linux-kernel - Re: [PATCH] Input: pwm-beeper - fix: scheduling while atomic

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Date:	Fri, 27 May 2016 16:38:44 -0700
From:	Dmitry Torokhov <dmitry.torokhov@...il.com>
To:	Manfred Schlaegl <manfred.schlaegl@....at>
Cc:	Thierry Reding <thierry.reding@...il.com>,
	Manfred Schlaegl <manfred.schlaegl@...zinger.com>,
	Luis de Bethencourt <luis@...ethencourt.com>,
	Olivier Sobrie <olivier@...rie.be>,
	linux-input@...r.kernel.org, linux-kernel@...r.kernel.org,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH] Input: pwm-beeper - fix: scheduling while atomic

On Fri, May 27, 2016 at 11:14:27AM +0200, Manfred Schlaegl wrote:
> Pwm config may sleep so defer it using a worker.
> 
> On a Freescale i.MX53 based board we ran into "BUG: scheduling while
> atomic" because input_inject_event locks interrupts, but
> imx_pwm_config_v2 sleeps.
> 
> Tested on Freescale i.MX53 SoC with 4.6.0.
> 
> Signed-off-by: Manfred Schlaegl <manfred.schlaegl@....at>

Applied, thank you.

> ---
>  drivers/input/misc/pwm-beeper.c | 69 ++++++++++++++++++++++++++++-------------
>  1 file changed, 48 insertions(+), 21 deletions(-)
> 
> diff --git a/drivers/input/misc/pwm-beeper.c b/drivers/input/misc/pwm-beeper.c
> index 8d71332..5f9655d 100644
> --- a/drivers/input/misc/pwm-beeper.c
> +++ b/drivers/input/misc/pwm-beeper.c
> @@ -20,21 +20,40 @@
>  #include <linux/platform_device.h>
>  #include <linux/pwm.h>
>  #include <linux/slab.h>
> +#include <linux/workqueue.h>
>  
>  struct pwm_beeper {
>  	struct input_dev *input;
>  	struct pwm_device *pwm;
> +	struct work_struct work;
>  	unsigned long period;
>  };
>  
>  #define HZ_TO_NANOSECONDS(x) (1000000000UL/(x))
>  
> +static void __pwm_beeper_set(struct pwm_beeper *beeper)
> +{
> +	unsigned long period = beeper->period;
> +
> +	if (period) {
> +		pwm_config(beeper->pwm, period / 2, period);
> +		pwm_enable(beeper->pwm);
> +	} else
> +		pwm_disable(beeper->pwm);
> +}
> +
> +static void pwm_beeper_work(struct work_struct *work)
> +{
> +	struct pwm_beeper *beeper =
> +		container_of(work, struct pwm_beeper, work);
> +
> +	__pwm_beeper_set(beeper);
> +}
> +
>  static int pwm_beeper_event(struct input_dev *input,
>  			    unsigned int type, unsigned int code, int value)
>  {
> -	int ret = 0;
>  	struct pwm_beeper *beeper = input_get_drvdata(input);
> -	unsigned long period;
>  
>  	if (type != EV_SND || value < 0)
>  		return -EINVAL;
> @@ -49,22 +68,31 @@ static int pwm_beeper_event(struct input_dev *input,
>  		return -EINVAL;
>  	}
>  
> -	if (value == 0) {
> -		pwm_disable(beeper->pwm);
> -	} else {
> -		period = HZ_TO_NANOSECONDS(value);
> -		ret = pwm_config(beeper->pwm, period / 2, period);
> -		if (ret)
> -			return ret;
> -		ret = pwm_enable(beeper->pwm);
> -		if (ret)
> -			return ret;
> -		beeper->period = period;
> -	}
> +	if (value == 0)
> +		beeper->period = 0;
> +	else
> +		beeper->period = HZ_TO_NANOSECONDS(value);
> +
> +	schedule_work(&beeper->work);
>  
>  	return 0;
>  }
>  
> +static void pwm_beeper_stop(struct pwm_beeper *beeper)
> +{
> +	cancel_work_sync(&beeper->work);
> +
> +	if (beeper->period)
> +		pwm_disable(beeper->pwm);
> +}
> +
> +static void pwm_beeper_close(struct input_dev *input)
> +{
> +	struct pwm_beeper *beeper = input_get_drvdata(input);
> +
> +	pwm_beeper_stop(beeper);
> +}
> +
>  static int pwm_beeper_probe(struct platform_device *pdev)
>  {
>  	unsigned long pwm_id = (unsigned long)dev_get_platdata(&pdev->dev);
> @@ -93,6 +121,8 @@ static int pwm_beeper_probe(struct platform_device *pdev)
>  	 */
>  	pwm_apply_args(beeper->pwm);
>  
> +	INIT_WORK(&beeper->work, pwm_beeper_work);
> +
>  	beeper->input = input_allocate_device();
>  	if (!beeper->input) {
>  		dev_err(&pdev->dev, "Failed to allocate input device\n");
> @@ -112,6 +142,7 @@ static int pwm_beeper_probe(struct platform_device *pdev)
>  	beeper->input->sndbit[0] = BIT(SND_TONE) | BIT(SND_BELL);
>  
>  	beeper->input->event = pwm_beeper_event;
> +	beeper->input->close = pwm_beeper_close;
>  
>  	input_set_drvdata(beeper->input, beeper);
>  
> @@ -141,7 +172,6 @@ static int pwm_beeper_remove(struct platform_device *pdev)
>  
>  	input_unregister_device(beeper->input);
>  
> -	pwm_disable(beeper->pwm);
>  	pwm_free(beeper->pwm);
>  
>  	kfree(beeper);
> @@ -153,8 +183,7 @@ static int __maybe_unused pwm_beeper_suspend(struct device *dev)
>  {
>  	struct pwm_beeper *beeper = dev_get_drvdata(dev);
>  
> -	if (beeper->period)
> -		pwm_disable(beeper->pwm);
> +	pwm_beeper_stop(beeper);
>  
>  	return 0;
>  }
> @@ -163,10 +192,8 @@ static int __maybe_unused pwm_beeper_resume(struct device *dev)
>  {
>  	struct pwm_beeper *beeper = dev_get_drvdata(dev);
>  
> -	if (beeper->period) {
> -		pwm_config(beeper->pwm, beeper->period / 2, beeper->period);
> -		pwm_enable(beeper->pwm);
> -	}
> +	if (beeper->period)
> +		__pwm_beeper_set(beeper);
>  
>  	return 0;
>  }
> -- 
> 2.1.4
> 

-- 
Dmitry