Re: Query on audio-graph-card DT binding

[Sameer Pujar <spujar@nvidia.com>]

On 10-01-2024 04:45, Kuninori Morimoto wrote:
>>>>                 /-----> codec1 endpoint
>>>>                /
>>>> CPU endpoint \
>>>>                 \-----> codec2 endpoint
>>> It sounds "Single CPU - Mult Codec" connection, and if my understanding
>>> was correct, current ASoC is not supporting it so far.
>> Yes, this is a typical TDM use case.
>> __soc_pcm_hw_params() call in soc-pcm.c loops over all CODECs for a
>> given rtd. So is there something else you are referring to which makes
>> ASoC core doesn't support it?
> Oops sorry, I was confused. asymmetry Multi CPU/Codec is supported on
> ASoC / Card2 on for-6.8 branch.
>> Also the binding properties of "audio-graph-card2" seem to be different
>> from "audio-graph-card". I am looking at a simpler extension of existing
>> bindings for Tegra audio without having to re-write the whole bindings.
>> If "remote-endpoint" can take phandle array it would be simpler from DT
>> point of view.
> Yes, "card2" and "card" are similar but different.
> I'm not DT-man, but I think remote-endpoint phandle array is not allowed ?

Yes, it is not allowed and there is DTC error. Exploring if there is an 
extension possible to allow phandle array.

> If my understanding was correct, you need to use multi endpoint in such
> case instead of phandle array.
>
> CPU
>          port {
>                  cpu_endpoint0: endpoint@0 { remote-endpoint = <&codec1_endpoint>; };
>                  cpu_endpoint1: endpoint@1 { remote-endpoint = <&codec2_endpoint>; };
>          };
>
> Codec1
>          port {
>                  codec1_endpoint: endpoint { remote-endpoint = <&cpu_endpoint0>; };
>          };
>
> Codec2
>          port {
>                  codec2_endpoint: endpoint { remote-endpoint = <&cpu_endpoint1>; };
>          };
>

This is a workaround. Note that CPU endpoint@1 doesn't exist and a dummy 
endpoint needs to be created. Like I mentioned in previous replies, the 
number of dummy endpoints that need to be created depends on how many 
CODECs user want to connect and it doesn't look scalable.