linux-kernel - Re: [PATCH 4/5] dt-bindings: iio: adc: adi,ad7606: add gain calibration support

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Message-ID: <uyreqaazupbt23vmf3pwxsaneimtahsuinlfmc77aaavt4nyl6@yofmvw3rndtx>
Date: Tue, 29 Apr 2025 22:45:39 +0200
From: Angelo Dureghello <adureghello@...libre.com>
To: David Lechner <dlechner@...libre.com>
Cc: Jonathan Cameron <jic23@...nel.org>, 
	Nuno Sá <nuno.sa@...log.com>, Andy Shevchenko <andy@...nel.org>, 
	Lars-Peter Clausen <lars@...afoo.de>, Michael Hennerich <Michael.Hennerich@...log.com>, 
	Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, 
	Conor Dooley <conor+dt@...nel.org>, linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org, 
	devicetree@...r.kernel.org
Subject: Re: [PATCH 4/5] dt-bindings: iio: adc: adi,ad7606: add gain
 calibration support

On 29.04.2025 10:26, David Lechner wrote:
> On 4/29/25 8:06 AM, Angelo Dureghello wrote:
> > From: Angelo Dureghello <adureghello@...libre.com>
> > 
> > Add gain calibration support by a per-channel resistor value.
> > 
> > Signed-off-by: Angelo Dureghello <adureghello@...libre.com>
> > ---
> >  Documentation/devicetree/bindings/iio/adc/adi,ad7606.yaml | 14 ++++++++++++++
> >  1 file changed, 14 insertions(+)
> > 
> > diff --git a/Documentation/devicetree/bindings/iio/adc/adi,ad7606.yaml b/Documentation/devicetree/bindings/iio/adc/adi,ad7606.yaml
> > index 29f12d650442b8ff2eb455306ce59a0e87867ddd..df30545fb52c89a814257443183303775a06a7f2 100644
> > --- a/Documentation/devicetree/bindings/iio/adc/adi,ad7606.yaml
> > +++ b/Documentation/devicetree/bindings/iio/adc/adi,ad7606.yaml
> > @@ -204,6 +204,15 @@ patternProperties:
> >            considered a bipolar differential channel. Otherwise it is bipolar
> >            single-ended.
> >  
> > +      adi,rfilter-ohms:
> > +        description:
> > +          For ADCs that supports gain calibration, this property must be set to
> > +          the value of the external RFilter resistor. Proper gain error
> > +          correction is applied based on this value.
> > +        default: 0
> > +        minimum: 0
> > +        maximum: 65536
> > +
> >      required:
> >        - reg
> >        - bipolar
> > @@ -271,6 +280,10 @@ allOf:
> >      then:
> >        properties:
> >          adi,sw-mode: false
> > +      patternProperties:
> > +        "^channel@[0-9a-f]+$":
> > +          properties:
> > +            adi,rfilter-ohms: false
> 
> I think this is in the wrong place. It would allow this property on ad7616, but
> ad7616 does not have this feature.
>

Looks like it cannot work on ad7616 due to

  - if:
      not:
        properties:
          compatible:
            enum:
              - adi,ad7606c-16
              - adi,ad7606c-18
    then:
      patternProperties:
        "^channel@[1-8]$": false


But maybe an additional patch should be added to add also adi,ad7606b
to the above enum.

Regards,
angelo


 
> 
> >      else:
> >        properties:
> >          pwms:
> > @@ -398,6 +411,7 @@ examples:
> >                  reg = <8>;
> >                  diff-channels = <8 8>;
> >                  bipolar;
> > +                adi,rfilter-ohms = <2048>;
> >              };
> >  
> >          };
> > 
>