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

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

[Akinobu Mita]

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>
---
 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
-- 
2.25.1

[PATCH 2/2] dt-bindings: hwmon: (pwm-fan) add retain-state-shutdown property

[Akinobu Mita]

Document new retain-state-shutdown property.

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>
---
 Documentation/devicetree/bindings/hwmon/pwm-fan.txt | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/Documentation/devicetree/bindings/hwmon/pwm-fan.txt b/Documentation/devicetree/bindings/hwmon/pwm-fan.txt
index 4509e688623a..c1b2c3ff7ba8 100644
--- a/Documentation/devicetree/bindings/hwmon/pwm-fan.txt
+++ b/Documentation/devicetree/bindings/hwmon/pwm-fan.txt
@@ -19,6 +19,8 @@ Optional properties:
 			  interrupts per revolution). The value must be
 			  greater than zero.
 
+- retain-state-shutdown: Retain the state of the PWM on shutdown.
+
 Example:
 	fan0: pwm-fan {
 		compatible = "pwm-fan";
-- 
2.25.1

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

[Guenter Roeck]

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

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

[Billy Tsai]

On 2021/10/11, 10:34 PM, "Guenter Roeck" <groeck7@gmail.com on behalf of linux@roeck-us.net> wrote:

    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

Reviewed-by: Billy Tsai <billy_tsai@aspeedtech.com>

Billy

    > > ---
    > >  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