Re: [alsa-devel] [PATCH v2 1/3] ALSA: core: keep track of boundary wrap-around

At Mon, 8 Oct 2012 12:11:56 -0500, Pierre-Louis Bossart wrote:

Keep track of boundary crossing when hw_ptr exceeds boundary limit and wraps-around. This will help keep track of total number of frames played/received at the kernel level

Signed-off-by: Pierre-Louis Bossart pierre-louis.bossart@linux.intel.com

include/sound/pcm.h | 1 + sound/core/pcm_lib.c | 26 +++++++++++++++++++++----- 2 files changed, 22 insertions(+), 5 deletions(-)

diff --git a/include/sound/pcm.h b/include/sound/pcm.h index cdca2ab..ba13e0b 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 */

• u64 hw_ptr_wrap; /* offset for hw_ptr due to boundary wrap-around */

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

diff --git a/sound/core/pcm_lib.c b/sound/core/pcm_lib.c index 7ae6719..ec996ca 100644 --- a/sound/core/pcm_lib.c +++ b/sound/core/pcm_lib.c @@ -315,6 +315,7 @@ static int snd_pcm_update_hw_ptr0(struct snd_pcm_substream *substream, unsigned long jdelta; unsigned long curr_jiffies; struct timespec curr_tstamp;

• int crossed_boundary = 0;

  old_hw_ptr = runtime->status->hw_ptr;

@@ -359,8 +360,10 @@ static int snd_pcm_update_hw_ptr0(struct snd_pcm_substream *substream, hdelta = curr_jiffies - runtime->hw_ptr_jiffies; if (hdelta > runtime->hw_ptr_buffer_jiffies/2) { hw_base += runtime->buffer_size;

• 		if (hw_base >= runtime->boundary)
  

• 		if (hw_base >= runtime->boundary) {
  		hw_base = 0;
  

• 			crossed_boundary++;
  

• 		}
  	new_hw_ptr = hw_base + pos;
  	goto __delta;
  }
  

@@ -370,8 +373,10 @@ static int snd_pcm_update_hw_ptr0(struct snd_pcm_substream *substream, /* pointer crosses the end of the ring buffer */ if (new_hw_ptr < old_hw_ptr) { hw_base += runtime->buffer_size;

• if (hw_base >= runtime->boundary)
  

• if (hw_base >= runtime->boundary) {
  hw_base = 0;
  

• 	crossed_boundary++;
  

• }
  

  new_hw_ptr = hw_base + pos; } __delta:

@@ -409,8 +414,10 @@ static int snd_pcm_update_hw_ptr0(struct snd_pcm_substream *substream, while (hdelta > xrun_threshold) { delta += runtime->buffer_size; hw_base += runtime->buffer_size;

• 	if (hw_base >= runtime->boundary)
  

• 	if (hw_base >= runtime->boundary) {
  	hw_base = 0;
  

• 		crossed_boundary++;
  

• 	}
  new_hw_ptr = hw_base + pos;
  hdelta -= runtime->hw_ptr_buffer_jiffies;
  

  }

@@ -455,8 +462,10 @@ static int snd_pcm_update_hw_ptr0(struct snd_pcm_substream *substream, /* the delta value is small or zero in most cases */ while (delta > 0) { new_hw_ptr += runtime->period_size;

• 	if (new_hw_ptr >= runtime->boundary)
  

• 	if (new_hw_ptr >= runtime->boundary) {
  	new_hw_ptr -= runtime->boundary;
  

• 		crossed_boundary--;
  

• 	}
  delta--;
  

  } /* align hw_base to buffer_size */

@@ -506,6 +515,11 @@ static int snd_pcm_update_hw_ptr0(struct snd_pcm_substream *substream, runtime->hw_ptr_base = hw_base; runtime->status->hw_ptr = new_hw_ptr; runtime->hw_ptr_jiffies = curr_jiffies;

• if (crossed_boundary) {

• BUG_ON(crossed_boundary > 1);
  

• BUG_ON(crossed_boundary < 0);
  

BUG_ON() is too hard for such sanity checks, since it leads to a kernel panic without recovery. Better to use WARN_ON() or snd_BUG_ON() snd_BUG_ON(crossed_boundary != 1);

Takashi

• runtime->hw_ptr_wrap += runtime->boundary;
  

• } if (runtime->tstamp_mode == SNDRV_PCM_TSTAMP_ENABLE) runtime->status->tstamp = curr_tstamp;

@@ -1660,8 +1674,10 @@ static int snd_pcm_lib_ioctl_reset(struct snd_pcm_substream *substream, if (snd_pcm_running(substream) && snd_pcm_update_hw_ptr(substream) >= 0) runtime->status->hw_ptr %= runtime->buffer_size;

• else

• else { runtime->status->hw_ptr = 0;

• runtime->hw_ptr_wrap = 0;
  

• } snd_pcm_stream_unlock_irqrestore(substream, flags); return 0;

}

1.7.9.5

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