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

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Date:	Mon, 12 Jan 2015 18:13:41 +0100
From:	Jean-Francois Moine <moinejf@...e.fr>
To:	Russell King - ARM Linux <linux@....linux.org.uk>
Cc:	Philipp Zabel <p.zabel@...gutronix.de>,
	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, 12 Jan 2015 14:04:56 +0000
Russell King - ARM Linux <linux@....linux.org.uk> wrote:

> On Mon, Jan 12, 2015 at 02:59:57PM +0100, Philipp Zabel wrote:
> > Am Montag, den 12.01.2015, 12:25 +0000 schrieb Russell King - ARM Linux:
> > > 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.

This is not the case in vexpress-v2p-ca15_a7.dts.

> So that's not going to work very well... because the AP register is a
> bitmask.
> 
> I guess we could specify a node unit and reg, which the code otherwise
> ignores, and specify a philipps,ap-mask = property for the audio ports
> instead.

Also, the video and audio ports must be distinguished. They could be
defined in different port groups.

Example from the Cubox:

	video-ports: ports@0 {
		port {
			tda998x_video: endpoint {
				remote-endpoint = <&lcd0_0>;
				nxp,video-port = <0x230145>;
			};
		};
	};
	audio-ports: ports@1 {
		port@0 {			/* AP1 = I2S */
			tda998x_i2s: endpoint@0 {
				remote-endpoint = <&audio1_i2s>;
				nxp,audio-port = <0x03>;
			};
		};
		port@1 {			 /* AP2 = S/PDIF */
			tda998x_spdif: endpoint@1 {
				remote-endpoint = <&audio1_spdif1>;
				nxp,audio-port = <0x04>;
			};
		};
	};

The port type is identified by the bit AP0.

-- 
Ken ar c'hentañ	|	      ** Breizh ha Linux atav! **
Jef		|		http://moinejf.free.fr/
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