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

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Date:   Wed, 12 Dec 2018 00:12:40 +0000
From:   Kuninori Morimoto <kuninori.morimoto.gx@...esas.com>
To:     Kuninori Morimoto <kuninori.morimoto.gx@...esas.com>
CC:     Tony Lindgren <tony@...mide.com>, Mark Brown <broonie@...nel.org>,
        Liam Girdwood <lgirdwood@...il.com>,
        Jaroslav Kysela <perex@...ex.cz>,
        Takashi Iwai <tiwai@...e.com>,
        "alsa-devel@...a-project.org" <alsa-devel@...a-project.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-omap@...r.kernel.org" <linux-omap@...r.kernel.org>,
        Sebastian Reichel <sre@...nel.org>,
        Jarkko Nikula <jarkko.nikula@...mer.com>,
        Peter Ujfalusi <peter.ujfalusi@...com>
Subject: Re: [PATCH 0/2] Graph fixes for using multiple endpoints per port

Hi Tony, again

> > The issue I have with that it does not then follow the binding doc :)
> > 
> > See this part in Documentation/devicetree/bindings/graph.txt:
> > 
> >  "If a single port is connected to more than one remote device, an
> >  'endpoint' child node must be provided for each link."

My understanding is that 1 "port" is for 1 "physical interface".
In sound case, it is 1 "DAI".
And, 1 "endpoint" is for 1 "connection".

	"If a single port is connected to more than one remote device, an
	'endpoint' child node must be provided for each link."

This meanns, "If 1 DAI (*1) is connected to multiple remote DAIs(*2),
this connection is indicated by multiple "endpoint"" or something like that.

(*2)
DAIA-endpoint---endpoint--\
DAIB-endpoint---endpoint-----DAI (*1)
DAIC-endpoint---endpoint--/

> > Isn't the I2C TDM case the same as "single port connecected to
> > more than one remote device" rather than multiple ports?

I re-checked https://lkml.org/lkml/2018/3/28/405.
Are MDM6600 / OMAP4 CPU portion, and are CPCAP / WL1285 Codec portion ?
Then, it is not yet supported (on ALSA SoC level?).
If my memory was correct, Lars-Peter had some idea for Mux,
But, not yet implemented I think.

audio-graph[-scu] / simple-card[-scu] are supporting DPCM,
but it is for multiple CPU - single Codec.

Best regards
---
Kuninori Morimoto