[alsa-devel] [PATCH v9 1/4] drm/i2c: tda998x: Add DT support for audio

[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 at 0 { /* pixel data according to video-ports */
> 		reg = <0x00>;
> 	};
> 	port at 1 { /* AP1: SPDIF0 */
> 		reg = <0x01>;
> 	};
> 	port at 2 { /* AP2: SPDIF1 */
> 		reg = <0x02>;
> 	};
> 	port at 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 at 0 is the video port, and then port at 1..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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