Re: [PATCH 1/2] hwmon: (pwm-fan) add option to stop fan on shutdown

[Rob Herring <robh@kernel.org>]

On Sun, Dec 22, 2019 at 11:10:22PM +0900, Akinobu Mita wrote:
> The pwm-fan driver leaves the fun running when shutting down the system.
> (On the other hand the gpio-fan driver stops it.)

Seemms like we should have consistent behavior independent of what the 
underlying implementation uses. Is there actually a case you'd want to 
leave the fan on? It seems strange to disable in suspend and leave on in 
shutdown.

Wouldn't the shutdown state depend if the PWM off state is high or low? 
IIRC, i.MX PWM has a quirk that the PWM disabled state is high. Doesn't 
it also depend on what the PWM driver does in shutdown?

Rob

> 
> This adds an optional property "disable-state-shutdown" in case someone
> wants to stop the fun running when shutting down the system.
> 
> Cc: Rob Herring <robh+dt@kernel.org>
> Cc: Mark Rutland <mark.rutland@arm.com>
> Cc: Kamil Debski <kamil@wypas.org>
> Cc: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
> Cc: Guenter Roeck <linux@roeck-us.net>
> Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
> ---
>  drivers/hwmon/pwm-fan.c | 24 ++++++++++++++++++++++--
>  1 file changed, 22 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/hwmon/pwm-fan.c b/drivers/hwmon/pwm-fan.c
> index 42ffd2e..8775d37 100644
> --- a/drivers/hwmon/pwm-fan.c
> +++ b/drivers/hwmon/pwm-fan.c
> @@ -33,6 +33,7 @@ struct pwm_fan_ctx {
>  	u8 pulses_per_revolution;
>  	ktime_t sample_start;
>  	struct timer_list rpm_timer;
> +	bool disable_state_shutdown;
>  
>  	unsigned int pwm_value;
>  	unsigned int pwm_fan_state;
> @@ -292,6 +293,9 @@ static int pwm_fan_probe(struct platform_device *pdev)
>  
>  	mutex_init(&ctx->lock);
>  
> +	ctx->disable_state_shutdown =
> +		of_property_read_bool(dev->of_node, "disable-state-shutdown");
> +
>  	ctx->pwm = devm_of_pwm_get(dev, dev->of_node, NULL);
>  	if (IS_ERR(ctx->pwm)) {
>  		ret = PTR_ERR(ctx->pwm);
> @@ -390,8 +394,7 @@ static int pwm_fan_probe(struct platform_device *pdev)
>  	return 0;
>  }
>  
> -#ifdef CONFIG_PM_SLEEP
> -static int pwm_fan_suspend(struct device *dev)
> +static int pwm_fan_disable(struct device *dev)
>  {
>  	struct pwm_fan_ctx *ctx = dev_get_drvdata(dev);
>  	struct pwm_args args;
> @@ -418,6 +421,22 @@ static int pwm_fan_suspend(struct device *dev)
>  	return 0;
>  }
>  
> +static void pwm_fan_shutdown(struct platform_device *pdev)
> +{
> +	struct pwm_fan_ctx *ctx = platform_get_drvdata(pdev);
> +
> +	if (!ctx->disable_state_shutdown)
> +		return;
> +
> +	pwm_fan_disable(&pdev->dev);
> +}
> +
> +#ifdef CONFIG_PM_SLEEP
> +static int pwm_fan_suspend(struct device *dev)
> +{
> +	return pwm_fan_disable(dev);
> +}
> +
>  static int pwm_fan_resume(struct device *dev)
>  {
>  	struct pwm_fan_ctx *ctx = dev_get_drvdata(dev);
> @@ -455,6 +474,7 @@ MODULE_DEVICE_TABLE(of, of_pwm_fan_match);
>  
>  static struct platform_driver pwm_fan_driver = {
>  	.probe		= pwm_fan_probe,
> +	.shutdown	= pwm_fan_shutdown,
>  	.driver	= {
>  		.name		= "pwm-fan",
>  		.pm		= &pwm_fan_pm,
> -- 
> 2.7.4
>