| Message ID | 1416476977-20118-1-git-send-email-padma.v@samsung.com (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | b2de1d20a05d8691cb1889c859de2ab56938b82a |
| Headers | show |
Hi, On 11/20/14, Padmavathi Venna <padma.v@samsung.com> wrote: > Cc: Sylwester Nawrocki <s.nawrocki@samsung.com> > Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com> > Signed-off-by: Padmavathi Venna <padma.v@samsung.com> > --- > sound/soc/samsung/i2s.c | 5 +++-- > 1 files changed, 3 insertions(+), 2 deletions(-) > > diff --git a/sound/soc/samsung/i2s.c b/sound/soc/samsung/i2s.c > index 0df6547..e1ace52 100644 > --- a/sound/soc/samsung/i2s.c > +++ b/sound/soc/samsung/i2s.c > @@ -494,7 +494,7 @@ static int i2s_set_sysclk(struct snd_soc_dai *dai, > if (dir == SND_SOC_CLOCK_IN) > mod |= 1 << i2s_regs->cdclkcon_off; > else > - mod &= 0 << i2s_regs->cdclkcon_off; > + mod &= ~(1 << i2s_regs->cdclkcon_off); > > i2s->rfs = rfs; > break; > @@ -551,10 +551,11 @@ static int i2s_set_sysclk(struct snd_soc_dai *dai, > } > > if (clk_id == 0) > - mod &= 0 << i2s_regs->rclksrc_off; > + mod &= ~(1 << i2s_regs->rclksrc_off); > else > mod |= 1 << i2s_regs->rclksrc_off; > > + break; > default: > dev_err(&i2s->pdev->dev, "We don't serve that!\n"); > return -EINVAL; > -- > 1.7.4.4 > Please ignore this patch as subject line is not proper. Thanks Padma > _______________________________________________ > Alsa-devel mailing list > Alsa-devel@alsa-project.org > http://mailman.alsa-project.org/mailman/listinfo/alsa-devel >
I was trying to find a bug in the timestamping logic I am working on and after some time I realized the USB audio class driver seems to have an issue. If I instrument the code in sound/usb/pcm.c, I see a offset of up to 6ms between the snd_usb_substream_playback_trigger and prepare_playback_urb steps [45053.102625] trigger_start [45053.108320] prepare_playback_urb My understanding is that empty URBs are submitted in the prepare step to avoid underflows, which is fine. The problem with that is that the trigger_tstamp value is captured before audio transfers actually start and there is a constant offset when trying to track audio/system time drifts or do basic a/v sync. Any suggestions on how to fix this? I can't figure out if this is an off-by-one error or another bug. Feedback welcome. -Pierre
Pierre-Louis Bossart wrote: > I was trying to find a bug in the timestamping logic I am working on > and after some time I realized the USB audio class driver seems to > have an issue. > If I instrument the code in sound/usb/pcm.c, I see a offset of up to > 6ms between the snd_usb_substream_playback_trigger and > prepare_playback_urb steps > > [45053.102625] trigger_start > [45053.108320] prepare_playback_urb > > My understanding is that empty URBs are submitted in the prepare step > to avoid underflows, which is fine. The problem with that is that the > trigger_tstamp value is captured before audio transfers actually start > and there is a constant offset when trying to track audio/system time > drifts or do basic a/v sync. Most other devices have a FIFO that gets filled quickly when the stream is started. This results in a small offset in the opposite direction. AFAICS you cannot avoid having an offset when trying to relate the trigger_tstamp value to the sample clock. Regards, Clemens
diff --git a/sound/soc/samsung/i2s.c b/sound/soc/samsung/i2s.c index 0df6547..e1ace52 100644 --- a/sound/soc/samsung/i2s.c +++ b/sound/soc/samsung/i2s.c @@ -494,7 +494,7 @@ static int i2s_set_sysclk(struct snd_soc_dai *dai, if (dir == SND_SOC_CLOCK_IN) mod |= 1 << i2s_regs->cdclkcon_off; else - mod &= 0 << i2s_regs->cdclkcon_off; + mod &= ~(1 << i2s_regs->cdclkcon_off); i2s->rfs = rfs; break; @@ -551,10 +551,11 @@ static int i2s_set_sysclk(struct snd_soc_dai *dai, } if (clk_id == 0) - mod &= 0 << i2s_regs->rclksrc_off; + mod &= ~(1 << i2s_regs->rclksrc_off); else mod |= 1 << i2s_regs->rclksrc_off; + break; default: dev_err(&i2s->pdev->dev, "We don't serve that!\n"); return -EINVAL;