From: Vinod Koul <vkoul@kernel.org>
To: Jaroslav Kysela <perex@perex.cz>
Cc: Charles Keepax <ckeepax@opensource.cirrus.com>,
alsa-devel@alsa-project.org, broonie@kernel.org,
Srinivas Kandagatla <srinivas.kandagatla@linaro.org>,
tiwai@suse.com, linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH] ALSA: compress: Fix gapless playback state machine
Date: Thu, 11 Jun 2020 16:32:28 +0530 [thread overview]
Message-ID: <20200611110228.GC1393454@vkoul-mobl> (raw)
In-Reply-To: <8bba7e36-af15-33ac-bfc7-d436030f08b7@perex.cz>
On 11-06-20, 12:40, Jaroslav Kysela wrote:
> Dne 11. 06. 20 v 11:44 Vinod Koul napsal(a):
> > On 11-06-20, 11:09, Jaroslav Kysela wrote:
> > > Dne 11. 06. 20 v 10:46 Charles Keepax napsal(a):
> > > > On Wed, Jun 10, 2020 at 04:28:20PM +0530, Vinod Koul wrote:
> > > > > On 10-06-20, 12:40, Jaroslav Kysela wrote:
> > > > > > Dne 10. 06. 20 v 12:07 Srinivas Kandagatla napsal(a):
> > > > > > > For gapless playback call to snd_compr_drain_notify() after
> > > > > > > partial drain should put the state to SNDRV_PCM_STATE_RUNNING
> > > > > > > rather than SNDRV_PCM_STATE_SETUP as the driver is ready to
> > > > > > > process the buffers for new track.
> > > > > > >
> > > > > > > With existing code, if we are playing 3 tracks in gapless, after
> > > > > > > partial drain finished on previous track 1 the state is set to
> > > > > > > SNDRV_PCM_STATE_SETUP which is then moved to SNDRV_PCM_STATE_PREPARED
> > > > > > > after data write. With this state calls to snd_compr_next_track() and
> > > > > > > few other calls will fail as they expect the state to be in
> > > > > > > SNDRV_PCM_STATE_RUNNING.
> > > > > > >
> > > > > > > Here is the sequence of events and state transitions:
> > > > > > >
> > > > > > > 1. set_params (Track 1), state = SNDRV_PCM_STATE_SETUP
> > > > > > > 2. set_metadata (Track 1), no state change, state = SNDRV_PCM_STATE_SETUP
> > > > > > > 3. fill and trigger start (Track 1), state = SNDRV_PCM_STATE_RUNNING
> > > > > > > 4. set_next_track (Track 2), state = SNDRV_PCM_STATE_RUNNING
> > > > > > > 5. partial_drain (Track 1), state = SNDRV_PCM_STATE_SETUP
> > > > > > > 6 snd_compr_drain_notify (Track 1), state = SNDRV_PCM_STATE_SETUP
> > > > > > > 7. fill data (Track 2), state = SNDRV_PCM_STATE_PREPARED
> > > > > > > 8. set_metadata (Track 3), no state change, state = SNDRV_PCM_STATE_PREPARED
> > > > > > > 9. set_next_track (Track 3), !! FAILURE as state != SNDRV_PCM_STATE_RUNNING
> > > > > >
> > > > > >
> > > > > > The snd_compr_drain_notify() is called only from snd_compr_stop(). Something
> > > > > > is missing in this sequence?
> > > > >
> > > > > It is supposed to be invoked by driver when partial drain is complete..
> > > > > both intel and sprd driver are calling this. snd_compr_stop is stop
> > > > > while draining case so legit
> > > > >
> > > >
> > > > Not sure I follow this statement, could you elaborate a bit?
> > > > snd_compr_stop putting the state to RUNNING seems fundamentally
> > > > broken to me, the whole point of snd_compr_stop is to take the
> > > > state out of RUNNING.
> > >
> > > Yes. I agree. It seems that the acknowledge for the partial drain should be
> > > handled differently.
> >
> > Yeah sorry I overlooked that case and was thinking of it being invoked
> > from driver!
> >
> > Yes this would make the snd_compr_stop() behave incorrectly.. so this
> > cant be done as proposed.
> >
> > But we still need to set the draining stream state properly and I am
> > thinking below now:
> >
> > diff --git a/sound/core/compress_offload.c b/sound/core/compress_offload.c
> > index 509290f2efa8..9aba851732d7 100644
> > --- a/sound/core/compress_offload.c
> > +++ b/sound/core/compress_offload.c
> > @@ -929,7 +929,9 @@ static int snd_compr_partial_drain(struct snd_compr_stream *stream)
> > }
> > stream->next_track = false;
> > - return snd_compress_wait_for_drain(stream);
> > + retval = snd_compress_wait_for_drain(stream);
> > + stream->runtime->state = SNDRV_PCM_STATE_RUNNING;
> > + return retval;
> > }
>
> I see a race possibility when the last track is too small and the driver
> signals the end-of-track twice. In this case the partial drain should not
> end with the running state. It would be probably better to separate partial
> / last track acknowledgements.
I completely agree that we should have separate acknowledgements here,
and going to rethink all state transitions for gapless here..
Thanks for the help
--
~Vinod
next prev parent reply other threads:[~2020-06-11 11:03 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-10 10:07 [RFC PATCH] ALSA: compress: Fix gapless playback state machine Srinivas Kandagatla
2020-06-10 10:40 ` Jaroslav Kysela
2020-06-10 10:56 ` Srinivas Kandagatla
2020-06-10 10:58 ` Vinod Koul
2020-06-11 8:46 ` Charles Keepax
2020-06-11 9:09 ` Jaroslav Kysela
2020-06-11 9:44 ` Vinod Koul
2020-06-11 10:40 ` Jaroslav Kysela
2020-06-11 11:02 ` Vinod Koul [this message]
2020-06-11 10:42 ` Charles Keepax
2020-06-11 11:05 ` Vinod Koul
2020-06-10 12:56 ` Pierre-Louis Bossart
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20200611110228.GC1393454@vkoul-mobl \
--to=vkoul@kernel.org \
--cc=alsa-devel@alsa-project.org \
--cc=broonie@kernel.org \
--cc=ckeepax@opensource.cirrus.com \
--cc=linux-kernel@vger.kernel.org \
--cc=perex@perex.cz \
--cc=srinivas.kandagatla@linaro.org \
--cc=tiwai@suse.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).