linux-kernel - Re: [PATCH] ASoC: arizona: Disable AIF TX/RX before configuring it

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Message-ID: <20140721162448.GD17528@sirena.org.uk>
Date:	Mon, 21 Jul 2014 17:24:48 +0100
From:	Mark Brown <broonie@...nel.org>
To:	Richard Fitzgerald <rf@...nsource.wolfsonmicro.com>
Cc:	Takashi Iwai <tiwai@...e.de>, perex@...ex.cz, lgirdwood@...il.com,
	patches@...nsource.wolfsonmicro.com, alsa-devel@...a-project.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ASoC: arizona: Disable AIF TX/RX before configuring it

On Mon, Jul 21, 2014 at 11:33:27AM +0100, Richard Fitzgerald wrote:
> On Mon, Jul 21, 2014 at 11:04:56AM +0200, Takashi Iwai wrote:
> > Richard Fitzgerald wrote:

> > > The case being fixed is like this:

> > > aplay 48kHz.wav; aplay 96kHz.wav

> > > The second open happens before pmdown_time so the AIF is still enabled.
> > > Writes to the AIF config registers only take effect if the AIF is disabled.
> > > Without this patch, the 96kHz.wav will play at 48kHz

> > If the glitch really matters, the driver can minimize by checking the
> > change of sample rate and doing temporary turn on/off only when
> > required.

> That's a fair point.

The case I was particularly worrying about here was simultaneous
playback and capture - we won't be changing rates here since these
devices currently require symmetry which is enforced via constraints but
we are likely to at least be starting multiple streams close to each
other frequently.

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