Re: Query on audio-graph-card DT binding

[Sameer Pujar <spujar@nvidia.com>]

On 09-01-2024 07:47, 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?

> But dummy CPU with Multi-CPU/Codec connection helps you ?
> I'm not 100% sure though...
> See
>          ${LINUX}/sound/soc/generic/audio-graph-card2-custom-sample.dtsi
>
> DT looks like
>
>          [Multi-CPU/Codec]
>                           +-+             +-+
>                  cpu   <--| |<-@--------->| |-> codec1
>                  dummy <--| |             | |-> codec2
>                           +-+             +-+
>
> Use Multi-CPU/Codec connection with dummy.
>
>          audio-graph-card2 {
>                  compatible = "audio-graph-card2";
>                  links = <&mcpu>;
>
>                  multi {
>                          ports@0 {
>                          /* [Multi-CPU] */
>                          mcpu:   port@0 { mcpu0_ep: endpoint { remote-endpoint = <&mcodec0_ep>; }; };
>                                  port@1 { mcpu1_ep: endpoint { remote-endpoint = <&cpu_ep>;     }; };
>                                  port@2 { mcpu2_ep: endpoint { remote-endpoint = <&dummy_ep>;   }; };
>                          };
>
>                          /* [Multi-Codec] */
>                          ports@1 {
>                                  port@0 { mcodec0_ep: endpoint { remote-endpoint = <&mcpu0_ep>;  }; };
>                                  port@1 { mcodec1_ep: endpoint { remote-endpoint = <&codec1_ep>; }; };
>                                  port@2 { mcodec2_ep: endpoint { remote-endpoint = <&codec2_ep>; }; };
>                          };
>                  };
>          };
>
>          test_cpu {
>                  compatible = "test-cpu";
>                  port { dummy_ep: endpoint { remote-endpoint = <&mcpu2_ep>; }; };
>          };

I looked at the 1:N (Semi-Multi) example in the references you shared. 
Seems like this is broken into multiple 1:1 links. Is this correct 
understanding?

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.