linux-kernel - Re: [PATCH v3 1/3] dt-bindings: iio: adc: Add AD4134

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Message-ID: <aTLVAAQH-I8Rc372@debian-BULLSEYE-live-builder-AMD64>
Date: Fri, 5 Dec 2025 09:50:08 -0300
From: Marcelo Schmitt <marcelo.schmitt1@...il.com>
To: Tomas Melin <tomas.melin@...sala.com>
Cc: Marcelo Schmitt <marcelo.schmitt@...log.com>, linux-iio@...r.kernel.org,
	devicetree@...r.kernel.org, linux-doc@...r.kernel.org,
	linux-kernel@...r.kernel.org, jic23@...nel.org, nuno.sa@...log.com,
	dlechner@...libre.com, andy@...nel.org,
	Michael.Hennerich@...log.com, robh@...nel.org, krzk+dt@...nel.org,
	conor+dt@...nel.org, corbet@....net,
	Conor Dooley <conor.dooley@...rochip.com>
Subject: Re: [PATCH v3 1/3] dt-bindings: iio: adc: Add AD4134

On 12/05, Tomas Melin wrote:
> Hi,
> 
> On 02/12/2025 22:55, Marcelo Schmitt wrote:
> > Add device tree documentation for AD4134 24-Bit, 4-channel simultaneous
> > sampling, precision ADC.
> > 
> > Reviewed-by: Conor Dooley <conor.dooley@...rochip.com>
> > Signed-off-by: Marcelo Schmitt <marcelo.schmitt@...log.com>
> > ---
> > Change log v2 -> v3:
> > - fixed typo in powerdown-gpios description.
> > - picked up Conor's review tag. 
> > 
> >  .../bindings/iio/adc/adi,ad4134.yaml          | 198 ++++++++++++++++++
...
> > +description: |
> > +  The AD4134 is a quad channel, low noise, simultaneous sampling, precision
> > +  analog-to-digital converter (ADC).
> > +  Specifications can be found at:
> > +    https://www.analog.com/media/en/technical-documentation/data-sheets/ad4134.pdf
> > +
> > +$ref: /schemas/spi/spi-peripheral-props.yaml#
> > +
> > +properties:
> > +    maxItems: 1
> > +
> > +  adi,asrc-mode:
> > +    $ref: /schemas/types.yaml#/definitions/string
> > +    description:
> > +      Asynchronous Sample Rate Converter (ASRC) operation mode control input.
> > +      Describes whether the MODE pin is set to a high level (for master mode
> > +      operation) or to a low level (for slave mode operation).
> > +    enum: [ high, low ]
> > +    default: low
> Since minimim I/O mode is only one currently supported, this should
> always be low, right? Is the property needed at this point?

Correct, it is expected that adi,asrc-mode will always be low for minimum I/O mode.
The property is not _needed_ but, according to dt-binding guidelines [1], it is
desired.

[1]: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/devicetree/bindings/writing-bindings.rst?h=v6.18#n17

> 
> > +
> > +  adi,dclkio:
> > +    description:
> > +      DCLK pin I/O direction control for when the device operates in Pin Control
> > +      Slave Mode or in SPI Control Mode. Describes if DEC0/DCLKIO pin is at a
> > +      high level (which configures DCLK as an output) or to set to a low level
> > +      (configuring DCLK for input).
> > +    enum: [ out, in ]
> > +    default: in
> > +
> > +  adi,dclkmode:
> > +    description:
> > +      DCLK mode control for when the device operates in Pin Control Slave Mode
> > +      or in SPI Control Mode. Describes whether the DEC1/DCLKMODE pin is set to
> > +      a high level (configuring the DCLK to operate in free running mode) or
> > +      to a low level (to configure DCLK to operate in gated mode).
> > +    enum: [ free-running, gated ]
> > +    default: gated
> In minimum I/O mode datasheet mentions this should always be gated.
> Perhaps this and adi,dclkio can be left out and added when driver gains
> other support than I/O mode?

Yes, that's also correct. A few properties are actually not needed for minimum
I/O mode (i.e. can have their values inferred from the minimum I/O mode requirements).
Sure, from developer's perspective it's easier to document only what the driver
uses. adi,dclkio, adi,dclkmode, adi,asrc-mode, powerdown-gpios, regulators, could
all be left to a latter time. Fine by me if dt maintainers agree with that.

With best regards,
Marcelo