linux-kernel - Re: [alsa-devel] [PATCH 4/4] ASoC: da7213: Improve 32KHz mode PLL locking

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Date:	Fri, 5 Aug 2016 11:30:01 +0100
From:	Mark Brown <broonie@...nel.org>
To:	Peter Meerwald-Stadler <pmeerw@...erw.net>
Cc:	Adam Thomson <Adam.Thomson.Opensource@...semi.com>,
	Liam Girdwood <lgirdwood@...il.com>,
	Jaroslav Kysela <perex@...ex.cz>,
	Takashi Iwai <tiwai@...e.com>, alsa-devel@...a-project.org,
	Support Opensource <support.opensource@...semi.com>,
	linux-kernel@...r.kernel.org, c.huber@...-electronic.com
Subject: Re: [alsa-devel] [PATCH 4/4] ASoC: da7213: Improve 32KHz mode PLL
 locking

On Fri, Aug 05, 2016 at 11:04:51AM +0200, Peter Meerwald-Stadler wrote:

> these registers cannot not found in the datasheet;
> maybe add descriptive #defines in da7213.h

> > +			snd_soc_write(codec, 0xF0, 0x8B);
> > +			snd_soc_write(codec, 0xF2, 0x03);
> > +			snd_soc_write(codec, 0xF0, 0x00);

It is very common for chips to have undocumented write sequences that
make tweaks based on test registers that are deliberately not
documented.  This looks like such a case, I'd imagine that register 0xf0
is a test key and 0xf2 contains a value being tweaked.

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