Re: [PATCH 3/3] dt-bindings: hwmon: max31790: Add pwmout-pin-as-tach-input property

[Chanh Nguyen]

On 12/03/2024 00:34, Rob Herring wrote:
> On Mon, Mar 11, 2024 at 06:13:47PM +0700, Chanh Nguyen wrote:
> > Add pwmout-pin-as-tach-input property.
> >
> > Signed-off-by: Chanh Nguyen <chanh@xxxxxxxxxxxxxxxxxxxxxx>
> > ---
> >   Documentation/devicetree/bindings/hwmon/max31790.yaml | 11 +++++++++++
> >   1 file changed, 11 insertions(+)
> >
> > diff --git a/Documentation/devicetree/bindings/hwmon/max31790.yaml b/Documentation/devicetree/bindings/hwmon/max31790.yaml
> > index 5a93e6bdebda..447cac17053a 100644
> > --- a/Documentation/devicetree/bindings/hwmon/max31790.yaml
> > +++ b/Documentation/devicetree/bindings/hwmon/max31790.yaml
> > @@ -25,6 +25,16 @@ properties:
> >     reg:
> >       maxItems: 1
> >   
> > +  pwmout-pin-as-tach-input:
> > +    description: |
> > +      An array of six integers responds to six PWM channels for
> > +      configuring the pwm to tach mode.
> > +      When set to 0, the associated PWMOUT produces a PWM waveform for
> > +      control of fan speed. When set to 1, PWMOUT becomes a TACH input
> > +    $ref: /schemas/types.yaml#/definitions/uint8-array
> > +    maxItems: 6
> > +    minItems: 6
>
> Seems incomplete. For example, fan tachs have different number of
> pulses per revolution, don't you need to know that too?
>
> There's a common fan binding now (or pending). You should use that and
> this property won't be needed.
>
> Rob

Thank Rob,

I checked in the 
Documentation/devicetree/bindings/hwmon/fan-common.yaml. I found the 
tach-ch property, but it seems define the tach channel used for fan.

  tach-ch:
    description:
      The tach channel used for the fan.
    $ref: /schemas/types.yaml#/definitions/uint8-array

I would like to define a new vendor property to configure the PWM-OUT 
pin to become a TACH-IN pin. So I introduce the 
"maxim,pwmout-pin-as-tach-input" property. Please help me share your 
comments!