linux-kernel - Re: [alsa-devel] [PATCH v3 1/9] ASoC: sun4i-i2s: Adjust regmap settings

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Date:   Wed, 9 Jan 2019 18:49:31 +0000
From:   Mark Brown <broonie@...nel.org>
To:     Chen-Yu Tsai <wens@...e.org>
Cc:     Jonas Karlman <jonas@...boo.se>,
        Code Kipper <codekipper@...il.com>,
        Linux-ALSA <alsa-devel@...a-project.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Liam Girdwood <lgirdwood@...il.com>,
        "Andrea Venturi (pers)" <be17068@...rbole.bo.it>,
        linux-sunxi <linux-sunxi@...glegroups.com>,
        Maxime Ripard <maxime.ripard@...e-electrons.com>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [alsa-devel] [PATCH v3 1/9] ASoC: sun4i-i2s: Adjust regmap
 settings

On Sun, Dec 23, 2018 at 11:16:31AM +0800, Chen-Yu Tsai wrote:

> This sounds like the flush is happening after DMA transfers and/or I2S
> operations have started, disrupting the order of the audio samples. I
> think that might be the case since the regcache is synced sequentially,
> and the FIFO control register is after the enable bits. That would imply
> that the device is taken out of runtime suspend after the .start_capture
> or .start_playback callbacks. Not sure if that's the case, but that would
> mean the bus clocks are still off at this point, and bypassing the cache
> and updating the bits is basically moot.

I would expect that the device needs to be resumed from suspend before
we start actually trying to transfer audio - there is stuff in the ASoC
core which is supposed to have appropriate gets but it's possible
something is going wrong there.

> I think there's something else happening here, but we need to figure it
> out instead of papering over it with something that "just works" but
> we don't know why it works.

I agree.

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