linux-kernel - Re: [PATCH v1 01/15] dt-bindings: iio: adc: ad7768-1: add synchronization over SPI property

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Message-ID: <Z4GWSgruwnkDfYSg@debian-BULLSEYE-live-builder-AMD64>
Date: Fri, 10 Jan 2025 18:51:06 -0300
From: Marcelo Schmitt <marcelo.schmitt1@...il.com>
To: Jonathan Santos <Jonathan.Santos@...log.com>
Cc: linux-iio@...r.kernel.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, lars@...afoo.de,
	Michael.Hennerich@...log.com, jic23@...nel.org, robh@...nel.org,
	krzk+dt@...nel.org, conor+dt@...nel.org
Subject: Re: [PATCH v1 01/15] dt-bindings: iio: adc: ad7768-1: add
 synchronization over SPI property

On 01/07, Jonathan Santos wrote:
> Add adi,sync-in-spi property to enable synchronization over SPI.
> This should be used in the case when the GPIO cannot provide a
> pulse synchronous with the base MCLK signal.
> 
> User can choose between SPI, GPIO synchronization or neither of them,
> but only if a external pulse can be provided, for example, by another
> device in a multidevice setup.
> 
> Signed-off-by: Jonathan Santos <Jonathan.Santos@...log.com>
> ---
>  .../bindings/iio/adc/adi,ad7768-1.yaml        | 24 ++++++++++++++++++-
>  1 file changed, 23 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/devicetree/bindings/iio/adc/adi,ad7768-1.yaml b/Documentation/devicetree/bindings/iio/adc/adi,ad7768-1.yaml
> index 3ce59d4d065f..55cec27bfe60 100644
> --- a/Documentation/devicetree/bindings/iio/adc/adi,ad7768-1.yaml
> +++ b/Documentation/devicetree/bindings/iio/adc/adi,ad7768-1.yaml
> @@ -47,6 +47,15 @@ properties:
>        in any way, for example if the filter decimation rate changes.
>        As the line is active low, it should be marked GPIO_ACTIVE_LOW.
>  
> +  adi,sync-in-spi:
> +    description:
> +      Enables synchronization of multiple devices over SPI. This property is
> +      used when a signal synchronous to the base MCLK signal cannot be provided
> +      via GPIO. It requires the SYNC_OUT pin to be connected to the SYNC_IN pin
> +      on the ADC. In the case of multiple devices, the SYNC_OUT pin of one device
> +      should be routed to the SYNC_IN pins of the other devices.
So, if I'm getting it right, /SYNC_IN may be driven by a GPIO (ADAQ7768-1
datasheet Figure 131), /SYNC_IN may be driven by own device /SYNC_OUT
(ADAQ7768-1 datasheet Figure 133), or /SYNC_IN may be driven by other AD7768-1
/SYNC_OUT pin (also Figure 133).
That is too much to describe with a boolean.

If David's suggestion of using a trigger-source doesn't fit, this property
should at least become an enum or string.

> +    type: boolean
> +
>    reset-gpios:
>      maxItems: 1
>  
> @@ -65,7 +74,6 @@ required:
>    - vref-supply
>    - spi-cpol
>    - spi-cpha
> -  - adi,sync-in-gpios
>  
>  patternProperties:
>    "^channel@([0-9]|1[0-5])$":
> @@ -89,6 +97,20 @@ patternProperties:
>  allOf:
>    - $ref: /schemas/spi/spi-peripheral-props.yaml#
>  
> +  # adi,sync-in-gpios and adi,sync-in-spi are mutually exclusive (neither is also valid)
> +  - if:
> +      required:
> +        - adi,sync-in-gpios
> +    then:
> +      properties:
> +        adi,sync-in-spi: false
> +  - if:
> +      required:
> +        - adi,sync-in-spi
> +    then:
> +      properties:
> +        adi,sync-in-gpios: false
> +
>  unevaluatedProperties: false
>  
>  examples:
> -- 
> 2.34.1
>