On Tue, 2018-07-03 at 17:41 +0200, Takashi Iwai wrote:
> On Tue, 03 Jul 2018 13:22:25 +0200,
> Liam Girdwood wrote:
> >
> > Currently ALSA core blocks userspace for about 10 seconds for PCM R/W IO.
> > This needs to be configurable for modern hardware like DSPs where no
> > pointer update in milliseconds can indicate terminal DSP errors.
> >
> > Add a substream variable to set the wait time in ms. This allows userspace
> > and drivers to recover more quickly from terminal DSP errors.
> >
> > Signed-off-by: Liam Girdwood <liam.r.girdwood@xxxxxxxxxxxxxxx>
> > ---
> >
> > Changes since V1 :-
> > o Remove API method and alow drivers to set directly.
> > o Validate time is driver supplied times.
> >
> > V2 :-
> > o Max wait calc now in ms.
> > o checkpatch.
> >
> > include/sound/pcm.h | 1 +
> > sound/core/pcm_lib.c | 12 +++++++++---
> > 2 files changed, 10 insertions(+), 3 deletions(-)
> >
> > diff --git a/include/sound/pcm.h b/include/sound/pcm.h
> > index e054c583d3b3..fcdf358a25f0 100644
> > --- a/include/sound/pcm.h
> > +++ b/include/sound/pcm.h
> > @@ -462,6 +462,7 @@ struct snd_pcm_substream {
> > /* -- timer section -- */
> > struct snd_timer *timer; /* timer */
> > unsigned timer_running: 1; /* time is running */
> > + long wait_time; /* time in ms for R/W to wait for avail */
> > /* -- next substream -- */
> > struct snd_pcm_substream *next;
> > /* -- linked substreams -- */
> > diff --git a/sound/core/pcm_lib.c b/sound/core/pcm_lib.c
> > index 44b5ae833082..82a41e4d7170 100644
> > --- a/sound/core/pcm_lib.c
> > +++ b/sound/core/pcm_lib.c
> > @@ -1832,12 +1832,18 @@ static int wait_for_avail(struct snd_pcm_substream
> > *substream,
> > if (runtime->no_period_wakeup)
> > wait_time = MAX_SCHEDULE_TIMEOUT;
> > else {
> > - wait_time = 10;
> > + /* use wait time from substream if available */
> > + if (substream->wait_time)
> > + wait_time = substream->wait_time;
> > + else
> > + wait_time = 10 * 1000; /* 10 secs */
> > +
> > if (runtime->rate) {
> > - long t = runtime->period_size * 2 / runtime->rate;
> > + long t = runtime->period_size * 2 /
> > + (runtime->rate / 1000);
> > wait_time = max(t, wait_time);
> > }
> > - wait_time = msecs_to_jiffies(wait_time * 1000);
> > + wait_time = msecs_to_jiffies(wait_time);
>
> I can take the patch as is, but would you like to keep runtime->rate
> max check also in the case with substream->wait_time set?
>
Good point, I was trying to keep the same constraints but it does seem like a
good idea if the driver is setting wait_time then it should be set correctly for
any hw_params. This also gives options to set wait time lower that two periods
too if desired.
> Also, substream->wait_time isn't cleared at each open, right?
> The driver can do it if wants, and the driver can set statically at
> creation time if wants, too.
SOF currently does this at creation time, but I can update this to be more
flexible in hw_params.
I'll send a V4.
Thanks
Liam
>
>
> thanks,
>
> Takashi
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