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

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Date:	Wed, 14 Jan 2015 11:46:58 +0100
From:	Philipp Zabel <p.zabel@...gutronix.de>
To:	Russell King - ARM Linux <linux@....linux.org.uk>
Cc:	Jyri Sarha <jsarha@...com>, Jean-Francois Moine <moinejf@...e.fr>,
	Andrew Jackson <Andrew.Jackson@....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

Hi Russell,

thanks for the clarification. 

Am Dienstag, den 13.01.2015, 19:54 +0000 schrieb Russell King - ARM
Linux:
[...]
> To represent that in DT, I would imagine we'd need something like this:
> 
> 	#address-cells = <1>;
> 	#size-cells = <0>;
> 	...
>         port@1 {                        /* AP1,2 = I2S */
> 		#address-cells = <1>;
> 		#size-cells = <0>;
>                 port-type = "i2s";
>                 reg = <0x01>;		/* WS */
>                 tda998x_i2s1: endpoint@2 {
> 			reg = <0x02>;	/* AP1 */
>                         remote-endpoint = <&audio1_i2s>;
>                 };
>                 tda998x_i2s2: endpoint@4 {
> 			reg = <0x04>;	/* AP2 */
>                         remote-endpoint = <&audio2_i2s>;
>                 };
>         };
>
> where audio1_i2s is operating in master mode, and audio2_i2s is
> operating in slave mode for both WS and SCLK.
> 
> If we can agree on that, then I'm happy with the proposed binding.
> (Remember that #address-cells and #size-cells are required in the
> parent where we have reg= in the child.)

So the question is mostly whether four I2S data pins with a single
shared WS/SCK input should be called "four I2S ports with shared clocks"
or "one I2S port with up to four data lanes". I'd lean towards the
latter.

How audio2_i2s is forced to synchronize its clock output to audio1_i2s
is a problem their bindings will have to handle.

regards
Philipp

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