linux-kernel - Re: [PATCH 5/7] dt-bindings: iio: adc: add ad458x

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Message-ID: <CAMknhBE_RoDg+EhqF5+UbqV1z7i1PvVRi3HC48SAsR5AYDF6TQ@mail.gmail.com>
Date: Tue, 24 Sep 2024 15:42:39 +0200
From: David Lechner <dlechner@...libre.com>
To: Antoniu Miclaus <antoniu.miclaus@...log.com>
Cc: Jonathan Cameron <jic23@...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>, Nuno Sa <nuno.sa@...log.com>, 
	Olivier Moysan <olivier.moysan@...s.st.com>, Uwe Kleine-König <ukleinek@...nel.org>, 
	Andy Shevchenko <andy@...nel.org>, Marcelo Schmitt <marcelo.schmitt@...log.com>, 
	Mike Looijmans <mike.looijmans@...ic.nl>, Marius Cristea <marius.cristea@...rochip.com>, 
	Dumitru Ceclan <mitrutzceclan@...il.com>, 
	João Paulo Gonçalves <joao.goncalves@...adex.com>, 
	AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>, 
	Alisa-Dariana Roman <alisadariana@...il.com>, Sergiu Cuciurean <sergiu.cuciurean@...log.com>, 
	Dragos Bogdan <dragos.bogdan@...log.com>, linux-iio@...r.kernel.org, 
	linux-kernel@...r.kernel.org, devicetree@...r.kernel.org, 
	linux-pwm@...r.kernel.org
Subject: Re: [PATCH 5/7] dt-bindings: iio: adc: add ad458x

On Mon, Sep 23, 2024 at 12:17 PM Antoniu Miclaus
<antoniu.miclaus@...log.com> wrote:
>
> Add devicetree bindings for ad458x DAS family.
>
> Signed-off-by: Antoniu Miclaus <antoniu.miclaus@...log.com>
> ---
>  .../bindings/iio/adc/adi,ad485x.yaml          | 82 +++++++++++++++++++
>  1 file changed, 82 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/iio/adc/adi,ad485x.yaml
>
> diff --git a/Documentation/devicetree/bindings/iio/adc/adi,ad485x.yaml b/Documentation/devicetree/bindings/iio/adc/adi,ad485x.yaml
> new file mode 100644
> index 000000000000..5f5bdfa9522b
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/iio/adc/adi,ad485x.yaml
> @@ -0,0 +1,82 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +# Copyright 2022 Analog Devices Inc.
> +%YAML 1.2
> +---

I think we could make the bindings a bit more complete (even if the
driver doesn't use everything yet). Some suggestions below.

> +$id: http://devicetree.org/schemas/iio/adc/adi,ad485x.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Analog Devices AD485X DAS family device driver
> +
> +maintainers:
> +  - Sergiu Cuciurean <sergiu.cuciurean@...log.com>
> +  - Dragos Bogdan <dragos.bogdan@...log.com>
> +  - Antoniu Miclaus <antoniu.miclaus@...log.com>
> +
> +description: |
> +  Analog Devices AD485X DAS family
> +
> +  https://www.analog.com/media/en/technical-documentation/data-sheets/ad4858.pdf

Links for other parts? (I only looked at this datasheet, so some of my
comments below might only apply to this part and not the others.)

Since this is a SPI peripheral, we should add...

$ref: /schemas/spi/spi-peripheral-props.yaml#

> +
> +properties:
> +  compatible:
> +    enum:
> +      - adi,ad4858
> +      - adi,ad4857
> +      - adi,ad4856
> +      - adi,ad4855
> +      - adi,ad4854
> +      - adi,ad4853
> +      - adi,ad4852
> +      - adi,ad4851
> +      - adi,ad4858i
> +
> +  reg:
> +    maxItems: 1
> +
> +  vcc-supply: true

Do we also need vee-supply (it can be a negative voltage or 0V)? Or is
vcc-supply the voltage between V_CC and V_EE?

> +
> +  vdd-supply: true
> +
> +  vddh-supply: true

Datasheet says V_DDL can be the same or separate supply as V_DDH, so
should probably also have vddl-supply: true.

> +
> +  vio-supply: true

What about reference supplies (REFIO and REFBUF)?

> +
> +  pwms:
> +    maxItems: 1

I suppose this is connected to the CNV pin? Probably worth adding a
description to say that since it isn't so obvious.

> +
> +  io-backends:
> +    maxItems: 1

For PD pin (power down):

pd-gpios:
    maxItems: 1

> +
> +  spi-max-frequency:
> +    maximum: 100000000

Datasheet says that minimum CSCK Period is 40 ns, so that would be
25000000 Hz max frequency.

> +
> +required:
> +  - compatible
> +  - reg
> +  - vcc-supply
> +  - vdd-supply
> +  - vddh-supply

Datasheet says to tie V_DDH to GND to disable LDO, so it sounds like
vddh-supply should be optional, not required.

> +  - vio-supply
> +  - pwms
> +
> +unevaluatedProperties: false
> +
> +examples:
> +  - |
> +    spi {
> +        #address-cells = <1>;
> +        #size-cells = <0>;
> +
> +        adc@0{
> +            compatible = "adi,ad4858";
> +            reg = <0>;
> +            spi-max-frequency = <10000000>;
> +            vcc-supply = <&vcc>;
> +            vdd-supply = <&vdd>;
> +            vddh-supply = <&vddh>;
> +            vio-supply = <&vio>;
> +            pwms = <&pwm_gen 0 0>;
> +            io-backends = <&iio_backend>;
> +        };
> +    };
> +...
> --
> 2.46.0
>