linux-kernel - RE: [PATCH v2 3/7] ASoC: pcm512x: Change register default to match actual content after reset

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Date:	Wed, 28 Jan 2015 20:42:06 +0000
From:	Peter Rosin <peda@...ntia.se>
To:	Mark Brown <broonie@...nel.org>, Peter Rosin <peda@...ator.liu.se>
CC:	"alsa-devel@...a-project.org" <alsa-devel@...a-project.org>,
	Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	"Kumar Gala" <galak@...eaurora.org>,
	Jaroslav Kysela <perex@...ex.cz>, Takashi Iwai <tiwai@...e.de>,
	Liam Girdwood <lgirdwood@...il.com>,
	Clemens Ladisch <clemens@...isch.de>,
	Lars-Peter Clausen <lars@...afoo.de>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v2 3/7] ASoC: pcm512x: Change register default to match
 actual content after reset

Hi Mark,

First of all, thanks for taking the rest of the series!

Mark Brown wrote:
> On Wed, Jan 28, 2015 at 03:16:08PM +0100, Peter Rosin wrote:
> 
> > @@ -78,7 +78,7 @@ static const struct reg_default
> pcm512x_reg_defaults[] = {
> >  	{ PCM512x_DIGITAL_VOLUME_2,  0x30 },
> >  	{ PCM512x_DIGITAL_VOLUME_3,  0x30 },
> >  	{ PCM512x_DIGITAL_MUTE_1,    0x22 },
> > -	{ PCM512x_DIGITAL_MUTE_2,    0x00 },
> > +	{ PCM512x_DIGITAL_MUTE_2,    0x02 },
> 
> The datasheet claims these have undefined values as reserved bits - what
> would be a more robust change here would be to remove the register
> default entirely so that we take the value the hardware has, giving
> robustness against any hardware revisions.  Of course the device has rather a
> lot of such reserved bits which is unfortunate.

Given the incompleteness of the datasheets this might be safest; a lot
of the reserved areas appear to have undocumented functions. But it
works as is of course, so it is not high priority... I don't know what happens
when this particular bit is cleared, but it doesn't change anything for the
pcm5142 that I am able to detect. So, no real problem with dropping 3/7.

Cheers,
Peter

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