linux-kernel - Re: [alsa-devel] [PATCH 0/2] Graph fixes for using multiple endpoints per port

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Date:   12 Dec 2018 15:51:56 +0900
From:   Kuninori Morimoto <kuninori.morimoto.gx@...esas.com>
To:     Tony Lindgren <tony@...mide.com>
Cc:     "alsa-devel@...a-project.org" <alsa-devel@...a-project.org>,
        "linux-omap@...r.kernel.org" <linux-omap@...r.kernel.org>,
        Liam Girdwood <lgirdwood@...il.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Takashi Iwai <tiwai@...e.com>,
        Peter Ujfalusi <peter.ujfalusi@...com>,
        Mark Brown <broonie@...nel.org>,
        Sebastian Reichel <sre@...nel.org>,
        Jarkko Nikula <jarkko.nikula@...mer.com>
Subject: Re: [alsa-devel] [PATCH 0/2] Graph fixes for using multiple    endpoints per port


Hi Tony, again

> > > 	https://patchwork.kernel.org/patch/10712877/
> > 
> > Hmm, so do you have multiple separate ports at the "&sound" node
> > hardware? If so then yeah multiple ports make sense.
> >
> > But if you only a single physical (I2S?) port at the
> > "&sound" node hardware, then IMO you should only have one
> > port and multiple endpoints there according to the graph.txt
> > binding doc.
> > 
> > In my McBSP case there is only a single physical I2S port
> > that can be TDM split into timeslots.
> 
> Mine has 4 DAIs. Each DAI can output 2ch.
> These will be merged and wil be 8ch TDM and goes to Codec.
> But hmm.. it is 4 DAIs, but 1 "physical" interface...
> 
> So, your patch seems correct, but will breaks DPCM...
> I will confirm it.

I thought "port" = "DAI", but yeah, "port" = "physical interface".
Then, my issue is that we can't judge DAI size from DT.
For example, MIXer case, 2 CPU DAIs are connected to 1 Codec.

	DAI0 --- CPU --- Codec
	DAI1 /

In this case, CPU side needs 2 DAIs,
Codec side needs 1 DAI only.
For both CPU/Codec case, OF graph will be like below,
and we can't judge DAIs size from this.

	port {
		ep0: endpint@0 {
			remote-endpoint = <xxx>;
		};
		ep1: endpint@1 {
			remote-endpoint = <xxx>;
		};
	}

To solve this issue, we need to use "reg" for it.
Then, we can get correct DAI ID.

	/* CPU has 2 DAIs */
	CPU {
		port {
			ep0: endpint@0 {
				reg = <0>;
				remote-endpoint = <xxx>;
			};
			ep1: endpint@1 {
				reg = <1>;
				remote-endpoint = <xxx>;
			};
		};
	}

	/* Codec has 1 DAI */
	Codec {
		port {
			reg = <0>;
			ep0: endpint@0 {
				remote-endpoint = <xxx>;
			};
			ep1: endpint@1 {
				remote-endpoint = <xxx>;
			};
		};
	}


Can you agree this ? we need extra patch,
but it can solve your / my problem.

Now I'm posting patches to merging
"audio-graph-card" and "DPCM ver audio-graph-card".
If you are OK, I will include above solution patch
to this patch-set.

Current audio-graph doesn't expect your use-case,
and I want to avoid conflict.

So, "merged" audio-graph should solve your use-case.
If you can agree about this, I will post patch-set.

Best regards
---
Kuninori Morimoto