linux-kernel - Re: [PATCH v5 02/14] dt-bindings: iio: adc: ad7768-1: add trigger-sources property

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Message-ID: <20250411-borax-shortlist-3a8511a09393@spud>
Date: Fri, 11 Apr 2025 17:30:37 +0100
From: Conor Dooley <conor@...nel.org>
To: Jonathan Santos <Jonathan.Santos@...log.com>
Cc: linux-iio@...r.kernel.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-gpio@...r.kernel.org,
	lars@...afoo.de, Michael.Hennerich@...log.com,
	marcelo.schmitt@...log.com, jic23@...nel.org, robh@...nel.org,
	krzk+dt@...nel.org, conor+dt@...nel.org, marcelo.schmitt1@...il.com,
	linus.walleij@...aro.org, brgl@...ev.pl, lgirdwood@...il.com,
	broonie@...nel.org, jonath4nns@...il.com, dlechner@...libre.com
Subject: Re: [PATCH v5 02/14] dt-bindings: iio: adc: ad7768-1: add
 trigger-sources property

On Fri, Apr 11, 2025 at 12:56:17PM -0300, Jonathan Santos wrote:
> In addition to GPIO synchronization, The AD7768-1 also supports
> synchronization over SPI, which use is recommended when the GPIO
> cannot provide a pulse synchronous with the base MCLK signal. It
> consists of looping back the SYNC_OUT to the SYNC_IN pin and send
> a command via SPI to trigger the synchronization.
> 
> Introduce the 'trigger-sources' property to support SPI-based
> synchronization, along with additional optional entries for the SPI
> offload trigger and the START signal via GPIO3.
> 
> While at it, add description to the interrupts property.
> 
> Signed-off-by: Jonathan Santos <Jonathan.Santos@...log.com>
> ---
> v5 Changes:
> * Include START pin and DRDY in the trigger-sources description.
> * Fixed "#trigger-source-cells" value and description.
> * sync-in-gpios is represented in the trigger-sources property.
> 
> v4 Changes:
> * none
> 
> v3 Changes:
> * Fixed dt-bindings errors.
> * Trigger-source is set as an alternative to sync-in-gpios, so we
>   don't break the previous ABI.
> * increased maxItems from trigger-sources to 2.
> 
> v2 Changes:
> * Patch added as replacement for adi,sync-in-spi patch.
> * addressed the request for a description to interrupts property.
> ---
>  .../bindings/iio/adc/adi,ad7768-1.yaml        | 38 +++++++++++++++++--
>  1 file changed, 35 insertions(+), 3 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/iio/adc/adi,ad7768-1.yaml b/Documentation/devicetree/bindings/iio/adc/adi,ad7768-1.yaml
> index 3ce59d4d065f..4c58dbe8f749 100644
> --- a/Documentation/devicetree/bindings/iio/adc/adi,ad7768-1.yaml
> +++ b/Documentation/devicetree/bindings/iio/adc/adi,ad7768-1.yaml
> @@ -26,7 +26,30 @@ properties:
>    clock-names:
>      const: mclk
>  
> +  trigger-sources:
> +    $ref: /schemas/types.yaml#/definitions/phandle-array
> +    minItems: 1
> +    maxItems: 3
> +    description: |
> +      A list of phandles referencing trigger source devices or GPIOs.
> +      Supports up to three entries, each representing a different type of
> +      trigger:
> +
> +        - First entry specifies the device responsible for driving the
> +          synchronization (SYNC_IN) pin, as an alternative to adi,sync-in-gpios.
> +          This can be a `gpio-trigger` or another `ad7768-1` device. If the
> +          device's own SYNC_OUT pin is internally connected to its SYNC_IN pin,
> +          reference the device itself or omit this property.
> +        - Second entry optionally defines a GPIO3 pin used as a START signal trigger.
> +        - Third entry specifies a GPIO line to act as a trigger for SPI offload.
> +
> +      Use the accompanying trigger source cell to identify the type of each entry.
> +
>    interrupts:
> +    description:
> +      Specifies the interrupt line associated with the ADC. This refers
> +      to the DRDY (Data Ready) pin, which signals when conversion results are
> +      available.
>      maxItems: 1
>  
>    '#address-cells':
> @@ -57,6 +80,15 @@ properties:
>    "#io-channel-cells":
>      const: 1
>  
> +  "#trigger-source-cells":
> +    description: |
> +      Indicates the trigger source type for each entry:
> +      0 = Synchronization GPIO-based trigger
> +      1 = Synchronization device trigger (e.g., another ad7768-1)
> +      2 = GPIO3 pin acting as START signal
> +      3 = DRDY pin acting as SPI offload trigger

I think the description here makes little sense, when the value is
required to be 1 by the following line. If these are permitted values
for things consuming this adc as a trigger source, you should specify
that IMO.

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