Re: [PATCH 1/2] dt-bindings: sound: ti,pcm3168a: Convert to json-schema

[Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>]

On 05/12/2022 09:00, Geert Uytterhoeven wrote:
> Hi Krzysztof,
> 
> Thanks for your comments!
> 
> On Sat, Dec 3, 2022 at 1:13 PM Krzysztof Kozlowski
> <krzysztof.kozlowski@linaro.org> wrote:
>> On 02/12/2022 13:55, Geert Uytterhoeven wrote:
>>> Convert the Texas Instruments PCM3168A Audio Codec Device Tree binding
>>> documentation to json-schema.
>>>
>>> Add missing properties.
>>> Drop unneeded pinctrl properties from example.
>>
>> Thank you for your patch. There is something to discuss/improve.
>>
>>> +description:
>>> +  The Texas Instruments PCM3168A is a 24-bit Multi-channel Audio CODEC with
>>> +  96/192kHz sampling rate, supporting both SPI and I2C bus access.
>>> +
>>> +properties:
>>> +  compatible:
>>> +    const: ti,pcm3168a
>>> +
>>> +  reg:
>>> +    maxItems: 1
>>> +
>>> +  clocks:
>>> +    items:
>>> +      - description: System clock input
>>> +
>>> +  clock-names:
>>> +    items:
>>> +      - const: scki
>>> +
>>> +  reset-gpios:
>>> +    items:
>>> +      - description: |
>>> +          GPIO line connected to the active-low RST pin of the codec.
>>> +            RST = low: device power-down
>>> +            RST = high: device is enabled
>>> +
>>> +  "#sound-dai-cells":
>>> +    enum: [0, 1]
>>
>> This is a bit unexpected. Looking at DTSes:
>> 1. I see in ulcb-kf.dtsi with cells==0, but two endpoints. The dai cells
>> seem unused? In such case shall dai-cells be skipped if we have endpoints?
>>
>> 2. in k3-j721e-common-proc-board.dts has cells=1, but user's phandle
>> does not have an argument, so practically it is ==0? The user -
>> sound/soc/ti/j721e-evm.c - just gets the node and does not use cells,
>> right? So even though dai-cells==1, it does not matter, because user
>> gets its own parsing?
>>
>> 3. The pcm3168a driver also does not have any xlate function, but it
>> registers to DAIs, so all uses should be with cells==1 to select proper
>> DAI...
> 
> I have no idea (DAI is magic to me), and hope the audio experts
> can provide some input...

It is a bit of magic to me too. Yet I think the correct usage of this is
with dai-cells=1. I think we can skip the choice here between
sound-dai-cells and endpoints (to allow only one) and only fix the value
here to =1.

This would also require changing
arch/arm64/boot/dts/renesas/ulcb-kf.dtsi to dai-cells=1.

Best regards,
Krzysztof