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

[Guenter Roeck <linux@roeck-us.net>]

On Thu, Sep 23, 2021 at 11:34:47AM +0900, Akinobu Mita wrote:
> This adds an optional property "retain-state-shutdown" as requested by
> Billy Tsai.
> 
> Billy said:
>  "Our platform is BMC that will use a PWM-FAN driver to control the fan
>  on the managed host. In our case, we do not want to stop the fan when
>  the BMC is reboot, which may cause the temperature of the managed host
>  not to be lowered."
> 
> Cc: Rob Herring <robh+dt@kernel.org>
> Cc: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
> Cc: Guenter Roeck <linux@roeck-us.net>
> Cc: Billy Tsai <billy_tsai@aspeedtech.com>
> Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>

For my reference (waiting for DT property approval):

Reviewed-by: Guenter Roeck <linux@roeck-us.net>

Guenter

> ---
>  drivers/hwmon/pwm-fan.c | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/hwmon/pwm-fan.c b/drivers/hwmon/pwm-fan.c
> index 17518b4cab1b..1ea0d0562c28 100644
> --- a/drivers/hwmon/pwm-fan.c
> +++ b/drivers/hwmon/pwm-fan.c
> @@ -38,6 +38,7 @@ struct pwm_fan_ctx {
>  	struct pwm_fan_tach *tachs;
>  	ktime_t sample_start;
>  	struct timer_list rpm_timer;
> +	bool retain_state_shutdown;
>  
>  	unsigned int pwm_value;
>  	unsigned int pwm_fan_state;
> @@ -312,6 +313,9 @@ static int pwm_fan_probe(struct platform_device *pdev)
>  
>  	mutex_init(&ctx->lock);
>  
> +	ctx->retain_state_shutdown =
> +		of_property_read_bool(dev->of_node, "retain-state-shutdown");
> +
>  	ctx->pwm = devm_of_pwm_get(dev, dev->of_node, NULL);
>  	if (IS_ERR(ctx->pwm))
>  		return dev_err_probe(dev, PTR_ERR(ctx->pwm), "Could not get PWM\n");
> @@ -492,7 +496,10 @@ static int pwm_fan_disable(struct device *dev)
>  
>  static void pwm_fan_shutdown(struct platform_device *pdev)
>  {
> -	pwm_fan_disable(&pdev->dev);
> +	struct pwm_fan_ctx *ctx = platform_get_drvdata(pdev);
> +
> +	if (!ctx->retain_state_shutdown)
> +		pwm_fan_disable(&pdev->dev);
>  }
>  
>  #ifdef CONFIG_PM_SLEEP