linux-kernel - Re: [PATCH] ASoC: soc-compress: Inherit atomicity from DAI link for Compress FE

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Message-ID: <CAEnQRZAj-FW-fCWsyupUDAH4Z2kTf0RL1acivyDHszMuU-75pg@mail.gmail.com>
Date:   Tue, 14 Mar 2023 18:37:20 +0200
From:   Daniel Baluta <daniel.baluta@...il.com>
To:     Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
Cc:     Daniel Baluta <daniel.baluta@....nxp.com>, broonie@...nel.org,
        alsa-devel@...a-project.org, lgirdwood@...il.com,
        kai.vehmanen@...ux.intel.com, ranjani.sridharan@...ux.intel.com,
        linux-kernel@...r.kernel.org, paul.olaru@....com
Subject: Re: [PATCH] ASoC: soc-compress: Inherit atomicity from DAI link for
 Compress FE

On Tue, Mar 14, 2023 at 6:14 PM Pierre-Louis Bossart
<pierre-louis.bossart@...ux.intel.com> wrote:
>
>
>
> On 3/14/23 10:34, Daniel Baluta wrote:
> > From: Daniel Baluta <daniel.baluta@....com>
> >
> > After commit bbf7d3b1c4f40 ("ASoC: soc-pcm: align BE 'atomicity' with
> > that of the FE") BE and FE atomicity must match.
> >
> > In the case of Compress PCM there is a mismatch in atomicity between FE
> > and BE and we get errors like this:
> >
> > [   36.434566]  sai1-wm8960-hifi: dpcm_be_connect: FE is atomic but BE
> > is nonatomic, invalid configuration
>
> Not clear on the 'FE is atomic' in the case of a compressed stream,
> which has to be handled with some sort of IPC, i.e. be nonatomic.
>

'FE is atomic' in this message is printed because this is the default value
of nonatomic field when PCM struct associated for a Compress PCM
struct is allocated.

No one changes 'nonatomic' field for Compress FE until my current patch.

> Also not sure why the FE is not set as nonatomic by the SOF parts?
> If it's needed for PCM, why wouldn't it be needed for compressed data?

FE is not touched for SOF parts. Only BE is set to nonatomic by SOF.

See: sound/soc/topology.c

»       /* Set nonatomic property for FE dai links as their trigger
action involves IPC's */
»       if (!link->no_pcm) {
»       »       link->nonatomic = true;
»       »       return 0;
»       }

FE for PCM is modified by sound/soc/soc-pcm.c

int soc_new_pcm(struct snd_soc_pcm_runtime *rtd, int num)
»       pcm->nonatomic = rtd->dai_link->nonatomic;

So, I guess people assumed that is enough to use RTD dai link to set
pcm->noatomic field
and didn't look at it in SOF.

When FE for Compress PCM is created, we don't use soc_new_pcm but instead
we use snd_pcm_new_internal which doesn't inherit the nonatomic field
of the rtd->dai_link
as Normal PCM does inside soc_pcm_new.

So, my patch makes sure we inherit the nonatomic field from
rtd->dai_link also for Compress PCM
similar with what already happens for Normal PCM.

tl;dr: when creating a Normal PCM pcm->nonatomic is inherited from RTD
DAI link. when creating a
Compress PCM pcm->nonatomic field is not set. This patch makes sure
that for Compres PCM
we also inherit nonatomic from RTD DAI link.

thanks,
Daniel.