Re: [PATCH 1/2] ARM: Dove: Add the audio devices in DT

From: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>
To: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Cc: Jean-Francois Moine <moinejf@free.fr>,
	Mark Rutland <mark.rutland@arm.com>,
	devicetree@vger.kernel.org, Russell King <linux@arm.linux.org.uk>,
	Jason Cooper <jason@lakedaemon.net>,
	Pawel Moll <pawel.moll@arm.com>,
	Stephen Warren <swarren@wwwdotorg.org>,
	linux-kernel@vger.kernel.org,
	Rob Herring <rob.herring@calxeda.com>,
	Gregory CLEMENT <gregory.clement@free-electrons.com>,
	linux-arm-kernel@lists.infradead.org,
	Ian Campbell <ian.campbell@citrix.com>
Subject: Re: [PATCH 1/2] ARM: Dove: Add the audio devices in DT
Date: Wed, 28 Aug 2013 14:16:32 +0200	[thread overview]
Message-ID: <521DEA20.8020103@gmail.com> (raw)
In-Reply-To: <20130828135827.2307c89e@skate>

On 08/28/13 13:58, Thomas Petazzoni wrote:
> On Wed, 28 Aug 2013 13:44:51 +0200, Sebastian Hesselbarth wrote:
>>>> Also, we'll need to distinguish between the different audio controllers
>>>> on a single SoC, i.e. i2s0 and i2s1. I suggest checking the (phys) reg
>>>> base passed.
>>>
>>> For what reason does the driver needs to know whether it's the instance
>>> 0 or instance 1 ? If it's needed for some specific reason, then there
>>> should probably be something like marvell,i2s-channel-id = <0> and
>>> marvell,i2s-channel-id = <1>.
>>
>> On Dove, audio1 has SPDIF out, audio0 hasn't. Russell also mentioned to
>> get rid of "i2s" and use "audio" instead. Most SoC's controllers are
>> i2s only but as soon as SPDIF comes into play, it is a different
>> interface protocol.
>>
>> I am fine with having a "marvell,channel-id" (no "i2s") to discriminate
>> the instances, although reg offset should be sufficient.
>
> Well, the reg offset is a possibility, but it's not really nice, and
> would have to be adapted to each and every SoC even if the reset of the
> audio IP is the same.
>
> Though, if the difference between the two units is the availability of
> SPDIF support, then we shouldn't encode the channel number, but instead
> the availability of SPDIF, i.e:
>
> 	audio0 {
> 		reg = <... ...>;
> 		compatible = "marvell,kirkwood-audio";
> 		marvell,has-spdif;

Agree, if you make it "marvell,has-spdif-in" and "marvell,has-spdif-out"
Dove has either i2s-only or i2s+spdifo, kirkwood has i2s+spdifo+spdifi
for the one audio controller available. Can't tell for Armada 370.

BTW, you might have followed some of the DT discussions with Mark
before; as he insists on having a separate sound card node, he might
argue that above property should be part of that node instead.

Last patch discussion [1] I followed on some spdif sound nodes, took the
patch up to v11 or so. Mainly, because the author updated it too
quickly, but looks like audio bindings are (still) worth a lot of
discussion.

[1] http://comments.gmane.org/gmane.linux.alsa.devel/112004

Sebastian

> 	};
>
> 	audio1 {
> 		reg = <... ...>;
> 		compatible = "marvell,kirkwood-audio";
> 	};