Re: Query on audio-graph-card DT binding

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 work?

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.