linux-kernel - Re: [PATCH v1 2/2] dt-bindings: ASoC: simple-card: Add system-clock-id property

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Date:   Wed, 26 Oct 2022 15:48:21 +0100
From:   Aidan MacDonald <aidanmacdonald.0x0@...il.com>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Cc:     broonie@...nel.org, lgirdwood@...il.com, robh+dt@...nel.org,
        krzysztof.kozlowski+dt@...aro.org,
        kuninori.morimoto.gx@...esas.com, perex@...ex.cz, tiwai@...e.com,
        alsa-devel@...a-project.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 2/2] dt-bindings: ASoC: simple-card: Add
 system-clock-id property

Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org> writes:

> And the remaining piece I don't get is that these are not bindings for
> codec, but for sound audio card. You want to set "system-clock-id"
> property for audio card, while putting clock from codec, which will be
> used to pass back to the codec... so it is a property of the codec, not
> of the audio card. IOW, NAU8821_CLK_* does not configure here the clock
> of the system, but only, only clock of the codec.

The system clock is controlled at the DAI level, it's specific to one
DAI on one component. The simple-card device node has sub-nodes for the
DAI links, and each DAI link node has sub-nodes for the DAIs within the
link. "system-clock-id" is a property on the DAI nodes, so it's not a
card-level property, just one part of the overall card definition.

Since the clock ID is something defined by the codec it would naturally
be a value defined by the codec, but the *configuration* of the codec is
part of the sound card because it depends on how everything is connected
together. If you used the same codec in a different machine it would
have a different configuration.

Regards,
Aidan