[v3,3/5] pwm-backlight: add support for PWM delays proprieties.

Submitted by Enric Balletbo i Serra on July 17, 2017, 9:28 p.m.

Details

Message ID 20170717212811.25374-3-enric.balletbo@collabora.com
State New
Headers show

Commit Message

Enric Balletbo i Serra July 17, 2017, 9:28 p.m.
Some panels (i.e. N116BGE-L41), in their power sequence specifications,
request a delay between set the PWM signal and enable the backlight and
between clear the PWM signal and disable the backlight. Add support for
the new post-pwm-on-delay-us and pwm-off-delay-us proprieties to meet
the timings.

Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
---
Changes since v2:
 - Move the pwm/enable sequence to another patch (Thierry Reding)
Changes since v1:
 - As suggested by Daniel Thompson
   - Do not assume power-on delay and power-off delay will be the same
 - Move the check of dt property to the parse dt function.

 drivers/video/backlight/pwm_bl.c | 17 +++++++++++++++++
 include/linux/pwm_backlight.h    |  1 +
 2 files changed, 18 insertions(+)

Comments

Daniel Thompson July 18, 2017, 9:38 a.m.
On 17/07/17 22:28, Enric Balletbo i Serra wrote:
> Some panels (i.e. N116BGE-L41), in their power sequence specifications,
> request a delay between set the PWM signal and enable the backlight and
> between clear the PWM signal and disable the backlight. Add support for
> the new post-pwm-on-delay-us and pwm-off-delay-us proprieties to meet
> the timings.
> 
> Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
> ---
> Changes since v2:
>   - Move the pwm/enable sequence to another patch (Thierry Reding)
> Changes since v1:
>   - As suggested by Daniel Thompson
>     - Do not assume power-on delay and power-off delay will be the same
>   - Move the check of dt property to the parse dt function.
> 
>   drivers/video/backlight/pwm_bl.c | 17 +++++++++++++++++
>   include/linux/pwm_backlight.h    |  1 +
>   2 files changed, 18 insertions(+)
> 
> diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c
> index 909a686..528155d 100644
> --- a/drivers/video/backlight/pwm_bl.c
> +++ b/drivers/video/backlight/pwm_bl.c
> @@ -10,6 +10,7 @@
>    * published by the Free Software Foundation.
>    */
>   
> +#include <linux/delay.h>
>   #include <linux/gpio/consumer.h>
>   #include <linux/gpio.h>
>   #include <linux/module.h>
> @@ -35,6 +36,7 @@ struct pwm_bl_data {
>   	struct gpio_desc	*enable_gpio;
>   	unsigned int		scale;
>   	bool			legacy;
> +	unsigned int		pwm_delay[2];

Two named members would be better here (eliminating the "magic" 0 and 1).


>   	int			(*notify)(struct device *,
>   					  int brightness);
>   	void			(*notify_after)(struct device *,
> @@ -56,6 +58,9 @@ static void pwm_backlight_power_on(struct pwm_bl_data *pb, int brightness)
>   
>   	pwm_enable(pb->pwm);
>   
> +	if (pb->pwm_delay[0])
> +		usleep_range(pb->pwm_delay[0], pb->pwm_delay[0] * 2);
> +
>   	if (pb->enable_gpio)
>   		gpiod_set_value_cansleep(pb->enable_gpio, 1);
>   
> @@ -70,6 +75,9 @@ static void pwm_backlight_power_off(struct pwm_bl_data *pb)
>   	if (pb->enable_gpio)
>   		gpiod_set_value_cansleep(pb->enable_gpio, 0);
>   
> +	if (pb->pwm_delay[1])
> +		usleep_range(pb->pwm_delay[1], pb->pwm_delay[1] * 2);
> +
>   	pwm_config(pb->pwm, 0, pb->period);
>   	pwm_disable(pb->pwm);
>   
> @@ -175,6 +183,14 @@ static int pwm_backlight_parse_dt(struct device *dev,
>   		data->max_brightness--;
>   	}
>   
> +	/*
> +	 * These values are optional and set as 0 by default, the out values
> +	 * are modified only if a valid u32 value can be decoded.
> +	 */
> +	of_property_read_u32(node, "post-pwm-on-delay-us",
> +			     &data->pwm_delay[0]);
> +	of_property_read_u32(node, "pwm-off-delay-us", &data->pwm_delay[1]);
> +
>   	data->enable_gpio = -EINVAL;
>   	return 0;
>   }
> @@ -273,6 +289,7 @@ static int pwm_backlight_probe(struct platform_device *pdev)
>   	pb->exit = data->exit;
>   	pb->dev = &pdev->dev;
>   	pb->enabled = false;
> +	memcpy(pb->pwm_delay, data->pwm_delay, sizeof(pb->pwm_delay));
>   
>   	pb->enable_gpio = devm_gpiod_get_optional(&pdev->dev, "enable",
>   						  GPIOD_ASIS);
> diff --git a/include/linux/pwm_backlight.h b/include/linux/pwm_backlight.h
> index efdd922..bf37131 100644
> --- a/include/linux/pwm_backlight.h
> +++ b/include/linux/pwm_backlight.h
> @@ -13,6 +13,7 @@ struct platform_pwm_backlight_data {
>   	unsigned int lth_brightness;
>   	unsigned int pwm_period_ns;
>   	unsigned int *levels;
> +	unsigned int pwm_delay[2];
>   	/* TODO remove once all users are switched to gpiod_* API */
>   	int enable_gpio;
>   	int (*init)(struct device *dev);
> 

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Pavel Machek July 20, 2017, 8:06 a.m.
Hi!

> >--- a/drivers/video/backlight/pwm_bl.c
> >+++ b/drivers/video/backlight/pwm_bl.c
> >@@ -10,6 +10,7 @@
> >   * published by the Free Software Foundation.
> >   */
> >+#include <linux/delay.h>
> >  #include <linux/gpio/consumer.h>
> >  #include <linux/gpio.h>
> >  #include <linux/module.h>
> >@@ -35,6 +36,7 @@ struct pwm_bl_data {
> >  	struct gpio_desc	*enable_gpio;
> >  	unsigned int		scale;
> >  	bool			legacy;
> >+	unsigned int		pwm_delay[2];
> 
> Two named members would be better here (eliminating the "magic" 0
>and 1).

My thought, too.

> >@@ -56,6 +58,9 @@ static void pwm_backlight_power_on(struct pwm_bl_data *pb, int brightness)
> >  	pwm_enable(pb->pwm);
> >+	if (pb->pwm_delay[0])
> >+		usleep_range(pb->pwm_delay[0], pb->pwm_delay[0] * 2);

Plus I'd just do the delay unconditionally :-).

Best regards,
								Pavel
Daniel Thompson July 20, 2017, 10:37 a.m.
On 20/07/17 09:06, Pavel Machek wrote:
> Hi!
> 
>>> --- a/drivers/video/backlight/pwm_bl.c
>>> +++ b/drivers/video/backlight/pwm_bl.c
>>> @@ -10,6 +10,7 @@
>>>    * published by the Free Software Foundation.
>>>    */
>>> +#include <linux/delay.h>
>>>   #include <linux/gpio/consumer.h>
>>>   #include <linux/gpio.h>
>>>   #include <linux/module.h>
>>> @@ -35,6 +36,7 @@ struct pwm_bl_data {
>>>   	struct gpio_desc	*enable_gpio;
>>>   	unsigned int		scale;
>>>   	bool			legacy;
>>> +	unsigned int		pwm_delay[2];
>>
>> Two named members would be better here (eliminating the "magic" 0
>> and 1).
> 
> My thought, too.
> 
>>> @@ -56,6 +58,9 @@ static void pwm_backlight_power_on(struct pwm_bl_data *pb, int brightness)
>>>   	pwm_enable(pb->pwm);
>>> +	if (pb->pwm_delay[0])
>>> +		usleep_range(pb->pwm_delay[0], pb->pwm_delay[0] * 2);
> 
> Plus I'd just do the delay unconditionally :-).

... does this still apply if this code is switched to msleep()?

msleep() has no wait avoidance[1] and if lots of drivers are reckless 
about sleeping for 10ms it soon starts to show up in the boot time 
(especially optimized ones).


Daniel.


[1] As it happens I can't see that many early bail out paths in
     usleep_range() either.
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Pavel Machek July 20, 2017, 11:05 a.m.
On Thu 2017-07-20 11:37:17, Daniel Thompson wrote:
> On 20/07/17 09:06, Pavel Machek wrote:
> >Hi!
> >
> >>>--- a/drivers/video/backlight/pwm_bl.c
> >>>+++ b/drivers/video/backlight/pwm_bl.c
> >>>@@ -10,6 +10,7 @@
> >>>   * published by the Free Software Foundation.
> >>>   */
> >>>+#include <linux/delay.h>
> >>>  #include <linux/gpio/consumer.h>
> >>>  #include <linux/gpio.h>
> >>>  #include <linux/module.h>
> >>>@@ -35,6 +36,7 @@ struct pwm_bl_data {
> >>>  	struct gpio_desc	*enable_gpio;
> >>>  	unsigned int		scale;
> >>>  	bool			legacy;
> >>>+	unsigned int		pwm_delay[2];
> >>
> >>Two named members would be better here (eliminating the "magic" 0
> >>and 1).
> >
> >My thought, too.
> >
> >>>@@ -56,6 +58,9 @@ static void pwm_backlight_power_on(struct pwm_bl_data *pb, int brightness)
> >>>  	pwm_enable(pb->pwm);
> >>>+	if (pb->pwm_delay[0])
> >>>+		usleep_range(pb->pwm_delay[0], pb->pwm_delay[0] * 2);
> >
> >Plus I'd just do the delay unconditionally :-).
> 
> ... does this still apply if this code is switched to msleep()?
> 
> msleep() has no wait avoidance[1] and if lots of drivers are reckless about
> sleeping for 10ms it soon starts to show up in the boot time (especially
> optimized ones).

No, not for msleep.

Best regards,
								Pavel

Patch hide | download patch | download mbox

diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c
index 909a686..528155d 100644
--- a/drivers/video/backlight/pwm_bl.c
+++ b/drivers/video/backlight/pwm_bl.c
@@ -10,6 +10,7 @@ 
  * published by the Free Software Foundation.
  */
 
+#include <linux/delay.h>
 #include <linux/gpio/consumer.h>
 #include <linux/gpio.h>
 #include <linux/module.h>
@@ -35,6 +36,7 @@  struct pwm_bl_data {
 	struct gpio_desc	*enable_gpio;
 	unsigned int		scale;
 	bool			legacy;
+	unsigned int		pwm_delay[2];
 	int			(*notify)(struct device *,
 					  int brightness);
 	void			(*notify_after)(struct device *,
@@ -56,6 +58,9 @@  static void pwm_backlight_power_on(struct pwm_bl_data *pb, int brightness)
 
 	pwm_enable(pb->pwm);
 
+	if (pb->pwm_delay[0])
+		usleep_range(pb->pwm_delay[0], pb->pwm_delay[0] * 2);
+
 	if (pb->enable_gpio)
 		gpiod_set_value_cansleep(pb->enable_gpio, 1);
 
@@ -70,6 +75,9 @@  static void pwm_backlight_power_off(struct pwm_bl_data *pb)
 	if (pb->enable_gpio)
 		gpiod_set_value_cansleep(pb->enable_gpio, 0);
 
+	if (pb->pwm_delay[1])
+		usleep_range(pb->pwm_delay[1], pb->pwm_delay[1] * 2);
+
 	pwm_config(pb->pwm, 0, pb->period);
 	pwm_disable(pb->pwm);
 
@@ -175,6 +183,14 @@  static int pwm_backlight_parse_dt(struct device *dev,
 		data->max_brightness--;
 	}
 
+	/*
+	 * These values are optional and set as 0 by default, the out values
+	 * are modified only if a valid u32 value can be decoded.
+	 */
+	of_property_read_u32(node, "post-pwm-on-delay-us",
+			     &data->pwm_delay[0]);
+	of_property_read_u32(node, "pwm-off-delay-us", &data->pwm_delay[1]);
+
 	data->enable_gpio = -EINVAL;
 	return 0;
 }
@@ -273,6 +289,7 @@  static int pwm_backlight_probe(struct platform_device *pdev)
 	pb->exit = data->exit;
 	pb->dev = &pdev->dev;
 	pb->enabled = false;
+	memcpy(pb->pwm_delay, data->pwm_delay, sizeof(pb->pwm_delay));
 
 	pb->enable_gpio = devm_gpiod_get_optional(&pdev->dev, "enable",
 						  GPIOD_ASIS);
diff --git a/include/linux/pwm_backlight.h b/include/linux/pwm_backlight.h
index efdd922..bf37131 100644
--- a/include/linux/pwm_backlight.h
+++ b/include/linux/pwm_backlight.h
@@ -13,6 +13,7 @@  struct platform_pwm_backlight_data {
 	unsigned int lth_brightness;
 	unsigned int pwm_period_ns;
 	unsigned int *levels;
+	unsigned int pwm_delay[2];
 	/* TODO remove once all users are switched to gpiod_* API */
 	int enable_gpio;
 	int (*init)(struct device *dev);