linux-kernel - Re: [PATCH v3 1/3] dt-bindings: hwmon: Add adt7475 fan/pwm properties

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Date: Mon, 20 May 2024 17:49:39 +0100
From: Conor Dooley <conor@...nel.org>
To: Chris Packham <chris.packham@...iedtelesis.co.nz>
Cc: jdelvare@...e.com, linux@...ck-us.net, robh@...nel.org,
	krzk+dt@...nel.org, conor+dt@...nel.org, ukleinek@...nel.org,
	linux-hwmon@...r.kernel.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-pwm@...r.kernel.org
Subject: Re: [PATCH v3 1/3] dt-bindings: hwmon: Add adt7475 fan/pwm properties

On Mon, May 20, 2024 at 03:03:19PM +1200, Chris Packham wrote:
> Add fan child nodes that allow describing the connections for the
> ADT7475 to the fans it controls. This also allows setting some
> initial values for the pwm duty cycle and frequency.
> 
> Signed-off-by: Chris Packham <chris.packham@...iedtelesis.co.nz>
> ---
> 
> Notes:
>     Changes in v3:
>     - Use the pwm provider/consumer bindings
>     Changes in v2:
>     - Document 0 as a valid value (leaves hardware as-is)
> 
>  .../devicetree/bindings/hwmon/adt7475.yaml    | 25 ++++++++++++++++++-
>  1 file changed, 24 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/devicetree/bindings/hwmon/adt7475.yaml b/Documentation/devicetree/bindings/hwmon/adt7475.yaml
> index 051c976ab711..99bd689ae0cd 100644
> --- a/Documentation/devicetree/bindings/hwmon/adt7475.yaml
> +++ b/Documentation/devicetree/bindings/hwmon/adt7475.yaml
> @@ -51,6 +51,15 @@ properties:
>        enum: [0, 1]
>        default: 1
>  
> +  "#pwm-cells":
> +    const: 4
> +    description: |
> +      Number of cells in a PWM specifier.
> +      - 0: The pwm channel
> +      - 1: The pwm frequency in hertz - 0, 11, 14, 22, 29, 35, 44, 58, 88, 22500

The standard binding is period in nanoseconds, not frequency in Hz.
What's gained from deviating from that?

> +      - 2: PWM flags 0 or PWM_POLARITY_INVERTED
> +      - 3: The default pwm duty cycle - 0-255

Same here I guess, why not match the units used for the period for the
duty cycle?

Cheers,
Conor.

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