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Date:   Mon, 10 Feb 2020 14:37:17 +0000
From:   Mark Brown <broonie@kernel.org>
To:     Peter Ujfalusi <peter.ujfalusi@ti.com>
Cc:     Takashi Iwai <tiwai@suse.de>, lgirdwood@gmail.com, tiwai@suse.com,
        perex@perex.cz, lars@metafoo.de, alsa-devel@alsa-project.org,
        vkoul@kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] ASoC: dmaengine_pcm: Consider DMA cache caused delay in
 pointer callback
Message-ID: <20200210143717.GO7685@sirena.org.uk>
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On Mon, Feb 10, 2020 at 04:28:44PM +0200, Peter Ujfalusi wrote:
> On 10/02/2020 16.21, Takashi Iwai wrote:

> >>  	delay +=3D codec_delay;
> >> =20
> >> -	runtime->delay =3D delay;
> >> +	runtime->delay +=3D delay;

> > Is it correct?
> > delay already takes runtime->delay as its basis, so it'll result in a
> > double.

> The delay here is coming from the DAI and the codec.
> The runtime->delay hold the PCM (DMA) caused delay.

I think Takashi's point here (and a query I have) is that we end up with

	delay =3D runtime->delay;
	delay +=3D stuff;
	runtime->delay +=3D delay;

which is equivalent to

	runtime->delay =3D (runtime->delay * 2) + stuff;

and that's a bit surprising.

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