linux-kernel - Re: [PATCH 1/3] dt-bindings: sound: Add Apple MCA I2S transceiver

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Date:   Tue, 9 Aug 2022 10:40:07 +0200
From:   Martin Povišer <povik+lin@...ebit.org>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Cc:     Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Jaroslav Kysela <perex@...ex.cz>,
        Takashi Iwai <tiwai@...e.com>,
        Philipp Zabel <p.zabel@...gutronix.de>, asahi@...ts.linux.dev,
        alsa-devel@...a-project.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] dt-bindings: sound: Add Apple MCA I2S transceiver



> On 9. 8. 2022, at 10:15, Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org> wrote:
> 
> On 09/08/2022 01:41, Martin Povišer wrote:
>> Add binding schema for MCA I2S transceiver found on Apple M1 and other
>> chips.
> 
> 
> Thank you for your patch. There is something to discuss/improve.
> 
>> +title: Apple MCA I2S transceiver
>> +
>> +description: |
>> +  MCA is an I2S transceiver peripheral found on M1 and other Apple chips. It is
>> +  composed of a number of identical clusters which can operate independently
>> +  or in an interlinked fashion. Up to 6 clusters have been seen on an MCA.
>> +
>> +maintainers:
>> +  - Martin Povišer <povik+lin@...ebit.org>

(...)

>> +  dmas:
>> +    minItems: 16
>> +    maxItems: 24
>> +    description:
>> +      DMA channels corresponding to the SERDES units in the peripheral. They are
>> +      listed in groups of four per cluster, and within the group they are given
>> +      as associated to the TXA, RXA, TXB, RXB units.
>> +
>> +  dma-names:
>> +    minItems: 16
>> +    maxItems: 24
>> +    items:
>> +      pattern: '^(tx|rx)[0-5][ab]$'
> 
> Use consistent quotes (everywhere " or ').

OK

> Describe the items because otherwise you allow any order. The list will
> be unfortunately quite long, but still readable enough.

Well, I would assume the ‘dmas’ property as described above has an implicit
natural order, and the dma-names are tied to it. You order it like the other
per-cluster properties, and then within the cluster the order is fixed to
'TXA, RXA, TXB, RXB’ (maybe the word ‘respectively’ thrown into the description
would have made it clearer).

Anyway that’s just discussing my assumptions. I can roll out the items list
for ‘dma-names’, if that’s what you mean. Or do you mean explicitly describing
the items in ‘dmas’ too?

>> +    description: |
>> +      Names for the DMA channels: 'tx'/'rx', then cluster number, then 'a'/'b'
>> +      based on the associated SERDES unit.
>> +

(...)

>> +
>> +additionalProperties: false
>> +
>> +examples:
>> +  - |
>> +    mca: mca@...00000 {
> 
> You called it I2S transceiver but isn't it also actually I2S controller?
> If yes, then the node name should be probably "i2s".

It’s a peripheral you use to transmit and receive samples over I2S, frankly
I don't know the nomenclature.

>> +      compatible = "apple,t6000-mca", "apple,mca";
>> +      reg = <0x9b600000 0x10000>,
>> +            <0x9b200000 0x20000>;
>> +
> 
> 
> Best regards,
> Krzysztof

All best,
Martin