[ALSA] pcm-midlevel: Add more strict buffer position checks based on jiffies

Some drivers like Intel8x0 or Intel HDA are broken for some hardware variants.
This patch adds more strict buffer position checks based on jiffies when
internal hw_ptr is updated. Enable xrun_debug to see mangling of wrong
positions.

As a side effect, the hw_ptr interrupt update routine might do slightly better
job when many interrupts are lost.
Signed-off-by: Jaroslav Kysela <perex@perex.cz>

include/sound/pcm.h

@@ -268,7 +268,8 @@ struct snd_pcm_runtime {
 	int overrange;
 	snd_pcm_uframes_t avail_max;
 	snd_pcm_uframes_t hw_ptr_base;	/* Position at buffer restart */
-	snd_pcm_uframes_t hw_ptr_interrupt; /* Position at interrupt time*/
+	snd_pcm_uframes_t hw_ptr_interrupt; /* Position at interrupt time */
+	unsigned long hw_ptr_jiffies;	/* Time when hw_ptr is updated */
 
 	/* -- HW params -- */
 	snd_pcm_access_t access;	/* access mode */

sound/core/pcm_lib.c

@@ -209,9 +209,11 @@ static int snd_pcm_update_hw_ptr_interrupt(struct snd_pcm_substream *substream)
 {
 	struct snd_pcm_runtime *runtime = substream->runtime;
 	snd_pcm_uframes_t pos;
-	snd_pcm_uframes_t new_hw_ptr, hw_ptr_interrupt, hw_base;
-	snd_pcm_sframes_t delta;
+	snd_pcm_uframes_t old_hw_ptr, new_hw_ptr, hw_ptr_interrupt, hw_base;
+	snd_pcm_sframes_t hdelta, delta;
+	unsigned long jdelta;
 
+	old_hw_ptr = runtime->status->hw_ptr;
 	pos = snd_pcm_update_hw_ptr_pos(substream, runtime);
 	if (pos == SNDRV_PCM_POS_XRUN) {
 		xrun(substream);
@@ -247,7 +249,30 @@ static int snd_pcm_update_hw_ptr_interrupt(struct snd_pcm_substream *substream)
 			new_hw_ptr = hw_base + pos;
 		}
 	}
-	if (delta > runtime->period_size) {
+	hdelta = new_hw_ptr - old_hw_ptr;
+	jdelta = jiffies - runtime->hw_ptr_jiffies;
+	if (((hdelta * HZ) / runtime->rate) > jdelta + HZ/100) {
+		delta = jdelta /
+			(((runtime->period_size * HZ) / runtime->rate)
+								+ HZ/100);
+		hw_ptr_error(substream,
+			     "hw_ptr skipping! [Q] "
+			     "(pos=%ld, delta=%ld, period=%ld, "
+			     "jdelta=%lu/%lu/%lu)\n",
+			     (long)pos, (long)hdelta,
+			     (long)runtime->period_size, jdelta,
+			     ((hdelta * HZ) / runtime->rate), delta);
+		hw_ptr_interrupt = runtime->hw_ptr_interrupt +
+				   runtime->period_size * delta;
+		if (hw_ptr_interrupt >= runtime->boundary)
+			hw_ptr_interrupt -= runtime->boundary;
+		/* rebase to interrupt position */
+		hw_base = new_hw_ptr = hw_ptr_interrupt;
+		/* align hw_base to buffer_size */
+		hw_base -= hw_base % runtime->buffer_size;
+		delta = 0;
+	}
+	if (delta > runtime->period_size + runtime->period_size / 2) {
 		hw_ptr_error(substream,
 			     "Lost interrupts? "
 			     "(stream=%i, delta=%ld, intr_ptr=%ld)\n",
@@ -263,6 +288,7 @@ static int snd_pcm_update_hw_ptr_interrupt(struct snd_pcm_substream *substream)
 
 	runtime->hw_ptr_base = hw_base;
 	runtime->status->hw_ptr = new_hw_ptr;
+	runtime->hw_ptr_jiffies = jiffies;
 	runtime->hw_ptr_interrupt = hw_ptr_interrupt;
 
 	return snd_pcm_update_hw_ptr_post(substream, runtime);
@@ -275,6 +301,7 @@ int snd_pcm_update_hw_ptr(struct snd_pcm_substream *substream)
 	snd_pcm_uframes_t pos;
 	snd_pcm_uframes_t old_hw_ptr, new_hw_ptr, hw_base;
 	snd_pcm_sframes_t delta;
+	unsigned long jdelta;
 
 	old_hw_ptr = runtime->status->hw_ptr;
 	pos = snd_pcm_update_hw_ptr_pos(substream, runtime);
@@ -286,14 +313,15 @@ int snd_pcm_update_hw_ptr(struct snd_pcm_substream *substream)
 	new_hw_ptr = hw_base + pos;
 
 	delta = new_hw_ptr - old_hw_ptr;
+	jdelta = jiffies - runtime->hw_ptr_jiffies;
 	if (delta < 0) {
 		delta += runtime->buffer_size;
 		if (delta < 0) {
 			hw_ptr_error(substream, 
 				     "Unexpected hw_pointer value [2] "
-				     "(stream=%i, pos=%ld, old_ptr=%ld)\n",
+				     "(stream=%i, pos=%ld, old_ptr=%ld, jdelta=%li)\n",
 				     substream->stream, (long)pos,
-				     (long)old_hw_ptr);
+				     (long)old_hw_ptr, jdelta);
 			return 0;
 		}
 		hw_base += runtime->buffer_size;
@@ -301,12 +329,13 @@ int snd_pcm_update_hw_ptr(struct snd_pcm_substream *substream)
 			hw_base = 0;
 		new_hw_ptr = hw_base + pos;
 	}
-	if (delta > runtime->period_size && runtime->periods > 1) {
+	if (((delta * HZ) / runtime->rate) > jdelta + HZ/100) {
 		hw_ptr_error(substream,
 			     "hw_ptr skipping! "
-			     "(pos=%ld, delta=%ld, period=%ld)\n",
+			     "(pos=%ld, delta=%ld, period=%ld, jdelta=%lu/%lu)\n",
 			     (long)pos, (long)delta,
-			     (long)runtime->period_size);
+			     (long)runtime->period_size, jdelta,
+			     ((delta * HZ) / runtime->rate));
 		return 0;
 	}
 	if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK &&
@@ -315,6 +344,7 @@ int snd_pcm_update_hw_ptr(struct snd_pcm_substream *substream)
 
 	runtime->hw_ptr_base = hw_base;
 	runtime->status->hw_ptr = new_hw_ptr;
+	runtime->hw_ptr_jiffies = jiffies;
 
 	return snd_pcm_update_hw_ptr_post(substream, runtime);
 }
@@ -1441,6 +1471,7 @@ static int snd_pcm_lib_ioctl_reset(struct snd_pcm_substream *substream,
 		runtime->status->hw_ptr %= runtime->buffer_size;
 	else
 		runtime->status->hw_ptr = 0;
+	runtime->hw_ptr_jiffies = jiffies;
 	snd_pcm_stream_unlock_irqrestore(substream, flags);
 	return 0;
 }