linux-kernel - Re: 回复: [PATCH v2 1/2] ASoC: dt-bindings: Add bindings for Cadence I2S-MC controller

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Date: Fri, 29 Mar 2024 12:42:22 +0100
From: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To: Xingyu Wu <xingyu.wu@...rfivetech.com>,
 Liam Girdwood <lgirdwood@...il.com>, Mark Brown <broonie@...nel.org>,
 Claudiu Beznea <Claudiu.Beznea@...rochip.com>,
 Jaroslav Kysela <perex@...ex.cz>, Takashi Iwai <tiwai@...e.com>,
 Rob Herring <robh+dt@...nel.org>,
 Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
 Conor Dooley <conor.dooley@...rochip.com>
Cc: "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
 "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
 "alsa-devel@...a-project.org" <alsa-devel@...a-project.org>,
 "linux-sound@...r.kernel.org" <linux-sound@...r.kernel.org>
Subject: Re: 回复: [PATCH v2 1/2] ASoC: dt-bindings: Add bindings for Cadence I2S-MC controller

On 29/03/2024 04:56, Xingyu Wu wrote:
>>> I want to keep the original IP compatible which can distinguish from the JH8100
>> SoC.
>>> Can I write it like this:
>>> compatible:
>>>    enum:
>>>           - starfive,jh8100-i2s
>>>    const: cdns,i2s-mc
>>>
>>> and I write this in the DTS:
>>> compatible = "starfive,jh8100-i2s", "cdns,i2s-mc";
>>
>> Can you provide any rationale for this? I asked "unless you have other
>> arguments", so where are the arguments?
>>
>> Nothing was explained in patch changelog. Nothing was provided in this email
>> thread.
> 
> I don't know if I understood what mark said[1]. Is it to keep the original IP and
> add other compatible?
> 
> [1] https://lore.kernel.org/all/27155281-573c-493d-96fe-1f28ebb0ce5e@sirena.org.uk/
> 

I stated and I keep my statement that such block is usually not usable
on its own and always needs some sort of quirks or SoC-specific
implementation. At least this is what I saw in other similar cases, but
not exactly I2S.

Therefore I think fallback is not usable here, thus please use only
starfive compatible. Drop the fallback. It could be added in the future
if I am proven wrong. If you think that fallback is usable alone, please
bring some real life case.

> Or should I only keep the compatible 'starfive,jh8110-i2s' and change the
> bindings name to same to this compatible?

Filename could be cdns,i2s-mc.yaml, assuming that's the name of original
IP block.

..

>>>>
>>>
>>> But this I2S can only use either DMA or interrupts.
>>
>> Just like many other components. DTS should reflect hardware. Hardware has
>> interrupts and DMA, right?
> 
> Yes. The hardware can use interrupts and provide the handshake interface of
> DMA to DMA controller. In software, we can choose only one between them.
> Do I keep them both in the bindings and provide the selection in the driver?

Yes.

Best regards,
Krzysztof