Re: [PATCH v6 01/12] dt-bindings: iio: adc: Add AD4170

[Jonathan Cameron <jic23@kernel.org>]

On Thu, 19 Jun 2025 16:35:48 +0100
Conor Dooley <conor@kernel.org> wrote:

> On Wed, Jun 18, 2025 at 02:34:57PM -0300, Marcelo Schmitt wrote:
> > Add device tree documentation for AD4170 and similar sigma-delta ADCs.
> > The AD4170 is a 24-bit, multichannel, sigma-delta ADC.
> > 
> > Signed-off-by: Marcelo Schmitt <marcelo.schmitt@analog.com>
> > ---
> > Change log v5 -> v6
> > - Made reference-buffer string type.
> > - Moved required section before patternProperties.
> > - Made avss, refin1n, refin2n documentation open to accepting positive and
> >   negative voltage specifications where appropriate.
> > 
> > The point of making avss-supply, refin1n-supply and refin2n-supply documentation
> > open to negative voltage values is to allow device tree to specify the regulator
> > true voltage level so the drivers won't need to workaround negative supplies in
> > the future.
> > 
> >  .../bindings/iio/adc/adi,ad4170.yaml          | 558 ++++++++++++++++++
> >  MAINTAINERS                                   |   7 +
> >  2 files changed, 565 insertions(+)
> >  create mode 100644 Documentation/devicetree/bindings/iio/adc/adi,ad4170.yaml
> > 
> > diff --git a/Documentation/devicetree/bindings/iio/adc/adi,ad4170.yaml b/Documentation/devicetree/bindings/iio/adc/adi,ad4170.yaml
> > new file mode 100644
> > index 000000000000..b7fe664bb87d
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/iio/adc/adi,ad4170.yaml
> > @@ -0,0 +1,558 @@
> > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> > +%YAML 1.2
> > +---
> > +$id: http://devicetree.org/schemas/iio/adc/adi,ad4170.yaml#
> > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > +
> > +title: Analog Devices AD4170 and similar Analog to Digital Converters
> > +
> > +maintainers:
> > +  - Marcelo Schmitt <marcelo.schmitt@analog.com>
> > +
> > +description: |
> > +  Analog Devices AD4170 series of Sigma-delta Analog to Digital Converters.
> > +  Specifications can be found at:
> > +    https://www.analog.com/media/en/technical-documentation/data-sheets/ad4170-4.pdf
> > +    https://www.analog.com/media/en/technical-documentation/data-sheets/ad4190-4.pdf
> > +    https://www.analog.com/media/en/technical-documentation/data-sheets/ad4195-4.pdf
> > +
> > +$ref: /schemas/spi/spi-peripheral-props.yaml#
> > +
> > +$defs:
> > +  reference-buffer:
> > +    description: |
> > +      Enable precharge buffer, full buffer, or skip reference buffering of
> > +      the positive/negative voltage reference. Because the output impedance
> > +      of the source driving the voltage reference inputs may be dynamic,
> > +      resistive/capacitive combinations of those inputs can cause DC gain
> > +      errors if the reference inputs go unbuffered into the ADC. Enable
> > +      reference buffering if the provided reference source has dynamic high
> > +      impedance output. Note the absolute voltage allowed on REFINn+ and REFINn-
> > +      inputs is from AVSS - 50 mV to AVDD + 50 mV when the reference buffers are
> > +      disabled but narrows to AVSS to AVDD when reference buffering is enabled
> > +      or in precharge mode.  
> 
> > The valid options for this property are:
> > +      0: Reference precharge buffer.
> > +      1: Full reference buffering.
> > +      2: Bypass reference buffers (buffering disabled).  
> 
> You forgot to remove this text. With that gone, I think this is
> Acked-by: Conor Dooley <conor.dooley@microchip.com>
> and that's explicitly an ack not an r-b cos I would like to see the lads
> being happy with what you've done.
Hi Conor, All,

I'm fine with it (late reply to earlier version) but I'm definitely keen to
get other opinions on this as we are setting a new standard for how to cleanly
handle excitation voltages etc in this binding.

Thanks

Jonathan