linux-kernel - Re: [PATCH v2] ASoC: dt-bindings: mediatek: mt8192: Add i2s-share properties

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Date:   Fri, 27 May 2022 15:05:42 -0400
From:   Nícolas F. R. A. Prado 
        <nfraprado@...labora.com>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Cc:     Mark Brown <broonie@...nel.org>, kernel@...labora.com,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>,
        Jiaxin Yu <jiaxin.yu@...iatek.com>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Liam Girdwood <lgirdwood@...il.com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        Shane Chien <shane.chien@...iatek.com>,
        alsa-devel@...a-project.org, devicetree@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-mediatek@...ts.infradead.org
Subject: Re: [PATCH v2] ASoC: dt-bindings: mediatek: mt8192: Add i2s-share
 properties

On Thu, May 26, 2022 at 08:49:39AM +0200, Krzysztof Kozlowski wrote:
> On 09/05/2022 22:58, Nícolas F. R. A. Prado wrote:
> > The Mediatek AFE PCM controller for MT8192 allows two I2S interfaces to
> > share the same clock and act as a single interface with both input and
> > output. Add patterns for these properties in the dt-binding. The
> > property is split into two patterns in order to allow all valid
> > interface pairings.
> > 
> > Signed-off-by: Nícolas F. R. A. Prado <nfraprado@...labora.com>
> > 
> > ---
> > The series from v1 of this patch was merged although some changes were
> > still needed in this patch, so the v1 of this patch was reverted [1] and
> > this standalone commit addresses the feedback from v1 and readds the
> > property.
> > 
> > [1] https://lore.kernel.org/all/20220509185625.580811-1-nfraprado@collabora.com
> > 
> > v1: https://lore.kernel.org/all/20220429203039.2207848-2-nfraprado@collabora.com/
> > 
> > Changes in v2:
> > - Added "mediatek," prefix to property
> > - Rewrote and added more information to property description
> > - Split into two patterns to validate that output-input pairings are
> >   done
> > 
> >  .../bindings/sound/mt8192-afe-pcm.yaml           | 16 ++++++++++++++++
> >  1 file changed, 16 insertions(+)
> > 
> > diff --git a/Documentation/devicetree/bindings/sound/mt8192-afe-pcm.yaml b/Documentation/devicetree/bindings/sound/mt8192-afe-pcm.yaml
> > index 7a25bc9b8060..2abf43c6c2c3 100644
> > --- a/Documentation/devicetree/bindings/sound/mt8192-afe-pcm.yaml
> > +++ b/Documentation/devicetree/bindings/sound/mt8192-afe-pcm.yaml
> > @@ -54,6 +54,22 @@ properties:
> >        - const: aud_infra_clk
> >        - const: aud_infra_26m_clk
> >  
> > +patternProperties:
> > +  "^mediatek,i2s[13579]-share$":
> > +    description:
> > +      Each I2S interface has a single data line, input if its index is even or
> > +      output if the index is odd. An input and an output I2S interface can be
> > +      used together as if they were a single I2S interface with both input and
> > +      output data lines by sharing the same clock. This property represents this
> > +      pairing. The value should be the name of the interface whose clock is
> > +      used, and the property name the other interface that depends on this
> > +      clock.
> > +    pattern: "^I2S[0268]$"
> > +
> > +  "^mediatek,i2s[0268]-share$":
> > +    description: Same as above.
> > +    pattern: "^I2S[13579]$"
> 
> Rob's question is still valid - why these are not phandles?

So, instead of having

	i2s9-share = "I2S8";

on the DT, you want us to have something like this:

        afe_i2s8: mediatek,i2s8 { };

        mediatek,i2s9 {
          mediatek,share-clock = <&afe_i2s8>;
        };

Or do you mean something else?

It seems like a lot more syntax to express the same thing (and the empty node
seems awkward), but if that's the DT way, I can change it no problem.

> 
> In any case you miss $ref.

Indeed, sorry, I'll add it in next version.

Thanks,
Nícolas