linux-kernel - Re: [PATCH v3 3/3] leds: leds-pwm: Defer led_pwm

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Message-ID: <5107864F.6060807@ti.com>
Date:	Tue, 29 Jan 2013 09:20:31 +0100
From:	Peter Ujfalusi <peter.ujfalusi@...com>
To:	Florian Vaussard <florian.vaussard@...l.ch>
CC:	Bryan Wu <cooloney@...il.com>, Richard Purdie <rpurdie@...ys.net>,
	Thierry Reding <thierry.reding@...onic-design.de>,
	<linux-leds@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 3/3] leds: leds-pwm: Defer led_pwm_set() if PWM can
 sleep

On 01/28/2013 03:00 PM, Florian Vaussard wrote:
> Call to led_pwm_set() can happen inside atomic context, like triggers.
> If the PWM call can sleep, defer using a worker.
> 
> Cc: Peter Ujfalusi <peter.ujfalusi@...com>
> Signed-off-by: Florian Vaussard <florian.vaussard@...l.ch>

Reviewed-by: Peter Ujfalusi <peter.ujfalusi@...com>

> ---
>  drivers/leds/leds-pwm.c |   50 +++++++++++++++++++++++++++++++++++++++-------
>  1 files changed, 42 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/leds/leds-pwm.c b/drivers/leds/leds-pwm.c
> index a1ea5f6..faf52c0 100644
> --- a/drivers/leds/leds-pwm.c
> +++ b/drivers/leds/leds-pwm.c
> @@ -23,12 +23,16 @@
>  #include <linux/pwm.h>
>  #include <linux/leds_pwm.h>
>  #include <linux/slab.h>
> +#include <linux/workqueue.h>
>  
>  struct led_pwm_data {
>  	struct led_classdev	cdev;
>  	struct pwm_device	*pwm;
> +	struct work_struct	work;
>  	unsigned int		active_low;
>  	unsigned int		period;
> +	int			duty;
> +	bool			can_sleep;
>  };
>  
>  struct led_pwm_priv {
> @@ -36,6 +40,26 @@ struct led_pwm_priv {
>  	struct led_pwm_data leds[0];
>  };
>  
> +static void __led_pwm_set(struct led_pwm_data *led_dat)
> +{
> +	int new_duty = led_dat->duty;
> +
> +	pwm_config(led_dat->pwm, new_duty, led_dat->period);
> +
> +	if (new_duty == 0)
> +		pwm_disable(led_dat->pwm);
> +	else
> +		pwm_enable(led_dat->pwm);
> +}
> +
> +static void led_pwm_work(struct work_struct *work)
> +{
> +	struct led_pwm_data *led_dat =
> +		container_of(work, struct led_pwm_data, work);
> +
> +	__led_pwm_set(led_dat);
> +}
> +
>  static void led_pwm_set(struct led_classdev *led_cdev,
>  	enum led_brightness brightness)
>  {
> @@ -44,13 +68,12 @@ static void led_pwm_set(struct led_classdev *led_cdev,
>  	unsigned int max = led_dat->cdev.max_brightness;
>  	unsigned int period =  led_dat->period;
>  
> -	if (brightness == 0) {
> -		pwm_config(led_dat->pwm, 0, period);
> -		pwm_disable(led_dat->pwm);
> -	} else {
> -		pwm_config(led_dat->pwm, brightness * period / max, period);
> -		pwm_enable(led_dat->pwm);
> -	}
> +	led_dat->duty = brightness * period / max;
> +
> +	if (led_dat->can_sleep)
> +		schedule_work(&led_dat->work);
> +	else
> +		__led_pwm_set(led_dat);
>  }
>  
>  static inline size_t sizeof_pwm_leds_priv(int num_leds)
> @@ -100,6 +123,10 @@ static struct led_pwm_priv *led_pwm_create_of(struct platform_device *pdev)
>  		led_dat->cdev.brightness = LED_OFF;
>  		led_dat->cdev.flags |= LED_CORE_SUSPENDRESUME;
>  
> +		led_dat->can_sleep = pwm_can_sleep(led_dat->pwm);
> +		if (led_dat->can_sleep)
> +			INIT_WORK(&led_dat->work, led_pwm_work);
> +
>  		ret = led_classdev_register(&pdev->dev, &led_dat->cdev);
>  		if (ret < 0) {
>  			dev_err(&pdev->dev, "failed to register for %s\n",
> @@ -153,6 +180,10 @@ static int led_pwm_probe(struct platform_device *pdev)
>  			led_dat->cdev.max_brightness = cur_led->max_brightness;
>  			led_dat->cdev.flags |= LED_CORE_SUSPENDRESUME;
>  
> +			led_dat->can_sleep = pwm_can_sleep(led_dat->pwm);
> +			if (led_dat->can_sleep)
> +				INIT_WORK(&led_dat->work, led_pwm_work);
> +
>  			ret = led_classdev_register(&pdev->dev, &led_dat->cdev);
>  			if (ret < 0)
>  				goto err;
> @@ -180,8 +211,11 @@ static int led_pwm_remove(struct platform_device *pdev)
>  	struct led_pwm_priv *priv = platform_get_drvdata(pdev);
>  	int i;
>  
> -	for (i = 0; i < priv->num_leds; i++)
> +	for (i = 0; i < priv->num_leds; i++) {
>  		led_classdev_unregister(&priv->leds[i].cdev);
> +		if (priv->leds[i].can_sleep)
> +			cancel_work_sync(&priv->leds[i].work);
> +	}
>  
>  	return 0;
>  }
> 


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