[PATCH v2 1/2] dt-bindings: hwmon: pwm-fan: Document default-pwm property

[PATCH v2 1/2] dt-bindings: hwmon: pwm-fan: Document default-pwm property

[Peter Korsgaard]

Similar to target-rpm from fan-common.yaml but for the default PWM setting
(0..255).

Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
---
Changes since v1:
- Rename to default-pwm

 Documentation/devicetree/bindings/hwmon/pwm-fan.yaml | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/Documentation/devicetree/bindings/hwmon/pwm-fan.yaml b/Documentation/devicetree/bindings/hwmon/pwm-fan.yaml
index 4e5abf7580cc..70f062b30985 100644
--- a/Documentation/devicetree/bindings/hwmon/pwm-fan.yaml
+++ b/Documentation/devicetree/bindings/hwmon/pwm-fan.yaml
@@ -46,6 +46,14 @@ properties:
 
   "#cooling-cells": true
 
+  default-pwm:
+    description:
+      The default fan PWM to use.
+    $ref: /schemas/types.yaml#/definitions/uint32
+    minimum: 0
+    maximum: 255
+    default: 255
+
 required:
   - compatible
   - pwms
-- 
2.39.2

[PATCH v2 2/2] hwmon: (pwm-fan): support default-pwm property to set default PWM value

[Peter Korsgaard]

For some use cases defaulting the PWM to full fan speed is not ideal
(noise, power consumption, ..), so support an optional default-pwm
property (0..255) to override the default PWM value.

Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
---
Changes since v1:
- Rename property to default-pwm
- Drop u32 cast

 drivers/hwmon/pwm-fan.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/drivers/hwmon/pwm-fan.c b/drivers/hwmon/pwm-fan.c
index b67bc9e833c0..a2a309f8e3ee 100644
--- a/drivers/hwmon/pwm-fan.c
+++ b/drivers/hwmon/pwm-fan.c
@@ -482,6 +482,7 @@ static int pwm_fan_probe(struct platform_device *pdev)
 	const struct hwmon_channel_info **channels;
 	u32 *fan_channel_config;
 	int channel_count = 1;	/* We always have a PWM channel. */
+	u32 default_pwm = MAX_PWM;
 	int i;
 
 	ctx = devm_kzalloc(dev, sizeof(*ctx), GFP_KERNEL);
@@ -527,11 +528,17 @@ static int pwm_fan_probe(struct platform_device *pdev)
 
 	ctx->enable_mode = pwm_disable_reg_enable;
 
+	of_property_read_u32(dev->of_node, "default-pwm", &default_pwm);
+	if (default_pwm > MAX_PWM) {
+		dev_err(dev, "Invalid default-pwm: %u > %d\n", default_pwm, MAX_PWM);
+		return -EINVAL;
+	}
+
 	/*
-	 * Set duty cycle to maximum allowed and enable PWM output as well as
+	 * Set duty cycle to default and enable PWM output as well as
 	 * the regulator. In case of error nothing is changed
 	 */
-	ret = set_pwm(ctx, MAX_PWM);
+	ret = set_pwm(ctx, default_pwm);
 	if (ret) {
 		dev_err(dev, "Failed to configure PWM: %d\n", ret);
 		return ret;
-- 
2.39.2

Re: [PATCH v2 1/2] dt-bindings: hwmon: pwm-fan: Document default-pwm property

[Rob Herring]

On Wed, Apr 24, 2024 at 10:24:47PM +0200, Peter Korsgaard wrote:
> Similar to target-rpm from fan-common.yaml but for the default PWM setting
> (0..255).
> 
> Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
> ---
> Changes since v1:
> - Rename to default-pwm
> 
>  Documentation/devicetree/bindings/hwmon/pwm-fan.yaml | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/hwmon/pwm-fan.yaml b/Documentation/devicetree/bindings/hwmon/pwm-fan.yaml
> index 4e5abf7580cc..70f062b30985 100644
> --- a/Documentation/devicetree/bindings/hwmon/pwm-fan.yaml
> +++ b/Documentation/devicetree/bindings/hwmon/pwm-fan.yaml
> @@ -46,6 +46,14 @@ properties:
>  
>    "#cooling-cells": true
>  
> +  default-pwm:
> +    description:
> +      The default fan PWM to use.
> +    $ref: /schemas/types.yaml#/definitions/uint32
> +    minimum: 0
> +    maximum: 255
> +    default: 255

See my comments on v1. Please give time for other reviewers a chance to 
comment.

Rob

Re: [PATCH v2 1/2] dt-bindings: hwmon: pwm-fan: Document default-pwm property

[Peter Korsgaard]

On 4/25/24 18:18, Rob Herring wrote:
> On Wed, Apr 24, 2024 at 10:24:47PM +0200, Peter Korsgaard wrote:
>> Similar to target-rpm from fan-common.yaml but for the default PWM setting
>> (0..255).
>>
>> Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
>> ---
>> Changes since v1:
>> - Rename to default-pwm
>>
>>   Documentation/devicetree/bindings/hwmon/pwm-fan.yaml | 8 ++++++++
>>   1 file changed, 8 insertions(+)
>>
>> diff --git a/Documentation/devicetree/bindings/hwmon/pwm-fan.yaml b/Documentation/devicetree/bindings/hwmon/pwm-fan.yaml
>> index 4e5abf7580cc..70f062b30985 100644
>> --- a/Documentation/devicetree/bindings/hwmon/pwm-fan.yaml
>> +++ b/Documentation/devicetree/bindings/hwmon/pwm-fan.yaml
>> @@ -46,6 +46,14 @@ properties:
>>   
>>     "#cooling-cells": true
>>   
>> +  default-pwm:
>> +    description:
>> +      The default fan PWM to use.
>> +    $ref: /schemas/types.yaml#/definitions/uint32
>> +    minimum: 0
>> +    maximum: 255
>> +    default: 255
> 
> See my comments on v1. Please give time for other reviewers a chance to
> comment.

Sorry. As far as I can see, Guenter explained why we cannot generically 
translate between a default PWM value and RPM.

Do you still want to move this default-pwm property to fan-common.yaml? 
If so, I can send a v3 doing that.

-- 
Bye, Peter Korsgaard