linux-kernel - Re: [PATCH v4 1/3] dt-bindings: hwmon: Add adt7475 fan/pwm properties

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Date: Wed, 29 May 2024 08:58:41 +0100
From: Conor Dooley <conor.dooley@...rochip.com>
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 v4 1/3] dt-bindings: hwmon: Add adt7475 fan/pwm properties

On Wed, May 29, 2024 at 10:56:36AM +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:
>     I realise there is still some discussion about how to express the
>     frequency and duty cycle. I have a personal preference for using hertz
>     for the frequency and 0-255 for the duty cycle but if the consensus is
>     to express these things some other way I'm fine with doing some math.

Probably worth carrying a link to it here:
https://lore.kernel.org/all/4de798f3-069e-4028-a5b5-5e6a639277e3@alliedtelesis.co.nz/

I asked Uwe to take a look & it's on his todo list.

Thanks,
Conor.

>     
>     Changes in v4:
>     - 0 is not a valid frequency value
>     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..bfef4c803bf7 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 - 11, 14, 22, 29, 35, 44, 58, 88, 22500
> +      - 2: PWM flags 0 or PWM_POLARITY_INVERTED
> +      - 3: The default pwm duty cycle - 0-255
> +
>  patternProperties:
>    "^adi,bypass-attenuator-in[0-4]$":
>      description: |
> @@ -81,6 +90,10 @@ patternProperties:
>        - smbalert#
>        - gpio
>  
> +  "^fan-[0-9]+$":
> +    $ref: fan-common.yaml#
> +    unevaluatedProperties: false
> +
>  required:
>    - compatible
>    - reg
> @@ -89,11 +102,12 @@ additionalProperties: false
>  
>  examples:
>    - |
> +    #include <dt-bindings/pwm/pwm.h>
>      i2c {
>        #address-cells = <1>;
>        #size-cells = <0>;
>  
> -      hwmon@2e {
> +      pwm: hwmon@2e {
>          compatible = "adi,adt7476";
>          reg = <0x2e>;
>          adi,bypass-attenuator-in0 = <1>;
> @@ -101,5 +115,14 @@ examples:
>          adi,pwm-active-state = <1 0 1>;
>          adi,pin10-function = "smbalert#";
>          adi,pin14-function = "tach4";
> +        #pwm-cells = <4>;
> +
> +        fan-0 {
> +          pwms = <&pwm 0 22500 PWM_POLARITY_INVERTED 255>;
> +        };
> +
> +        fan-1 {
> +          pwms = <&pwm 2 22500 PWM_POLARITY_INVERTED 255>;
> +        };
>        };
>      };
> -- 
> 2.45.1
> 

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