Re: [alsa-devel] [PATCH] ALSA: pcm - introduce soc_delay

At Mon, 23 Jul 2012 15:36:37 +0530, Vinod Koul wrote:

In many modern SoCs the audio DSP can buffer the PCM ring buffer data. Today we have no means to represent this buffering and ALSA wrongly detects an overrun when hw_ptr reaches app_ptr value, though DSP may still have some buffered data.

This patch tries to add a new field "soc_delay" to represent buffering done in DSPs. This value is also used for the xrun calculations in ALSA.

Signed-off-by: Vinod Koul vinod.koul@linux.intel.com

-- Once we are okay with this approach, I will send a follow up patch which adds this notion in ASoC and uses this to compute cpu_dai delay. The codec_dai delay along with FIFO delay from cpu_dai should be added and reresented by today's notion of delay.

Hmm, it's confusing to have both delay and soc_delay fields.

And, if the XRUN detection is the only problem, we can provide a flag to correct avail with runtime->delay.

---

include/sound/pcm.h | 1 + sound/core/pcm_lib.c | 14 +++++++++++--- sound/core/pcm_native.c | 6 +++--- 3 files changed, 15 insertions(+), 6 deletions(-)

diff --git a/include/sound/pcm.h b/include/sound/pcm.h index a55d5db..405deb7 100644 --- a/include/sound/pcm.h +++ b/include/sound/pcm.h @@ -281,6 +281,7 @@ struct snd_pcm_runtime { unsigned long hw_ptr_jiffies; /* Time when hw_ptr is updated */ unsigned long hw_ptr_buffer_jiffies; /* buffer time in jiffies */ snd_pcm_sframes_t delay; /* extra delay; typically FIFO size */

• snd_pcm_sframes_t soc_delay; /* extra delay; typically delay incurred in soc */

  /* -- HW params -- */ snd_pcm_access_t access; /* access mode */

diff --git a/sound/core/pcm_lib.c b/sound/core/pcm_lib.c index 8f312fa..4977012 100644 --- a/sound/core/pcm_lib.c +++ b/sound/core/pcm_lib.c @@ -292,7 +292,15 @@ int snd_pcm_update_state(struct snd_pcm_substream *substream, return -EPIPE; } } else {

• if (avail >= runtime->stop_threshold) {
  

• snd_pcm_uframes_t actual_avail;
  

• if (avail < runtime->soc_delay)
  

• 	actual_avail = avail;
  

• else
  

• 	actual_avail = avail - runtime->soc_delay;
  

• if (actual_avail  >= runtime->stop_threshold) {
  

• 	snd_printd(KERN_ERR  "avail > stop_threshold!!\n");
  

• 	snd_printd(KERN_ERR  "actual_avail %ld, avail %ld, soc_delay %ld!!\n",
  

• 			actual_avail, avail,  runtime->soc_delay);
  

Don't add debug prints here. This is no kernel error, and XRUN is already informed in xrun() function.

thanks,

Takashi

	xrun(substream);
	return -EPIPE;
}

@@ -440,9 +448,9 @@ static int snd_pcm_update_hw_ptr0(struct snd_pcm_substream *substream, if (runtime->hw.info & SNDRV_PCM_INFO_BATCH) goto no_jiffies_check; hdelta = delta;

• if (hdelta < runtime->delay)

• if (hdelta < (runtime->delay + runtime->soc_delay)) goto no_jiffies_check;

• hdelta -= runtime->delay;

• hdelta -= (runtime->delay + runtime->soc_delay); jdelta = curr_jiffies - runtime->hw_ptr_jiffies; if (((hdelta * HZ) / runtime->rate) > jdelta + HZ/100) { delta = jdelta /

diff --git a/sound/core/pcm_native.c b/sound/core/pcm_native.c index 53b5ada..fc2d664 100644 --- a/sound/core/pcm_native.c +++ b/sound/core/pcm_native.c @@ -606,13 +606,13 @@ int snd_pcm_status(struct snd_pcm_substream *substream, if (runtime->status->state == SNDRV_PCM_STATE_RUNNING || runtime->status->state == SNDRV_PCM_STATE_DRAINING) { status->delay = runtime->buffer_size - status->avail;

• 	status->delay += runtime->delay;
  

• 	status->delay += runtime->delay + runtime->soc_delay;
  

  } else status->delay = 0; } else { status->avail = snd_pcm_capture_avail(runtime); if (runtime->status->state == SNDRV_PCM_STATE_RUNNING)

• 	status->delay = status->avail + runtime->delay;
  

• 	status->delay = status->avail + runtime->delay + runtime->soc_delay;
  

  else status->delay = 0; }

@@ -2442,7 +2442,7 @@ static int snd_pcm_delay(struct snd_pcm_substream *substream, n = snd_pcm_playback_hw_avail(runtime); else n = snd_pcm_capture_avail(runtime);

• n += runtime->delay;
  

• n += runtime->delay + runtime->soc_delay;
  

  break; case SNDRV_PCM_STATE_XRUN: err = -EPIPE;

-- 1.7.0.4