linux-kernel - Re: [PATCH 1/2] ARM: Dove: Add the audio devices in DT

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Date:	Thu, 29 Aug 2013 11:13:03 +0100
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	Jean-Francois Moine <moinejf@...e.fr>
Cc:	Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>,
	Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>,
	Mark Rutland <mark.rutland@....com>,
	devicetree@...r.kernel.org, Jason Cooper <jason@...edaemon.net>,
	Pawel Moll <pawel.moll@....com>,
	Stephen Warren <swarren@...dotorg.org>,
	linux-kernel@...r.kernel.org,
	Rob Herring <rob.herring@...xeda.com>,
	Gregory CLEMENT <gregory.clement@...e-electrons.com>,
	linux-arm-kernel@...ts.infradead.org,
	Ian Campbell <ian.campbell@...rix.com>
Subject: Re: [PATCH 1/2] ARM: Dove: Add the audio devices in DT

On Thu, Aug 29, 2013 at 12:07:04PM +0200, Jean-Francois Moine wrote:
> On Wed, 28 Aug 2013 14:16:32 +0200
> Sebastian Hesselbarth <sebastian.hesselbarth@...il.com> wrote:
> 
> 	[snip]
> > > Though, if the difference between the two units is the availability of
> > > SPDIF support, then we shouldn't encode the channel number, but instead
> > > the availability of SPDIF, i.e:
> > >
> > > 	audio0 {
> > > 		reg = <... ...>;
> > > 		compatible = "marvell,kirkwood-audio";
> > > 		marvell,has-spdif;  
> > 
> > Agree, if you make it "marvell,has-spdif-in" and "marvell,has-spdif-out"
> > Dove has either i2s-only or i2s+spdifo, kirkwood has i2s+spdifo+spdifi
> > for the one audio controller available. Can't tell for Armada 370.
> > 
> > BTW, you might have followed some of the DT discussions with Mark
> > before; as he insists on having a separate sound card node, he might
> > argue that above property should be part of that node instead.
> 
> Yes. For the Cubox, the card will be described by something like:
> 
> 	sound {
> 		compatible = "simple-audio";
> 		audio-controller = <&audio1>;
> 		audio-codec = <&spdif>;
> 		codec-dai-name = "dit-hifi";
> 	};
> 
> with:
> 
> 	spdif: spdif {
>  		compatible = "linux,spdif-dit";
> 	};
> 
> Then, the audio driver will know about s/pdif on the first open.

I can tell that neither of you have taken notice of what I said about
the "has" stuff - it's completely useless to the driver, it conveys no
useful information.

Moreover, the above isn't going to be the answer to this.  With DPCM
you need:

1. two DAI links to be setup:
1a. one to connect the CPU DAI to the dummy codec
1b. one to connect the dummy platform/CPU DAI to the SPDIF codec
2. DAPM routes to connect the CPU DAI audio stream(s) to the Codec stream(s)

If you have both I2S and SPDIF, then you need another DAI link and a
few more DAPM routes.  Even if you have just one codec connected, you
will need this structure so that the CPU DAI knows which audio outputs
are to be enabled.  If no DAPM routes exist, the CPU DAI will not enable
any outputs.

Or at least that's the theory when ASoC DPCM eventually works.
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