Re: [alsa-devel] [PATCH] ASoC: Intel: Atom: read timestamp moved to period_elapsed

[Pierre-Louis Bossart]

On 7/10/19 6:15 PM, Curtis Malainey wrote:
> On Tue, Jul 9, 2019 at 4:45 AM Andy Shevchenko
> <andriy.shevchenko@xxxxxxxxxxxxxxx> wrote:
> > On Mon, Jul 08, 2019 at 09:01:47PM -0700, Alex Levin wrote:
> > > sst_platform_pcm_pointer is called from both snd_pcm_period_elapsed and
> > > from snd_pcm_ioctl. Calling read timestamp results in recalculating
> > > pcm_delay and buffer_ptr (sst_calc_tstamp) which consumes buffers in a
> > > faster rate than intended.
> > > In a tested BSW system with chtrt5650, for a rate of 48000, the
> > > measured rate was sometimes 10 times more than that.
> > > After moving the timestamp read to period elapsed, buffer consumption is
> > > as expected.
> >
> >  From code prospective it looks good. You may take mine
> > Reviewed-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
> >
> > Though I'm not an expert in the area, Pierre and / or Liam should give
> > their blessing.
> Agreed, Liam or Pierre should also give their ok since this is one of
> the closed source firmware drivers.
>
> Reviewed-by: Curtis Malainey <cujomalainey@xxxxxxxxxxxx>

Humm, this first review after my Summer break isn't straightforward.

By moving the timestamp update to the period elapsed event, don't you 
prevent the use of this driver in no-interrupt mode - which I understood 
as the baseline for Chrome?

And I also don't get how this timestamp might lead to 10x speed issues, 
this driver has been around for a number of years and that specific 
error was never seen. What is different in this platform and can this be 
seen e.g. on a Cyan device?


> > > Signed-off-by: Alex Levin <levinale@xxxxxxxxxxxx>
> > > ---
> > >   sound/soc/intel/atom/sst-mfld-platform-pcm.c | 23 +++++++++++++-------
> > >   1 file changed, 15 insertions(+), 8 deletions(-)
> > >
> > > diff --git a/sound/soc/intel/atom/sst-mfld-platform-pcm.c b/sound/soc/intel/atom/sst-mfld-platform-pcm.c
> > > index 0e8b1c5eec88..196af0b30b41 100644
> > > --- a/sound/soc/intel/atom/sst-mfld-platform-pcm.c
> > > +++ b/sound/soc/intel/atom/sst-mfld-platform-pcm.c
> > > @@ -265,16 +265,28 @@ static void sst_period_elapsed(void *arg)
> > >   {
> > >        struct snd_pcm_substream *substream = arg;
> > >        struct sst_runtime_stream *stream;
> > > -     int status;
> > > +     struct snd_soc_pcm_runtime *rtd;
> > > +     int status, ret_val;
> > >
> > >        if (!substream || !substream->runtime)
> > >                return;
> > >        stream = substream->runtime->private_data;
> > >        if (!stream)
> > >                return;
> > > +
> > > +     rtd = substream->private_data;
> > > +     if (!rtd)
> > > +             return;
> > > +
> > >        status = sst_get_stream_status(stream);
> > >        if (status != SST_PLATFORM_RUNNING)
> > >                return;
> > > +
> > > +     ret_val = stream->ops->stream_read_tstamp(sst->dev, &stream->stream_info);
> > > +     if (ret_val) {
> > > +             dev_err(rtd->dev, "stream_read_tstamp err code = %d\n", ret_val);
> > > +             return;
> > > +     }
> > >        snd_pcm_period_elapsed(substream);
> > >   }
> > >
> > > @@ -658,20 +670,15 @@ static snd_pcm_uframes_t sst_platform_pcm_pointer
> > >                        (struct snd_pcm_substream *substream)
> > >   {
> > >        struct sst_runtime_stream *stream;
> > > -     int ret_val, status;
> > > +     int status;
> > >        struct pcm_stream_info *str_info;
> > > -     struct snd_soc_pcm_runtime *rtd = substream->private_data;
> > >
> > >        stream = substream->runtime->private_data;
> > >        status = sst_get_stream_status(stream);
> > >        if (status == SST_PLATFORM_INIT)
> > >                return 0;
> > > +
> > >        str_info = &stream->stream_info;
> > > -     ret_val = stream->ops->stream_read_tstamp(sst->dev, str_info);
> > > -     if (ret_val) {
> > > -             dev_err(rtd->dev, "sst: error code = %d\n", ret_val);
> > > -             return ret_val;
> > > -     }
> > >        substream->runtime->delay = str_info->pcm_delay;
> > >        return str_info->buffer_ptr;
> > >   }
> > > --
> > > 2.22.0.410.gd8fdbe21b5-goog
> >
> > --
> > With Best Regards,
> > Andy Shevchenko
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