};
> +
> +module_platform_driver(pwm_tach_driver);
> +
> +MODULE_DESCRIPTION("PWM based Generic Tachometer driver");
> +MODULE_AUTHOR("Laxman Dewangan <ldewangan@nvidia.com>");
> +MODULE_AUTHOR("Rajkumar Rampelli <rrajk@nvidia.com>");
> +MODULE_LICENSE("GPL v2");
>
--
To unsubscribe from this list: send the line "unsubscribe linux-pwm" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Guenter Roeck Feb. 21, 2018, 2:46 p.m. | #2
On 02/20/2018 11:15 PM, Mikko Perttunen wrote:
> AIUI, the PWM framework already exposes a sysfs node with period information. We should just use that instead of adding a new driver for this.
> 

I am kind of lost. Please explain.

Are you saying that we should drop the pwm-fan driver as well (which goes
the opposite way), as well as any other drivers doing anything with pwm signals,
because after all those signals are already exposed to userspace a sysfs attributes,
and a kernel driver to abstract those values is thus not needed ?

> In any case, we cannot add something like this to device tree since it's not a hardware device.
> 

So you are saying there is no means to express in devicetree that
a pwm input is connected to a fan ? How is that not hardware ?

If so, how do you express in devicetree that a pwm signal is connected
to anything ?

Guenter

> Mikko
> 
> On 21.02.2018 08:58, Rajkumar Rampelli wrote:
>> Add generic PWM based tachometer driver via HWMON interface
>> to report the RPM of motor. This drivers get the period/duty
>> cycle from PWM IP which captures the motor PWM output.
>>
>> This driver implements a simple interface for monitoring the speed of
>> a fan and exposes it in roatations per minute (RPM) to the user space
>> by using the hwmon's sysfs interface
>>
>> Signed-off-by: Rajkumar Rampelli <rrajk@nvidia.com>
>> ---
>>  Documentation/hwmon/generic-pwm-tachometer |  17 +++++
>>  drivers/hwmon/Kconfig                      |  10 +++
>>  drivers/hwmon/Makefile                     |   1 +
>>  drivers/hwmon/generic-pwm-tachometer.c     | 112 +++++++++++++++++++++++++++++
>>  4 files changed, 140 insertions(+)
>>  create mode 100644 Documentation/hwmon/generic-pwm-tachometer
>>  create mode 100644 drivers/hwmon/generic-pwm-tachometer.c
>>
>> diff --git a/Documentation/hwmon/generic-pwm-tachometer b/Documentation/hwmon/generic-pwm-tachometer
>> new file mode 100644
>> index 0000000..e0713ee
>> --- /dev/null
>> +++ b/Documentation/hwmon/generic-pwm-tachometer
>> @@ -0,0 +1,17 @@
>> +Kernel driver generic-pwm-tachometer
>> +====================================
>> +
>> +This driver enables the use of a PWM module to monitor a fan. It uses the
>> +generic PWM interface and can be used on SoCs as along as the SoC supports
>> +Tachometer controller that moniors the Fan speed in periods.
>> +
>> +Author: Rajkumar Rampelli <rrajk@nvidia.com>
>> +
>> +Description
>> +-----------
>> +
>> +The driver implements a simple interface for monitoring the Fan speed using
>> +PWM module and Tachometer controller. It requests period value through PWM
>> +capture interface to Tachometer and measures the Rotations per minute using
>> +received period value. It exposes the Fan speed in RPM to the user space by
>> +using the hwmon's sysfs interface.
>> diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
>> index ef23553..8912dcb 100644
>> --- a/drivers/hwmon/Kconfig
>> +++ b/drivers/hwmon/Kconfig
>> @@ -1878,6 +1878,16 @@ config SENSORS_XGENE
>>        If you say yes here you get support for the temperature
>>        and power sensors for APM X-Gene SoC.
>>
>> +config GENERIC_PWM_TACHOMETER
>> +    tristate "Generic PWM based tachometer driver"
>> +    depends on PWM
>> +    help
>> +      Enables a driver to use PWM signal from motor to use
>> +      for measuring the motor speed. The RPM is captured by
>> +      PWM modules which has PWM capture capability and this
>> +      drivers reads the captured data from PWM IP to convert
>> +      it to speed in RPM.
>> +
>>  if ACPI
>>
>>  comment "ACPI drivers"
>> diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
>> index f814b4a..9dcc374 100644
>> --- a/drivers/hwmon/Makefile
>> +++ b/drivers/hwmon/Makefile
>> @@ -175,6 +175,7 @@ obj-$(CONFIG_SENSORS_WM8350)    += wm8350-hwmon.o
>>  obj-$(CONFIG_SENSORS_XGENE)    += xgene-hwmon.o
>>
>>  obj-$(CONFIG_PMBUS)        += pmbus/
>> +obj-$(CONFIG_GENERIC_PWM_TACHOMETER) += generic-pwm-tachometer.o
>>
>>  ccflags-$(CONFIG_HWMON_DEBUG_CHIP) := -DDEBUG
>>
>> diff --git a/drivers/hwmon/generic-pwm-tachometer.c b/drivers/hwmon/generic-pwm-tachometer.c
>> new file mode 100644
>> index 0000000..9354d43
>> --- /dev/null
>> +++ b/drivers/hwmon/generic-pwm-tachometer.c
>> @@ -0,0 +1,112 @@
>> +/*
>> + * Copyright (c) 2017-2018, NVIDIA CORPORATION.  All rights reserved.
>> + *
>> + * This program is free software; you can redistribute it and/or modify it
>> + * under the terms and conditions of the GNU General Public License,
>> + * version 2, as published by the Free Software Foundation.
>> + *
>> + * This program is distributed in the hope it will be useful, but WITHOUT
>> + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
>> + * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
>> + * more details.
>> + *
>> + */
>> +
>> +#include <linux/module.h>
>> +#include <linux/platform_device.h>
>> +#include <linux/err.h>
>> +#include <linux/pwm.h>
>> +#include <linux/hwmon.h>
>> +#include <linux/hwmon-sysfs.h>
>> +
>> +struct pwm_hwmon_tach {
>> +    struct device        *dev;
>> +    struct pwm_device    *pwm;
>> +    struct device        *hwmon;
>> +};
>> +
>> +static ssize_t show_rpm(struct device *dev, struct device_attribute *attr,
>> +            char *buf)
>> +{
>> +    struct pwm_hwmon_tach *ptt = dev_get_drvdata(dev);
>> +    struct pwm_device *pwm = ptt->pwm;
>> +    struct pwm_capture result;
>> +    int err;
>> +    unsigned int rpm = 0;
>> +
>> +    err = pwm_capture(pwm, &result, 0);
>> +    if (err < 0) {
>> +        dev_err(ptt->dev, "Failed to capture PWM: %d\n", err);
>> +        return err;
>> +    }
>> +
>> +    if (result.period)
>> +        rpm = DIV_ROUND_CLOSEST_ULL(60ULL * NSEC_PER_SEC,
>> +                        result.period);
>> +
>> +    return sprintf(buf, "%u\n", rpm);
>> +}
>> +
>> +static SENSOR_DEVICE_ATTR(rpm, 0444, show_rpm, NULL, 0);
>> +
>> +static struct attribute *pwm_tach_attrs[] = {
>> +    &sensor_dev_attr_rpm.dev_attr.attr,
>> +    NULL,
>> +};
>> +
>> +ATTRIBUTE_GROUPS(pwm_tach);
>> +
>> +static int pwm_tach_probe(struct platform_device *pdev)
>> +{
>> +    struct pwm_hwmon_tach *ptt;
>> +    int err;
>> +
>> +    ptt = devm_kzalloc(&pdev->dev, sizeof(*ptt), GFP_KERNEL);
>> +    if (!ptt)
>> +        return -ENOMEM;
>> +
>> +    ptt->dev = &pdev->dev;
>> +
>> +    platform_set_drvdata(pdev, ptt);
>> +    dev_set_drvdata(&pdev->dev, ptt);
>> +
>> +    ptt->pwm = devm_of_pwm_get(&pdev->dev, pdev->dev.of_node, NULL);
>> +    if (IS_ERR(ptt->pwm)) {
>> +        err = PTR_ERR(ptt->pwm);
>> +        dev_err(&pdev->dev, "Failed to get pwm handle, err: %d\n",
>> +            err);
>> +        return err;
>> +    }
>> +
>> +    ptt->hwmon = devm_hwmon_device_register_with_groups(&pdev->dev,
>> +                     "pwm_tach", ptt, pwm_tach_groups);
>> +    if (IS_ERR(ptt->hwmon)) {
>> +        err = PTR_ERR_OR_ZERO(ptt->hwmon);
>> +        dev_err(&pdev->dev, "Failed to register hwmon device: %d\n",
>> +            err);
>> +        return err;
>> +    }
>> +
>> +    return 0;
>> +}
>> +
>> +static const struct of_device_id pwm_tach_of_match[] = {
>> +    { .compatible = "generic-pwm-tachometer" },
>> +    {}
>> +};
>> +MODULE_DEVICE_TABLE(of, pwm_tach_of_match);
>> +
>> +static struct platform_driver pwm_tach_driver = {
>> +    .driver = {
>> +        .name = "generic-pwm-tachometer",
>> +        .of_match_table = pwm_tach_of_match,
>> +    },
>> +    .probe = pwm_tach_probe,
>> +};
>> +
>> +module_platform_driver(pwm_tach_driver);
>> +
>> +MODULE_DESCRIPTION("PWM based Generic Tachometer driver");
>> +MODULE_AUTHOR("Laxman Dewangan <ldewangan@nvidia.com>");
>> +MODULE_AUTHOR("Rajkumar Rampelli <rrajk@nvidia.com>");
>> +MODULE_LICENSE("GPL v2");
>>
> 

--
To unsubscribe from this list: send the line "unsubscribe linux-pwm" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Guenter Roeck Feb. 21, 2018, 2:50 p.m. | #3
On 02/20/2018 10:58 PM, Rajkumar Rampelli wrote:
> Add generic PWM based tachometer driver via HWMON interface
> to report the RPM of motor. This drivers get the period/duty
> cycle from PWM IP which captures the motor PWM output.
> 
> This driver implements a simple interface for monitoring the speed of
> a fan and exposes it in roatations per minute (RPM) to the user space
> by using the hwmon's sysfs interface
> 
> Signed-off-by: Rajkumar Rampelli <rrajk@nvidia.com>
> ---
>   Documentation/hwmon/generic-pwm-tachometer |  17 +++++
>   drivers/hwmon/Kconfig                      |  10 +++
>   drivers/hwmon/Makefile                     |   1 +
>   drivers/hwmon/generic-pwm-tachometer.c     | 112 +++++++++++++++++++++++++++++
>   4 files changed, 140 insertions(+)
>   create mode 100644 Documentation/hwmon/generic-pwm-tachometer
>   create mode 100644 drivers/hwmon/generic-pwm-tachometer.c
> 
> diff --git a/Documentation/hwmon/generic-pwm-tachometer b/Documentation/hwmon/generic-pwm-tachometer
> new file mode 100644
> index 0000000..e0713ee
> --- /dev/null
> +++ b/Documentation/hwmon/generic-pwm-tachometer
> @@ -0,0 +1,17 @@
> +Kernel driver generic-pwm-tachometer
> +====================================
> +
> +This driver enables the use of a PWM module to monitor a fan. It uses the
> +generic PWM interface and can be used on SoCs as along as the SoC supports
> +Tachometer controller that moniors the Fan speed in periods.
> +
> +Author: Rajkumar Rampelli <rrajk@nvidia.com>
> +
> +Description
> +-----------
> +
> +The driver implements a simple interface for monitoring the Fan speed using
> +PWM module and Tachometer controller. It requests period value through PWM
> +capture interface to Tachometer and measures the Rotations per minute using
> +received period value. It exposes the Fan speed in RPM to the user space by
> +using the hwmon's sysfs interface.
> diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
> index ef23553..8912dcb 100644
> --- a/drivers/hwmon/Kconfig
> +++ b/drivers/hwmon/Kconfig
> @@ -1878,6 +1878,16 @@ config SENSORS_XGENE
>   	  If you say yes here you get support for the temperature
>   	  and power sensors for APM X-Gene SoC.
>   
> +config GENERIC_PWM_TACHOMETER
> +	tristate "Generic PWM based tachometer driver"
> +	depends on PWM
> +	help
> +	  Enables a driver to use PWM signal from motor to use
> +	  for measuring the motor speed. The RPM is captured by
> +	  PWM modules which has PWM capture capability and this
> +	  drivers reads the captured data from PWM IP to convert
> +	  it to speed in RPM.
> +
>   if ACPI
>   
>   comment "ACPI drivers"
> diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
> index f814b4a..9dcc374 100644
> --- a/drivers/hwmon/Makefile
> +++ b/drivers/hwmon/Makefile
> @@ -175,6 +175,7 @@ obj-$(CONFIG_SENSORS_WM8350)	+= wm8350-hwmon.o
>   obj-$(CONFIG_SENSORS_XGENE)	+= xgene-hwmon.o
>   
>   obj-$(CONFIG_PMBUS)		+= pmbus/
> +obj-$(CONFIG_GENERIC_PWM_TACHOMETER) += generic-pwm-tachometer.o
>   
>   ccflags-$(CONFIG_HWMON_DEBUG_CHIP) := -DDEBUG
>   
> diff --git a/drivers/hwmon/generic-pwm-tachometer.c b/drivers/hwmon/generic-pwm-tachometer.c
> new file mode 100644
> index 0000000..9354d43
> --- /dev/null
> +++ b/drivers/hwmon/generic-pwm-tachometer.c
> @@ -0,0 +1,112 @@
> +/*
> + * Copyright (c) 2017-2018, NVIDIA CORPORATION.  All rights reserved.
> + *
> + * This program is free software; you can redistribute it and/or modify it
> + * under the terms and conditions of the GNU General Public License,
> + * version 2, as published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope it will be useful, but WITHOUT
> + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
> + * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
> + * more details.
> + *
> + */
> +
> +#include <linux/module.h>
> +#include <linux/platform_device.h>
> +#include <linux/err.h>
> +#include <linux/pwm.h>
> +#include <linux/hwmon.h>
> +#include <linux/hwmon-sysfs.h>
> +
> +struct pwm_hwmon_tach {
> +	struct device		*dev;
> +	struct pwm_device	*pwm;
> +	struct device		*hwmon;
> +};
> +
> +static ssize_t show_rpm(struct device *dev, struct device_attribute *attr,
> +			char *buf)
> +{
> +	struct pwm_hwmon_tach *ptt = dev_get_drvdata(dev);
> +	struct pwm_device *pwm = ptt->pwm;
> +	struct pwm_capture result;
> +	int err;
> +	unsigned int rpm = 0;
> +
> +	err = pwm_capture(pwm, &result, 0);
> +	if (err < 0) {
> +		dev_err(ptt->dev, "Failed to capture PWM: %d\n", err);
> +		return err;
> +	}
> +
> +	if (result.period)
> +		rpm = DIV_ROUND_CLOSEST_ULL(60ULL * NSEC_PER_SEC,
> +					    result.period);
> +
> +	return sprintf(buf, "%u\n", rpm);
> +}
> +
> +static SENSOR_DEVICE_ATTR(rpm, 0444, show_rpm, NULL, 0);
> +
> +static struct attribute *pwm_tach_attrs[] = {
> +	&sensor_dev_attr_rpm.dev_attr.attr,
> +	NULL,
> +};

"rpm" is not a standard hwmon sysfs attribute. If you don't provide
a single standard hwmon sysfs attribute, having a hwmon driver is pointless.

> +
> +ATTRIBUTE_GROUPS(pwm_tach);
> +
> +static int pwm_tach_probe(struct platform_device *pdev)
> +{
> +	struct pwm_hwmon_tach *ptt;
> +	int err;
> +
> +	ptt = devm_kzalloc(&pdev->dev, sizeof(*ptt), GFP_KERNEL);
> +	if (!ptt)
> +		return -ENOMEM;
> +
> +	ptt->dev = &pdev->dev;
> +
> +	platform_set_drvdata(pdev, ptt);
> +	dev_set_drvdata(&pdev->dev, ptt);
> +

None of those is used.

> +	ptt->pwm = devm_of_pwm_get(&pdev->dev, pdev->dev.of_node, NULL);
> +	if (IS_ERR(ptt->pwm)) {
> +		err = PTR_ERR(ptt->pwm);
> +		dev_err(&pdev->dev, "Failed to get pwm handle, err: %d\n",
> +			err);
> +		return err;
> +	}
> +
> +	ptt->hwmon = devm_hwmon_device_register_with_groups(&pdev->dev,
> +					 "pwm_tach", ptt, pwm_tach_groups);

Please use the new API - devm_hwmon_device_register_with_info -
for new drivers.

> +	if (IS_ERR(ptt->hwmon)) {
> +		err = PTR_ERR_OR_ZERO(ptt->hwmon);
> +		dev_err(&pdev->dev, "Failed to register hwmon device: %d\n",
> +			err);
> +		return err;
> +	}

Please no noise on failure. The failure is going to be a memory allocation failure,
which is reported already, and user space will be informed with the error code.

> +
> +	return 0;
> +}
> +
> +static const struct of_device_id pwm_tach_of_match[] = {
> +	{ .compatible = "generic-pwm-tachometer" },
> +	{}
> +};
> +MODULE_DEVICE_TABLE(of, pwm_tach_of_match);
> +
> +static struct platform_driver pwm_tach_driver = {
> +	.driver = {
> +		.name = "generic-pwm-tachometer",
> +		.of_match_table = pwm_tach_of_match,
> +	},
> +	.probe = pwm_tach_probe,
> +};
> +
> +module_platform_driver(pwm_tach_driver);
> +
> +MODULE_DESCRIPTION("PWM based Generic Tachometer driver");
> +MODULE_AUTHOR("Laxman Dewangan <ldewangan@nvidia.com>");
> +MODULE_AUTHOR("Rajkumar Rampelli <rrajk@nvidia.com>");
> +MODULE_LICENSE("GPL v2");
> 

--
To unsubscribe from this list: send the line "unsubscribe linux-pwm" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Mikko Perttunen Feb. 21, 2018, 3:20 p.m. | #4
On 21.02.2018 16:46, Guenter Roeck wrote:
> On 02/20/2018 11:15 PM, Mikko Perttunen wrote:
>> AIUI, the PWM framework already exposes a sysfs node with period
>> information. We should just use that instead of adding a new driver
>> for this.
>>
>
> I am kind of lost. Please explain.
>
> Are you saying that we should drop the pwm-fan driver as well (which goes
> the opposite way), as well as any other drivers doing anything with pwm
> signals,
> because after all those signals are already exposed to userspace a sysfs
> attributes,
> and a kernel driver to abstract those values is thus not needed ?

The only thing this driver does is do a constant division in 
kernelspace. I'm not really seeing why that couldn't be done in 
userspace. But if you think it's appropriate to do the RPM conversion in 
kernelspace then I'm not greatly opposed to that.

>
>> In any case, we cannot add something like this to device tree since
>> it's not a hardware device.
>>
>
> So you are saying there is no means to express in devicetree that
> a pwm input is connected to a fan ? How is that not hardware ?
>
> If so, how do you express in devicetree that a pwm signal is connected
> to anything ?

If we want to describe that the tachometer is connected to a fan, then 
we should have a fan node in the board's device tree. We don't have a 
chip that has a thing called "generic-pwm-tachometer" attached to it. 
(We have chips that have a "nvidia,tegra186-tachometer", so it's proper 
to have that.)

Thanks,
Mikko

>
> Guenter
>
>> Mikko
>>
>> On 21.02.2018 08:58, Rajkumar Rampelli wrote:
>>> Add generic PWM based tachometer driver via HWMON interface
>>> to report the RPM of motor. This drivers get the period/duty
>>> cycle from PWM IP which captures the motor PWM output.
>>>
>>> This driver implements a simple interface for monitoring the speed of
>>> a fan and exposes it in roatations per minute (RPM) to the user space
>>> by using the hwmon's sysfs interface
>>>
>>> Signed-off-by: Rajkumar Rampelli <rrajk@nvidia.com>
>>> ---
>>>  Documentation/hwmon/generic-pwm-tachometer |  17 +++++
>>>  drivers/hwmon/Kconfig                      |  10 +++
>>>  drivers/hwmon/Makefile                     |   1 +
>>>  drivers/hwmon/generic-pwm-tachometer.c     | 112
>>> +++++++++++++++++++++++++++++
>>>  4 files changed, 140 insertions(+)
>>>  create mode 100644 Documentation/hwmon/generic-pwm-tachometer
>>>  create mode 100644 drivers/hwmon/generic-pwm-tachometer.c
>>>
>>> diff --git a/Documentation/hwmon/generic-pwm-tachometer
>>> b/Documentation/hwmon/generic-pwm-tachometer
>>> new file mode 100644
>>> index 0000000..e0713ee
>>> --- /dev/null
>>> +++ b/Documentation/hwmon/generic-pwm-tachometer
>>> @@ -0,0 +1,17 @@
>>> +Kernel driver generic-pwm-tachometer
>>> +====================================
>>> +
>>> +This driver enables the use of a PWM module to monitor a fan. It
>>> uses the
>>> +generic PWM interface and can be used on SoCs as along as the SoC
>>> supports
>>> +Tachometer controller that moniors the Fan speed in periods.
>>> +
>>> +Author: Rajkumar Rampelli <rrajk@nvidia.com>
>>> +
>>> +Description
>>> +-----------
>>> +
>>> +The driver implements a simple interface for monitoring the Fan
>>> speed using
>>> +PWM module and Tachometer controller. It requests period value
>>> through PWM
>>> +capture interface to Tachometer and measures the Rotations per
>>> minute using
>>> +received period value. It exposes the Fan speed in RPM to the user
>>> space by
>>> +using the hwmon's sysfs interface.
>>> diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
>>> index ef23553..8912dcb 100644
>>> --- a/drivers/hwmon/Kconfig
>>> +++ b/drivers/hwmon/Kconfig
>>> @@ -1878,6 +1878,16 @@ config SENSORS_XGENE
>>>        If you say yes here you get support for the temperature
>>>        and power sensors for APM X-Gene SoC.
>>>
>>> +config GENERIC_PWM_TACHOMETER
>>> +    tristate "Generic PWM based tachometer driver"
>>> +    depends on PWM
>>> +    help
>>> +      Enables a driver to use PWM signal from motor to use
>>> +      for measuring the motor speed. The RPM is captured by
>>> +      PWM modules which has PWM capture capability and this
>>> +      drivers reads the captured data from PWM IP to convert
>>> +      it to speed in RPM.
>>> +
>>>  if ACPI
>>>
>>>  comment "ACPI drivers"
>>> diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
>>> index f814b4a..9dcc374 100644
>>> --- a/drivers/hwmon/Makefile
>>> +++ b/drivers/hwmon/Makefile
>>> @@ -175,6 +175,7 @@ obj-$(CONFIG_SENSORS_WM8350)    += wm8350-hwmon.o
>>>  obj-$(CONFIG_SENSORS_XGENE)    += xgene-hwmon.o
>>>
>>>  obj-$(CONFIG_PMBUS)        += pmbus/
>>> +obj-$(CONFIG_GENERIC_PWM_TACHOMETER) += generic-pwm-tachometer.o
>>>
>>>  ccflags-$(CONFIG_HWMON_DEBUG_CHIP) := -DDEBUG
>>>
>>> diff --git a/drivers/hwmon/generic-pwm-tachometer.c
>>> b/drivers/hwmon/generic-pwm-tachometer.c
>>> new file mode 100644
>>> index 0000000..9354d43
>>> --- /dev/null
>>> +++ b/drivers/hwmon/generic-pwm-tachometer.c
>>> @@ -0,0 +1,112 @@
>>> +/*
>>> + * Copyright (c) 2017-2018, NVIDIA CORPORATION.  All rights reserved.
>>> + *
>>> + * This program is free software; you can redistribute it and/or
>>> modify it
>>> + * under the terms and conditions of the GNU General Public License,
>>> + * version 2, as published by the Free Software Foundation.
>>> + *
>>> + * This program is distributed in the hope it will be useful, but
>>> WITHOUT
>>> + * ANY WARRANTY; without even the implied warranty of
>>> MERCHANTABILITY or
>>> + * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public
>>> License for
>>> + * more details.
>>> + *
>>> + */
>>> +
>>> +#include <linux/module.h>
>>> +#include <linux/platform_device.h>
>>> +#include <linux/err.h>
>>> +#include <linux/pwm.h>
>>> +#include <linux/hwmon.h>
>>> +#include <linux/hwmon-sysfs.h>
>>> +
>>> +struct pwm_hwmon_tach {
>>> +    struct device        *dev;
>>> +    struct pwm_device    *pwm;
>>> +    struct device        *hwmon;
>>> +};
>>> +
>>> +static ssize_t show_rpm(struct device *dev, struct device_attribute
>>> *attr,
>>> +            char *buf)
>>> +{
>>> +    struct pwm_hwmon_tach *ptt = dev_get_drvdata(dev);
>>> +    struct pwm_device *pwm = ptt->pwm;
>>> +    struct pwm_capture result;
>>> +    int err;
>>> +    unsigned int rpm = 0;
>>> +
>>> +    err = pwm_capture(pwm, &result, 0);
>>> +    if (err < 0) {
>>> +        dev_err(ptt->dev, "Failed to capture PWM: %d\n", err);
>>> +        return err;
>>> +    }
>>> +
>>> +    if (result.period)
>>> +        rpm = DIV_ROUND_CLOSEST_ULL(60ULL * NSEC_PER_SEC,
>>> +                        result.period);
>>> +
>>> +    return sprintf(buf, "%u\n", rpm);
>>> +}
>>> +
>>> +static SENSOR_DEVICE_ATTR(rpm, 0444, show_rpm, NULL, 0);
>>> +
>>> +static struct attribute *pwm_tach_attrs[] = {
>>> +    &sensor_dev_attr_rpm.dev_attr.attr,
>>> +    NULL,
>>> +};
>>> +
>>> +ATTRIBUTE_GROUPS(pwm_tach);
>>> +
>>> +static int pwm_tach_probe(struct platform_device *pdev)
>>> +{
>>> +    struct pwm_hwmon_tach *ptt;
>>> +    int err;
>>> +
>>> +    ptt = devm_kzalloc(&pdev->dev, sizeof(*ptt), GFP_KERNEL);
>>> +    if (!ptt)
>>> +        return -ENOMEM;
>>> +
>>> +    ptt->dev = &pdev->dev;
>>> +
>>> +    platform_set_drvdata(pdev, ptt);
>>> +    dev_set_drvdata(&pdev->dev, ptt);
>>> +
>>> +    ptt->pwm = devm_of_pwm_get(&pdev->dev, pdev->dev.of_node, NULL);
>>> +    if (IS_ERR(ptt->pwm)) {
>>> +        err = PTR_ERR(ptt->pwm);
>>> +        dev_err(&pdev->dev, "Failed to get pwm handle, err: %d\n",
>>> +            err);
>>> +        return err;
>>> +    }
>>> +
>>> +    ptt->hwmon = devm_hwmon_device_register_with_groups(&pdev->dev,
>>> +                     "pwm_tach", ptt, pwm_tach_groups);
>>> +    if (IS_ERR(ptt->hwmon)) {
>>> +        err = PTR_ERR_OR_ZERO(ptt->hwmon);
>>> +        dev_err(&pdev->dev, "Failed to register hwmon device: %d\n",
>>> +            err);
>>> +        return err;
>>> +    }
>>> +
>>> +    return 0;
>>> +}
>>> +
>>> +static const struct of_device_id pwm_tach_of_match[] = {
>>> +    { .compatible = "generic-pwm-tachometer" },
>>> +    {}
>>> +};
>>> +MODULE_DEVICE_TABLE(of, pwm_tach_of_match);
>>> +
>>> +static struct platform_driver pwm_tach_driver = {
>>> +    .driver = {
>>> +        .name = "generic-pwm-tachometer",
>>> +        .of_match_table = pwm_tach_of_match,
>>> +    },
>>> +    .probe = pwm_tach_probe,
>>> +};
>>> +
>>> +module_platform_driver(pwm_tach_driver);
>>> +
>>> +MODULE_DESCRIPTION("PWM based Generic Tachometer driver");
>>> +MODULE_AUTHOR("Laxman Dewangan <ldewangan@nvidia.com>");
>>> +MODULE_AUTHOR("Rajkumar Rampelli <rrajk@nvidia.com>");
>>> +MODULE_LICENSE("GPL v2");
>>>
>>
>
--
To unsubscribe from this list: send the line "unsubscribe linux-pwm" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Guenter Roeck Feb. 21, 2018, 4:08 p.m. | #5
On Wed, Feb 21, 2018 at 05:20:29PM +0200, Mikko Perttunen wrote:
> On 21.02.2018 16:46, Guenter Roeck wrote:
> >On 02/20/2018 11:15 PM, Mikko Perttunen wrote:
> >>AIUI, the PWM framework already exposes a sysfs node with period
> >>information. We should just use that instead of adding a new driver
> >>for this.
> >>
> >
> >I am kind of lost. Please explain.
> >
> >Are you saying that we should drop the pwm-fan driver as well (which goes
> >the opposite way), as well as any other drivers doing anything with pwm
> >signals,
> >because after all those signals are already exposed to userspace a sysfs
> >attributes,
> >and a kernel driver to abstract those values is thus not needed ?
> 
> The only thing this driver does is do a constant division in kernelspace.
> I'm not really seeing why that couldn't be done in userspace. But if you
> think it's appropriate to do the RPM conversion in kernelspace then I'm not
> greatly opposed to that.
> 
Isn't that true for any conversion from and to pwm values ? Voltages,
for example ? Should those be handled in userspace as well ?

Note that I am not entirely convinced that the approach suggested in this
patch series makes sense. Patch 4 seems to move the notion of a tachometer
into the pwm subsystem. I am not really convinced that this makes sense
(maybe all that code should be in the hwmon driver instead, or in a thermal
driver if the author prefers). But that is a different issue. The question
you raised is if there should be any abstraction to or from raw pwm values
in the kernel.

> >
> >>In any case, we cannot add something like this to device tree since
> >>it's not a hardware device.
> >>
> >
> >So you are saying there is no means to express in devicetree that
> >a pwm input is connected to a fan ? How is that not hardware ?
> >
> >If so, how do you express in devicetree that a pwm signal is connected
> >to anything ?
> 
> If we want to describe that the tachometer is connected to a fan, then we
> should have a fan node in the board's device tree. We don't have a chip that
> has a thing called "generic-pwm-tachometer" attached to it. (We have chips
> that have a "nvidia,tegra186-tachometer", so it's proper to have that.)
> 
So you are concerned about the property name ? I don't really care how
it is called.

Guenter

> Thanks,
> Mikko
> 
> >
> >Guenter
> >
> >>Mikko
> >>
> >>On 21.02.2018 08:58, Rajkumar Rampelli wrote:
> >>>Add generic PWM based tachometer driver via HWMON interface
> >>>to report the RPM of motor. This drivers get the period/duty
> >>>cycle from PWM IP which captures the motor PWM output.
> >>>
> >>>This driver implements a simple interface for monitoring the speed of
> >>>a fan and exposes it in roatations per minute (RPM) to the user space
> >>>by using the hwmon's sysfs interface
> >>>
> >>>Signed-off-by: Rajkumar Rampelli <rrajk@nvidia.com>
> >>>---
> >>> Documentation/hwmon/generic-pwm-tachometer |  17 +++++
> >>> drivers/hwmon/Kconfig                      |  10 +++
> >>> drivers/hwmon/Makefile                     |   1 +
> >>> drivers/hwmon/generic-pwm-tachometer.c     | 112
> >>>+++++++++++++++++++++++++++++
> >>> 4 files changed, 140 insertions(+)
> >>> create mode 100644 Documentation/hwmon/generic-pwm-tachometer
> >>> create mode 100644 drivers/hwmon/generic-pwm-tachometer.c
> >>>
> >>>diff --git a/Documentation/hwmon/generic-pwm-tachometer
> >>>b/Documentation/hwmon/generic-pwm-tachometer
> >>>new file mode 100644
> >>>index 0000000..e0713ee
> >>>--- /dev/null
> >>>+++ b/Documentation/hwmon/generic-pwm-tachometer
> >>>@@ -0,0 +1,17 @@
> >>>+Kernel driver generic-pwm-tachometer
> >>>+====================================
> >>>+
> >>>+This driver enables the use of a PWM module to monitor a fan. It
> >>>uses the
> >>>+generic PWM interface and can be used on SoCs as along as the SoC
> >>>supports
> >>>+Tachometer controller that moniors the Fan speed in periods.
> >>>+
> >>>+Author: Rajkumar Rampelli <rrajk@nvidia.com>
> >>>+
> >>>+Description
> >>>+-----------
> >>>+
> >>>+The driver implements a simple interface for monitoring the Fan
> >>>speed using
> >>>+PWM module and Tachometer controller. It requests period value
> >>>through PWM
> >>>+capture interface to Tachometer and measures the Rotations per
> >>>minute using
> >>>+received period value. It exposes the Fan speed in RPM to the user
> >>>space by
> >>>+using the hwmon's sysfs interface.
> >>>diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
> >>>index ef23553..8912dcb 100644
> >>>--- a/drivers/hwmon/Kconfig
> >>>+++ b/drivers/hwmon/Kconfig
> >>>@@ -1878,6 +1878,16 @@ config SENSORS_XGENE
> >>>       If you say yes here you get support for the temperature
> >>>       and power sensors for APM X-Gene SoC.
> >>>
> >>>+config GENERIC_PWM_TACHOMETER
> >>>+    tristate "Generic PWM based tachometer driver"
> >>>+    depends on PWM
> >>>+    help
> >>>+      Enables a driver to use PWM signal from motor to use
> >>>+      for measuring the motor speed. The RPM is captured by
> >>>+      PWM modules which has PWM capture capability and this
> >>>+      drivers reads the captured data from PWM IP to convert
> >>>+      it to speed in RPM.
> >>>+
> >>> if ACPI
> >>>
> >>> comment "ACPI drivers"
> >>>diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
> >>>index f814b4a..9dcc374 100644
> >>>--- a/drivers/hwmon/Makefile
> >>>+++ b/drivers/hwmon/Makefile
> >>>@@ -175,6 +175,7 @@ obj-$(CONFIG_SENSORS_WM8350)    += wm8350-hwmon.o
> >>> obj-$(CONFIG_SENSORS_XGENE)    += xgene-hwmon.o
> >>>
> >>> obj-$(CONFIG_PMBUS)        += pmbus/
> >>>+obj-$(CONFIG_GENERIC_PWM_TACHOMETER) += generic-pwm-tachometer.o
> >>>
> >>> ccflags-$(CONFIG_HWMON_DEBUG_CHIP) := -DDEBUG
> >>>
> >>>diff --git a/drivers/hwmon/generic-pwm-tachometer.c
> >>>b/drivers/hwmon/generic-pwm-tachometer.c
> >>>new file mode 100644
> >>>index 0000000..9354d43
> >>>--- /dev/null
> >>>+++ b/drivers/hwmon/generic-pwm-tachometer.c
> >>>@@ -0,0 +1,112 @@
> >>>+/*
> >>>+ * Copyright (c) 2017-2018, NVIDIA CORPORATION.  All rights reserved.
> >>>+ *
> >>>+ * This program is free software; you can redistribute it and/or
> >>>modify it
> >>>+ * under the terms and conditions of the GNU General Public License,
> >>>+ * version 2, as published by the Free Software Foundation.
> >>>+ *
> >>>+ * This program is distributed in the hope it will be useful, but
> >>>WITHOUT
> >>>+ * ANY WARRANTY; without even the implied warranty of
> >>>MERCHANTABILITY or
> >>>+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public
> >>>License for
> >>>+ * more details.
> >>>+ *
> >>>+ */
> >>>+
> >>>+#include <linux/module.h>
> >>>+#include <linux/platform_device.h>
> >>>+#include <linux/err.h>
> >>>+#include <linux/pwm.h>
> >>>+#include <linux/hwmon.h>
> >>>+#include <linux/hwmon-sysfs.h>
> >>>+
> >>>+struct pwm_hwmon_tach {
> >>>+    struct device        *dev;
> >>>+    struct pwm_device    *pwm;
> >>>+    struct device        *hwmon;
> >>>+};
> >>>+
> >>>+static ssize_t show_rpm(struct device *dev, struct device_attribute
> >>>*attr,
> >>>+            char *buf)
> >>>+{
> >>>+    struct pwm_hwmon_tach *ptt = dev_get_drvdata(dev);
> >>>+    struct pwm_device *pwm = ptt->pwm;
> >>>+    struct pwm_capture result;
> >>>+    int err;
> >>>+    unsigned int rpm = 0;
> >>>+
> >>>+    err = pwm_capture(pwm, &result, 0);
> >>>+    if (err < 0) {
> >>>+        dev_err(ptt->dev, "Failed to capture PWM: %d\n", err);
> >>>+        return err;
> >>>+    }
> >>>+
> >>>+    if (result.period)
> >>>+        rpm = DIV_ROUND_CLOSEST_ULL(60ULL * NSEC_PER_SEC,
> >>>+                        result.period);
> >>>+
> >>>+    return sprintf(buf, "%u\n", rpm);
> >>>+}
> >>>+
> >>>+static SENSOR_DEVICE_ATTR(rpm, 0444, show_rpm, NULL, 0);
> >>>+
> >>>+static struct attribute *pwm_tach_attrs[] = {
> >>>+    &sensor_dev_attr_rpm.dev_attr.attr,
> >>>+    NULL,
> >>>+};
> >>>+
> >>>+ATTRIBUTE_GROUPS(pwm_tach);
> >>>+
> >>>+static int pwm_tach_probe(struct platform_device *pdev)
> >>>+{
> >>>+    struct pwm_hwmon_tach *ptt;
> >>>+    int err;
> >>>+
> >>>+    ptt = devm_kzalloc(&pdev->dev, sizeof(*ptt), GFP_KERNEL);
> >>>+    if (!ptt)
> >>>+        return -ENOMEM;
> >>>+
> >>>+    ptt->dev = &pdev->dev;
> >>>+
> >>>+    platform_set_drvdata(pdev, ptt);
> >>>+    dev_set_drvdata(&pdev->dev, ptt);
> >>>+
> >>>+    ptt->pwm = devm_of_pwm_get(&pdev->dev, pdev->dev.of_node, NULL);
> >>>+    if (IS_ERR(ptt->pwm)) {
> >>>+        err = PTR_ERR(ptt->pwm);
> >>>+        dev_err(&pdev->dev, "Failed to get pwm handle, err: %d\n",
> >>>+            err);
> >>>+        return err;
> >>>+    }
> >>>+
> >>>+    ptt->hwmon = devm_hwmon_device_register_with_groups(&pdev->dev,
> >>>+                     "pwm_tach", ptt, pwm_tach_groups);
> >>>+    if (IS_ERR(ptt->hwmon)) {
> >>>+        err = PTR_ERR_OR_ZERO(ptt->hwmon);
> >>>+        dev_err(&pdev->dev, "Failed to register hwmon device: %d\n",
> >>>+            err);
> >>>+        return err;
> >>>+    }
> >>>+
> >>>+    return 0;
> >>>+}
> >>>+
> >>>+static const struct of_device_id pwm_tach_of_match[] = {
> >>>+    { .compatible = "generic-pwm-tachometer" },
> >>>+    {}
> >>>+};
> >>>+MODULE_DEVICE_TABLE(of, pwm_tach_of_match);
> >>>+
> >>>+static struct platform_driver pwm_tach_driver = {
> >>>+    .driver = {
> >>>+        .name = "generic-pwm-tachometer",
> >>>+        .of_match_table = pwm_tach_of_match,
> >>>+    },
> >>>+    .probe = pwm_tach_probe,
> >>>+};
> >>>+
> >>>+module_platform_driver(pwm_tach_driver);
> >>>+
> >>>+MODULE_DESCRIPTION("PWM based Generic Tachometer driver");
> >>>+MODULE_AUTHOR("Laxman Dewangan <ldewangan@nvidia.com>");
> >>>+MODULE_AUTHOR("Rajkumar Rampelli <rrajk@nvidia.com>");
> >>>+MODULE_LICENSE("GPL v2");
> >>>
> >>
> >
--
To unsubscribe from this list: send the line "unsubscribe linux-pwm" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Rajkumar Rampelli Feb. 23, 2018, 11:45 a.m. | #6
On Wednesday 21 February 2018 09:38 PM, Guenter Roeck wrote:
> On Wed, Feb 21, 2018 at 05:20:29PM +0200, Mikko Perttunen wrote:
>> On 21.02.2018 16:46, Guenter Roeck wrote:
>>> On 02/20/2018 11:15 PM, Mikko Perttunen wrote:
>>>> AIUI, the PWM framework already exposes a sysfs node with period
>>>> information. We should just use that instead of adding a new driver
>>>> for this.
>>>>
>>> I am kind of lost. Please explain.
>>>
>>> Are you saying that we should drop the pwm-fan driver as well (which goes
>>> the opposite way), as well as any other drivers doing anything with pwm
>>> signals,
>>> because after all those signals are already exposed to userspace a sysfs
>>> attributes,
>>> and a kernel driver to abstract those values is thus not needed ?
>> The only thing this driver does is do a constant division in kernelspace.
>> I'm not really seeing why that couldn't be done in userspace. But if you
>> think it's appropriate to do the RPM conversion in kernelspace then I'm not
>> greatly opposed to that.
>>
> Isn't that true for any conversion from and to pwm values ? Voltages,
> for example ? Should those be handled in userspace as well ?
>
> Note that I am not entirely convinced that the approach suggested in this
> patch series makes sense. Patch 4 seems to move the notion of a tachometer
> into the pwm subsystem. I am not really convinced that this makes sense
> (maybe all that code should be in the hwmon driver instead, or in a thermal
> driver if the author prefers). But that is a different issue. The question
> you raised is if there should be any abstraction to or from raw pwm values
> in the kernel.
Since tachometer driver implements PWM capture callback feature, I have 
added it under pwm driver as pwm-tegra-tachometer.c driver.
If the best approach is to have this tachometer driver under hwmon 
driver then I will move it to hwmon driver.
>
>>>> In any case, we cannot add something like this to device tree since
>>>> it's not a hardware device.
>>>>
>>> So you are saying there is no means to express in devicetree that
>>> a pwm input is connected to a fan ? How is that not hardware ?
>>>
>>> If so, how do you express in devicetree that a pwm signal is connected
>>> to anything ?
>> If we want to describe that the tachometer is connected to a fan, then we
>> should have a fan node in the board's device tree. We don't have a chip that
>> has a thing called "generic-pwm-tachometer" attached to it. (We have chips
>> that have a "nvidia,tegra186-tachometer", so it's proper to have that.)
>>
> So you are concerned about the property name ? I don't really care how
> it is called.
>
> Guenter
>
>> Thanks,
>> Mikko
>>
>>> Guenter
>>>
>>>> Mikko
>>>>
>>>> On 21.02.2018 08:58, Rajkumar Rampelli wrote:
>>>>> Add generic PWM based tachometer driver via HWMON interface
>>>>> to report the RPM of motor. This drivers get the period/duty
>>>>> cycle from PWM IP which captures the motor PWM output.
>>>>>
>>>>> This driver implements a simple interface for monitoring the speed of
>>>>> a fan and exposes it in roatations per minute (RPM) to the user space
>>>>> by using the hwmon's sysfs interface
>>>>>
>>>>> Signed-off-by: Rajkumar Rampelli <rrajk@nvidia.com>
>>>>> ---
>>>>> Documentation/hwmon/generic-pwm-tachometer |  17 +++++
>>>>> drivers/hwmon/Kconfig                      |  10 +++
>>>>> drivers/hwmon/Makefile                     |   1 +
>>>>> drivers/hwmon/generic-pwm-tachometer.c     | 112
>>>>> +++++++++++++++++++++++++++++
>>>>> 4 files changed, 140 insertions(+)
>>>>> create mode 100644 Documentation/hwmon/generic-pwm-tachometer
>>>>> create mode 100644 drivers/hwmon/generic-pwm-tachometer.c
>>>>>
>>>>> diff --git a/Documentation/hwmon/generic-pwm-tachometer
>>>>> b/Documentation/hwmon/generic-pwm-tachometer
>>>>> new file mode 100644
>>>>> index 0000000..e0713ee
>>>>> --- /dev/null
>>>>> +++ b/Documentation/hwmon/generic-pwm-tachometer
>>>>> @@ -0,0 +1,17 @@
>>>>> +Kernel driver generic-pwm-tachometer
>>>>> +====================================
>>>>> +
>>>>> +This driver enables the use of a PWM module to monitor a fan. It
>>>>> uses the
>>>>> +generic PWM interface and can be used on SoCs as along as the SoC
>>>>> supports
>>>>> +Tachometer controller that moniors the Fan speed in periods.
>>>>> +
>>>>> +Author: Rajkumar Rampelli <rrajk@nvidia.com>
>>>>> +
>>>>> +Description
>>>>> +-----------
>>>>> +
>>>>> +The driver implements a simple interface for monitoring the Fan
>>>>> speed using
>>>>> +PWM module and Tachometer controller. It requests period value
>>>>> through PWM
>>>>> +capture interface to Tachometer and measures the Rotations per
>>>>> minute using
>>>>> +received period value. It exposes the Fan speed in RPM to the user
>>>>> space by
>>>>> +using the hwmon's sysfs interface.
>>>>> diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
>>>>> index ef23553..8912dcb 100644
>>>>> --- a/drivers/hwmon/Kconfig
>>>>> +++ b/drivers/hwmon/Kconfig
>>>>> @@ -1878,6 +1878,16 @@ config SENSORS_XGENE
>>>>>        If you say yes here you get support for the temperature
>>>>>        and power sensors for APM X-Gene SoC.
>>>>>
>>>>> +config GENERIC_PWM_TACHOMETER
>>>>> +    tristate "Generic PWM based tachometer driver"
>>>>> +    depends on PWM
>>>>> +    help
>>>>> +      Enables a driver to use PWM signal from motor to use
>>>>> +      for measuring the motor speed. The RPM is captured by
>>>>> +      PWM modules which has PWM capture capability and this
>>>>> +      drivers reads the captured data from PWM IP to convert
>>>>> +      it to speed in RPM.
>>>>> +
>>>>> if ACPI
>>>>>
>>>>> comment "ACPI drivers"
>>>>> diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
>>>>> index f814b4a..9dcc374 100644
>>>>> --- a/drivers/hwmon/Makefile
>>>>> +++ b/drivers/hwmon/Makefile
>>>>> @@ -175,6 +175,7 @@ obj-$(CONFIG_SENSORS_WM8350)    += wm8350-hwmon.o
>>>>> obj-$(CONFIG_SENSORS_XGENE)    += xgene-hwmon.o
>>>>>
>>>>> obj-$(CONFIG_PMBUS)        += pmbus/
>>>>> +obj-$(CONFIG_GENERIC_PWM_TACHOMETER) += generic-pwm-tachometer.o
>>>>>
>>>>> ccflags-$(CONFIG_HWMON_DEBUG_CHIP) := -DDEBUG
>>>>>
>>>>> diff --git a/drivers/hwmon/generic-pwm-tachometer.c
>>>>> b/drivers/hwmon/generic-pwm-tachometer.c
>>>>> new file mode 100644
>>>>> index 0000000..9354d43
>>>>> --- /dev/null
>>>>> +++ b/drivers/hwmon/generic-pwm-tachometer.c
>>>>> @@ -0,0 +1,112 @@
>>>>> +/*
>>>>> + * Copyright (c) 2017-2018, NVIDIA CORPORATION.  All rights reserved.
>>>>> + *
>>>>> + * This program is free software; you can redistribute it and/or
>>>>> modify it
>>>>> + * under the terms and conditions of the GNU General Public License,
>>>>> + * version 2, as published by the Free Software Foundation.
>>>>> + *
>>>>> + * This program is distributed in the hope it will be useful, but
>>>>> WITHOUT
>>>>> + * ANY WARRANTY; without even the implied warranty of
>>>>> MERCHANTABILITY or
>>>>> + * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public
>>>>> License for
>>>>> + * more details.
>>>>> + *
>>>>> + */
>>>>> +
>>>>> +#include <linux/module.h>
>>>>> +#include <linux/platform_device.h>
>>>>> +#include <linux/err.h>
>>>>> +#include <linux/pwm.h>
>>>>> +#include <linux/hwmon.h>
>>>>> +#include <linux/hwmon-sysfs.h>
>>>>> +
>>>>> +struct pwm_hwmon_tach {
>>>>> +    struct device        *dev;
>>>>> +    struct pwm_device    *pwm;
>>>>> +    struct device        *hwmon;
>>>>> +};
>>>>> +
>>>>> +static ssize_t show_rpm(struct device *dev, struct device_attribute
>>>>> *attr,
>>>>> +            char *buf)
>>>>> +{
>>>>> +    struct pwm_hwmon_tach *ptt = dev_get_drvdata(dev);
>>>>> +    struct pwm_device *pwm = ptt->pwm;
>>>>> +    struct pwm_capture result;
>>>>> +    int err;
>>>>> +    unsigned int rpm = 0;
>>>>> +
>>>>> +    err = pwm_capture(pwm, &result, 0);
>>>>> +    if (err < 0) {
>>>>> +        dev_err(ptt->dev, "Failed to capture PWM: %d\n", err);
>>>>> +        return err;
>>>>> +    }
>>>>> +
>>>>> +    if (result.period)
>>>>> +        rpm = DIV_ROUND_CLOSEST_ULL(60ULL * NSEC_PER_SEC,
>>>>> +                        result.period);
>>>>> +
>>>>> +    return sprintf(buf, "%u\n", rpm);
>>>>> +}
>>>>> +
>>>>> +static SENSOR_DEVICE_ATTR(rpm, 0444, show_rpm, NULL, 0);
>>>>> +
>>>>> +static struct attribute *pwm_tach_attrs[] = {
>>>>> +    &sensor_dev_attr_rpm.dev_attr.attr,
>>>>> +    NULL,
>>>>> +};
>>>>> +
>>>>> +ATTRIBUTE_GROUPS(pwm_tach);
>>>>> +
>>>>> +static int pwm_tach_probe(struct platform_device *pdev)
>>>>> +{
>>>>> +    struct pwm_hwmon_tach *ptt;
>>>>> +    int err;
>>>>> +
>>>>> +    ptt = devm_kzalloc(&pdev->dev, sizeof(*ptt), GFP_KERNEL);
>>>>> +    if (!ptt)
>>>>> +        return -ENOMEM;
>>>>> +
>>>>> +    ptt->dev = &pdev->dev;
>>>>> +
>>>>> +    platform_set_drvdata(pdev, ptt);
>>>>> +    dev_set_drvdata(&pdev->dev, ptt);
>>>>> +
>>>>> +    ptt->pwm = devm_of_pwm_get(&pdev->dev, pdev->dev.of_node, NULL);
>>>>> +    if (IS_ERR(ptt->pwm)) {
>>>>> +        err = PTR_ERR(ptt->pwm);
>>>>> +        dev_err(&pdev->dev, "Failed to get pwm handle, err: %d\n",
>>>>> +            err);
>>>>> +        return err;
>>>>> +    }
>>>>> +
>>>>> +    ptt->hwmon = devm_hwmon_device_register_with_groups(&pdev->dev,
>>>>> +                     "pwm_tach", ptt, pwm_tach_groups);
>>>>> +    if (IS_ERR(ptt->hwmon)) {
>>>>> +        err = PTR_ERR_OR_ZERO(ptt->hwmon);
>>>>> +        dev_err(&pdev->dev, "Failed to register hwmon device: %d\n",
>>>>> +            err);
>>>>> +        return err;
>>>>> +    }
>>>>> +
>>>>> +    return 0;
>>>>> +}
>>>>> +
>>>>> +static const struct of_device_id pwm_tach_of_match[] = {
>>>>> +    { .compatible = "generic-pwm-tachometer" },
>>>>> +    {}
>>>>> +};
>>>>> +MODULE_DEVICE_TABLE(of, pwm_tach_of_match);
>>>>> +
>>>>> +static struct platform_driver pwm_tach_driver = {
>>>>> +    .driver = {
>>>>> +        .name = "generic-pwm-tachometer",
>>>>> +        .of_match_table = pwm_tach_of_match,
>>>>> +    },
>>>>> +    .probe = pwm_tach_probe,
>>>>> +};
>>>>> +
>>>>> +module_platform_driver(pwm_tach_driver);
>>>>> +
>>>>> +MODULE_DESCRIPTION("PWM based Generic Tachometer driver");
>>>>> +MODULE_AUTHOR("Laxman Dewangan <ldewangan@nvidia.com>");
>>>>> +MODULE_AUTHOR("Rajkumar Rampelli <rrajk@nvidia.com>");
>>>>> +MODULE_LICENSE("GPL v2");
>>>>>

--
To unsubscribe from this list: send the line "unsubscribe linux-pwm" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Rajkumar Rampelli Feb. 28, 2018, 5:38 a.m. | #7
On Wednesday 21 February 2018 08:20 PM, Guenter Roeck wrote:
> On 02/20/2018 10:58 PM, Rajkumar Rampelli wrote:
>> Add generic PWM based tachometer driver via HWMON interface
>> to report the RPM of motor. This drivers get the period/duty
>> cycle from PWM IP which captures the motor PWM output.
>>
>> This driver implements a simple interface for monitoring the speed of
>> a fan and exposes it in roatations per minute (RPM) to the user space
>> by using the hwmon's sysfs interface
>>
>> Signed-off-by: Rajkumar Rampelli <rrajk@nvidia.com>
>> ---
>>   Documentation/hwmon/generic-pwm-tachometer |  17 +++++
>>   drivers/hwmon/Kconfig                      |  10 +++
>>   drivers/hwmon/Makefile                     |   1 +
>>   drivers/hwmon/generic-pwm-tachometer.c     | 112 
>> +++++++++++++++++++++++++++++
>>   4 files changed, 140 insertions(+)
>>   create mode 100644 Documentation/hwmon/generic-pwm-tachometer
>>   create mode 100644 drivers/hwmon/generic-pwm-tachometer.c
>>
>> diff --git a/Documentation/hwmon/generic-pwm-tachometer 
>> b/Documentation/hwmon/generic-pwm-tachometer
>> new file mode 100644
>> index 0000000..e0713ee
>> --- /dev/null
>> +++ b/Documentation/hwmon/generic-pwm-tachometer
>> @@ -0,0 +1,17 @@
>> +Kernel driver generic-pwm-tachometer
>> +====================================
>> +
>> +This driver enables the use of a PWM module to monitor a fan. It 
>> uses the
>> +generic PWM interface and can be used on SoCs as along as the SoC 
>> supports
>> +Tachometer controller that moniors the Fan speed in periods.
>> +
>> +Author: Rajkumar Rampelli <rrajk@nvidia.com>
>> +
>> +Description
>> +-----------
>> +
>> +The driver implements a simple interface for monitoring the Fan 
>> speed using
>> +PWM module and Tachometer controller. It requests period value 
>> through PWM
>> +capture interface to Tachometer and measures the Rotations per 
>> minute using
>> +received period value. It exposes the Fan speed in RPM to the user 
>> space by
>> +using the hwmon's sysfs interface.
>> diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
>> index ef23553..8912dcb 100644
>> --- a/drivers/hwmon/Kconfig
>> +++ b/drivers/hwmon/Kconfig
>> @@ -1878,6 +1878,16 @@ config SENSORS_XGENE
>>         If you say yes here you get support for the temperature
>>         and power sensors for APM X-Gene SoC.
>>   +config GENERIC_PWM_TACHOMETER
>> +    tristate "Generic PWM based tachometer driver"
>> +    depends on PWM
>> +    help
>> +      Enables a driver to use PWM signal from motor to use
>> +      for measuring the motor speed. The RPM is captured by
>> +      PWM modules which has PWM capture capability and this
>> +      drivers reads the captured data from PWM IP to convert
>> +      it to speed in RPM.
>> +
>>   if ACPI
>>     comment "ACPI drivers"
>> diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
>> index f814b4a..9dcc374 100644
>> --- a/drivers/hwmon/Makefile
>> +++ b/drivers/hwmon/Makefile
>> @@ -175,6 +175,7 @@ obj-$(CONFIG_SENSORS_WM8350)    += wm8350-hwmon.o
>>   obj-$(CONFIG_SENSORS_XGENE)    += xgene-hwmon.o
>>     obj-$(CONFIG_PMBUS)        += pmbus/
>> +obj-$(CONFIG_GENERIC_PWM_TACHOMETER) += generic-pwm-tachometer.o
>>     ccflags-$(CONFIG_HWMON_DEBUG_CHIP) := -DDEBUG
>>   diff --git a/drivers/hwmon/generic-pwm-tachometer.c 
>> b/drivers/hwmon/generic-pwm-tachometer.c
>> new file mode 100644
>> index 0000000..9354d43
>> --- /dev/null
>> +++ b/drivers/hwmon/generic-pwm-tachometer.c
>> @@ -0,0 +1,112 @@
>> +/*
>> + * Copyright (c) 2017-2018, NVIDIA CORPORATION.  All rights reserved.
>> + *
>> + * This program is free software; you can redistribute it and/or 
>> modify it
>> + * under the terms and conditions of the GNU General Public License,
>> + * version 2, as published by the Free Software Foundation.
>> + *
>> + * This program is distributed in the hope it will be useful, but 
>> WITHOUT
>> + * ANY WARRANTY; without even the implied warranty of 
>> MERCHANTABILITY or
>> + * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public 
>> License for
>> + * more details.
>> + *
>> + */
>> +
>> +#include <linux/module.h>
>> +#include <linux/platform_device.h>
>> +#include <linux/err.h>
>> +#include <linux/pwm.h>
>> +#include <linux/hwmon.h>
>> +#include <linux/hwmon-sysfs.h>
>> +
>> +struct pwm_hwmon_tach {
>> +    struct device        *dev;
>> +    struct pwm_device    *pwm;
>> +    struct device        *hwmon;
>> +};
>> +
>> +static ssize_t show_rpm(struct device *dev, struct device_attribute 
>> *attr,
>> +            char *buf)
>> +{
>> +    struct pwm_hwmon_tach *ptt = dev_get_drvdata(dev);
>> +    struct pwm_device *pwm = ptt->pwm;
>> +    struct pwm_capture result;
>> +    int err;
>> +    unsigned int rpm = 0;
>> +
>> +    err = pwm_capture(pwm, &result, 0);
>> +    if (err < 0) {
>> +        dev_err(ptt->dev, "Failed to capture PWM: %d\n", err);
>> +        return err;
>> +    }
>> +
>> +    if (result.period)
>> +        rpm = DIV_ROUND_CLOSEST_ULL(60ULL * NSEC_PER_SEC,
>> +                        result.period);
>> +
>> +    return sprintf(buf, "%u\n", rpm);
>> +}
>> +
>> +static SENSOR_DEVICE_ATTR(rpm, 0444, show_rpm, NULL, 0);
>> +
>> +static struct attribute *pwm_tach_attrs[] = {
>> +    &sensor_dev_attr_rpm.dev_attr.attr,
>> +    NULL,
>> +};
>
> "rpm" is not a standard hwmon sysfs attribute. If you don't provide
> a single standard hwmon sysfs attribute, having a hwmon driver is 
> pointless.
Guenter Roeck,
I will define a new hwmon sysfs attribute node called 
"hwmon_tachometer_attributes" in hwmon.h like below and update the same 
in tachometer hwmon driver. Is it fine ?
enum hwmon_tachometer_attributes {
         hwmon_tachometer_rpm,
};
>> +
>> +ATTRIBUTE_GROUPS(pwm_tach);
>> +
>> +static int pwm_tach_probe(struct platform_device *pdev)
>> +{
>> +    struct pwm_hwmon_tach *ptt;
>> +    int err;
>> +
>> +    ptt = devm_kzalloc(&pdev->dev, sizeof(*ptt), GFP_KERNEL);
>> +    if (!ptt)
>> +        return -ENOMEM;
>> +
>> +    ptt->dev = &pdev->dev;
>> +
>> +    platform_set_drvdata(pdev, ptt);
>> +    dev_set_drvdata(&pdev->dev, ptt);
>> +
>
> None of those is used.
I will take care in next version of patches.
>
>> +    ptt->pwm = devm_of_pwm_get(&pdev->dev, pdev->dev.of_node, NULL);
>> +    if (IS_ERR(ptt->pwm)) {
>> +        err = PTR_ERR(ptt->pwm);
>> +        dev_err(&pdev->dev, "Failed to get pwm handle, err: %d\n",
>> +            err);
>> +        return err;
>> +    }
>> +
>> +    ptt->hwmon = devm_hwmon_device_register_with_groups(&pdev->dev,
>> +                     "pwm_tach", ptt, pwm_tach_groups);
>
> Please use the new API - devm_hwmon_device_register_with_info -
> for new drivers.
Sure, will take care.
>
>> +    if (IS_ERR(ptt->hwmon)) {
>> +        err = PTR_ERR_OR_ZERO(ptt->hwmon);
>> +        dev_err(&pdev->dev, "Failed to register hwmon device: %d\n",
>> +            err);
>> +        return err;
>> +    }
>
> Please no noise on failure. The failure is going to be a memory 
> allocation failure,
> which is reported already, and user space will be informed with the 
> error code.
I will take care.
--
To unsubscribe from this list: send the line "unsubscribe linux-pwm" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Guenter Roeck Feb. 28, 2018, 5:58 a.m. | #8
On 02/27/2018 09:38 PM, Rajkumar Rampelli wrote:
> 
> On Wednesday 21 February 2018 08:20 PM, Guenter Roeck wrote:
>> On 02/20/2018 10:58 PM, Rajkumar Rampelli wrote:
>>> Add generic PWM based tachometer driver via HWMON interface
>>> to report the RPM of motor. This drivers get the period/duty
>>> cycle from PWM IP which captures the motor PWM output.
>>>
>>> This driver implements a simple interface for monitoring the speed of
>>> a fan and exposes it in roatations per minute (RPM) to the user space
>>> by using the hwmon's sysfs interface
>>>
>>> Signed-off-by: Rajkumar Rampelli <rrajk@nvidia.com>
>>> ---
>>>   Documentation/hwmon/generic-pwm-tachometer |  17 +++++
>>>   drivers/hwmon/Kconfig                      |  10 +++
>>>   drivers/hwmon/Makefile                     |   1 +
>>>   drivers/hwmon/generic-pwm-tachometer.c     | 112 +++++++++++++++++++++++++++++
>>>   4 files changed, 140 insertions(+)
>>>   create mode 100644 Documentation/hwmon/generic-pwm-tachometer
>>>   create mode 100644 drivers/hwmon/generic-pwm-tachometer.c
>>>
>>> diff --git a/Documentation/hwmon/generic-pwm-tachometer b/Documentation/hwmon/generic-pwm-tachometer
>>> new file mode 100644
>>> index 0000000..e0713ee
>>> --- /dev/null
>>> +++ b/Documentation/hwmon/generic-pwm-tachometer
>>> @@ -0,0 +1,17 @@
>>> +Kernel driver generic-pwm-tachometer
>>> +====================================
>>> +
>>> +This driver enables the use of a PWM module to monitor a fan. It uses the
>>> +generic PWM interface and can be used on SoCs as along as the SoC supports
>>> +Tachometer controller that moniors the Fan speed in periods.
>>> +
>>> +Author: Rajkumar Rampelli <rrajk@nvidia.com>
>>> +
>>> +Description
>>> +-----------
>>> +
>>> +The driver implements a simple interface for monitoring the Fan speed using
>>> +PWM module and Tachometer controller. It requests period value through PWM
>>> +capture interface to Tachometer and measures the Rotations per minute using
>>> +received period value. It exposes the Fan speed in RPM to the user space by
>>> +using the hwmon's sysfs interface.
>>> diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
>>> index ef23553..8912dcb 100644
>>> --- a/drivers/hwmon/Kconfig
>>> +++ b/drivers/hwmon/Kconfig
>>> @@ -1878,6 +1878,16 @@ config SENSORS_XGENE
>>>         If you say yes here you get support for the temperature
>>>         and power sensors for APM X-Gene SoC.
>>>   +config GENERIC_PWM_TACHOMETER
>>> +    tristate "Generic PWM based tachometer driver"
>>> +    depends on PWM
>>> +    help
>>> +      Enables a driver to use PWM signal from motor to use
>>> +      for measuring the motor speed. The RPM is captured by
>>> +      PWM modules which has PWM capture capability and this
>>> +      drivers reads the captured data from PWM IP to convert
>>> +      it to speed in RPM.
>>> +
>>>   if ACPI
>>>     comment "ACPI drivers"
>>> diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
>>> index f814b4a..9dcc374 100644
>>> --- a/drivers/hwmon/Makefile
>>> +++ b/drivers/hwmon/Makefile
>>> @@ -175,6 +175,7 @@ obj-$(CONFIG_SENSORS_WM8350)    += wm8350-hwmon.o
>>>   obj-$(CONFIG_SENSORS_XGENE)    += xgene-hwmon.o
>>>     obj-$(CONFIG_PMBUS)        += pmbus/
>>> +obj-$(CONFIG_GENERIC_PWM_TACHOMETER) += generic-pwm-tachometer.o
>>>     ccflags-$(CONFIG_HWMON_DEBUG_CHIP) := -DDEBUG
>>>   diff --git a/drivers/hwmon/generic-pwm-tachometer.c b/drivers/hwmon/generic-pwm-tachometer.c
>>> new file mode 100644
>>> index 0000000..9354d43
>>> --- /dev/null
>>> +++ b/drivers/hwmon/generic-pwm-tachometer.c
>>> @@ -0,0 +1,112 @@
>>> +/*
>>> + * Copyright (c) 2017-2018, NVIDIA CORPORATION.  All rights reserved.
>>> + *
>>> + * This program is free software; you can redistribute it and/or modify it
>>> + * under the terms and conditions of the GNU General Public License,
>>> + * version 2, as published by the Free Software Foundation.
>>> + *
>>> + * This program is distributed in the hope it will be useful, but WITHOUT
>>> + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
>>> + * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
>>> + * more details.
>>> + *
>>> + */
>>> +
>>> +#include <linux/module.h>
>>> +#include <linux/platform_device.h>
>>> +#include <linux/err.h>
>>> +#include <linux/pwm.h>
>>> +#include <linux/hwmon.h>
>>> +#include <linux/hwmon-sysfs.h>
>>> +
>>> +struct pwm_hwmon_tach {
>>> +    struct device        *dev;
>>> +    struct pwm_device    *pwm;
>>> +    struct device        *hwmon;
>>> +};
>>> +
>>> +static ssize_t show_rpm(struct device *dev, struct device_attribute *attr,
>>> +            char *buf)
>>> +{
>>> +    struct pwm_hwmon_tach *ptt = dev_get_drvdata(dev);
>>> +    struct pwm_device *pwm = ptt->pwm;
>>> +    struct pwm_capture result;
>>> +    int err;
>>> +    unsigned int rpm = 0;
>>> +
>>> +    err = pwm_capture(pwm, &result, 0);
>>> +    if (err < 0) {
>>> +        dev_err(ptt->dev, "Failed to capture PWM: %d\n", err);
>>> +        return err;
>>> +    }
>>> +
>>> +    if (result.period)
>>> +        rpm = DIV_ROUND_CLOSEST_ULL(60ULL * NSEC_PER_SEC,
>>> +                        result.period);
>>> +
>>> +    return sprintf(buf, "%u\n", rpm);
>>> +}
>>> +
>>> +static SENSOR_DEVICE_ATTR(rpm, 0444, show_rpm, NULL, 0);
>>> +
>>> +static struct attribute *pwm_tach_attrs[] = {
>>> +    &sensor_dev_attr_rpm.dev_attr.attr,
>>> +    NULL,
>>> +};
>>
>> "rpm" is not a standard hwmon sysfs attribute. If you don't provide
>> a single standard hwmon sysfs attribute, having a hwmon driver is pointless.
> Guenter Roeck,
> I will define a new hwmon sysfs attribute node called "hwmon_tachometer_attributes" in hwmon.h like below and update the same in tachometer hwmon driver. Is it fine ?
> enum hwmon_tachometer_attributes {

Are you kidding me ?

Guenter
--
To unsubscribe from this list: send the line "unsubscribe linux-pwm" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Rajkumar Rampelli Feb. 28, 2018, 6:12 a.m. | #9
On Wednesday 28 February 2018 11:28 AM, Guenter Roeck wrote:
> On 02/27/2018 09:38 PM, Rajkumar Rampelli wrote:
>>
>> On Wednesday 21 February 2018 08:20 PM, Guenter Roeck wrote:
>>> On 02/20/2018 10:58 PM, Rajkumar Rampelli wrote:
>>>> Add generic PWM based tachometer driver via HWMON interface
>>>> to report the RPM of motor. This drivers get the period/duty
>>>> cycle from PWM IP which captures the motor PWM output.
>>>>
>>>> This driver implements a simple interface for monitoring the speed of
>>>> a fan and exposes it in roatations per minute (RPM) to the user space
>>>> by using the hwmon's sysfs interface
>>>>
>>>> Signed-off-by: Rajkumar Rampelli <rrajk@nvidia.com>
>>>> ---
>>>>   Documentation/hwmon/generic-pwm-tachometer |  17 +++++
>>>>   drivers/hwmon/Kconfig                      |  10 +++
>>>>   drivers/hwmon/Makefile                     |   1 +
>>>>   drivers/hwmon/generic-pwm-tachometer.c     | 112 
>>>> +++++++++++++++++++++++++++++
>>>>   4 files changed, 140 insertions(+)
>>>>   create mode 100644 Documentation/hwmon/generic-pwm-tachometer
>>>>   create mode 100644 drivers/hwmon/generic-pwm-tachometer.c
>>>>
>>>> diff --git a/Documentation/hwmon/generic-pwm-tachometer 
>>>> b/Documentation/hwmon/generic-pwm-tachometer
>>>> new file mode 100644
>>>> index 0000000..e0713ee
>>>> --- /dev/null
>>>> +++ b/Documentation/hwmon/generic-pwm-tachometer
>>>> @@ -0,0 +1,17 @@
>>>> +Kernel driver generic-pwm-tachometer
>>>> +====================================
>>>> +
>>>> +This driver enables the use of a PWM module to monitor a fan. It 
>>>> uses the
>>>> +generic PWM interface and can be used on SoCs as along as the SoC 
>>>> supports
>>>> +Tachometer controller that moniors the Fan speed in periods.
>>>> +
>>>> +Author: Rajkumar Rampelli <rrajk@nvidia.com>
>>>> +
>>>> +Description
>>>> +-----------
>>>> +
>>>> +The driver implements a simple interface for monitoring the Fan 
>>>> speed using
>>>> +PWM module and Tachometer controller. It requests period value 
>>>> through PWM
>>>> +capture interface to Tachometer and measures the Rotations per 
>>>> minute using
>>>> +received period value. It exposes the Fan speed in RPM to the user 
>>>> space by
>>>> +using the hwmon's sysfs interface.
>>>> diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
>>>> index ef23553..8912dcb 100644
>>>> --- a/drivers/hwmon/Kconfig
>>>> +++ b/drivers/hwmon/Kconfig
>>>> @@ -1878,6 +1878,16 @@ config SENSORS_XGENE
>>>>         If you say yes here you get support for the temperature
>>>>         and power sensors for APM X-Gene SoC.
>>>>   +config GENERIC_PWM_TACHOMETER
>>>> +    tristate "Generic PWM based tachometer driver"
>>>> +    depends on PWM
>>>> +    help
>>>> +      Enables a driver to use PWM signal from motor to use
>>>> +      for measuring the motor speed. The RPM is captured by
>>>> +      PWM modules which has PWM capture capability and this
>>>> +      drivers reads the captured data from PWM IP to convert
>>>> +      it to speed in RPM.
>>>> +
>>>>   if ACPI
>>>>     comment "ACPI drivers"
>>>> diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
>>>> index f814b4a..9dcc374 100644
>>>> --- a/drivers/hwmon/Makefile
>>>> +++ b/drivers/hwmon/Makefile
>>>> @@ -175,6 +175,7 @@ obj-$(CONFIG_SENSORS_WM8350)    += wm8350-hwmon.o
>>>>   obj-$(CONFIG_SENSORS_XGENE)    += xgene-hwmon.o
>>>>     obj-$(CONFIG_PMBUS)        += pmbus/
>>>> +obj-$(CONFIG_GENERIC_PWM_TACHOMETER) += generic-pwm-tachometer.o
>>>>     ccflags-$(CONFIG_HWMON_DEBUG_CHIP) := -DDEBUG
>>>>   diff --git a/drivers/hwmon/generic-pwm-tachometer.c 
>>>> b/drivers/hwmon/generic-pwm-tachometer.c
>>>> new file mode 100644
>>>> index 0000000..9354d43
>>>> --- /dev/null
>>>> +++ b/drivers/hwmon/generic-pwm-tachometer.c
>>>> @@ -0,0 +1,112 @@
>>>> +/*
>>>> + * Copyright (c) 2017-2018, NVIDIA CORPORATION.  All rights reserved.
>>>> + *
>>>> + * This program is free software; you can redistribute it and/or 
>>>> modify it
>>>> + * under the terms and conditions of the GNU General Public License,
>>>> + * version 2, as published by the Free Software Foundation.
>>>> + *
>>>> + * This program is distributed in the hope it will be useful, but 
>>>> WITHOUT
>>>> + * ANY WARRANTY; without even the implied warranty of 
>>>> MERCHANTABILITY or
>>>> + * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public 
>>>> License for
>>>> + * more details.
>>>> + *
>>>> + */
>>>> +
>>>> +#include <linux/module.h>
>>>> +#include <linux/platform_device.h>
>>>> +#include <linux/err.h>
>>>> +#include <linux/pwm.h>
>>>> +#include <linux/hwmon.h>
>>>> +#include <linux/hwmon-sysfs.h>
>>>> +
>>>> +struct pwm_hwmon_tach {
>>>> +    struct device        *dev;
>>>> +    struct pwm_device    *pwm;
>>>> +    struct device        *hwmon;
>>>> +};
>>>> +
>>>> +static ssize_t show_rpm(struct device *dev, struct 
>>>> device_attribute *attr,
>>>> +            char *buf)
>>>> +{
>>>> +    struct pwm_hwmon_tach *ptt = dev_get_drvdata(dev);
>>>> +    struct pwm_device *pwm = ptt->pwm;
>>>> +    struct pwm_capture result;
>>>> +    int err;
>>>> +    unsigned int rpm = 0;
>>>> +
>>>> +    err = pwm_capture(pwm, &result, 0);
>>>> +    if (err < 0) {
>>>> +        dev_err(ptt->dev, "Failed to capture PWM: %d\n", err);
>>>> +        return err;
>>>> +    }
>>>> +
>>>> +    if (result.period)
>>>> +        rpm = DIV_ROUND_CLOSEST_ULL(60ULL * NSEC_PER_SEC,
>>>> +                        result.period);
>>>> +
>>>> +    return sprintf(buf, "%u\n", rpm);
>>>> +}
>>>> +
>>>> +static SENSOR_DEVICE_ATTR(rpm, 0444, show_rpm, NULL, 0);
>>>> +
>>>> +static struct attribute *pwm_tach_attrs[] = {
>>>> +    &sensor_dev_attr_rpm.dev_attr.attr,
>>>> +    NULL,
>>>> +};
>>>
>>> "rpm" is not a standard hwmon sysfs attribute. If you don't provide
>>> a single standard hwmon sysfs attribute, having a hwmon driver is 
>>> pointless.
>> Guenter Roeck,
>> I will define a new hwmon sysfs attribute node called 
>> "hwmon_tachometer_attributes" in hwmon.h like below and update the 
>> same in tachometer hwmon driver. Is it fine ?
>> enum hwmon_tachometer_attributes {
>
> Are you kidding me ?
>
> Guenter
Sorry, I just wanted to confirm whether my understanding is correct or 
not before implementing it actually.
Or, shall I add this attribute as a part of fan attributes with 
"hwmon_fan_rpm" ? or any other way to do it ? I need your inputs in 
fixing this.

--
To unsubscribe from this list: send the line "unsubscribe linux-pwm" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Mikko Perttunen Feb. 28, 2018, 7:03 a.m. | #10
On 02/28/2018 08:12 AM, Rajkumar Rampelli wrote:
> 
> On Wednesday 28 February 2018 11:28 AM, Guenter Roeck wrote:
>> On 02/27/2018 09:38 PM, Rajkumar Rampelli wrote:
>>>
>>> On Wednesday 21 February 2018 08:20 PM, Guenter Roeck wrote:
>>>> On 02/20/2018 10:58 PM, Rajkumar Rampelli wrote:
>>>>> Add generic PWM based tachometer driver via HWMON interface
>>>>> to report the RPM of motor. This drivers get the period/duty
>>>>> cycle from PWM IP which captures the motor PWM output.
>>>>>
>>>>> This driver implements a simple interface for monitoring the speed of
>>>>> a fan and exposes it in roatations per minute (RPM) to the user space
>>>>> by using the hwmon's sysfs interface
>>>>>
>>>>> Signed-off-by: Rajkumar Rampelli <rrajk@nvidia.com>
>>>>> ---
>>>>>   Documentation/hwmon/generic-pwm-tachometer |  17 +++++
>>>>>   drivers/hwmon/Kconfig                      |  10 +++
>>>>>   drivers/hwmon/Makefile                     |   1 +
>>>>>   drivers/hwmon/generic-pwm-tachometer.c     | 112 
>>>>> +++++++++++++++++++++++++++++
>>>>>   4 files changed, 140 insertions(+)
>>>>>   create mode 100644 Documentation/hwmon/generic-pwm-tachometer
>>>>>   create mode 100644 drivers/hwmon/generic-pwm-tachometer.c
>>>>>
>>>>> diff --git a/Documentation/hwmon/generic-pwm-tachometer 
>>>>> b/Documentation/hwmon/generic-pwm-tachometer
>>>>> new file mode 100644
>>>>> index 0000000..e0713ee
>>>>> --- /dev/null
>>>>> +++ b/Documentation/hwmon/generic-pwm-tachometer
>>>>> @@ -0,0 +1,17 @@
>>>>> +Kernel driver generic-pwm-tachometer
>>>>> +====================================
>>>>> +
>>>>> +This driver enables the use of a PWM module to monitor a fan. It 
>>>>> uses the
>>>>> +generic PWM interface and can be used on SoCs as along as the SoC 
>>>>> supports
>>>>> +Tachometer controller that moniors the Fan speed in periods.
>>>>> +
>>>>> +Author: Rajkumar Rampelli <rrajk@nvidia.com>
>>>>> +
>>>>> +Description
>>>>> +-----------
>>>>> +
>>>>> +The driver implements a simple interface for monitoring the Fan 
>>>>> speed using
>>>>> +PWM module and Tachometer controller. It requests period value 
>>>>> through PWM
>>>>> +capture interface to Tachometer and measures the Rotations per 
>>>>> minute using
>>>>> +received period value. It exposes the Fan speed in RPM to the user 
>>>>> space by
>>>>> +using the hwmon's sysfs interface.
>>>>> diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
>>>>> index ef23553..8912dcb 100644
>>>>> --- a/drivers/hwmon/Kconfig
>>>>> +++ b/drivers/hwmon/Kconfig
>>>>> @@ -1878,6 +1878,16 @@ config SENSORS_XGENE
>>>>>         If you say yes here you get support for the temperature
>>>>>         and power sensors for APM X-Gene SoC.
>>>>>   +config GENERIC_PWM_TACHOMETER
>>>>> +    tristate "Generic PWM based tachometer driver"
>>>>> +    depends on PWM
>>>>> +    help
>>>>> +      Enables a driver to use PWM signal from motor to use
>>>>> +      for measuring the motor speed. The RPM is captured by
>>>>> +      PWM modules which has PWM capture capability and this
>>>>> +      drivers reads the captured data from PWM IP to convert
>>>>> +      it to speed in RPM.
>>>>> +
>>>>>   if ACPI
>>>>>     comment "ACPI drivers"
>>>>> diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
>>>>> index f814b4a..9dcc374 100644
>>>>> --- a/drivers/hwmon/Makefile
>>>>> +++ b/drivers/hwmon/Makefile
>>>>> @@ -175,6 +175,7 @@ obj-$(CONFIG_SENSORS_WM8350)    += wm8350-hwmon.o
>>>>>   obj-$(CONFIG_SENSORS_XGENE)    += xgene-hwmon.o
>>>>>     obj-$(CONFIG_PMBUS)        += pmbus/
>>>>> +obj-$(CONFIG_GENERIC_PWM_TACHOMETER) += generic-pwm-tachometer.o
>>>>>     ccflags-$(CONFIG_HWMON_DEBUG_CHIP) := -DDEBUG
>>>>>   diff --git a/drivers/hwmon/generic-pwm-tachometer.c 
>>>>> b/drivers/hwmon/generic-pwm-tachometer.c
>>>>> new file mode 100644
>>>>> index 0000000..9354d43
>>>>> --- /dev/null
>>>>> +++ b/drivers/hwmon/generic-pwm-tachometer.c
>>>>> @@ -0,0 +1,112 @@
>>>>> +/*
>>>>> + * Copyright (c) 2017-2018, NVIDIA CORPORATION.  All rights reserved.
>>>>> + *
>>>>> + * This program is free software; you can redistribute it and/or 
>>>>> modify it
>>>>> + * under the terms and conditions of the GNU General Public License,
>>>>> + * version 2, as published by the Free Software Foundation.
>>>>> + *
>>>>> + * This program is distributed in the hope it will be useful, but 
>>>>> WITHOUT
>>>>> + * ANY WARRANTY; without even the implied warranty of 
>>>>> MERCHANTABILITY or
>>>>> + * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public 
>>>>> License for
>>>>> + * more details.
>>>>> + *
>>>>> + */
>>>>> +
>>>>> +#include <linux/module.h>
>>>>> +#include <linux/platform_device.h>
>>>>> +#include <linux/err.h>
>>>>> +#include <linux/pwm.h>
>>>>> +#include <linux/hwmon.h>
>>>>> +#include <linux/hwmon-sysfs.h>
>>>>> +
>>>>> +struct pwm_hwmon_tach {
>>>>> +    struct device        *dev;
>>>>> +    struct pwm_device    *pwm;
>>>>> +    struct device        *hwmon;
>>>>> +};
>>>>> +
>>>>> +static ssize_t show_rpm(struct device *dev, struct 
>>>>> device_attribute *attr,
>>>>> +            char *buf)
>>>>> +{
>>>>> +    struct pwm_hwmon_tach *ptt = dev_get_drvdata(dev);
>>>>> +    struct pwm_device *pwm = ptt->pwm;
>>>>> +    struct pwm_capture result;
>>>>> +    int err;
>>>>> +    unsigned int rpm = 0;
>>>>> +
>>>>> +    err = pwm_capture(pwm, &result, 0);
>>>>> +    if (err < 0) {
>>>>> +        dev_err(ptt->dev, "Failed to capture PWM: %d\n", err);
>>>>> +        return err;
>>>>> +    }
>>>>> +
>>>>> +    if (result.period)
>>>>> +        rpm = DIV_ROUND_CLOSEST_ULL(60ULL * NSEC_PER_SEC,
>>>>> +                        result.period);
>>>>> +
>>>>> +    return sprintf(buf, "%u\n", rpm);
>>>>> +}
>>>>> +
>>>>> +static SENSOR_DEVICE_ATTR(rpm, 0444, show_rpm, NULL, 0);
>>>>> +
>>>>> +static struct attribute *pwm_tach_attrs[] = {
>>>>> +    &sensor_dev_attr_rpm.dev_attr.attr,
>>>>> +    NULL,
>>>>> +};
>>>>
>>>> "rpm" is not a standard hwmon sysfs attribute. If you don't provide
>>>> a single standard hwmon sysfs attribute, having a hwmon driver is 
>>>> pointless.
>>> Guenter Roeck,
>>> I will define a new hwmon sysfs attribute node called 
>>> "hwmon_tachometer_attributes" in hwmon.h like below and update the 
>>> same in tachometer hwmon driver. Is it fine ?
>>> enum hwmon_tachometer_attributes {
>>
>> Are you kidding me ?
>>
>> Guenter
> Sorry, I just wanted to confirm whether my understanding is correct or 
> not before implementing it actually.
> Or, shall I add this attribute as a part of fan attributes with 
> "hwmon_fan_rpm" ? or any other way to do it ? I need your inputs in 
> fixing this.

I think he wants the attribute to be named according to the properties 
in this document: 
https://www.kernel.org/doc/Documentation/hwmon/sysfs-interface. I guess 
the attribute would then map to fan1_input, though I'm not sure if 
that's 100% correct either since this could technically be attached to 
something other than a fan. But I would think in practice that's not a 
big concern.

Guenter,
Please correct me as well if I'm wrong.

Thank you,
Mikko

> 
> -- 
> To unsubscribe from this list: send the line "unsubscribe linux-tegra" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
--
To unsubscribe from this list: send the line "unsubscribe linux-pwm" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Guenter Roeck Feb. 28, 2018, 2:29 p.m. | #11
On 02/27/2018 11:03 PM, Mikko Perttunen wrote:
> On 02/28/2018 08:12 AM, Rajkumar Rampelli wrote:
>>
>> On Wednesday 28 February 2018 11:28 AM, Guenter Roeck wrote:
>>> On 02/27/2018 09:38 PM, Rajkumar Rampelli wrote:
>>>>
>>>> On Wednesday 21 February 2018 08:20 PM, Guenter Roeck wrote:
>>>>> On 02/20/2018 10:58 PM, Rajkumar Rampelli wrote:
>>>>>> Add generic PWM based tachometer driver via HWMON interface
>>>>>> to report the RPM of motor. This drivers get the period/duty
>>>>>> cycle from PWM IP which captures the motor PWM output.
>>>>>>
>>>>>> This driver implements a simple interface for monitoring the speed of
>>>>>> a fan and exposes it in roatations per minute (RPM) to the user space
>>>>>> by using the hwmon's sysfs interface
>>>>>>
>>>>>> Signed-off-by: Rajkumar Rampelli <rrajk@nvidia.com>
>>>>>> ---
>>>>>>   Documentation/hwmon/generic-pwm-tachometer |  17 +++++
>>>>>>   drivers/hwmon/Kconfig                      |  10 +++
>>>>>>   drivers/hwmon/Makefile                     |   1 +
>>>>>>   drivers/hwmon/generic-pwm-tachometer.c     | 112 +++++++++++++++++++++++++++++
>>>>>>   4 files changed, 140 insertions(+)
>>>>>>   create mode 100644 Documentation/hwmon/generic-pwm-tachometer
>>>>>>   create mode 100644 drivers/hwmon/generic-pwm-tachometer.c
>>>>>>
>>>>>> diff --git a/Documentation/hwmon/generic-pwm-tachometer b/Documentation/hwmon/generic-pwm-tachometer
>>>>>> new file mode 100644
>>>>>> index 0000000..e0713ee
>>>>>> --- /dev/null
>>>>>> +++ b/Documentation/hwmon/generic-pwm-tachometer
>>>>>> @@ -0,0 +1,17 @@
>>>>>> +Kernel driver generic-pwm-tachometer
>>>>>> +====================================
>>>>>> +
>>>>>> +This driver enables the use of a PWM module to monitor a fan. It uses the
>>>>>> +generic PWM interface and can be used on SoCs as along as the SoC supports
>>>>>> +Tachometer controller that moniors the Fan speed in periods.
>>>>>> +
>>>>>> +Author: Rajkumar Rampelli <rrajk@nvidia.com>
>>>>>> +
>>>>>> +Description
>>>>>> +-----------
>>>>>> +
>>>>>> +The driver implements a simple interface for monitoring the Fan speed using
>>>>>> +PWM module and Tachometer controller. It requests period value through PWM
>>>>>> +capture interface to Tachometer and measures the Rotations per minute using
>>>>>> +received period value. It exposes the Fan speed in RPM to the user space by
>>>>>> +using the hwmon's sysfs interface.
>>>>>> diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
>>>>>> index ef23553..8912dcb 100644
>>>>>> --- a/drivers/hwmon/Kconfig
>>>>>> +++ b/drivers/hwmon/Kconfig
>>>>>> @@ -1878,6 +1878,16 @@ config SENSORS_XGENE
>>>>>>         If you say yes here you get support for the temperature
>>>>>>         and power sensors for APM X-Gene SoC.
>>>>>>   +config GENERIC_PWM_TACHOMETER
>>>>>> +    tristate "Generic PWM based tachometer driver"
>>>>>> +    depends on PWM
>>>>>> +    help
>>>>>> +      Enables a driver to use PWM signal from motor to use
>>>>>> +      for measuring the motor speed. The RPM is captured by
>>>>>> +      PWM modules which has PWM capture capability and this
>>>>>> +      drivers reads the captured data from PWM IP to convert
>>>>>> +      it to speed in RPM.
>>>>>> +
>>>>>>   if ACPI
>>>>>>     comment "ACPI drivers"
>>>>>> diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
>>>>>> index f814b4a..9dcc374 100644
>>>>>> --- a/drivers/hwmon/Makefile
>>>>>> +++ b/drivers/hwmon/Makefile
>>>>>> @@ -175,6 +175,7 @@ obj-$(CONFIG_SENSORS_WM8350)    += wm8350-hwmon.o
>>>>>>   obj-$(CONFIG_SENSORS_XGENE)    += xgene-hwmon.o
>>>>>>     obj-$(CONFIG_PMBUS)        += pmbus/
>>>>>> +obj-$(CONFIG_GENERIC_PWM_TACHOMETER) += generic-pwm-tachometer.o
>>>>>>     ccflags-$(CONFIG_HWMON_DEBUG_CHIP) := -DDEBUG
>>>>>>   diff --git a/drivers/hwmon/generic-pwm-tachometer.c b/drivers/hwmon/generic-pwm-tachometer.c
>>>>>> new file mode 100644
>>>>>> index 0000000..9354d43
>>>>>> --- /dev/null
>>>>>> +++ b/drivers/hwmon/generic-pwm-tachometer.c
>>>>>> @@ -0,0 +1,112 @@
>>>>>> +/*
>>>>>> + * Copyright (c) 2017-2018, NVIDIA CORPORATION.  All rights reserved.
>>>>>> + *
>>>>>> + * This program is free software; you can redistribute it and/or modify it
>>>>>> + * under the terms and conditions of the GNU General Public License,
>>>>>> + * version 2, as published by the Free Software Foundation.
>>>>>> + *
>>>>>> + * This program is distributed in the hope it will be useful, but WITHOUT
>>>>>> + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
>>>>>> + * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
>>>>>> + * more details.
>>>>>> + *
>>>>>> + */
>>>>>> +
>>>>>> +#include <linux/module.h>
>>>>>> +#include <linux/platform_device.h>
>>>>>> +#include <linux/err.h>
>>>>>> +#include <linux/pwm.h>
>>>>>> +#include <linux/hwmon.h>
>>>>>> +#include <linux/hwmon-sysfs.h>
>>>>>> +
>>>>>> +struct pwm_hwmon_tach {
>>>>>> +    struct device        *dev;
>>>>>> +    struct pwm_device    *pwm;
>>>>>> +    struct device        *hwmon;
>>>>>> +};
>>>>>> +
>>>>>> +static ssize_t show_rpm(struct device *dev, struct device_attribute *attr,
>>>>>> +            char *buf)
>>>>>> +{
>>>>>> +    struct pwm_hwmon_tach *ptt = dev_get_drvdata(dev);
>>>>>> +    struct pwm_device *pwm = ptt->pwm;
>>>>>> +    struct pwm_capture result;
>>>>>> +    int err;
>>>>>> +    unsigned int rpm = 0;
>>>>>> +
>>>>>> +    err = pwm_capture(pwm, &result, 0);
>>>>>> +    if (err < 0) {
>>>>>> +        dev_err(ptt->dev, "Failed to capture PWM: %d\n", err);
>>>>>> +        return err;
>>>>>> +    }
>>>>>> +
>>>>>> +    if (result.period)
>>>>>> +        rpm = DIV_ROUND_CLOSEST_ULL(60ULL * NSEC_PER_SEC,
>>>>>> +                        result.period);
>>>>>> +
>>>>>> +    return sprintf(buf, "%u\n", rpm);
>>>>>> +}
>>>>>> +
>>>>>> +static SENSOR_DEVICE_ATTR(rpm, 0444, show_rpm, NULL, 0);
>>>>>> +
>>>>>> +static struct attribute *pwm_tach_attrs[] = {
>>>>>> +    &sensor_dev_attr_rpm.dev_attr.attr,
>>>>>> +    NULL,
>>>>>> +};
>>>>>
>>>>> "rpm" is not a standard hwmon sysfs attribute. If you don't provide
>>>>> a single standard hwmon sysfs attribute, having a hwmon driver is pointless.
>>>> Guenter Roeck,
>>>> I will define a new hwmon sysfs attribute node called "hwmon_tachometer_attributes" in hwmon.h like below and update the same in tachometer hwmon driver. Is it fine ?
>>>> enum hwmon_tachometer_attributes {
>>>
>>> Are you kidding me ?
>>>
>>> Guenter
>> Sorry, I just wanted to confirm whether my understanding is correct or not before implementing it actually.
>> Or, shall I add this attribute as a part of fan attributes with "hwmon_fan_rpm" ? or any other way to do it ? I need your inputs in fixing this.
> 
> I think he wants the attribute to be named according to the properties in this document: https://www.kernel.org/doc/Documentation/hwmon/sysfs-interface. I guess the attribute would then map to fan1_input, though I'm not sure if that's 100% correct either since this could technically be attached to something other than a fan. But I would think in practice that's not a big concern.
> 
> Guenter,
> Please correct me as well if I'm wrong.
> 
You are absolutely correct.

While I am not opposed to ABI changes, the merits of those would need to be
discussed on the mailing list. But replacing "fan1_input" with "rpm" is
not an acceptable ABI change, even if it may measure something that turns
but isn't a fan.

If this _is_ in fact supposed to be used for something else but fans, we
would have to discuss what that might be, and if hwmon is the appropriate
subsystem to measure and report it. This does to some degree lead back to
my concern of having the "fan" part of this patch series in the pwm core.
I am still not sure if that makes sense.

Thanks,
Guenter

> Thank you,
> Mikko
> 
>>
>> -- 
>> To unsubscribe from this list: send the line "unsubscribe linux-tegra" in
>> the body of a message to majordomo@vger.kernel.org
>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> -- 
> To unsubscribe from this list: send the line "unsubscribe linux-hwmon" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> 

--
To unsubscribe from this list: send the line "unsubscribe linux-pwm" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Rob Herring March 1, 2018, 10:08 p.m. | #12
On Wed, Feb 21, 2018 at 05:20:29PM +0200, Mikko Perttunen wrote:
> On 21.02.2018 16:46, Guenter Roeck wrote:
> > On 02/20/2018 11:15 PM, Mikko Perttunen wrote:
> > > AIUI, the PWM framework already exposes a sysfs node with period
> > > information. We should just use that instead of adding a new driver
> > > for this.
> > > 
> > 
> > I am kind of lost. Please explain.
> > 
> > Are you saying that we should drop the pwm-fan driver as well (which goes
> > the opposite way), as well as any other drivers doing anything with pwm
> > signals,
> > because after all those signals are already exposed to userspace a sysfs
> > attributes,
> > and a kernel driver to abstract those values is thus not needed ?
> 
> The only thing this driver does is do a constant division in kernelspace.
> I'm not really seeing why that couldn't be done in userspace. But if you
> think it's appropriate to do the RPM conversion in kernelspace then I'm not
> greatly opposed to that.
> 
> > 
> > > In any case, we cannot add something like this to device tree since
> > > it's not a hardware device.
> > > 
> > 
> > So you are saying there is no means to express in devicetree that
> > a pwm input is connected to a fan ? How is that not hardware ?
> > 
> > If so, how do you express in devicetree that a pwm signal is connected
> > to anything ?
> 
> If we want to describe that the tachometer is connected to a fan, then we
> should have a fan node in the board's device tree. We don't have a chip that
> has a thing called "generic-pwm-tachometer" attached to it. (We have chips
> that have a "nvidia,tegra186-tachometer", so it's proper to have that.)

We already have some fan control bindings in the tree. Follow those. 
There's only so many ways to control fans, so lets have some alignment. 
And yes, we should have a fan node. 

Rob
--
To unsubscribe from this list: send the line "unsubscribe linux-pwm" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Rajkumar Rampelli March 7, 2018, 9:47 a.m. | #13
On Wednesday 28 February 2018 07:59 PM, Guenter Roeck wrote:
> On 02/27/2018 11:03 PM, Mikko Perttunen wrote:
>> On 02/28/2018 08:12 AM, Rajkumar Rampelli wrote:
>>>
>>> On Wednesday 28 February 2018 11:28 AM, Guenter Roeck wrote:
>>>> On 02/27/2018 09:38 PM, Rajkumar Rampelli wrote:
>>>>>
>>>>> On Wednesday 21 February 2018 08:20 PM, Guenter Roeck wrote:
>>>>>> On 02/20/2018 10:58 PM, Rajkumar Rampelli wrote:
>>>>>>> Add generic PWM based tachometer driver via HWMON interface
>>>>>>> to report the RPM of motor. This drivers get the period/duty
>>>>>>> cycle from PWM IP which captures the motor PWM output.
>>>>>>>
>>>>>>> This driver implements a simple interface for monitoring the 
>>>>>>> speed of
>>>>>>> a fan and exposes it in roatations per minute (RPM) to the user 
>>>>>>> space
>>>>>>> by using the hwmon's sysfs interface
>>>>>>>
>>>>>>> Signed-off-by: Rajkumar Rampelli <rrajk@nvidia.com>
>>>>>>> ---
>>>>>>>   Documentation/hwmon/generic-pwm-tachometer |  17 +++++
>>>>>>>   drivers/hwmon/Kconfig                      |  10 +++
>>>>>>>   drivers/hwmon/Makefile                     |   1 +
>>>>>>>   drivers/hwmon/generic-pwm-tachometer.c     | 112 
>>>>>>> +++++++++++++++++++++++++++++
>>>>>>>   4 files changed, 140 insertions(+)
>>>>>>>   create mode 100644 Documentation/hwmon/generic-pwm-tachometer
>>>>>>>   create mode 100644 drivers/hwmon/generic-pwm-tachometer.c
>>>>>>>
>>>>>>> diff --git a/Documentation/hwmon/generic-pwm-tachometer 
>>>>>>> b/Documentation/hwmon/generic-pwm-tachometer
>>>>>>> new file mode 100644
>>>>>>> index 0000000..e0713ee
>>>>>>> --- /dev/null
>>>>>>> +++ b/Documentation/hwmon/generic-pwm-tachometer
>>>>>>> @@ -0,0 +1,17 @@
>>>>>>> +Kernel driver generic-pwm-tachometer
>>>>>>> +====================================
>>>>>>> +
>>>>>>> +This driver enables the use of a PWM module to monitor a fan. 
>>>>>>> It uses the
>>>>>>> +generic PWM interface and can be used on SoCs as along as the 
>>>>>>> SoC supports
>>>>>>> +Tachometer controller that moniors the Fan speed in periods.
>>>>>>> +
>>>>>>> +Author: Rajkumar Rampelli <rrajk@nvidia.com>
>>>>>>> +
>>>>>>> +Description
>>>>>>> +-----------
>>>>>>> +
>>>>>>> +The driver implements a simple interface for monitoring the Fan 
>>>>>>> speed using
>>>>>>> +PWM module and Tachometer controller. It requests period value 
>>>>>>> through PWM
>>>>>>> +capture interface to Tachometer and measures the Rotations per 
>>>>>>> minute using
>>>>>>> +received period value. It exposes the Fan speed in RPM to the 
>>>>>>> user space by
>>>>>>> +using the hwmon's sysfs interface.
>>>>>>> diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
>>>>>>> index ef23553..8912dcb 100644
>>>>>>> --- a/drivers/hwmon/Kconfig
>>>>>>> +++ b/drivers/hwmon/Kconfig
>>>>>>> @@ -1878,6 +1878,16 @@ config SENSORS_XGENE
>>>>>>>         If you say yes here you get support for the temperature
>>>>>>>         and power sensors for APM X-Gene SoC.
>>>>>>>   +config GENERIC_PWM_TACHOMETER
>>>>>>> +    tristate "Generic PWM based tachometer driver"
>>>>>>> +    depends on PWM
>>>>>>> +    help
>>>>>>> +      Enables a driver to use PWM signal from motor to use
>>>>>>> +      for measuring the motor speed. The RPM is captured by
>>>>>>> +      PWM modules which has PWM capture capability and this
>>>>>>> +      drivers reads the captured data from PWM IP to convert
>>>>>>> +      it to speed in RPM.
>>>>>>> +
>>>>>>>   if ACPI
>>>>>>>     comment "ACPI drivers"
>>>>>>> diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
>>>>>>> index f814b4a..9dcc374 100644
>>>>>>> --- a/drivers/hwmon/Makefile
>>>>>>> +++ b/drivers/hwmon/Makefile
>>>>>>> @@ -175,6 +175,7 @@ obj-$(CONFIG_SENSORS_WM8350)    += 
>>>>>>> wm8350-hwmon.o
>>>>>>>   obj-$(CONFIG_SENSORS_XGENE)    += xgene-hwmon.o
>>>>>>>     obj-$(CONFIG_PMBUS)        += pmbus/
>>>>>>> +obj-$(CONFIG_GENERIC_PWM_TACHOMETER) += generic-pwm-tachometer.o
>>>>>>>     ccflags-$(CONFIG_HWMON_DEBUG_CHIP) := -DDEBUG
>>>>>>>   diff --git a/drivers/hwmon/generic-pwm-tachometer.c 
>>>>>>> b/drivers/hwmon/generic-pwm-tachometer.c
>>>>>>> new file mode 100644
>>>>>>> index 0000000..9354d43
>>>>>>> --- /dev/null
>>>>>>> +++ b/drivers/hwmon/generic-pwm-tachometer.c
>>>>>>> @@ -0,0 +1,112 @@
>>>>>>> +/*
>>>>>>> + * Copyright (c) 2017-2018, NVIDIA CORPORATION.  All rights 
>>>>>>> reserved.
>>>>>>> + *
>>>>>>> + * This program is free software; you can redistribute it 
>>>>>>> and/or modify it
>>>>>>> + * under the terms and conditions of the GNU General Public 
>>>>>>> License,
>>>>>>> + * version 2, as published by the Free Software Foundation.
>>>>>>> + *
>>>>>>> + * This program is distributed in the hope it will be useful, 
>>>>>>> but WITHOUT
>>>>>>> + * ANY WARRANTY; without even the implied warranty of 
>>>>>>> MERCHANTABILITY or
>>>>>>> + * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General 
>>>>>>> Public License for
>>>>>>> + * more details.
>>>>>>> + *
>>>>>>> + */
>>>>>>> +
>>>>>>> +#include <linux/module.h>
>>>>>>> +#include <linux/platform_device.h>
>>>>>>> +#include <linux/err.h>
>>>>>>> +#include <linux/pwm.h>
>>>>>>> +#include <linux/hwmon.h>
>>>>>>> +#include <linux/hwmon-sysfs.h>
>>>>>>> +
>>>>>>> +struct pwm_hwmon_tach {
>>>>>>> +    struct device        *dev;
>>>>>>> +    struct pwm_device    *pwm;
>>>>>>> +    struct device        *hwmon;
>>>>>>> +};
>>>>>>> +
>>>>>>> +static ssize_t show_rpm(struct device *dev, struct 
>>>>>>> device_attribute *attr,
>>>>>>> +            char *buf)
>>>>>>> +{
>>>>>>> +    struct pwm_hwmon_tach *ptt = dev_get_drvdata(dev);
>>>>>>> +    struct pwm_device *pwm = ptt->pwm;
>>>>>>> +    struct pwm_capture result;
>>>>>>> +    int err;
>>>>>>> +    unsigned int rpm = 0;
>>>>>>> +
>>>>>>> +    err = pwm_capture(pwm, &result, 0);
>>>>>>> +    if (err < 0) {
>>>>>>> +        dev_err(ptt->dev, "Failed to capture PWM: %d\n", err);
>>>>>>> +        return err;
>>>>>>> +    }
>>>>>>> +
>>>>>>> +    if (result.period)
>>>>>>> +        rpm = DIV_ROUND_CLOSEST_ULL(60ULL * NSEC_PER_SEC,
>>>>>>> +                        result.period);
>>>>>>> +
>>>>>>> +    return sprintf(buf, "%u\n", rpm);
>>>>>>> +}
>>>>>>> +
>>>>>>> +static SENSOR_DEVICE_ATTR(rpm, 0444, show_rpm, NULL, 0);
>>>>>>> +
>>>>>>> +static struct attribute *pwm_tach_attrs[] = {
>>>>>>> +    &sensor_dev_attr_rpm.dev_attr.attr,
>>>>>>> +    NULL,
>>>>>>> +};
>>>>>>
>>>>>> "rpm" is not a standard hwmon sysfs attribute. If you don't provide
>>>>>> a single standard hwmon sysfs attribute, having a hwmon driver is 
>>>>>> pointless.
>>>>> Guenter Roeck,
>>>>> I will define a new hwmon sysfs attribute node called 
>>>>> "hwmon_tachometer_attributes" in hwmon.h like below and update the 
>>>>> same in tachometer hwmon driver. Is it fine ?
>>>>> enum hwmon_tachometer_attributes {
>>>>
>>>> Are you kidding me ?
>>>>
>>>> Guenter
>>> Sorry, I just wanted to confirm whether my understanding is correct 
>>> or not before implementing it actually.
>>> Or, shall I add this attribute as a part of fan attributes with 
>>> "hwmon_fan_rpm" ? or any other way to do it ? I need your inputs in 
>>> fixing this.
>>
>> I think he wants the attribute to be named according to the 
>> properties in this document: 
>> https://www.kernel.org/doc/Documentation/hwmon/sysfs-interface. I 
>> guess the attribute would then map to fan1_input, though I'm not sure 
>> if that's 100% correct either since this could technically be 
>> attached to something other than a fan. But I would think in practice 
>> that's not a big concern.
>>
>> Guenter,
>> Please correct me as well if I'm wrong.
>>
> You are absolutely correct.
>
> While I am not opposed to ABI changes, the merits of those would need 
> to be
> discussed on the mailing list. But replacing "fan1_input" with "rpm" is
> not an acceptable ABI change, even if it may measure something that turns
> but isn't a fan.
>
> If this _is_ in fact supposed to be used for something else but fans, we
> would have to discuss what that might be, and if hwmon is the appropriate
> subsystem to measure and report it. This does to some degree lead back to
> my concern of having the "fan" part of this patch series in the pwm core.
> I am still not sure if that makes sense.
>
> Thanks,
> Guenter
I am planning to add tachometer support in pwm-fan.c driver 
(drivers/hwmon/) instead of adding new generic-pwm-tachometer.c driver. 
Measuring RPM value will be done in pwm-fan driver itself using pwm 
capture feature and will add new sysfs attributes under this driver to 
report rpm value of fan.
>
>> Thank you,
>> Mikko
>>
>>>
>>> -- 
>>> To unsubscribe from this list: send the line "unsubscribe 
>>> linux-tegra" in
>>> the body of a message to majordomo@vger.kernel.org
>>> More majordomo info at http://vger.kernel.org/majordomo-info.html
>> -- 
>> To unsubscribe from this list: send the line "unsubscribe 
>> linux-hwmon" in
>> the body of a message to majordomo@vger.kernel.org
>> More majordomo info at http://vger.kernel.org/majordomo-info.html
>>
>

--
To unsubscribe from this list: send the line "unsubscribe linux-pwm" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Guenter Roeck March 7, 2018, 2:20 p.m. | #14
On 03/07/2018 01:47 AM, Rajkumar Rampelli wrote:
> 
> 
> On Wednesday 28 February 2018 07:59 PM, Guenter Roeck wrote:
>> On 02/27/2018 11:03 PM, Mikko Perttunen wrote:
>>> On 02/28/2018 08:12 AM, Rajkumar Rampelli wrote:
>>>>
>>>> On Wednesday 28 February 2018 11:28 AM, Guenter Roeck wrote:
>>>>> On 02/27/2018 09:38 PM, Rajkumar Rampelli wrote:
>>>>>>
>>>>>> On Wednesday 21 February 2018 08:20 PM, Guenter Roeck wrote:
>>>>>>> On 02/20/2018 10:58 PM, Rajkumar Rampelli wrote:
>>>>>>>> Add generic PWM based tachometer driver via HWMON interface
>>>>>>>> to report the RPM of motor. This drivers get the period/duty
>>>>>>>> cycle from PWM IP which captures the motor PWM output.
>>>>>>>>
>>>>>>>> This driver implements a simple interface for monitoring the speed of
>>>>>>>> a fan and exposes it in roatations per minute (RPM) to the user space
>>>>>>>> by using the hwmon's sysfs interface
>>>>>>>>
>>>>>>>> Signed-off-by: Rajkumar Rampelli <rrajk@nvidia.com>
>>>>>>>> ---
>>>>>>>>   Documentation/hwmon/generic-pwm-tachometer |  17 +++++
>>>>>>>>   drivers/hwmon/Kconfig                      |  10 +++
>>>>>>>>   drivers/hwmon/Makefile                     |   1 +
>>>>>>>>   drivers/hwmon/generic-pwm-tachometer.c     | 112 +++++++++++++++++++++++++++++
>>>>>>>>   4 files changed, 140 insertions(+)
>>>>>>>>   create mode 100644 Documentation/hwmon/generic-pwm-tachometer
>>>>>>>>   create mode 100644 drivers/hwmon/generic-pwm-tachometer.c
>>>>>>>>
>>>>>>>> diff --git a/Documentation/hwmon/generic-pwm-tachometer b/Documentation/hwmon/generic-pwm-tachometer
>>>>>>>> new file mode 100644
>>>>>>>> index 0000000..e0713ee
>>>>>>>> --- /dev/null
>>>>>>>> +++ b/Documentation/hwmon/generic-pwm-tachometer
>>>>>>>> @@ -0,0 +1,17 @@
>>>>>>>> +Kernel driver generic-pwm-tachometer
>>>>>>>> +====================================
>>>>>>>> +
>>>>>>>> +This driver enables the use of a PWM module to monitor a fan. It uses the
>>>>>>>> +generic PWM interface and can be used on SoCs as along as the SoC supports
>>>>>>>> +Tachometer controller that moniors the Fan speed in periods.
>>>>>>>> +
>>>>>>>> +Author: Rajkumar Rampelli <rrajk@nvidia.com>
>>>>>>>> +
>>>>>>>> +Description
>>>>>>>> +-----------
>>>>>>>> +
>>>>>>>> +The driver implements a simple interface for monitoring the Fan speed using
>>>>>>>> +PWM module and Tachometer controller. It requests period value through PWM
>>>>>>>> +capture interface to Tachometer and measures the Rotations per minute using
>>>>>>>> +received period value. It exposes the Fan speed in RPM to the user space by
>>>>>>>> +using the hwmon's sysfs interface.
>>>>>>>> diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
>>>>>>>> index ef23553..8912dcb 100644
>>>>>>>> --- a/drivers/hwmon/Kconfig
>>>>>>>> +++ b/drivers/hwmon/Kconfig
>>>>>>>> @@ -1878,6 +1878,16 @@ config SENSORS_XGENE
>>>>>>>>         If you say yes here you get support for the temperature
>>>>>>>>         and power sensors for APM X-Gene SoC.
>>>>>>>>   +config GENERIC_PWM_TACHOMETER
>>>>>>>> +    tristate "Generic PWM based tachometer driver"
>>>>>>>> +    depends on PWM
>>>>>>>> +    help
>>>>>>>> +      Enables a driver to use PWM signal from motor to use
>>>>>>>> +      for measuring the motor speed. The RPM is captured by
>>>>>>>> +      PWM modules which has PWM capture capability and this
>>>>>>>> +      drivers reads the captured data from PWM IP to convert
>>>>>>>> +      it to speed in RPM.
>>>>>>>> +
>>>>>>>>   if ACPI
>>>>>>>>     comment "ACPI drivers"
>>>>>>>> diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
>>>>>>>> index f814b4a..9dcc374 100644
>>>>>>>> --- a/drivers/hwmon/Makefile
>>>>>>>> +++ b/drivers/hwmon/Makefile
>>>>>>>> @@ -175,6 +175,7 @@ obj-$(CONFIG_SENSORS_WM8350)    += wm8350-hwmon.o
>>>>>>>>   obj-$(CONFIG_SENSORS_XGENE)    += xgene-hwmon.o
>>>>>>>>     obj-$(CONFIG_PMBUS)        += pmbus/
>>>>>>>> +obj-$(CONFIG_GENERIC_PWM_TACHOMETER) += generic-pwm-tachometer.o
>>>>>>>>     ccflags-$(CONFIG_HWMON_DEBUG_CHIP) := -DDEBUG
>>>>>>>>   diff --git a/drivers/hwmon/generic-pwm-tachometer.c b/drivers/hwmon/generic-pwm-tachometer.c
>>>>>>>> new file mode 100644
>>>>>>>> index 0000000..9354d43
>>>>>>>> --- /dev/null
>>>>>>>> +++ b/drivers/hwmon/generic-pwm-tachometer.c
>>>>>>>> @@ -0,0 +1,112 @@
>>>>>>>> +/*
>>>>>>>> + * Copyright (c) 2017-2018, NVIDIA CORPORATION.  All rights reserved.
>>>>>>>> + *
>>>>>>>> + * This program is free software; you can redistribute it and/or modify it
>>>>>>>> + * under the terms and conditions of the GNU General Public License,
>>>>>>>> + * version 2, as published by the Free Software Foundation.
>>>>>>>> + *
>>>>>>>> + * This program is distributed in the hope it will be useful, but WITHOUT
>>>>>>>> + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
>>>>>>>> + * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
>>>>>>>> + * more details.
>>>>>>>> + *
>>>>>>>> + */
>>>>>>>> +
>>>>>>>> +#include <linux/module.h>
>>>>>>>> +#include <linux/platform_device.h>
>>>>>>>> +#include <linux/err.h>
>>>>>>>> +#include <linux/pwm.h>
>>>>>>>> +#include <linux/hwmon.h>
>>>>>>>> +#include <linux/hwmon-sysfs.h>
>>>>>>>> +
>>>>>>>> +struct pwm_hwmon_tach {
>>>>>>>> +    struct device        *dev;
>>>>>>>> +    struct pwm_device    *pwm;
>>>>>>>> +    struct device        *hwmon;
>>>>>>>> +};
>>>>>>>> +
>>>>>>>> +static ssize_t show_rpm(struct device *dev, struct device_attribute *attr,
>>>>>>>> +            char *buf)
>>>>>>>> +{
>>>>>>>> +    struct pwm_hwmon_tach *ptt = dev_get_drvdata(dev);
>>>>>>>> +    struct pwm_device *pwm = ptt->pwm;
>>>>>>>> +    struct pwm_capture result;
>>>>>>>> +    int err;
>>>>>>>> +    unsigned int rpm = 0;
>>>>>>>> +
>>>>>>>> +    err = pwm_capture(pwm, &result, 0);
>>>>>>>> +    if (err < 0) {
>>>>>>>> +        dev_err(ptt->dev, "Failed to capture PWM: %d\n", err);
>>>>>>>> +        return err;
>>>>>>>> +    }
>>>>>>>> +
>>>>>>>> +    if (result.period)
>>>>>>>> +        rpm = DIV_ROUND_CLOSEST_ULL(60ULL * NSEC_PER_SEC,
>>>>>>>> +                        result.period);
>>>>>>>> +
>>>>>>>> +    return sprintf(buf, "%u\n", rpm);
>>>>>>>> +}
>>>>>>>> +
>>>>>>>> +static SENSOR_DEVICE_ATTR(rpm, 0444, show_rpm, NULL, 0);
>>>>>>>> +
>>>>>>>> +static struct attribute *pwm_tach_attrs[] = {
>>>>>>>> +    &sensor_dev_attr_rpm.dev_attr.attr,
>>>>>>>> +    NULL,
>>>>>>>> +};
>>>>>>>
>>>>>>> "rpm" is not a standard hwmon sysfs attribute. If you don't provide
>>>>>>> a single standard hwmon sysfs attribute, having a hwmon driver is pointless.
>>>>>> Guenter Roeck,
>>>>>> I will define a new hwmon sysfs attribute node called "hwmon_tachometer_attributes" in hwmon.h like below and update the same in tachometer hwmon driver. Is it fine ?
>>>>>> enum hwmon_tachometer_attributes {
>>>>>
>>>>> Are you kidding me ?
>>>>>
>>>>> Guenter
>>>> Sorry, I just wanted to confirm whether my understanding is correct or not before implementing it actually.
>>>> Or, shall I add this attribute as a part of fan attributes with "hwmon_fan_rpm" ? or any other way to do it ? I need your inputs in fixing this.
>>>
>>> I think he wants the attribute to be named according to the properties in this document: https://www.kernel.org/doc/Documentation/hwmon/sysfs-interface. I guess the attribute would then map to fan1_input, though I'm not sure if that's 100% correct either since this could technically be attached to something other than a fan. But I would think in practice that's not a big concern.
>>>
>>> Guenter,
>>> Please correct me as well if I'm wrong.
>>>
>> You are absolutely correct.
>>
>> While I am not opposed to ABI changes, the merits of those would need to be
>> discussed on the mailing list. But replacing "fan1_input" with "rpm" is
>> not an acceptable ABI change, even if it may measure something that turns
>> but isn't a fan.
>>
>> If this _is_ in fact supposed to be used for something else but fans, we
>> would have to discuss what that might be, and if hwmon is the appropriate
>> subsystem to measure and report it. This does to some degree lead back to
>> my concern of having the "fan" part of this patch series in the pwm core.
>> I am still not sure if that makes sense.
>>
>> Thanks,
>> Guenter
> I am planning to add tachometer support in pwm-fan.c driver (drivers/hwmon/) instead of adding new generic-pwm-tachometer.c driver. Measuring RPM value will be done in pwm-fan driver itself using pwm capture feature and will add new sysfs attributes under this driver to report rpm value of fan.

There is an existing attribute to report the RPM of fans. It is called fan[1..n]_input.

"replacing "fan1_input" with "rpm" is not an acceptable ABI change"

Preemptive NACK.

Guenter

>>
>>> Thank you,
>>> Mikko
>>>
>>>>
>>>> -- 
>>>> To unsubscribe from this list: send the line "unsubscribe linux-tegra" in
>>>> the body of a message to majordomo@vger.kernel.org
>>>> More majordomo info at http://vger.kernel.org/majordomo-info.html
>>> -- 
>>> To unsubscribe from this list: send the line "unsubscribe linux-hwmon" in
>>> the body of a message to majordomo@vger.kernel.org
>>> More majordomo info at http://vger.kernel.org/majordomo-info.html
>>>
>>
> 
> 

--
To unsubscribe from this list: send the line "unsubscribe linux-pwm" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Laxman Dewangan March 8, 2018, 6:06 a.m. | #15
On Wednesday 07 March 2018 07:50 PM, Guenter Roeck wrote:
> On 03/07/2018 01:47 AM, Rajkumar Rampelli wrote:
>>
>>>
>>> While I am not opposed to ABI changes, the merits of those would 
>>> need to be
>>> discussed on the mailing list. But replacing "fan1_input" with "rpm" is
>>> not an acceptable ABI change, even if it may measure something that 
>>> turns
>>> but isn't a fan.
>>>
>>> If this _is_ in fact supposed to be used for something else but 
>>> fans, we
>>> would have to discuss what that might be, and if hwmon is the 
>>> appropriate
>>> subsystem to measure and report it. This does to some degree lead 
>>> back to
>>> my concern of having the "fan" part of this patch series in the pwm 
>>> core.
>>> I am still not sure if that makes sense.
>>>
>>> Thanks,
>>> Guenter
>> I am planning to add tachometer support in pwm-fan.c driver 
>> (drivers/hwmon/) instead of adding new generic-pwm-tachometer.c 
>> driver. Measuring RPM value will be done in pwm-fan driver itself 
>> using pwm capture feature and will add new sysfs attributes under 
>> this driver to report rpm value of fan.
>
> There is an existing attribute to report the RPM of fans. It is called 
> fan[1..n]_input.
>
> "replacing "fan1_input" with "rpm" is not an acceptable ABI change"
>
> Preemptive NACK.

The RPM is measured speed via PWM signal capture  which is output from fan.
So should we have the fan[1..n]_output_rpm?


--
To unsubscribe from this list: send the line "unsubscribe linux-pwm" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Mikko Perttunen March 8, 2018, 7:57 a.m. | #16
On 07.03.2018 16:20, Guenter Roeck wrote:
> On 03/07/2018 01:47 AM, Rajkumar Rampelli wrote:
>>
>>
>> On Wednesday 28 February 2018 07:59 PM, Guenter Roeck wrote:
>>> On 02/27/2018 11:03 PM, Mikko Perttunen wrote:
>>>> On 02/28/2018 08:12 AM, Rajkumar Rampelli wrote:
>>>>>
>>>>> On Wednesday 28 February 2018 11:28 AM, Guenter Roeck wrote:
>>>>>> On 02/27/2018 09:38 PM, Rajkumar Rampelli wrote:
>>>>>>>
>>>>>>> On Wednesday 21 February 2018 08:20 PM, Guenter Roeck wrote:
>>>>>>>> On 02/20/2018 10:58 PM, Rajkumar Rampelli wrote:
>>>>>>>>> Add generic PWM based tachometer driver via HWMON interface
>>>>>>>>> to report the RPM of motor. This drivers get the period/duty
>>>>>>>>> cycle from PWM IP which captures the motor PWM output.
>>>>>>>>>
>>>>>>>>> This driver implements a simple interface for monitoring the
>>>>>>>>> speed of
>>>>>>>>> a fan and exposes it in roatations per minute (RPM) to the user
>>>>>>>>> space
>>>>>>>>> by using the hwmon's sysfs interface
>>>>>>>>>
>>>>>>>>> Signed-off-by: Rajkumar Rampelli <rrajk@nvidia.com>
>>>>>>>>> ---
>>>>>>>>>   Documentation/hwmon/generic-pwm-tachometer |  17 +++++
>>>>>>>>>   drivers/hwmon/Kconfig                      |  10 +++
>>>>>>>>>   drivers/hwmon/Makefile                     |   1 +
>>>>>>>>>   drivers/hwmon/generic-pwm-tachometer.c     | 112
>>>>>>>>> +++++++++++++++++++++++++++++
>>>>>>>>>   4 files changed, 140 insertions(+)
>>>>>>>>>   create mode 100644 Documentation/hwmon/generic-pwm-tachometer
>>>>>>>>>   create mode 100644 drivers/hwmon/generic-pwm-tachometer.c
>>>>>>>>>
>>>>>>>>> diff --git a/Documentation/hwmon/generic-pwm-tachometer
>>>>>>>>> b/Documentation/hwmon/generic-pwm-tachometer
>>>>>>>>> new file mode 100644
>>>>>>>>> index 0000000..e0713ee
>>>>>>>>> --- /dev/null
>>>>>>>>> +++ b/Documentation/hwmon/generic-pwm-tachometer
>>>>>>>>> @@ -0,0 +1,17 @@
>>>>>>>>> +Kernel driver generic-pwm-tachometer
>>>>>>>>> +====================================
>>>>>>>>> +
>>>>>>>>> +This driver enables the use of a PWM module to monitor a fan.
>>>>>>>>> It uses the
>>>>>>>>> +generic PWM interface and can be used on SoCs as along as the
>>>>>>>>> SoC supports
>>>>>>>>> +Tachometer controller that moniors the Fan speed in periods.
>>>>>>>>> +
>>>>>>>>> +Author: Rajkumar Rampelli <rrajk@nvidia.com>
>>>>>>>>> +
>>>>>>>>> +Description
>>>>>>>>> +-----------
>>>>>>>>> +
>>>>>>>>> +The driver implements a simple interface for monitoring the
>>>>>>>>> Fan speed using
>>>>>>>>> +PWM module and Tachometer controller. It requests period value
>>>>>>>>> through PWM
>>>>>>>>> +capture interface to Tachometer and measures the Rotations per
>>>>>>>>> minute using
>>>>>>>>> +received period value. It exposes the Fan speed in RPM to the
>>>>>>>>> user space by
>>>>>>>>> +using the hwmon's sysfs interface.
>>>>>>>>> diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
>>>>>>>>> index ef23553..8912dcb 100644
>>>>>>>>> --- a/drivers/hwmon/Kconfig
>>>>>>>>> +++ b/drivers/hwmon/Kconfig
>>>>>>>>> @@ -1878,6 +1878,16 @@ config SENSORS_XGENE
>>>>>>>>>         If you say yes here you get support for the temperature
>>>>>>>>>         and power sensors for APM X-Gene SoC.
>>>>>>>>>   +config GENERIC_PWM_TACHOMETER
>>>>>>>>> +    tristate "Generic PWM based tachometer driver"
>>>>>>>>> +    depends on PWM
>>>>>>>>> +    help
>>>>>>>>> +      Enables a driver to use PWM signal from motor to use
>>>>>>>>> +      for measuring the motor speed. The RPM is captured by
>>>>>>>>> +      PWM modules which has PWM capture capability and this
>>>>>>>>> +      drivers reads the captured data from PWM IP to convert
>>>>>>>>> +      it to speed in RPM.
>>>>>>>>> +
>>>>>>>>>   if ACPI
>>>>>>>>>     comment "ACPI drivers"
>>>>>>>>> diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
>>>>>>>>> index f814b4a..9dcc374 100644
>>>>>>>>> --- a/drivers/hwmon/Makefile
>>>>>>>>> +++ b/drivers/hwmon/Makefile
>>>>>>>>> @@ -175,6 +175,7 @@ obj-$(CONFIG_SENSORS_WM8350)    +=
>>>>>>>>> wm8350-hwmon.o
>>>>>>>>>   obj-$(CONFIG_SENSORS_XGENE)    += xgene-hwmon.o
>>>>>>>>>     obj-$(CONFIG_PMBUS)        += pmbus/
>>>>>>>>> +obj-$(CONFIG_GENERIC_PWM_TACHOMETER) += generic-pwm-tachometer.o
>>>>>>>>>     ccflags-$(CONFIG_HWMON_DEBUG_CHIP) := -DDEBUG
>>>>>>>>>   diff --git a/drivers/hwmon/generic-pwm-tachometer.c
>>>>>>>>> b/drivers/hwmon/generic-pwm-tachometer.c
>>>>>>>>> new file mode 100644
>>>>>>>>> index 0000000..9354d43
>>>>>>>>> --- /dev/null
>>>>>>>>> +++ b/drivers/hwmon/generic-pwm-tachometer.c
>>>>>>>>> @@ -0,0 +1,112 @@
>>>>>>>>> +/*
>>>>>>>>> + * Copyright (c) 2017-2018, NVIDIA CORPORATION.  All rights
>>>>>>>>> reserved.
>>>>>>>>> + *
>>>>>>>>> + * This program is free software; you can redistribute it
>>>>>>>>> and/or modify it
>>>>>>>>> + * under the terms and conditions of the GNU General Public
>>>>>>>>> License,
>>>>>>>>> + * version 2, as published by the Free Software Foundation.
>>>>>>>>> + *
>>>>>>>>> + * This program is distributed in the hope it will be useful,
>>>>>>>>> but WITHOUT
>>>>>>>>> + * ANY WARRANTY; without even the implied warranty of
>>>>>>>>> MERCHANTABILITY or
>>>>>>>>> + * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General
>>>>>>>>> Public License for
>>>>>>>>> + * more details.
>>>>>>>>> + *
>>>>>>>>> + */
>>>>>>>>> +
>>>>>>>>> +#include <linux/module.h>
>>>>>>>>> +#include <linux/platform_device.h>
>>>>>>>>> +#include <linux/err.h>
>>>>>>>>> +#include <linux/pwm.h>
>>>>>>>>> +#include <linux/hwmon.h>
>>>>>>>>> +#include <linux/hwmon-sysfs.h>
>>>>>>>>> +
>>>>>>>>> +struct pwm_hwmon_tach {
>>>>>>>>> +    struct device        *dev;
>>>>>>>>> +    struct pwm_device    *pwm;
>>>>>>>>> +    struct device        *hwmon;
>>>>>>>>> +};
>>>>>>>>> +
>>>>>>>>> +static ssize_t show_rpm(struct device *dev, struct
>>>>>>>>> device_attribute *attr,
>>>>>>>>> +            char *buf)
>>>>>>>>> +{
>>>>>>>>> +    struct pwm_hwmon_tach *ptt = dev_get_drvdata(dev);
>>>>>>>>> +    struct pwm_device *pwm = ptt->pwm;
>>>>>>>>> +    struct pwm_capture result;
>>>>>>>>> +    int err;
>>>>>>>>> +    unsigned int rpm = 0;
>>>>>>>>> +
>>>>>>>>> +    err = pwm_capture(pwm, &result, 0);
>>>>>>>>> +    if (err < 0) {
>>>>>>>>> +        dev_err(ptt->dev, "Failed to capture PWM: %d\n", err);
>>>>>>>>> +        return err;
>>>>>>>>> +    }
>>>>>>>>> +
>>>>>>>>> +    if (result.period)
>>>>>>>>> +        rpm = DIV_ROUND_CLOSEST_ULL(60ULL * NSEC_PER_SEC,
>>>>>>>>> +                        result.period);
>>>>>>>>> +
>>>>>>>>> +    return sprintf(buf, "%u\n", rpm);
>>>>>>>>> +}
>>>>>>>>> +
>>>>>>>>> +static SENSOR_DEVICE_ATTR(rpm, 0444, show_rpm, NULL, 0);
>>>>>>>>> +
>>>>>>>>> +static struct attribute *pwm_tach_attrs[] = {
>>>>>>>>> +    &sensor_dev_attr_rpm.dev_attr.attr,
>>>>>>>>> +    NULL,
>>>>>>>>> +};
>>>>>>>>
>>>>>>>> "rpm" is not a standard hwmon sysfs attribute. If you don't provide
>>>>>>>> a single standard hwmon sysfs attribute, having a hwmon driver
>>>>>>>> is pointless.
>>>>>>> Guenter Roeck,
>>>>>>> I will define a new hwmon sysfs attribute node called
>>>>>>> "hwmon_tachometer_attributes" in hwmon.h like below and update
>>>>>>> the same in tachometer hwmon driver. Is it fine ?
>>>>>>> enum hwmon_tachometer_attributes {
>>>>>>
>>>>>> Are you kidding me ?
>>>>>>
>>>>>> Guenter
>>>>> Sorry, I just wanted to confirm whether my understanding is correct
>>>>> or not before implementing it actually.
>>>>> Or, shall I add this attribute as a part of fan attributes with
>>>>> "hwmon_fan_rpm" ? or any other way to do it ? I need your inputs in
>>>>> fixing this.
>>>>
>>>> I think he wants the attribute to be named according to the
>>>> properties in this document:
>>>> https://www.kernel.org/doc/Documentation/hwmon/sysfs-interface. I
>>>> guess the attribute would then map to fan1_input, though I'm not
>>>> sure if that's 100% correct either since this could technically be
>>>> attached to something other than a fan. But I would think in
>>>> practice that's not a big concern.
>>>>
>>>> Guenter,
>>>> Please correct me as well if I'm wrong.
>>>>
>>> You are absolutely correct.
>>>
>>> While I am not opposed to ABI changes, the merits of those would need
>>> to be
>>> discussed on the mailing list. But replacing "fan1_input" with "rpm" is
>>> not an acceptable ABI change, even if it may measure something that
>>> turns
>>> but isn't a fan.
>>>
>>> If this _is_ in fact supposed to be used for something else but fans, we
>>> would have to discuss what that might be, and if hwmon is the
>>> appropriate
>>> subsystem to measure and report it. This does to some degree lead
>>> back to
>>> my concern of having the "fan" part of this patch series in the pwm
>>> core.
>>> I am still not sure if that makes sense.
>>>
>>> Thanks,
>>> Guenter
>> I am planning to add tachometer support in pwm-fan.c driver
>> (drivers/hwmon/) instead of adding new generic-pwm-tachometer.c
>> driver. Measuring RPM value will be done in pwm-fan driver itself
>> using pwm capture feature and will add new sysfs attributes under this
>> driver to report rpm value of fan.
>
> There is an existing attribute to report the RPM of fans. It is called
> fan[1..n]_input.
>
> "replacing "fan1_input" with "rpm" is not an acceptable ABI change"
>
> Preemptive NACK.
>
> Guenter
>

I think the idea here (based on personal discussion with Rajkumar) was 
to add a "new" sysfs attribute the driver exports, but that attribute 
would be the existing fan[1..n]_input.

Mikko

>>>
>>>> Thank you,
>>>> Mikko
>>>>
>>>>>
>>>>> --
>>>>> To unsubscribe from this list: send the line "unsubscribe
>>>>> linux-tegra" in
>>>>> the body of a message to majordomo@vger.kernel.org
>>>>> More majordomo info at http://vger.kernel.org/majordomo-info.html
>>>> --
>>>> To unsubscribe from this list: send the line "unsubscribe
>>>> linux-hwmon" in
>>>> the body of a message to majordomo@vger.kernel.org
>>>> More majordomo info at http://vger.kernel.org/majordomo-info.html
>>>>
>>>
>>
>>
>
--
To unsubscribe from this list: send the line "unsubscribe linux-pwm" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Guenter Roeck March 8, 2018, 2:31 p.m. | #17
On 03/07/2018 10:06 PM, Laxman Dewangan wrote:
> 
> 
> On Wednesday 07 March 2018 07:50 PM, Guenter Roeck wrote:
>> On 03/07/2018 01:47 AM, Rajkumar Rampelli wrote:
>>>
>>>>
>>>> While I am not opposed to ABI changes, the merits of those would need to be
>>>> discussed on the mailing list. But replacing "fan1_input" with "rpm" is
>>>> not an acceptable ABI change, even if it may measure something that turns
>>>> but isn't a fan.
>>>>
>>>> If this _is_ in fact supposed to be used for something else but fans, we
>>>> would have to discuss what that might be, and if hwmon is the appropriate
>>>> subsystem to measure and report it. This does to some degree lead back to
>>>> my concern of having the "fan" part of this patch series in the pwm core.
>>>> I am still not sure if that makes sense.
>>>>
>>>> Thanks,
>>>> Guenter
>>> I am planning to add tachometer support in pwm-fan.c driver (drivers/hwmon/) instead of adding new generic-pwm-tachometer.c driver. Measuring RPM value will be done in pwm-fan driver itself using pwm capture feature and will add new sysfs attributes under this driver to report rpm value of fan.
>>
>> There is an existing attribute to report the RPM of fans. It is called fan[1..n]_input.
>>
>> "replacing "fan1_input" with "rpm" is not an acceptable ABI change"
>>
>> Preemptive NACK.
> 
> The RPM is measured speed via PWM signal capture  which is output from fan.
> So should we have the fan[1..n]_output_rpm?
> 

No. I hear you clearly that you for some reason dislike fan[1..n]_input.
While ABIs are not always to our liking, that doesn't mean that we get
to change them at our whim. If that is not acceptable for you, I can't
help you. And you can't change inX_input to inX_voltage either, sorry.

Guenter
--
To unsubscribe from this list: send the line "unsubscribe linux-pwm" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Guenter Roeck March 8, 2018, 2:33 p.m. | #18
On 03/07/2018 11:57 PM, Mikko Perttunen wrote:
> 
> 
> On 07.03.2018 16:20, Guenter Roeck wrote:
>> On 03/07/2018 01:47 AM, Rajkumar Rampelli wrote:
>>>
>>>
>>> On Wednesday 28 February 2018 07:59 PM, Guenter Roeck wrote:
>>>> On 02/27/2018 11:03 PM, Mikko Perttunen wrote:
>>>>> On 02/28/2018 08:12 AM, Rajkumar Rampelli wrote:
>>>>>>
>>>>>> On Wednesday 28 February 2018 11:28 AM, Guenter Roeck wrote:
>>>>>>> On 02/27/2018 09:38 PM, Rajkumar Rampelli wrote:
>>>>>>>>
>>>>>>>> On Wednesday 21 February 2018 08:20 PM, Guenter Roeck wrote:
>>>>>>>>> On 02/20/2018 10:58 PM, Rajkumar Rampelli wrote:
>>>>>>>>>> Add generic PWM based tachometer driver via HWMON interface
>>>>>>>>>> to report the RPM of motor. This drivers get the period/duty
>>>>>>>>>> cycle from PWM IP which captures the motor PWM output.
>>>>>>>>>>
>>>>>>>>>> This driver implements a simple interface for monitoring the
>>>>>>>>>> speed of
>>>>>>>>>> a fan and exposes it in roatations per minute (RPM) to the user
>>>>>>>>>> space
>>>>>>>>>> by using the hwmon's sysfs interface
>>>>>>>>>>
>>>>>>>>>> Signed-off-by: Rajkumar Rampelli <rrajk@nvidia.com>
>>>>>>>>>> ---
>>>>>>>>>>   Documentation/hwmon/generic-pwm-tachometer |  17 +++++
>>>>>>>>>>   drivers/hwmon/Kconfig                      |  10 +++
>>>>>>>>>>   drivers/hwmon/Makefile                     |   1 +
>>>>>>>>>>   drivers/hwmon/generic-pwm-tachometer.c     | 112
>>>>>>>>>> +++++++++++++++++++++++++++++
>>>>>>>>>>   4 files changed, 140 insertions(+)
>>>>>>>>>>   create mode 100644 Documentation/hwmon/generic-pwm-tachometer
>>>>>>>>>>   create mode 100644 drivers/hwmon/generic-pwm-tachometer.c
>>>>>>>>>>
>>>>>>>>>> diff --git a/Documentation/hwmon/generic-pwm-tachometer
>>>>>>>>>> b/Documentation/hwmon/generic-pwm-tachometer
>>>>>>>>>> new file mode 100644
>>>>>>>>>> index 0000000..e0713ee
>>>>>>>>>> --- /dev/null
>>>>>>>>>> +++ b/Documentation/hwmon/generic-pwm-tachometer
>>>>>>>>>> @@ -0,0 +1,17 @@
>>>>>>>>>> +Kernel driver generic-pwm-tachometer
>>>>>>>>>> +====================================
>>>>>>>>>> +
>>>>>>>>>> +This driver enables the use of a PWM module to monitor a fan.
>>>>>>>>>> It uses the
>>>>>>>>>> +generic PWM interface and can be used on SoCs as along as the
>>>>>>>>>> SoC supports
>>>>>>>>>> +Tachometer controller that moniors the Fan speed in periods.
>>>>>>>>>> +
>>>>>>>>>> +Author: Rajkumar Rampelli <rrajk@nvidia.com>
>>>>>>>>>> +
>>>>>>>>>> +Description
>>>>>>>>>> +-----------
>>>>>>>>>> +
>>>>>>>>>> +The driver implements a simple interface for monitoring the
>>>>>>>>>> Fan speed using
>>>>>>>>>> +PWM module and Tachometer controller. It requests period value
>>>>>>>>>> through PWM
>>>>>>>>>> +capture interface to Tachometer and measures the Rotations per
>>>>>>>>>> minute using
>>>>>>>>>> +received period value. It exposes the Fan speed in RPM to the
>>>>>>>>>> user space by
>>>>>>>>>> +using the hwmon's sysfs interface.
>>>>>>>>>> diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
>>>>>>>>>> index ef23553..8912dcb 100644
>>>>>>>>>> --- a/drivers/hwmon/Kconfig
>>>>>>>>>> +++ b/drivers/hwmon/Kconfig
>>>>>>>>>> @@ -1878,6 +1878,16 @@ config SENSORS_XGENE
>>>>>>>>>>         If you say yes here you get support for the temperature
>>>>>>>>>>         and power sensors for APM X-Gene SoC.
>>>>>>>>>>   +config GENERIC_PWM_TACHOMETER
>>>>>>>>>> +    tristate "Generic PWM based tachometer driver"
>>>>>>>>>> +    depends on PWM
>>>>>>>>>> +    help
>>>>>>>>>> +      Enables a driver to use PWM signal from motor to use
>>>>>>>>>> +      for measuring the motor speed. The RPM is captured by
>>>>>>>>>> +      PWM modules which has PWM capture capability and this
>>>>>>>>>> +      drivers reads the captured data from PWM IP to convert
>>>>>>>>>> +      it to speed in RPM.
>>>>>>>>>> +
>>>>>>>>>>   if ACPI
>>>>>>>>>>     comment "ACPI drivers"
>>>>>>>>>> diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
>>>>>>>>>> index f814b4a..9dcc374 100644
>>>>>>>>>> --- a/drivers/hwmon/Makefile
>>>>>>>>>> +++ b/drivers/hwmon/Makefile
>>>>>>>>>> @@ -175,6 +175,7 @@ obj-$(CONFIG_SENSORS_WM8350)    +=
>>>>>>>>>> wm8350-hwmon.o
>>>>>>>>>>   obj-$(CONFIG_SENSORS_XGENE)    += xgene-hwmon.o
>>>>>>>>>>     obj-$(CONFIG_PMBUS)        += pmbus/
>>>>>>>>>> +obj-$(CONFIG_GENERIC_PWM_TACHOMETER) += generic-pwm-tachometer.o
>>>>>>>>>>     ccflags-$(CONFIG_HWMON_DEBUG_CHIP) := -DDEBUG
>>>>>>>>>>   diff --git a/drivers/hwmon/generic-pwm-tachometer.c
>>>>>>>>>> b/drivers/hwmon/generic-pwm-tachometer.c
>>>>>>>>>> new file mode 100644
>>>>>>>>>> index 0000000..9354d43
>>>>>>>>>> --- /dev/null
>>>>>>>>>> +++ b/drivers/hwmon/generic-pwm-tachometer.c
>>>>>>>>>> @@ -0,0 +1,112 @@
>>>>>>>>>> +/*
>>>>>>>>>> + * Copyright (c) 2017-2018, NVIDIA CORPORATION.  All rights
>>>>>>>>>> reserved.
>>>>>>>>>> + *
>>>>>>>>>> + * This program is free software; you can redistribute it
>>>>>>>>>> and/or modify it
>>>>>>>>>> + * under the terms and conditions of the GNU General Public
>>>>>>>>>> License,
>>>>>>>>>> + * version 2, as published by the Free Software Foundation.
>>>>>>>>>> + *
>>>>>>>>>> + * This program is distributed in the hope it will be useful,
>>>>>>>>>> but WITHOUT
>>>>>>>>>> + * ANY WARRANTY; without even the implied warranty of
>>>>>>>>>> MERCHANTABILITY or
>>>>>>>>>> + * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General
>>>>>>>>>> Public License for
>>>>>>>>>> + * more details.
>>>>>>>>>> + *
>>>>>>>>>> + */
>>>>>>>>>> +
>>>>>>>>>> +#include <linux/module.h>
>>>>>>>>>> +#include <linux/platform_device.h>
>>>>>>>>>> +#include <linux/err.h>
>>>>>>>>>> +#include <linux/pwm.h>
>>>>>>>>>> +#include <linux/hwmon.h>
>>>>>>>>>> +#include <linux/hwmon-sysfs.h>
>>>>>>>>>> +
>>>>>>>>>> +struct pwm_hwmon_tach {
>>>>>>>>>> +    struct device        *dev;
>>>>>>>>>> +    struct pwm_device    *pwm;
>>>>>>>>>> +    struct device        *hwmon;
>>>>>>>>>> +};
>>>>>>>>>> +
>>>>>>>>>> +static ssize_t show_rpm(struct device *dev, struct
>>>>>>>>>> device_attribute *attr,
>>>>>>>>>> +            char *buf)
>>>>>>>>>> +{
>>>>>>>>>> +    struct pwm_hwmon_tach *ptt = dev_get_drvdata(dev);
>>>>>>>>>> +    struct pwm_device *pwm = ptt->pwm;
>>>>>>>>>> +    struct pwm_capture result;
>>>>>>>>>> +    int err;
>>>>>>>>>> +    unsigned int rpm = 0;
>>>>>>>>>> +
>>>>>>>>>> +    err = pwm_capture(pwm, &result, 0);
>>>>>>>>>> +    if (err < 0) {
>>>>>>>>>> +        dev_err(ptt->dev, "Failed to capture PWM: %d\n", err);
>>>>>>>>>> +        return err;
>>>>>>>>>> +    }
>>>>>>>>>> +
>>>>>>>>>> +    if (result.period)
>>>>>>>>>> +        rpm = DIV_ROUND_CLOSEST_ULL(60ULL * NSEC_PER_SEC,
>>>>>>>>>> +                        result.period);
>>>>>>>>>> +
>>>>>>>>>> +    return sprintf(buf, "%u\n", rpm);
>>>>>>>>>> +}
>>>>>>>>>> +
>>>>>>>>>> +static SENSOR_DEVICE_ATTR(rpm, 0444, show_rpm, NULL, 0);
>>>>>>>>>> +
>>>>>>>>>> +static struct attribute *pwm_tach_attrs[] = {
>>>>>>>>>> +    &sensor_dev_attr_rpm.dev_attr.attr,
>>>>>>>>>> +    NULL,
>>>>>>>>>> +};
>>>>>>>>>
>>>>>>>>> "rpm" is not a standard hwmon sysfs attribute. If you don't provide
>>>>>>>>> a single standard hwmon sysfs attribute, having a hwmon driver
>>>>>>>>> is pointless.
>>>>>>>> Guenter Roeck,
>>>>>>>> I will define a new hwmon sysfs attribute node called
>>>>>>>> "hwmon_tachometer_attributes" in hwmon.h like below and update
>>>>>>>> the same in tachometer hwmon driver. Is it fine ?
>>>>>>>> enum hwmon_tachometer_attributes {
>>>>>>>
>>>>>>> Are you kidding me ?
>>>>>>>
>>>>>>> Guenter
>>>>>> Sorry, I just wanted to confirm whether my understanding is correct
>>>>>> or not before implementing it actually.
>>>>>> Or, shall I add this attribute as a part of fan attributes with
>>>>>> "hwmon_fan_rpm" ? or any other way to do it ? I need your inputs in
>>>>>> fixing this.
>>>>>
>>>>> I think he wants the attribute to be named according to the
>>>>> properties in this document:
>>>>> https://www.kernel.org/doc/Documentation/hwmon/sysfs-interface. I
>>>>> guess the attribute would then map to fan1_input, though I'm not
>>>>> sure if that's 100% correct either since this could technically be
>>>>> attached to something other than a fan. But I would think in
>>>>> practice that's not a big concern.
>>>>>
>>>>> Guenter,
>>>>> Please correct me as well if I'm wrong.
>>>>>
>>>> You are absolutely correct.
>>>>
>>>> While I am not opposed to ABI changes, the merits of those would need
>>>> to be
>>>> discussed on the mailing list. But replacing "fan1_input" with "rpm" is
>>>> not an acceptable ABI change, even if it may measure something that
>>>> turns
>>>> but isn't a fan.
>>>>
>>>> If this _is_ in fact supposed to be used for something else but fans, we
>>>> would have to discuss what that might be, and if hwmon is the
>>>> appropriate
>>>> subsystem to measure and report it. This does to some degree lead
>>>> back to
>>>> my concern of having the "fan" part of this patch series in the pwm
>>>> core.
>>>> I am still not sure if that makes sense.
>>>>
>>>> Thanks,
>>>> Guenter
>>> I am planning to add tachometer support in pwm-fan.c driver
>>> (drivers/hwmon/) instead of adding new generic-pwm-tachometer.c
>>> driver. Measuring RPM value will be done in pwm-fan driver itself
>>> using pwm capture feature and will add new sysfs attributes under this
>>> driver to report rpm value of fan.
>>
>> There is an existing attribute to report the RPM of fans. It is called
>> fan[1..n]_input.
>>
>> "replacing "fan1_input" with "rpm" is not an acceptable ABI change"
>>
>> Preemptive NACK.
>>
>> Guenter
>>
> 
> I think the idea here (based on personal discussion with Rajkumar) was to add a "new" sysfs attribute the driver exports, but that attribute would be the existing fan[1..n]_input.
> 

Ah, sorry, in this case misunderstanding on my side.

Guenter
--
To unsubscribe from this list: send the line "unsubscribe linux-pwm" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Laxman Dewangan March 8, 2018, 3:21 p.m. | #19
On Thursday 08 March 2018 08:01 PM, Guenter Roeck wrote:
> On 03/07/2018 10:06 PM, Laxman Dewangan wrote:
>>
>>
>> The RPM is measured speed via PWM signal capture  which is output 
>> from fan.
>> So should we have the fan[1..n]_output_rpm?
>>
>
> No. I hear you clearly that you for some reason dislike fan[1..n]_input.
> While ABIs are not always to our liking, that doesn't mean that we get
> to change them at our whim. If that is not acceptable for you, I can't
> help you. And you can't change inX_input to inX_voltage either, sorry.

My opinion is only to not use "input" as this is not really the input to 
fan.
--
To unsubscribe from this list: send the line "unsubscribe linux-pwm" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html

Patch

diff --git a/Documentation/hwmon/generic-pwm-tachometer b/Documentation/hwmon/generic-pwm-tachometer
new file mode 100644
index 0000000..e0713ee
--- /dev/null
+++ b/Documentation/hwmon/generic-pwm-tachometer
@@ -0,0 +1,17 @@ 
+Kernel driver generic-pwm-tachometer
+====================================
+
+This driver enables the use of a PWM module to monitor a fan. It uses the
+generic PWM interface and can be used on SoCs as along as the SoC supports
+Tachometer controller that moniors the Fan speed in periods.
+
+Author: Rajkumar Rampelli <rrajk@nvidia.com>
+
+Description
+-----------
+
+The driver implements a simple interface for monitoring the Fan speed using
+PWM module and Tachometer controller. It requests period value through PWM
+capture interface to Tachometer and measures the Rotations per minute using
+received period value. It exposes the Fan speed in RPM to the user space by
+using the hwmon's sysfs interface.
diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
index ef23553..8912dcb 100644
--- a/drivers/hwmon/Kconfig
+++ b/drivers/hwmon/Kconfig
@@ -1878,6 +1878,16 @@  config SENSORS_XGENE
 	  If you say yes here you get support for the temperature
 	  and power sensors for APM X-Gene SoC.
 
+config GENERIC_PWM_TACHOMETER
+	tristate "Generic PWM based tachometer driver"
+	depends on PWM
+	help
+	  Enables a driver to use PWM signal from motor to use
+	  for measuring the motor speed. The RPM is captured by
+	  PWM modules which has PWM capture capability and this
+	  drivers reads the captured data from PWM IP to convert
+	  it to speed in RPM.
+
 if ACPI
 
 comment "ACPI drivers"
diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
index f814b4a..9dcc374 100644
--- a/drivers/hwmon/Makefile
+++ b/drivers/hwmon/Makefile
@@ -175,6 +175,7 @@  obj-$(CONFIG_SENSORS_WM8350)	+= wm8350-hwmon.o
 obj-$(CONFIG_SENSORS_XGENE)	+= xgene-hwmon.o
 
 obj-$(CONFIG_PMBUS)		+= pmbus/
+obj-$(CONFIG_GENERIC_PWM_TACHOMETER) += generic-pwm-tachometer.o
 
 ccflags-$(CONFIG_HWMON_DEBUG_CHIP) := -DDEBUG
 
diff --git a/drivers/hwmon/generic-pwm-tachometer.c b/drivers/hwmon/generic-pwm-tachometer.c
new file mode 100644
index 0000000..9354d43
--- /dev/null
+++ b/drivers/hwmon/generic-pwm-tachometer.c
@@ -0,0 +1,112 @@ 
+/*
+ * Copyright (c) 2017-2018, NVIDIA CORPORATION.  All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ *
+ */
+
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/err.h>
+#include <linux/pwm.h>
+#include <linux/hwmon.h>
+#include <linux/hwmon-sysfs.h>
+
+struct pwm_hwmon_tach {
+	struct device		*dev;
+	struct pwm_device	*pwm;
+	struct device		*hwmon;
+};
+
+static ssize_t show_rpm(struct device *dev, struct device_attribute *attr,
+			char *buf)
+{
+	struct pwm_hwmon_tach *ptt = dev_get_drvdata(dev);
+	struct pwm_device *pwm = ptt->pwm;
+	struct pwm_capture result;
+	int err;
+	unsigned int rpm = 0;
+
+	err = pwm_capture(pwm, &result, 0);
+	if (err < 0) {
+		dev_err(ptt->dev, "Failed to capture PWM: %d\n", err);
+		return err;
+	}
+
+	if (result.period)
+		rpm = DIV_ROUND_CLOSEST_ULL(60ULL * NSEC_PER_SEC,
+					    result.period);
+
+	return sprintf(buf, "%u\n", rpm);
+}
+
+static SENSOR_DEVICE_ATTR(rpm, 0444, show_rpm, NULL, 0);
+
+static struct attribute *pwm_tach_attrs[] = {
+	&sensor_dev_attr_rpm.dev_attr.attr,
+	NULL,
+};
+
+ATTRIBUTE_GROUPS(pwm_tach);
+
+static int pwm_tach_probe(struct platform_device *pdev)
+{
+	struct pwm_hwmon_tach *ptt;
+	int err;
+
+	ptt = devm_kzalloc(&pdev->dev, sizeof(*ptt), GFP_KERNEL);
+	if (!ptt)
+		return -ENOMEM;
+
+	ptt->dev = &pdev->dev;
+
+	platform_set_drvdata(pdev, ptt);
+	dev_set_drvdata(&pdev->dev, ptt);
+
+	ptt->pwm = devm_of_pwm_get(&pdev->dev, pdev->dev.of_node, NULL);
+	if (IS_ERR(ptt->pwm)) {
+		err = PTR_ERR(ptt->pwm);
+		dev_err(&pdev->dev, "Failed to get pwm handle, err: %d\n",
+			err);
+		return err;
+	}
+
+	ptt->hwmon = devm_hwmon_device_register_with_groups(&pdev->dev,
+					 "pwm_tach", ptt, pwm_tach_groups);
+	if (IS_ERR(ptt->hwmon)) {
+		err = PTR_ERR_OR_ZERO(ptt->hwmon);
+		dev_err(&pdev->dev, "Failed to register hwmon device: %d\n",
+			err);
+		return err;
+	}
+
+	return 0;
+}
+
+static const struct of_device_id pwm_tach_of_match[] = {
+	{ .compatible = "generic-pwm-tachometer" },
+	{}
+};
+MODULE_DEVICE_TABLE(of, pwm_tach_of_match);
+
+static struct platform_driver pwm_tach_driver = {
+	.driver = {
+		.name = "generic-pwm-tachometer",
+		.of_match_table = pwm_tach_of_match,
+	},
+	.probe = pwm_tach_probe,
+};
+
+module_platform_driver(pwm_tach_driver);
+
+MODULE_DESCRIPTION("PWM based Generic Tachometer driver");
+MODULE_AUTHOR("Laxman Dewangan <ldewangan@nvidia.com>");
+MODULE_AUTHOR("Rajkumar Rampelli <rrajk@nvidia.com>");
+MODULE_LICENSE("GPL v2");