linux-kernel - Re: [PATCH 10/15] dt-bindings: iio: adc: adi,ad4030: Add adi,clock-mode

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Message-ID: <033e8639-67db-4397-b8c1-d1b7774eb9fe@baylibre.com>
Date: Sat, 30 Aug 2025 13:02:28 -0500
From: David Lechner <dlechner@...libre.com>
To: Marcelo Schmitt <marcelo.schmitt@...log.com>, linux-iio@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
 devicetree@...r.kernel.org, linux-spi@...r.kernel.org
Cc: jic23@...nel.org, Michael.Hennerich@...log.com, nuno.sa@...log.com,
 eblanc@...libre.com, andy@...nel.org, corbet@....net, robh@...nel.org,
 krzk+dt@...nel.org, conor+dt@...nel.org, broonie@...nel.org,
 Jonathan.Cameron@...wei.com, andriy.shevchenko@...ux.intel.com,
 ahaslam@...libre.com, sergiu.cuciurean@...log.com, marcelo.schmitt1@...il.com
Subject: Re: [PATCH 10/15] dt-bindings: iio: adc: adi,ad4030: Add
 adi,clock-mode

On 8/29/25 7:43 PM, Marcelo Schmitt wrote:
> AD4030 and similar designs support three different options for the clock
> that frames ADC output data. Each option implies a different hardware
> configuration for reading ADC data. Document AD4030 clock mode options.
> 
> Co-developed-by: Sergiu Cuciurean <sergiu.cuciurean@...log.com>
> Signed-off-by: Sergiu Cuciurean <sergiu.cuciurean@...log.com>
> Signed-off-by: Marcelo Schmitt <marcelo.schmitt@...log.com>
> ---
>  .../devicetree/bindings/iio/adc/adi,ad4030.yaml      | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/iio/adc/adi,ad4030.yaml b/Documentation/devicetree/bindings/iio/adc/adi,ad4030.yaml
> index bee85087a7b2..1e4e025b835f 100644
> --- a/Documentation/devicetree/bindings/iio/adc/adi,ad4030.yaml
> +++ b/Documentation/devicetree/bindings/iio/adc/adi,ad4030.yaml
> @@ -78,6 +78,18 @@ properties:
>    interrupt-names:
>      const: busy
>  
> +  adi,clock-mode:
> +    $ref: /schemas/types.yaml#/definitions/string
> +    enum: [ spi, echo, host ]
> +    default: spi
> +    description:
> +      Describes how the clock that frames ADC data output is setup.
> +      spi  - Spi-compatible. Normal SPI operation clocking.
> +      echo - Echo-clock. Synchronous clock echoing to ease timing requirements
> +             when using isolation on the digital interface.
> +      host - Host. The Host clock mode uses an internal oscillator to clock out
> +             the data bits. In this mode, the spi controller is not driving SCLK.
> +
>  required:
>    - compatible
>    - reg

I think this would make sense as a common property in spi-peripheral-props.yaml
as this is something that is not specific to just this ADC and also requires
a supporting SPI controller with the matching wiring.

I would also tweak the names and descriptions a bit to describe how it is wired
rather than how it is used.

  spi-sclk-source:
    enum: [ controller, echo, peripheral ]
    default: controller
    description: |
      Indicates how the SCLK is wired.
      controller: The SCLK line is driven by the controller (typical SPI bus).
      echo: The SCLK line is driven by the controller and the peripheral echos
        the clock back to an input on the controller on a second line.
      peripheral: The SCLK line from the controller is not connected to the
        peripheral and an independent clock output driven by the peripheral is
        connected to an input on the controller.