linux-kernel - Re: [PATCH v9 1/4] drm/i2c: tda998x: Add DT support for audio

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Date:	Mon, 12 Jan 2015 14:59:57 +0100
From:	Philipp Zabel <p.zabel@...gutronix.de>
To:	Russell King - ARM Linux <linux@....linux.org.uk>
Cc:	Jean-Francois Moine <moinejf@...e.fr>,
	Andrew Jackson <Andrew.Jackson@....com>,
	Jyri Sarha <jsarha@...com>, Mark Brown <broonie@...nel.org>,
	Dave Airlie <airlied@...il.com>,
	"alsa-devel@...a-project.org" <alsa-devel@...a-project.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v9 1/4] drm/i2c: tda998x: Add DT support for audio

Am Montag, den 12.01.2015, 12:25 +0000 schrieb Russell King - ARM Linux:
> On Mon, Jan 12, 2015 at 10:25:28AM +0100, Philipp Zabel wrote:
> > Jean-Francois' reply already reflects this, but the 'port' nodes should
> > correspond to physical ports of the device if possible. If you can
> > configure the device to have dedicated input pins for I2S, SPDIF0, and
> > SPDIF1 at the same time, they should appear in the device tree as
> > separate ports:
> > 
> > tda998x: hdmi-encoder {
> > 	port@0 { /* pixel data according to video-ports */
> > 		reg = <0x00>;
> > 	};
> > 	port@1 { /* AP1: SPDIF0 */
> > 		reg = <0x01>;
> > 	};
> > 	port@2 { /* AP2: SPDIF1 */
> > 		reg = <0x02>;
> > 	};
> > 	port@3 { /* AP3: I2S */
> > 		reg = <0x03>;
> > 	};
> > };
> > 
> > The tda998x binding would define how the ports are numbered, some
> > correspondence to the AP pin numbers would be good.
> 
> It's not quite that simple, because the SPDIF AP pins are multiplexed
> with the I2S pins - and there is variation between chip models and
> packages.
>
> So, it's probably best if port@0 is the video port, and then port@...n
> can describe the audio inputs, including a property which specifies
> whether they are I2S or SPDIF, and the value to be programmed into
> the AP enable register (which is a bit field of the AP pins which
> should be unmasked.)  I guess we can re-use the reg= property for that
> value, since video will always be zero.

Note that of_graph_parse_endpoint interprets the port node's reg
property as port id. And the unit address part of the node name should
match the first address in the reg property.

regards
Philipp

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