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

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Date:   Sun, 29 May 2022 10:02:07 +0200
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Nícolas F. R. A. Prado 
        <nfraprado@...labora.com>
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 27/05/2022 21:05, Nícolas F. R. A. Prado wrote:
> 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?

Not entirely. This is a binding for mediatek,mt8192-audio, not for I2S9,
so the property should be in this binding referencing your existing I2S
devices.

> 
> 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.

Hm, then the follow up question: why you do not have i2s8 defined in DTS?


Best regards,
Krzysztof