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

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Date:   Tue, 31 Jul 2018 15:56:52 +0200
From:   Takashi Iwai <tiwai@...e.de>
To:     Mark Brown <broonie@...nel.org>
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, 31 Jul 2018 15:51:15 +0200,
Mark Brown wrote:
> 
> 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.

Then basically Akshu's patch does the correct thing, I suppose.


Takashi