[alsa-devel] [PATCH v3 1/3] ALSA: core: keep track of boundary wrap-around

[Pierre-Louis Bossart]

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 at linux.intel.com>
---
 include/sound/pcm.h  |    1 +
 sound/core/pcm_lib.c |   25 ++++++++++++++++++++-----
 2 files changed, 21 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..bbc6ba4 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 +515,10 @@ 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) {
+		snd_BUG_ON(crossed_boundary != 1);
+		runtime->hw_ptr_wrap += runtime->boundary;
+	}
 	if (runtime->tstamp_mode == SNDRV_PCM_TSTAMP_ENABLE)
 		runtime->status->tstamp = curr_tstamp;
 
@@ -1660,8 +1673,10 @@ 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