[alsa-devel] [PATCH 7/8] ALSA: pcm: Add card sync_irq field

[Takashi Iwai]

On Tue, 19 Nov 2019 17:36:46 +0100,
Ranjani Sridharan wrote:
> 
> On Tue, 2019-11-19 at 09:24 +0100, Takashi Iwai wrote:
> > On Tue, 19 Nov 2019 08:40:25 +0100,
> > Ranjani Sridharan wrote:
> > > 
> > > > > 
> > > > > Hi Takashi,
> > > > > 
> > > > > I just realized that In the SOF driver, we only set the
> > > > > component
> > > > > driver ops. The pcm ops are set when creating the new pcm. So,
> > > > > should I
> > > > > also add the sync_stop op in the component driver and set the
> > > > > pcm
> > > > > sync_stop op to point to the component sync_stop op? Just
> > > > > wanted to
> > > > > confirm if I am on the right track.
> > > > 
> > > > Yes, I didn't touch this yet, but that's the way to go I suppose.
> > > > One caveat is that this ops is optional and needs NULL as
> > > > default,
> > > > hence you'd need to set only when defined, like copy_user, page
> > > > or
> > > > mmap ops, at least.
> > > 
> > > Hi Takashi,
> > > 
> > > This is what I tried in the SOF driver:
> > > https://github.com/thesofproject/linux/pull/1513/commits
> > > 
> > > And it seems to cause the system to hang when I stop the stream and
> > > I
> > > have no meaningful logs to pinpoint to the problem. Could you
> > > please
> > > have a look at the 4 commits that I have added to your series and
> > > let
> > > me know what I could be missing? 
> > 
> > I couldn't find anything obvious.  Could you try without changing
> > snd_sof_pcm_period_elapsed(), i.e. only adding the stuff and calling
> > sync_stop, in order to see whether the additional stuff broke
> > anything?
> It is indeed the removal of snd_sof_pcm_period_elapsed() that makes the
> device hang when the stream is stoppped. But that's a bit surprising
> given that all I tried was using the snd_pcm_period_elapsed() directly
> instead of scheduling the delayed work to call it.

If I read the code correctly, this can't work irrelevantly from the
sync_stop stuff.  The call of period_elapsed is from
hda_dsp_stream_check() which is performed in bus->reg_lock spinlock in
hda_dsp_stream_threaded_handler().  Meanwhile, the XRUN trigger goes
to hda_dsp_pcm_trigger() that follows hda_dsp_stream_trigger(), and
this function expects the sleepable context due to
snd_sof_dsp_read_poll_timeout() call.

So something like below works?


Takashi

--- a/sound/soc/sof/intel/hda-stream.c
+++ b/sound/soc/sof/intel/hda-stream.c
@@ -592,8 +592,11 @@ static bool hda_dsp_stream_check(struct hdac_bus *bus, u32 status)
 				continue;
 
 			/* Inform ALSA only in case not do that with IPC */
-			if (sof_hda->no_ipc_position)
-				snd_sof_pcm_period_elapsed(s->substream);
+			if (sof_hda->no_ipc_position) {
+				spin_unlock_irq(&bus->reg_lock);
+				snd_pcm_period_elapsed(s->substream);
+				spin_lock_irq(&bus->reg_lock);
+			}
 		}
 	}