Re: [PATCH] ALSA: ASoc: Add regulator support to CS4270 codec driver

[Daniel Mack <daniel@caiaq.de>]

On Mon, Nov 30, 2009 at 04:12:09PM +0000, Mark Brown wrote:
> On Mon, Nov 30, 2009 at 04:57:42PM +0100, Daniel Mack wrote:
> 
> > The current aproach does not work reliably, unfortunately. It turns out
> > that the codec necessarily needs its analogue supply to maintain its
> > state. For all other operations (iow, any of the volatges not applied),
> > it has to be held in reset mode. I did that manually by driving the GPIO
> > directly before, but with the current regulator framework support,
> > that's not possible anymore.
> 
> This is one of the reasons why your previous code looked suspect to me,
> actually - since the CODEC driver had no idea that you'd suspended the
> device it'd do things like try to write volume updates to the device
> while you were keeping the power off.

Yes, I totally agree. It's just that the whole power regulator framework
was new to me, and hence I didn't use and fully understand it. Once you
know what it is designed for, it all makes sense.

> When runtime PM hits in 2.6.33 I intend to try to enable support for it
> in ASoC, it's relatively straightforward I think.  Unfortunately it'll
> end up depending on the platform bus on the relevant platform being
> capable of runtime pm but that should become more widely supported as
> things progress.
> 
> Given this I would suggest doing the same thing the other drivers are
> doing and only turning things off when the device is suspended (either
> via the explicit functions or via set_bias_level()) and then let the
> ASoC core deal with actually doing the suspend - it's probably less
> hassle for you that way.  Converting to use the shared register I/O code
> in soc-cache.c might also help here.

Ok, I'll first post a new version for the regulators again and will care
for the rest later :)

Daniel