PM / devfreq: Add support for QCOM devfreq FW

The firmware present in some QCOM chipsets offloads the steps necessary for
changing the frequency of some devices (Eg: L3). This driver implements the
devfreq interface for this firmware so that various governors could be used
to scale the frequency of these devices.

Signed-off-by: Saravana Kannan <skannan@codeaurora.org>
---
 .../bindings/devfreq/devfreq-qcom-fw.txt           |  31 ++
 drivers/devfreq/Kconfig                            |  14 +
 drivers/devfreq/Makefile                           |   1 +
 drivers/devfreq/devfreq_qcom_fw.c                  | 326 +++++++++++++++++++++
 4 files changed, 372 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/devfreq/devfreq-qcom-fw.txt
 create mode 100644 drivers/devfreq/devfreq_qcom_fw.c

Hi,

On 2018년 05월 17일 15:02, Saravana Kannan wrote:
> The firmware present in some QCOM chipsets offloads the steps necessary for
> changing the frequency of some devices (Eg: L3). This driver implements the
> devfreq interface for this firmware so that various governors could be used
> to scale the frequency of these devices.

The description doesn't include what kind of firmware. You have to explain
the type and role of firmware. And it doesn't contain the description of correlation
between 'qcom,devfreq-fw' and 'qcom,devfreq-fw-voter'.

> 
> Signed-off-by: Saravana Kannan <skannan@codeaurora.org>
> ---
>  .../bindings/devfreq/devfreq-qcom-fw.txt           |  31 ++
>  drivers/devfreq/Kconfig                            |  14 +
>  drivers/devfreq/Makefile                           |   1 +
>  drivers/devfreq/devfreq_qcom_fw.c                  | 326 +++++++++++++++++++++
>  4 files changed, 372 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/devfreq/devfreq-qcom-fw.txt
>  create mode 100644 drivers/devfreq/devfreq_qcom_fw.c
> 
> diff --git a/Documentation/devicetree/bindings/devfreq/devfreq-qcom-fw.txt b/Documentation/devicetree/bindings/devfreq/devfreq-qcom-fw.txt
> new file mode 100644
> index 0000000..5e1aecf
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/devfreq/devfreq-qcom-fw.txt
> @@ -0,0 +1,31 @@
> +QCOM Devfreq FW device
> +
> +Some Qualcomm Technologies, Inc. (QTI) chipsets have a FW that offloads the

you better to change the FW for more readability.
- s/FW/firmware

> +steps for frequency switching. The qcom,devfreq-fw represents this FW as a
- s/FW/firmware

Usually, DVFS feature uses the 'frequency scaling' word.
- s/frequency switching/frequency scaling

> +device. Sometimes, multiple entities want to vote on the frequency request
> +that is sent to the FW. The qcom,devfreq-fw-voter represents these voters as

s/FW/firmware

> +child devices of the corresponding qcom,devfreq-fw device.
> +
> +Required properties:
> +- compatible:		Must be "qcom,devfreq-fw" or "qcom,devfreq-fw-voter"

The use of 'devfreq' word is not proper because 'devfreq' is framework name.
I think you have to use the specific SoC name for the compatible. In the future,
if you need to support the new SoC with this driver, just you can add the new compatible.

> +Only for qcom,devfreq-fw:
> +- reg:			Pairs of physical base addresses and region sizes of
> +			memory mapped registers.
> +- reg-names:		Names of the bases for the above registers. Expected
> +			bases are: "en-base", "lut-base" and "perf-base".

It is not possible to understand what are meaning of "en-base", "lut-base" and "perf-base".
because they depend on specific H/W specification. You have to add the detailed description
why they are necessary. Also, you should explain whether thery are mandatory or optional.

> +
> +Example:
> +
> +	qcom,devfreq-l3 {
> +		compatible = "qcom,devfreq-fw";
> +		reg-names = "en-base", "lut-base", "perf-base";
> +		reg = <0x18321000 0x4>, <0x18321110 0x600>, <0x18321920 0x4>;
> +
> +		qcom,cpu0-l3 {
> +			compatible = "qcom,devfreq-fw-voter";
> +		};
> +
> +		qcom,cpu4-l3 {
> +			compatible = "qcom,devfreq-fw-voter";
> +		};
> +	};
> diff --git a/drivers/devfreq/Kconfig b/drivers/devfreq/Kconfig
> index 6a172d3..8503018 100644
> --- a/drivers/devfreq/Kconfig
> +++ b/drivers/devfreq/Kconfig
> @@ -113,6 +113,20 @@ config ARM_RK3399_DMC_DEVFREQ
>            It sets the frequency for the memory controller and reads the usage counts
>            from hardware.
>  
> +config ARM_QCOM_DEVFREQ_FW
> +	bool "Qualcomm Technologies Inc. DEVFREQ FW driver"
> +	depends on ARCH_QCOM
> +	select DEVFREQ_GOV_PERFORMANCE
> +	select DEVFREQ_GOV_POWERSAVE
> +	select DEVFREQ_GOV_USERSPACE
> +	default n
> +	help
> +	  The firmware present in some QCOM chipsets offloads the steps
> +	  necessary for changing the frequency of some devices (Eg: L3). This
> +	  driver implements the devfreq interface for this firmware so that
> +	  various governors could be used to scale the frequency of these
> +	  devices.

As I commented, you need to add a description of what kind of firmwar.

> +
>  source "drivers/devfreq/event/Kconfig"
>  
>  endif # PM_DEVFREQ
> diff --git a/drivers/devfreq/Makefile b/drivers/devfreq/Makefile
> index 32b8d4d..f1cc8990 100644
> --- a/drivers/devfreq/Makefile
> +++ b/drivers/devfreq/Makefile
> @@ -11,6 +11,7 @@ obj-$(CONFIG_DEVFREQ_GOV_PASSIVE)	+= governor_passive.o
>  obj-$(CONFIG_ARM_EXYNOS_BUS_DEVFREQ)	+= exynos-bus.o
>  obj-$(CONFIG_ARM_RK3399_DMC_DEVFREQ)	+= rk3399_dmc.o
>  obj-$(CONFIG_ARM_TEGRA_DEVFREQ)		+= tegra-devfreq.o
> +obj-$(CONFIG_ARM_QCOM_DEVFREQ_FW)	+= devfreq_qcom_fw.o
>  
>  # DEVFREQ Event Drivers
>  obj-$(CONFIG_PM_DEVFREQ_EVENT)		+= event/
> diff --git a/drivers/devfreq/devfreq_qcom_fw.c b/drivers/devfreq/devfreq_qcom_fw.c
> new file mode 100644
> index 0000000..3e85f76
> --- /dev/null
> +++ b/drivers/devfreq/devfreq_qcom_fw.c
> @@ -0,0 +1,326 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (c) 2018, The Linux Foundation. All rights reserved.

Is it right? or Qualcomm?

> + */
> +
> +#include <linux/err.h>
> +#include <linux/errno.h>
> +#include <linux/init.h>
> +#include <linux/io.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/of_address.h>
> +#include <linux/of_platform.h>
> +#include <linux/platform_device.h>
> +#include <linux/slab.h>
> +#include <linux/list.h>
> +#include <linux/devfreq.h>
> +#include <linux/pm_opp.h>
> +
> +#define INIT_RATE			300000000UL
> +#define XO_RATE				19200000UL
> +#define LUT_MAX_ENTRIES			40U
> +#define LUT_ROW_SIZE			32

I don't know what are the meaning of 'XO', 'LUT'.

> +
> +struct devfreq_qcom_fw {
> +	void __iomem *perf_base;
> +	struct devfreq_dev_profile dp;
> +	struct list_head ;
> +	struct list_head voter;
> +	unsigned int index;
> +};
> +
> +static DEFINE_SPINLOCK(voter_lock);
> +
> +static int devfreq_qcom_fw_target(struct device *dev, unsigned long *freq,
> +				  u32 flags)
> +{
> +	struct devfreq_qcom_fw *d = dev_get_drvdata(dev), *pd, *v;
> +	struct devfreq_dev_profile *p = &d->dp;
> +	unsigned int index;
> +	unsigned long lflags;
> +	struct dev_pm_opp *opp;
> +	void __iomem *perf_base = d->perf_base;
> +
> +	opp = devfreq_recommended_opp(dev, freq, flags);
> +	if (!IS_ERR(opp))
> +		dev_pm_opp_put(opp);
> +	else
> +		return PTR_ERR(opp);
> +
> +	for (index = 0; index < p->max_state; index++)
> +		if (p->freq_table[index] == *freq)
> +			break;
> +
> +	if (index >= p->max_state) {
> +		dev_err(dev, "Unable to find index for freq (%lu)!\n", *freq);
> +		return -EINVAL;
> +	}
> +
> +	d->index = index;
> +
> +	spin_lock_irqsave(&voter_lock, lflags);
> +	/* Voter */
> +	if (!perf_base) {
> +		pd = dev_get_drvdata(dev->parent);
> +		list_for_each_entry(v, &pd->voters, voter)
> +			index = max(index, v->index);
> +		perf_base = pd->perf_base;
> +	}
> +
> +	writel_relaxed(index, perf_base);
> +	spin_unlock_irqrestore(&voter_lock, lflags);
> +
> +	return 0;
> +}
> +
> +static int devfreq_qcom_fw_get_cur_freq(struct device *dev,
> +						 unsigned long *freq)
> +{
> +	struct devfreq_qcom_fw *d = dev_get_drvdata(dev);
> +	struct devfreq_dev_profile *p = &d->dp;
> +	unsigned int index;
> +
> +	/* Voter */
> +	if (!d->perf_base) {
> +		index = d->index;
> +	} else {
> +		index = readl_relaxed(d->perf_base);
> +		index = min(index, p->max_state - 1);
> +	}
> +	*freq = p->freq_table[index];
> +
> +	return 0;
> +}
> +
> +static int devfreq_qcom_populate_opp(struct platform_device *pdev)
> +{
> +	struct device *dev = &pdev->dev;
> +	u32 data, src, lval, i;
> +	unsigned long freq, prev_freq;
> +	struct resource *res;
> +	void __iomem *lut_base;
> +
> +	res = platform_get_resource_byname(pdev, IORESOURCE_MEM, "lut-base");
> +	if (!res) {
> +		dev_err(dev, "Unable to find lut-base!\n");
> +		return -EINVAL;
> +	}
> +
> +	lut_base = devm_ioremap(dev, res->start, resource_size(res));
> +	if (!lut_base) {
> +		dev_err(dev, "Unable to map lut-base\n");
> +		return -ENOMEM;
> +	}
> +
> +	for (i = 0; i < LUT_MAX_ENTRIES; i++) {
> +		data = readl_relaxed(lut_base + i * LUT_ROW_SIZE);
> +		src = ((data & GENMASK(31, 30)) >> 30);
> +		lval = (data & GENMASK(7, 0));
> +		freq = src ? XO_RATE * lval : INIT_RATE;

You need to define the global definitions such as XXX_MASK, XXX_SHIFT
for the readability. And add the role of 'lval' and why have to multiply
'lavl' to 'XO_RATE'.

> +
> +		/*
> +		 * Two of the same frequencies with the same core counts means
> +		 * end of table.
> +		 */
> +		if (i > 0 && prev_freq == freq)
> +			break;
> +
> +		dev_pm_opp_add(&pdev->dev, freq, 0);
> +
> +		prev_freq = freq;
> +	}
> +
> +	devm_iounmap(dev, lut_base);
> +
> +	return 0;
> +}
> +
> +static int devfreq_qcom_init_hw(struct platform_device *pdev)
> +{
> +	struct devfreq_qcom_fw *d;
> +	struct resource *res;
> +	struct device *dev = &pdev->dev;
> +	int ret = 0;
> +	void __iomem *en_base;
> +
> +	d = devm_kzalloc(dev, sizeof(*d), GFP_KERNEL);
> +	if (!d)
> +		return -ENOMEM;
> +
> +	res = platform_get_resource_byname(pdev, IORESOURCE_MEM, "en-base");
> +	if (!res) {
> +		dev_err(dev, "Unable to find en-base!\n");
> +		return -EINVAL;
> +	}
> +
> +	en_base = devm_ioremap(dev, res->start, resource_size(res));
> +	if (!en_base) {
> +		dev_err(dev, "Unable to map en-base\n");
> +		return -ENOMEM;
> +	}
> +
> +	/* FW should be enabled state to proceed */
> +	if (!(readl_relaxed(en_base) & 1)) {
> +		dev_err(dev, "FW not enabled\n");
> +		return -ENODEV;
> +	}
> +
> +	devm_iounmap(dev, en_base);
> +
> +	ret = devfreq_qcom_populate_opp(pdev);
> +	if (ret) {
> +		dev_err(dev, "Failed to read LUT\n");
> +		return ret;
> +	}
> +
> +	res = platform_get_resource_byname(pdev, IORESOURCE_MEM, "perf-base");
> +	if (!res) {
> +		dev_err(dev, "Unable to find perf-base!\n");
> +		ret = -EINVAL;
> +		goto out;
> +	}
> +
> +	d->perf_base = devm_ioremap(dev, res->start, resource_size(res));
> +	if (!d->perf_base) {
> +		dev_err(dev, "Unable to map perf-base\n");
> +		ret = -ENOMEM;
> +		goto out;
> +	}
> +
> +	INIT_LIST_HEAD(&d->voters);
> +	dev_set_drvdata(dev, d);
> +
> +out:
> +	if (ret)
> +		dev_pm_opp_remove_table(dev);
> +	return ret;
> +}
> +
> +static int devfreq_qcom_copy_opp(struct device *src_dev, struct device *dst_dev)
> +{
> +	unsigned long freq;
> +	int i, cnt, ret = 0;
> +	struct dev_pm_opp *opp;
> +
> +	if (!src_dev)
> +		return -ENODEV;
> +
> +	cnt = dev_pm_opp_get_opp_count(src_dev);
> +	if (!cnt)
> +		return -EINVAL;
> +
> +	for (i = 0, freq = 0; i < cnt; i++, freq++) {
> +		opp = dev_pm_opp_find_freq_ceil(src_dev, &freq);
> +		if (IS_ERR(opp)) {
> +			ret = -EINVAL;
> +			break;
> +		}
> +		dev_pm_opp_put(opp);
> +
> +		ret = dev_pm_opp_add(dst_dev, freq, 0);
> +		if (ret)
> +			break;
> +	}
> +
> +	if (ret)
> +		dev_pm_opp_remove_table(dst_dev);
> +	return ret;
> +}
> +
> +static int devfreq_qcom_init_voter(struct platform_device *pdev)
> +{
> +	struct device *dev = &pdev->dev;
> +	struct device *par_dev = dev->parent;
> +	struct devfreq_qcom_fw *d, *pd = dev_get_drvdata(par_dev);
> +	int ret = 0;
> +
> +	d = devm_kzalloc(dev, sizeof(*d), GFP_KERNEL);
> +	if (!d)
> +		return -ENOMEM;
> +
> +	ret = devfreq_qcom_copy_opp(dev->parent, dev);
> +	if (ret) {
> +		dev_err(dev, "Failed to copy parent OPPs\n");
> +		return ret;
> +	}
> +
> +	list_add(&d->voter, &pd->voters);
> +	dev_set_drvdata(dev, d);
> +
> +	return 0;
> +}
> +
> +static int devfreq_qcom_fw_driver_probe(struct platform_device *pdev)
> +{
> +	struct device *dev = &pdev->dev;
> +	int ret = 0;
> +	struct devfreq_qcom_fw *d;
> +	struct devfreq_dev_profile *p;
> +	struct devfreq *df;
> +
> +	if (!of_device_get_match_data(dev))
> +		ret = devfreq_qcom_init_voter(pdev);
> +	else
> +		ret = devfreq_qcom_init_hw(pdev);
> +	if (ret) {
> +		dev_err(dev, "Unable to probe device!\n");
> +		return ret;
> +	}
> +
> +	/*
> +	 * If device has voter children, do no register directly with devfreq
> +	 */
> +	if (of_get_available_child_count(dev->of_node)) {
> +		of_platform_populate(dev->of_node, NULL, NULL, dev);
> +		dev_info(dev, "Devfreq QCOM FW parent device initialized.\n");
> +		return 0;
> +	}
> +
> +	d = dev_get_drvdata(dev);
> +	p = &d->dp;
> +	p->polling_ms = 50;
> +	p->target = devfreq_qcom_fw_target;
> +	p->get_cur_freq = devfreq_qcom_fw_get_cur_freq;
> +
> +	df = devm_devfreq_add_device(dev, p, "performance", NULL);
> +	if (IS_ERR(df)) {
> +		dev_err(dev, "Unable to register Devfreq QCOM FW device!\n");
> +		return PTR_ERR(df);
> +	}
> +
> +	dev_info(dev, "Devfreq QCOM FW device registered.\n");
> +
> +	return 0;
> +}
> +
> +static const struct of_device_id match_table[] = {
> +	{ .compatible = "qcom,devfreq-fw", .data = (void *) 1 },
> +	{ .compatible = "qcom,devfreq-fw-voter", .data = (void *) 0 },
> +	{}
> +};
> +
> +static struct platform_driver devfreq_qcom_fw_driver = {
> +	.probe = devfreq_qcom_fw_driver_probe,
> +	.driver = {
> +		.name = "devfreq-qcom-fw",
> +		.of_match_table = match_table,
> +		.owner = THIS_MODULE,
> +	},
> +};
> +
> +static int __init devfreq_qcom_fw_init(void)
> +{
> +	return platform_driver_register(&devfreq_qcom_fw_driver);
> +}
> +subsys_initcall(devfreq_qcom_fw_init);
> +
> +static void __exit devfreq_qcom_fw_exit(void)
> +{
> +	platform_driver_unregister(&devfreq_qcom_fw_driver);
> +}
> +module_exit(devfreq_qcom_fw_exit);
> +
> +MODULE_DESCRIPTION("Devfreq QCOM FW");
> +MODULE_LICENSE("GPL v2");
>

On 2018-05-17 19:28, Chanwoo Choi wrote:
> Hi,
> 
> On 2018년 05월 17일 15:02, Saravana Kannan wrote:
>> The firmware present in some QCOM chipsets offloads the steps 
>> necessary for
>> changing the frequency of some devices (Eg: L3). This driver 
>> implements the
>> devfreq interface for this firmware so that various governors could be 
>> used
>> to scale the frequency of these devices.
> 
> The description doesn't include what kind of firmware. You have to 
> explain
> the type and role of firmware.

Not exactly sure what you mean. I described exactly what the firmware 
does. Not sure what you mean by what kind of firmware. I just understand 
the interface with it -- not the implementation of the firmware or 
hardware.

> And it doesn't contain the description
> of correlation
> between 'qcom,devfreq-fw' and 'qcom,devfreq-fw-voter'.
> 

Will do.

>> 
>> Signed-off-by: Saravana Kannan <skannan@codeaurora.org>
>> ---
>>  .../bindings/devfreq/devfreq-qcom-fw.txt           |  31 ++
>>  drivers/devfreq/Kconfig                            |  14 +
>>  drivers/devfreq/Makefile                           |   1 +
>>  drivers/devfreq/devfreq_qcom_fw.c                  | 326 
>> +++++++++++++++++++++
>>  4 files changed, 372 insertions(+)
>>  create mode 100644 
>> Documentation/devicetree/bindings/devfreq/devfreq-qcom-fw.txt
>>  create mode 100644 drivers/devfreq/devfreq_qcom_fw.c
>> 
>> diff --git 
>> a/Documentation/devicetree/bindings/devfreq/devfreq-qcom-fw.txt 
>> b/Documentation/devicetree/bindings/devfreq/devfreq-qcom-fw.txt
>> new file mode 100644
>> index 0000000..5e1aecf
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/devfreq/devfreq-qcom-fw.txt
>> @@ -0,0 +1,31 @@
>> +QCOM Devfreq FW device
>> +
>> +Some Qualcomm Technologies, Inc. (QTI) chipsets have a FW that 
>> offloads the
>> +child devices of the corresponding qcom,devfreq-fw device.
>> +
>> +Required properties:
>> +- compatible:		Must be "qcom,devfreq-fw" or "qcom,devfreq-fw-voter"
> 
> The use of 'devfreq' word is not proper because 'devfreq' is framework 
> name.
> I think you have to use the specific SoC name for the compatible.

I don't think it's mandatory to use chip name. Typically you pick the IP 
name. This IP is a firmware just for scaling device frequency - so 
called it qcom,devfreq-fw. I'll see what the DT maintainers say about 
this.

> In the future,
> if you need to support the new SoC with this driver, just you can add
> the new compatible.
> 
>> +Only for qcom,devfreq-fw:
>> +- reg:			Pairs of physical base addresses and region sizes of
>> +			memory mapped registers.
>> +- reg-names:		Names of the bases for the above registers. Expected
>> +			bases are: "en-base", "lut-base" and "perf-base".
> 
> It is not possible to understand what are meaning of "en-base",
> "lut-base" and "perf-base".
> because they depend on specific H/W specification. You have to add the
> detailed description
> why they are necessary. Also, you should explain whether thery are
> mandatory or optional.

The are all mandatory, that's why I didn't have the "Optional" heading. 
I can add descriptions.

> 
>> +
>> +Example:
>> +
>> +	qcom,devfreq-l3 {
>> +		compatible = "qcom,devfreq-fw";
>> +		reg-names = "en-base", "lut-base", "perf-base";
>> +		reg = <0x18321000 0x4>, <0x18321110 0x600>, <0x18321920 0x4>;
>> +
>> +		qcom,cpu0-l3 {
>> +			compatible = "qcom,devfreq-fw-voter";
>> +		};
>> +
>> +		qcom,cpu4-l3 {
>> +			compatible = "qcom,devfreq-fw-voter";
>> +		};
>> +	};
>> diff --git a/drivers/devfreq/Kconfig b/drivers/devfreq/Kconfig
>> index 6a172d3..8503018 100644
>> --- a/drivers/devfreq/Kconfig
>> +++ b/drivers/devfreq/Kconfig
>> @@ -113,6 +113,20 @@ config ARM_RK3399_DMC_DEVFREQ
>>            It sets the frequency for the memory controller and reads 
>> the usage counts
>>            from hardware.
>> 
>> +config ARM_QCOM_DEVFREQ_FW
>> +	bool "Qualcomm Technologies Inc. DEVFREQ FW driver"
>> +	depends on ARCH_QCOM
>> +	select DEVFREQ_GOV_PERFORMANCE
>> +	select DEVFREQ_GOV_POWERSAVE
>> +	select DEVFREQ_GOV_USERSPACE
>> +	default n
>> +	help
>> +	  The firmware present in some QCOM chipsets offloads the steps
>> +	  necessary for changing the frequency of some devices (Eg: L3). 
>> This
>> +	  driver implements the devfreq interface for this firmware so that
>> +	  various governors could be used to scale the frequency of these
>> +	  devices.
> 
> As I commented, you need to add a description of what kind of firmwar.

Again, not sure what you mean by "what kind of firmware". It's exactly 
what I've described here. Can you please elaborate?

>> +
>>  source "drivers/devfreq/event/Kconfig"
>> 
>>  endif # PM_DEVFREQ
>> diff --git a/drivers/devfreq/Makefile b/drivers/devfreq/Makefile
>> index 32b8d4d..f1cc8990 100644
>> --- a/drivers/devfreq/Makefile
>> +++ b/drivers/devfreq/Makefile
>> @@ -11,6 +11,7 @@ obj-$(CONFIG_DEVFREQ_GOV_PASSIVE)	+= 
>> governor_passive.o
>>  obj-$(CONFIG_ARM_EXYNOS_BUS_DEVFREQ)	+= exynos-bus.o
>>  obj-$(CONFIG_ARM_RK3399_DMC_DEVFREQ)	+= rk3399_dmc.o
>>  obj-$(CONFIG_ARM_TEGRA_DEVFREQ)		+= tegra-devfreq.o
>> +obj-$(CONFIG_ARM_QCOM_DEVFREQ_FW)	+= devfreq_qcom_fw.o
>> 
>>  # DEVFREQ Event Drivers
>>  obj-$(CONFIG_PM_DEVFREQ_EVENT)		+= event/
>> diff --git a/drivers/devfreq/devfreq_qcom_fw.c 
>> b/drivers/devfreq/devfreq_qcom_fw.c
>> new file mode 100644
>> index 0000000..3e85f76
>> --- /dev/null
>> +++ b/drivers/devfreq/devfreq_qcom_fw.c
>> @@ -0,0 +1,326 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +/*
>> + * Copyright (c) 2018, The Linux Foundation. All rights reserved.
> 
> Is it right? or Qualcomm?

Yup, it's right.

> 
>> + */
>> +
>> +#include <linux/err.h>
>> +#include <linux/errno.h>
>> +#include <linux/init.h>
>> +#include <linux/io.h>
>> +#include <linux/kernel.h>
>> +#include <linux/module.h>
>> +#include <linux/of.h>
>> +#include <linux/of_address.h>
>> +#include <linux/of_platform.h>
>> +#include <linux/platform_device.h>
>> +#include <linux/slab.h>
>> +#include <linux/list.h>
>> +#include <linux/devfreq.h>
>> +#include <linux/pm_opp.h>
>> +
>> +#define INIT_RATE			300000000UL
>> +#define XO_RATE				19200000UL
>> +#define LUT_MAX_ENTRIES			40U
>> +#define LUT_ROW_SIZE			32
> 
> I don't know what are the meaning of 'XO', 'LUT'.

XO is a very common term for crystal oscillator. I don't want to change 
these symbols.
LUT stands for Look up table. But I can rename it to FREQ_TBL_.

Thanks,
Saravana
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Hi Saravana,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on linus/master]
[also build test WARNING on v4.17-rc5 next-20180517]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]

url:    https://github.com/0day-ci/linux/commits/Saravana-Kannan/PM-devfreq-Add-support-for-QCOM-devfreq-FW/20180518-230524
config: arm-allmodconfig (attached as .config)
compiler: arm-linux-gnueabi-gcc (Debian 7.2.0-11) 7.2.0
reproduce:
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # save the attached .config to linux build tree
        make.cross ARCH=arm 

Note: it may well be a FALSE warning. FWIW you are at least aware of it now.
http://gcc.gnu.org/wiki/Better_Uninitialized_Warnings

All warnings (new ones prefixed by >>):

   drivers//devfreq/devfreq_qcom_fw.c: In function 'devfreq_qcom_fw_driver_probe':
>> drivers//devfreq/devfreq_qcom_fw.c:127:26: warning: 'prev_freq' may be used uninitialized in this function [-Wmaybe-uninitialized]
      if (i > 0 && prev_freq == freq)
                   ~~~~~~~~~~^~~~~~~
   drivers//devfreq/devfreq_qcom_fw.c:101:22: note: 'prev_freq' was declared here
     unsigned long freq, prev_freq;
                         ^~~~~~~~~

vim +/prev_freq +127 drivers//devfreq/devfreq_qcom_fw.c

    96	
    97	static int devfreq_qcom_populate_opp(struct platform_device *pdev)
    98	{
    99		struct device *dev = &pdev->dev;
   100		u32 data, src, lval, i;
   101		unsigned long freq, prev_freq;
   102		struct resource *res;
   103		void __iomem *lut_base;
   104	
   105		res = platform_get_resource_byname(pdev, IORESOURCE_MEM, "lut-base");
   106		if (!res) {
   107			dev_err(dev, "Unable to find lut-base!\n");
   108			return -EINVAL;
   109		}
   110	
   111		lut_base = devm_ioremap(dev, res->start, resource_size(res));
   112		if (!lut_base) {
   113			dev_err(dev, "Unable to map lut-base\n");
   114			return -ENOMEM;
   115		}
   116	
   117		for (i = 0; i < LUT_MAX_ENTRIES; i++) {
   118			data = readl_relaxed(lut_base + i * LUT_ROW_SIZE);
   119			src = ((data & GENMASK(31, 30)) >> 30);
   120			lval = (data & GENMASK(7, 0));
   121			freq = src ? XO_RATE * lval : INIT_RATE;
   122	
   123			/*
   124			 * Two of the same frequencies with the same core counts means
   125			 * end of table.
   126			 */
 > 127			if (i > 0 && prev_freq == freq)
   128				break;
   129	
   130			dev_pm_opp_add(&pdev->dev, freq, 0);
   131	
   132			prev_freq = freq;
   133		}
   134	
   135		devm_iounmap(dev, lut_base);
   136	
   137		return 0;
   138	}
   139	

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