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

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Date:   Tue, 11 Dec 2018 16:19:50 -0800
From:   Tony Lindgren <tony@...mide.com>
To:     Kuninori Morimoto <kuninori.morimoto.gx@...esas.com>
Cc:     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

* Kuninori Morimoto <kuninori.morimoto.gx@...esas.com> [181211 23:16]:
> 
> Hi Tony
> 
> > 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."
> > 
> > Isn't the I2C TDM case the same as "single port connecected to
> > more than one remote device" rather than multiple ports?
> > 
> > To me it seems we're currently only handling the multiple ports
> > case, and not multiple endpoints for a port. Other than fixing
> > that, things should work just as earlier with my two patches.
> > That is unless I accidentally broke something.
> > 
> > So just trying to correct the binding usage. Or am I missing
> > something?
> 
> I'm not 100% sure your "I2C TDM case", but you can check
> multi-endpoint sample on "Example: Multi DAI with DPCM" below.
> "pcm3168a" is using multi-endpoint.
> Does this help you ?
> 
> 	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.

Regards,

Tony