linux-kernel - Re: [PATCH 1/2] dt-bindings: iio: dac: add docs for ad8460

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Date: Sat, 11 May 2024 13:47:26 -0500
From: David Lechner <dlechner@...libre.com>
To: Jonathan Cameron <jic23@...nel.org>
Cc: Mariel Tinaco <Mariel.Tinaco@...log.com>, linux-iio@...r.kernel.org, 
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Lars-Peter Clausen <lars@...afoo.de>, Rob Herring <robh@...nel.org>, 
	Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, 
	Liam Girdwood <lgirdwood@...il.com>, Mark Brown <broonie@...nel.org>, 
	Michael Hennerich <Michael.Hennerich@...log.com>, Marcelo Schmitt <marcelo.schmitt1@...il.com>, 
	Dimitri Fedrau <dima.fedrau@...il.com>, Guenter Roeck <linux@...ck-us.net>
Subject: Re: [PATCH 1/2] dt-bindings: iio: dac: add docs for ad8460

On Sat, May 11, 2024 at 11:25 AM Jonathan Cameron <jic23@...nel.org> wrote:
>
> On Fri, 10 May 2024 12:28:19 -0500
> David Lechner <dlechner@...libre.com> wrote:
>
> > On Fri, May 10, 2024 at 1:42 AM Mariel Tinaco <Mariel.Tinaco@...log.com> wrote:
> > >
> > > This adds the bindings documentation for the 14-bit
> > > High Voltage, High Current, Waveform Generator
> > > Digital-to-Analog converter.
> > >
> > > Signed-off-by: Mariel Tinaco <Mariel.Tinaco@...log.com>
> > > ---
> > >  .../bindings/iio/dac/adi,ad8460.yaml          | 67 +++++++++++++++++++
> > >  MAINTAINERS                                   |  7 ++
> > >  2 files changed, 74 insertions(+)
> > >  create mode 100644 Documentation/devicetree/bindings/iio/dac/adi,ad8460.yaml
> > >
> > > diff --git a/Documentation/devicetree/bindings/iio/dac/adi,ad8460.yaml b/Documentation/devicetree/bindings/iio/dac/adi,ad8460.yaml
> > > new file mode 100644
> > > index 000000000..924f76209
> > > --- /dev/null
> > > +++ b/Documentation/devicetree/bindings/iio/dac/adi,ad8460.yaml
> > > @@ -0,0 +1,67 @@
> > > +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
> > > +# Copyright 2024 Analog Devices Inc.
> > > +%YAML 1.2
> > > +---
> > > +$id: http://devicetree.org/schemas/iio/dac/adi,ad8460.yaml#
> > > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > > +
> > > +title: Analog Devices AD8460 DAC
> > > +
> > > +maintainers:
> > > +  - Mariel Tinaco <mariel.tinaco@...log.com>
> > > +
> > > +description: |
> > > +  Analog Devices AD8460 110 V High Voltage, 1 A High Current,
> > > +  Arbitrary Waveform Generator with Integrated 14-Bit High Speed DAC
> > > +  https://www.analog.com/media/en/technical-documentation/data-sheets/ad8460.pdf
> > > +
> > > +properties:
> > > +  compatible:
> > > +    enum:
> > > +      - adi,ad8460
> > > +
> > > +  reg:
> > > +    maxItems: 1
> > > +
> > > +  spi-max-frequency:
> > > +    maximum: 20000000
> > > +
> > > +  vref-supply:
> >
> > It would be nice to make the property name match the pin name since
> > there is more than one reference voltage input.
> >
> > refio-1p2v-supply:
> >
> > > +    description: Drive voltage in the range of 1.2V maximum to as low as
> > > +      low as 0.12V through the REF_IO pin to adjust full scale output span
> >
> > I don't seen anything in the datasheet named REF_IO. Is this a typo
> > and it should be REFIO_1P2V?
> >
> > > +
> > > +  clocks:
> > > +    description: The clock for the DAC. This is the sync clock
> > > +
> > > +  adi,rset-ohms:
> > > +    description: Specify value of external resistor connected to FS_ADJ pin
> > > +      to establish internal HVDAC's reference current I_REF
> > > +    minimum: 2000
> > > +    maximum: 20000
> > > +
> >
> > I see lots more pins on the datasheet, many of which should be trivial
> > to add bindings for (we prefer to have the bindings as complete as
> > possible even if the driver doesn't implement everything). Potential
> > candidates:
> >
> > sdn-reset-gpios: (active high)
> > reset-gpios: (active low)
> > sdn-io-gpios: (active high)
> >
> > hvcc-supply:
> > hvee-supply:
> > vcc-5v-supply:
> > vref-5v-supply:
> > dvdd-3p3v-supply:
> > avdd-3p3v-supply:
> >
> > It also looks like there is a parallel interface for data, so I would
> > expect to see an io-backends property that links to the PHY used for
> > handling that.
> >
> Ultimately yes, but the parallel interface might require some decisions on
> binding that are non obvious until it's actually implemented. So maybe
> don't need that bit from the start.  The rest I agree should be here.
>
>

Since the driver patch uses a DMA channel that isn't documented here,
I am assuming that the parallel interface is being used so we do need
to consider it now. :-)