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

[Chanh Nguyen]

On 18/03/2024 17:02, Krzysztof Kozlowski wrote:
> On 18/03/2024 10:48, Chanh Nguyen wrote:
> > On 11/03/2024 23:56, Krzysztof Kozlowski wrote:
> > > On 11/03/2024 12:13, Chanh Nguyen wrote:
> > > > Add pwmout-pin-as-tach-input property.
> > >
> > > Why is this split from original binding? This does not make much
> > > sense... Add complete hardware description.
> >
> > Ok Krzysztof, I will merg the "[PATCH 1/3] dt-bindings: hwmon: Add maxim
> > max31790 driver bindings" commit and "[PATCH 3/3] dt-bindings: hwmon:
> > max31790: Add pwmout-pin-as-tach-input property" commit.
>
> Later I checked your driver code and this explains a bit. However first
> patch should explain that instead. The split is fine, but just lack of
> rationale is confusing.

Thank Krzysztof. I'll try to explain in detail each patch in v2.

> > > > 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
> > >
> > > No vendor prefix, so generic property... but where is it defined?
> >
> > Thank Krzysztof! It is not generic property, I'll add the vendor prefix.
> >
> > I'll update the "pwmout-pin-as-tach-input" to
> > "maxim,pwmout-pin-as-tach-input" at v2.
>
> Except that you should really look into common properties and use them.
> Or explain why do you need new property?
>
> Best regards,
> Krzysztof

I'm also discussing with Rob Herring that on patch 3/3, I checked in the 
Documentation/devicetree/bindings/hwmon/fan-common.yaml. I found the 
tach-ch property, but it seems to define the tach channel used for the 
fan. It does not match my purpose. I want to configure the PWM-OUT pin 
to become a TACH-IN pin. I wonder if I can use the tach-ch property for 
my purpose.