linux-kernel - Re: [PATCH 1/3] ASoC: dt-bindings: mediatek: mt8192: Add i2s-share properties

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Date:   Thu, 5 May 2022 16:48:31 +0800
From:   Jiaxin Yu <jiaxin.yu@...iatek.com>
To:     AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>,
        "Nícolas F. R. A. Prado" <nfraprado@...labora.com>,
        "Mark Brown" <broonie@...nel.org>
CC:     <kernel@...labora.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 1/3] ASoC: dt-bindings: mediatek: mt8192: Add i2s-share
 properties

On Thu, 2022-05-05 at 10:08 +0200, AngeloGioacchino Del Regno wrote:
> Il 29/04/22 22:30, Nícolas F. R. A. Prado ha scritto:
> > The Mediatek AFE PCM controller for MT8192 allows sharing of an I2S
> > bus
> > between two busses. Add a pattern for these properties in the
> > dt-binding.
> > 
> > Signed-off-by: Nícolas F. R. A. Prado <nfraprado@...labora.com>
> > ---
> > 
> >   Documentation/devicetree/bindings/sound/mt8192-afe-pcm.yaml | 5
> > +++++
> >   1 file changed, 5 insertions(+)
> > 
> > diff --git a/Documentation/devicetree/bindings/sound/mt8192-afe-
> > pcm.yaml b/Documentation/devicetree/bindings/sound/mt8192-afe-
> > pcm.yaml
> > index 7a25bc9b8060..5b03c8dbf318 100644
> > --- a/Documentation/devicetree/bindings/sound/mt8192-afe-pcm.yaml
> > +++ b/Documentation/devicetree/bindings/sound/mt8192-afe-pcm.yaml
> > @@ -54,6 +54,11 @@ properties:
> >         - const: aud_infra_clk
> >         - const: aud_infra_26m_clk
> >   
> > +patternProperties:
> > +  "^i2s[0-35-9]-share$":
> > +    description: Name of the I2S bus that is shared with this bus
> > +    pattern: "^I2S[0-35-9]$"
> > +
> >   required:
> >     - compatible
> >     - interrupts
> > 
> 
> The only other way of doing this would be to complicate this in the
> driver
> so that we can do something like
> 
> "i2s-share = <0 2>";  instead of  i2s0-share = "I2S2";
> 
> ...and I don't think that this would be any more straightforward than
> the
> provided way.
> 
> There's an improvement that we can do to that pattern description
> though,
> which would be explaining that declaring 'i2s0-share = "I2S2"' means
> that
> I2S2's data pin will be used as DATA-OUT, while i2s0 is DATA-IN.
> 
> Another thing that comes to mind here is that this is a MediaTek
> specific
> property and *not* a generic one, which means that both the driver
> and
> this binding should be fixed to get a "mediatek," prefix, so, this
> property
> should - in reality - be "mediatek,i2s[0-35-9]-share" instead.
> 
> I think that everyone agrees about that, but let's see what the
> others say.
> 
> Cheers,
> Angelo

Hi Angelo,

'i2s0-share = "I2S2"' means that if we want use I2S0, there need open
I2S2 to provide clock. Conversely, if we want to use I2S2, we don't
need to open I2S0. However, MediaTek I2S0 and I2S2 hardware are
generally designed as input. So usually we use 'i2s0-share = "I2S1"'.
Even numbers represent input, odd numbers represent output.

Yes, I think adding the "mediatek," prefix is the right way to define a
non-generic property.

Best Regards,
Jiaxin Yu