linux-kernel - Re: [PATCH v3 1/2] dt-bindings: hwmon: amc6821: add fan and PWM output

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Message-ID: <8064282a-17aa-4b97-b5d9-1b4a8b0dc40b@roeck-us.net>
Date: Mon, 31 Mar 2025 09:01:08 -0700
From: Guenter Roeck <linux@...ck-us.net>
To: Francesco Dolcini <francesco@...cini.it>, Jean Delvare
 <jdelvare@...e.com>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
 <conor+dt@...nel.org>, Farouk Bouabid <farouk.bouabid@...rry.de>,
 Quentin Schulz <quentin.schulz@...rry.de>
Cc: Francesco Dolcini <francesco.dolcini@...adex.com>,
 linux-hwmon@...r.kernel.org, devicetree@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 1/2] dt-bindings: hwmon: amc6821: add fan and PWM
 output

On 3/31/25 08:52, Francesco Dolcini wrote:
> From: Francesco Dolcini <francesco.dolcini@...adex.com>
> 
> Add properties to describe the fan and the PWM controller output.
> 
> Link: https://www.ti.com/lit/gpn/amc6821
> Signed-off-by: Francesco Dolcini <francesco.dolcini@...adex.com>
> ---
> v3:
>   - explicitly describe the fan, use standard PWM and FAN bindings
>   - pwm.yaml cannot be referenced, because of the $nodename pattern that is
>     enforced there
> v2: https://lore.kernel.org/all/20250224180801.128685-2-francesco@dolcini.it/
>   - no changes
> v1: https://lore.kernel.org/all/20250218165633.106867-2-francesco@dolcini.it/
> ---
>   .../devicetree/bindings/hwmon/ti,amc6821.yaml      | 14 +++++++++++++-
>   1 file changed, 13 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/devicetree/bindings/hwmon/ti,amc6821.yaml b/Documentation/devicetree/bindings/hwmon/ti,amc6821.yaml
> index 5d33f1a23d03..94aca9c378e6 100644
> --- a/Documentation/devicetree/bindings/hwmon/ti,amc6821.yaml
> +++ b/Documentation/devicetree/bindings/hwmon/ti,amc6821.yaml
> @@ -28,6 +28,13 @@ properties:
>     i2c-mux:
>       type: object
>   
> +  fan:
> +    $ref: fan-common.yaml#
> +    unevaluatedProperties: false
> +
> +  "#pwm-cells":
> +    const: 3
> +
>   required:
>     - compatible
>     - reg
> @@ -50,9 +57,14 @@ examples:
>           #address-cells = <1>;
>           #size-cells = <0>;
>   
> -        fan@18 {
> +        fan_controller: fan@18 {
>               compatible = "ti,amc6821";
>               reg = <0x18>;
> +            #pwm-cells = <3>;
> +
> +            fan {
> +                pwms = <&fan_controller 0 40000 0>;

There is no explanation for the parameters. I guess that the first is the index and the
second is the frequency. The index is not used and can be dropped (there is just a single
channel), and the frequency only makes sense if it can actually be configured.

Either case, the fields need to be documented.

Thanks,
Guenter

> +            };
>           };
>       };
>