linux-kernel - Re: [PATCH 2/3] ASoC: tas571x: New driver for TI TAS571x power amplifiers

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Message-ID: <20150424092839.GI22845@sirena.org.uk>
Date:	Fri, 24 Apr 2015 10:28:39 +0100
From:	Mark Brown <broonie@...nel.org>
To:	Kevin Cernekee <cernekee@...omium.org>
Cc:	Liam Girdwood <lgirdwood@...il.com>, dgreid@...omium.org,
	Andrew Bresticker <abrestic@...omium.org>,
	Olof Johansson <olofj@...omium.org>,
	alsa-devel@...a-project.org, devicetree@...r.kernel.org,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Lars-Peter Clausen <lars@...afoo.de>
Subject: Re: [PATCH 2/3] ASoC: tas571x: New driver for TI TAS571x power
 amplifiers

On Thu, Apr 23, 2015 at 05:47:49PM -0700, Kevin Cernekee wrote:

> This is mostly working OK, but regcache_sync() assumes that the
> hardware registers have been reset back to the default values.  The
> "pdn" GPIO doesn't actually reset the state of the tas571x; it just
> makes I2C inaccessible and inhibits audio output.  So if the factory
> default for mute is 0, corner cases like this fail:

...

> Aside from unnecessarily pulsing the reset GPIO when transitioning
> back from SND_SOC_BIAS_OFF or overriding regcache_default_sync(), can
> you think of a way to work around this?

Do you need to work around it?  If the register map is being perserved
you don't need to sync so just don't do it - it's just that the normal
expectation would be that power down would cause the register map to be
reset.

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