linux-kernel - Re: [alsa-devel] [PATCH] ASoC: soc-pcm: Use delay set in pointer function

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Message-ID: <20180731135115.GD5719@sirena.org.uk>
Date:   Tue, 31 Jul 2018 14:51:15 +0100
From:   Mark Brown <broonie@...nel.org>
To:     Takashi Iwai <tiwai@...e.de>
Cc:     "Agrawal, Akshu" <Akshu.Agrawal@....com>,
        Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>,
        "moderated list:SOUND - SOC LAYER / DYNAMIC AUDIO POWER MANAGEM..." 
        <alsa-devel@...a-project.org>, Alexander.Deucher@....com,
        djkurtz@...omium.org, Liam Girdwood <lgirdwood@...il.com>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [alsa-devel] [PATCH] ASoC: soc-pcm: Use delay set in pointer
 function

On Tue, Jul 31, 2018 at 03:29:35PM +0200, Takashi Iwai wrote:
> Mark Brown wrote:

> > > > However since it's not supposed to be providing any DMA a CPU DAI really
> > > > shouldn't be doing this...

> > > Well, if so, the CPU dai also cannot get the exact base delay
> > > corresponding to the reported position, either, no?

> > It can know how much delay it's adding internally between its input and
> > output, which feeds into the overall delay experienced by the user.

> But isn't it merely the additional delay that should be applied on top
> of the existing runtime->delay?

Yes.  I'm saying that if the CPU DAI thinks it can figure out the base
delay something is confused.

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