linux-kernel - Re: [PATCH 3/6] ASoC: ux500: Drop pinctrl sleep support

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Date:	Thu, 9 May 2013 10:41:03 +0100
From:	Mark Brown <broonie@...nel.org>
To:	Fabio Baltieri <fabio.baltieri@...aro.org>
Cc:	Liam Girdwood <lgirdwood@...il.com>, alsa-devel@...a-project.org,
	linux-kernel@...r.kernel.org,
	Linus Walleij <linus.walleij@...aro.org>,
	Lee Jones <lee.jones@...aro.org>,
	Ola Lilja <ola.o.lilja@...ricsson.com>
Subject: Re: [PATCH 3/6] ASoC: ux500: Drop pinctrl sleep support

On Wed, May 08, 2013 at 05:48:05PM +0200, Fabio Baltieri wrote:
> On Wed, May 08, 2013 at 03:29:38PM +0100, Mark Brown wrote:

> > So if these pins are being shared between the instances then surely
> > there are other interdependencies that need to be taken care of Is that
> > happening?  For example if the clocks are shared then is the code
> > currently stopping the interfaces being configured with incompatible
> > sample rates or word sizes?

> That's an interesting point.  Mixed format, rate and channel counts
> seems to work just fine, but that's probably because the supported rate
> and format is locked by the codec to 48k + S16_LE.  This is in line with
> what is specified on the ab8500 datasheet:
> 
> ---
> The AB8500 audio module exchanges audio data through the two digital
> interfaces at a fixed 48 kHz rate in different formats with up to 8
> channels per interface.
> ---

That sounds like there's still some potential problems with the channel
count, though?

> On the other side, I don't think anybody is using the ux500 with
> anything else than the ab8500, so I don't even know how would I test and
> fix this.

The fix should simply be a case of setting constraints when opening
additional interfaces based on the configuration of the primary
interface.  You can test this sort of thing by simply verifying that it
doesn't break the existing cases.

> > Well, most things would probably be able to get some small benefit from
> > doing this, it's just that we've not had any real support for managing
> > pin muxing - one of the goals of adding pinctrl is to make it easier to
> > deploy this sort of thing.

> Pin muxing is handled transparently.  The real problem is sleep mode
> switching, but that's really not needed if the codec has a proper low
> power mode.

I'm not following that at all I'm afraid - I don't understand the
relevance of the CODEC?

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