linux-kernel - Re: 回复: 回复: [PATCH v1 1/2] dt-bindings: ASoC: Add PDM controller for the StarFive JH8100 SoC

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Message-ID: <9307ba55-834a-4aa9-b993-a54e5ab4b3be@linaro.org>
Date: Fri, 8 Mar 2024 11:05:22 +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>,
 Takashi Iwai <tiwai@...e.com>, Jaroslav Kysela <perex@...ex.cz>,
 Rob Herring <robh+dt@...nel.org>,
 Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
 Conor Dooley <conor.dooley@...rochip.com>
Cc: Walker Chen <walker.chen@...rfivetech.com>,
 "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: 回复: [PATCH v1 1/2] dt-bindings: ASoC: Add PDM controller for the StarFive JH8100 SoC

On 08/03/2024 10:19, Xingyu Wu wrote:
>> On 08/03/2024 08:49, Xingyu Wu wrote:
>>>>> +
>>>>> +  starfive,pdm-modulex:
>>>>> +    $ref: /schemas/types.yaml#/definitions/uint32
>>>>> +    enum: [0, 1]
>>>>> +    description:
>>>>> +      The module x will be using in PDM controller. Default use module 0.
>>>>
>>>> This is an index of the block instance? If so, then it's not allowed.
>>>> Otherwise I don't understand the description.
>>>>
>>>
>>> No, this is just one instance. The PDM have two internal and independent
>> modules or called channels.
>>> They can be configured and used separately, and the user can choose which
>> channel to use.
>>>
>>
>> Do the modulex differ? Why different boards would choose one over another?
>>
> 
> They are same. The choice between them is base on the match with I2S.
> The DMA data channel of hardware between them is fixed linked:
> PDM module 0 --> I2S channel 0,
> PDM module 1 --> I2S channel 1
> I2S uses higher-number channels first for capture (like channel 1), so PDM should skips module 0 and uses module 1.
> Oh, I just thought of a way to fix them that change the priority of I2S channel to use lower-number channels first and PDM need not skip module0.
> 

Hm, then maybe this should be somehow linked with choice of I2C channel?
Do you have anywhere a link to complete DTS with sound card?

Best regards,
Krzysztof