Re: [PATCH 1/3] dt-bindings: iio: adc: Add GPADC for Allwinner A523

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] Incorrect fallback compatible string 'allwinner,sun20i-d1-gpadc' violating backward compatibility guarantees.
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commit 48f3b1ab2ee7aee8d556d5b6595c00af83e47dad
Author: Michal Piekos <michal.piekos@mmpsystems.pl>

dt-bindings: iio: adc: Add GPADC for Allwinner A523

This commit adds device tree binding support for the GPADC on the Allwinner
A523. It updates the existing sun20i-d1-gpadc binding to accommodate the
A523's requirement for two separate clocks instead of one.

> diff --git a/Documentation/devicetree/bindings/iio/adc/allwinner,sun20i-d1-gpadc.yaml b/Documentation/devicetree/bindings/iio/adc/allwinner,sun20i-d1-gpadc.yaml
> index da605a051b949..89da96cd705f0 100644
> --- a/Documentation/devicetree/bindings/iio/adc/allwinner,sun20i-d1-gpadc.yaml
> +++ b/Documentation/devicetree/bindings/iio/adc/allwinner,sun20i-d1-gpadc.yaml
> @@ -17,6 +17,7 @@ properties:
>        - items:
>            - enum:
>                - allwinner,sun50i-h616-gpadc
> +              - allwinner,sun55i-a523-gpadc
>            - const: allwinner,sun20i-d1-gpadc

Since the A523 requires two clocks (bus and mod) and the D1 only requires
one, does using the D1 compatible as a fallback violate backward
compatibility guarantees?

If an older kernel boots with this new device tree, it will match the
allwinner,sun20i-d1-gpadc fallback and bind the legacy driver. The legacy
D1 driver only fetches and enables the first clock listed (the bus clock).

Will this leave the required mod clock disabled, causing the ADC hardware
reads to timeout? 

Should allwinner,sun55i-a523-gpadc be defined as a standalone compatible
string without a fallback instead?

[ ... ]

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Sashiko AI review · https://sashiko.dev/#/patchset/20260510-sunxi-a523-gpadc-v1-0-4f6b0f4000fb@mmpsystems.pl?part=1