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

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Message-ID: <20150112122527.GF12302@n2100.arm.linux.org.uk>
Date:	Mon, 12 Jan 2015 12:25:27 +0000
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	Philipp Zabel <p.zabel@...gutronix.de>
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

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.

-- 
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