linux-kernel - Re: [PATCH 2/3] ASoC: wm8940: Rewrite code to set proper clocks

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Date:   Tue, 7 Jun 2022 14:13:09 +0200
From:   Lukasz Majewski <lukma@...x.de>
To:     Mark Brown <broonie@...nel.org>
Cc:     Liam Girdwood <lgirdwood@...il.com>, linux-kernel@...r.kernel.org,
        patches@...nsource.cirrus.com, alsa-devel@...a-project.org,
        Takashi Iwai <tiwai@...e.com>, Jaroslav Kysela <perex@...ex.cz>
Subject: Re: [PATCH 2/3] ASoC: wm8940: Rewrite code to set proper clocks

Hi Mark,

> On Mon, Jun 06, 2022 at 05:44:40PM +0200, Lukasz Majewski wrote:
> > Without this change, the wm8940 driver is not working when
> > set_sysclk callback (wm8940_set_dai_sysclk) is called with
> > freqency not listed in the switch clause.  
> 
> > This change adjusts this driver to allow non-standard frequency
> > set (just after the boot) being adjusted afterwards by the sound
> > system core code.  
> 
> I don't entirely follow the above - in what way might the core adjust
> the clocking, and why would we want to allow the use of invalid
> clocks? Surely that just makes error checking worse.

Hmm, it is a bit complicated.

When I enabed wm8940 support in mainline - the first call to
wm8940_set_dai_sysclk (the set_sysclk callback) required mclk = 11997070
frequency.

With the current code [1] the initialization of the codec returns
-EINVAL and the codec is not supported in the system:

asoc-simple-card: probe of sound failed with error -22



The approach used in this patch set to fix the above issue is based on
one already present in-tree for wm8974 codec.

> 
> > Code in this commit is based on previous change done for wm8974
> > (SHA1: 51b2bb3f2568e6d9d81a001d38b8d70c2ba4af99).  
> 
> Please include human readable descriptions of things like commits and
> issues being discussed in e-mail in your mails, this makes them much
> easier for humans to read especially when they have no internet
> access. 

Ok, I will add some more verbose description. The aforementioned SHA1
is referring to commit already in-tree, so you would find it easily
even without the Internet.

> I do frequently catch up on my mail on flights or while
> otherwise travelling so this is even more pressing for me than just
> being about making things a bit easier to read.

+1

Links:

[1] -
https://elixir.bootlin.com/linux/v5.18.1/source/sound/soc/codecs/wm8940.c#L614

Best regards,

Lukasz Majewski

--

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Phone: (+49)-8142-66989-59 Fax: (+49)-8142-66989-80 Email: lukma@...x.de

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