ALSA: pcm_lib - cleanup & merge hw_ptr update functions

Do general cleanup in snd_pcm_update_hw_ptr*() routines and merge them.
The main change is hw_ptr_interrupt variable removal to simplify code
logic. This variable can be computed directly from hw_ptr.

Ensure that updated hw_ptr is not lower than previous one (it was possible
with old code in some obscure situations when interrupt was delayed or
the lowlevel driver returns wrong ring buffer position value).

Signed-off-by: Jaroslav Kysela <perex@perex.cz>

1 files changed, 97 insertions, 182 deletions

diff --git a/sound/core/pcm_lib.c b/sound/core/pcm_lib.c
index 1990afb8a735..70a4f7428d78 100644
--- a/sound/core/pcm_lib.c
+++ b/sound/core/pcm_lib.c
@@ -172,6 +172,7 @@ static void xrun(struct snd_pcm_substream *substream)
 #define hw_ptr_error(substream, fmt, args...)				\
 	do {								\
 		if (xrun_debug(substream, XRUN_DEBUG_BASIC)) {		\
+			xrun_log_show(substream);			\
 			if (printk_ratelimit()) {			\
 				snd_printd("PCM: " fmt, ##args);	\
 			}						\
@@ -188,7 +189,6 @@ struct hwptr_log_entry {
 	snd_pcm_uframes_t buffer_size;
 	snd_pcm_uframes_t old_hw_ptr;
 	snd_pcm_uframes_t hw_ptr_base;
-	snd_pcm_uframes_t hw_ptr_interrupt;
 };
 
 struct snd_pcm_hwptr_log {
@@ -220,7 +220,6 @@ static void xrun_log(struct snd_pcm_substream *substream,
 	entry->buffer_size = runtime->buffer_size;;
 	entry->old_hw_ptr = runtime->status->hw_ptr;
 	entry->hw_ptr_base = runtime->hw_ptr_base;
-	entry->hw_ptr_interrupt = runtime->hw_ptr_interrupt;;
 	log->idx = (log->idx + 1) % XRUN_LOG_CNT;
 }
 
@@ -241,14 +240,13 @@ static void xrun_log_show(struct snd_pcm_substream *substream)
 		entry = &log->entries[idx];
 		if (entry->period_size == 0)
 			break;
-		snd_printd("hwptr log: %s: j=%lu, pos=0x%lx/0x%lx/0x%lx, "
-			   "hwptr=0x%lx, hw_base=0x%lx, hw_intr=0x%lx\n",
+		snd_printd("hwptr log: %s: j=%lu, pos=%ld/%ld/%ld, "
+			   "hwptr=%ld/%ld\n",
 			   name, entry->jiffies, (unsigned long)entry->pos,
 			   (unsigned long)entry->period_size,
 			   (unsigned long)entry->buffer_size,
 			   (unsigned long)entry->old_hw_ptr,
-			   (unsigned long)entry->hw_ptr_base,
-			   (unsigned long)entry->hw_ptr_interrupt);
+			   (unsigned long)entry->hw_ptr_base);
 		idx++;
 		idx %= XRUN_LOG_CNT;
 	}
@@ -265,33 +263,6 @@ static void xrun_log_show(struct snd_pcm_substream *substream)
 
 #endif
 
-static snd_pcm_uframes_t
-snd_pcm_update_hw_ptr_pos(struct snd_pcm_substream *substream,
-			  struct snd_pcm_runtime *runtime)
-{
-	snd_pcm_uframes_t pos;
-
-	pos = substream->ops->pointer(substream);
-	if (pos == SNDRV_PCM_POS_XRUN)
-		return pos; /* XRUN */
-	if (pos >= runtime->buffer_size) {
-		if (printk_ratelimit()) {
-			char name[16];
-			pcm_debug_name(substream, name, sizeof(name));
-			xrun_log_show(substream);
-			snd_printd(KERN_ERR  "BUG: %s, pos = 0x%lx, "
-				   "buffer size = 0x%lx, period size = 0x%lx\n",
-				   name, pos, runtime->buffer_size,
-				   runtime->period_size);
-		}
-		pos = 0;
-	}
-	pos -= pos % runtime->min_align;
-	if (xrun_debug(substream, XRUN_DEBUG_LOG))
-		xrun_log(substream, pos);
-	return pos;
-}
-
 static int snd_pcm_update_hw_ptr_post(struct snd_pcm_substream *substream,
 				      struct snd_pcm_runtime *runtime)
 {
@@ -319,72 +290,88 @@ static int snd_pcm_update_hw_ptr_post(struct snd_pcm_substream *substream,
 	return 0;
 }
 
-static int snd_pcm_update_hw_ptr_interrupt(struct snd_pcm_substream *substream)
+static int snd_pcm_update_hw_ptr0(struct snd_pcm_substream *substream,
+				  unsigned int in_interrupt)
 {
 	struct snd_pcm_runtime *runtime = substream->runtime;
 	snd_pcm_uframes_t pos;
-	snd_pcm_uframes_t old_hw_ptr, new_hw_ptr, hw_ptr_interrupt, hw_base;
+	snd_pcm_uframes_t old_hw_ptr, new_hw_ptr, 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);
+	pos = substream->ops->pointer(substream);
 	if (pos == SNDRV_PCM_POS_XRUN) {
 		xrun(substream);
 		return -EPIPE;
 	}
-	if (xrun_debug(substream, XRUN_DEBUG_PERIODUPDATE)) {
-		char name[16];
-		pcm_debug_name(substream, name, sizeof(name));
-		snd_printd("period_update: %s: pos=0x%x/0x%x/0x%x, "
-			   "hwptr=0x%lx, hw_base=0x%lx, hw_intr=0x%lx\n",
-			   name, (unsigned int)pos,
-			   (unsigned int)runtime->period_size,
-			   (unsigned int)runtime->buffer_size,
-			   (unsigned long)old_hw_ptr,
-			   (unsigned long)runtime->hw_ptr_base,
-			   (unsigned long)runtime->hw_ptr_interrupt);
+	if (pos >= runtime->buffer_size) {
+		if (printk_ratelimit()) {
+			char name[16];
+			pcm_debug_name(substream, name, sizeof(name));
+			xrun_log_show(substream);
+			snd_printd(KERN_ERR  "BUG: %s, pos = %ld, "
+				   "buffer size = %ld, period size = %ld\n",
+				   name, pos, runtime->buffer_size,
+				   runtime->period_size);
+		}
+		pos = 0;
 	}
+	pos -= pos % runtime->min_align;
+	if (xrun_debug(substream, XRUN_DEBUG_LOG))
+		xrun_log(substream, pos);
 	hw_base = runtime->hw_ptr_base;
 	new_hw_ptr = hw_base + pos;
-	hw_ptr_interrupt = runtime->hw_ptr_interrupt + runtime->period_size;
-	delta = new_hw_ptr - hw_ptr_interrupt;
-	if (hw_ptr_interrupt >= runtime->boundary) {
-		hw_ptr_interrupt -= runtime->boundary;
-		if (hw_base < runtime->boundary / 2)
-			/* hw_base was already lapped; recalc delta */
-			delta = new_hw_ptr - hw_ptr_interrupt;
-	}
-	if (delta < 0) {
-		if (runtime->periods == 1 || new_hw_ptr < old_hw_ptr)
-			delta += runtime->buffer_size;
-		if (delta < 0) {
-			xrun_log_show(substream);
-			hw_ptr_error(substream, 
-				     "Unexpected hw_pointer value "
-				     "(stream=%i, pos=%ld, intr_ptr=%ld)\n",
-				     substream->stream, (long)pos,
-				     (long)hw_ptr_interrupt);
-#if 1
-			/* simply skipping the hwptr update seems more
-			 * robust in some cases, e.g. on VMware with
-			 * inaccurate timer source
-			 */
-			return 0; /* skip this update */
-#else
-			/* 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;
-#endif
-		} else {
+	if (in_interrupt) {
+		/* we know that one period was processed */
+		/* delta = "expected next hw_ptr" for in_interrupt != 0 */
+		delta = old_hw_ptr - (old_hw_ptr % runtime->period_size)
+			+ runtime->period_size;
+		if (delta > new_hw_ptr) {
 			hw_base += runtime->buffer_size;
 			if (hw_base >= runtime->boundary)
 				hw_base = 0;
 			new_hw_ptr = hw_base + pos;
+			goto __delta;
 		}
 	}
+	/* new_hw_ptr might be lower than old_hw_ptr in case when */
+	/* 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)
+			hw_base = 0;
+		new_hw_ptr = hw_base + pos;
+	}
+      __delta:
+	delta = (new_hw_ptr - old_hw_ptr) % runtime->boundary;
+	if (xrun_debug(substream, in_interrupt ?
+			XRUN_DEBUG_PERIODUPDATE : XRUN_DEBUG_HWPTRUPDATE)) {
+		char name[16];
+		pcm_debug_name(substream, name, sizeof(name));
+		snd_printd("%s_update: %s: pos=%u/%u/%u, "
+			   "hwptr=%ld/%ld/%ld/%ld\n",
+			   in_interrupt ? "period" : "hwptr",
+			   name,
+			   (unsigned int)pos,
+			   (unsigned int)runtime->period_size,
+			   (unsigned int)runtime->buffer_size,
+			   (unsigned long)delta,
+			   (unsigned long)old_hw_ptr,
+			   (unsigned long)new_hw_ptr,
+			   (unsigned long)runtime->hw_ptr_base);
+	}
+	/* something must be really wrong */
+	if (delta >= runtime->buffer_size) {
+		hw_ptr_error(substream,
+			       "Unexpected hw_pointer value %s"
+			       "(stream=%i, pos=%ld, new_hw_ptr=%ld, "
+			       "old_hw_ptr=%ld)\n",
+				     in_interrupt ? "[Q] " : "[P]",
+				     substream->stream, (long)pos,
+				     (long)new_hw_ptr, (long)old_hw_ptr);
+		return 0;
+	}
 
 	/* Do jiffies check only in xrun_debug mode */
 	if (!xrun_debug(substream, XRUN_DEBUG_JIFFIESCHECK))
@@ -396,7 +383,7 @@ static int snd_pcm_update_hw_ptr_interrupt(struct snd_pcm_substream *substream)
 	 */
 	if (runtime->hw.info & SNDRV_PCM_INFO_BATCH)
 		goto no_jiffies_check;
-	hdelta = new_hw_ptr - old_hw_ptr;
+	hdelta = delta;
 	if (hdelta < runtime->delay)
 		goto no_jiffies_check;
 	hdelta -= runtime->delay;
@@ -405,45 +392,49 @@ static int snd_pcm_update_hw_ptr_interrupt(struct snd_pcm_substream *substream)
 		delta = jdelta /
 			(((runtime->period_size * HZ) / runtime->rate)
 								+ HZ/100);
-		xrun_log_show(substream);
+		/* move new_hw_ptr according jiffies not pos variable */
+		new_hw_ptr = old_hw_ptr;
+		/* use loop to avoid checks for delta overflows */
+		/* 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)
+				new_hw_ptr -= runtime->boundary;
+			delta--;
+		}
+		/* align hw_base to buffer_size */
+		hw_base = new_hw_ptr - (new_hw_ptr % runtime->buffer_size);
+		delta = 0;
 		hw_ptr_error(substream,
-			     "hw_ptr skipping! [Q] "
+			     "hw_ptr skipping! %s"
 			     "(pos=%ld, delta=%ld, period=%ld, "
-			     "jdelta=%lu/%lu/%lu)\n",
+			     "jdelta=%lu/%lu/%lu, hw_ptr=%ld/%ld)\n",
+			     in_interrupt ? "[Q] " : "",
 			     (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;
+			     ((hdelta * HZ) / runtime->rate), delta,
+			     (unsigned long)old_hw_ptr,
+			     (unsigned long)new_hw_ptr);
 	}
  no_jiffies_check:
 	if (delta > runtime->period_size + runtime->period_size / 2) {
-		xrun_log_show(substream);
 		hw_ptr_error(substream,
-			     "Lost interrupts? "
-			     "(stream=%i, delta=%ld, intr_ptr=%ld)\n",
+			     "Lost interrupts? %s"
+			     "(stream=%i, delta=%ld, new_hw_ptr=%ld, "
+			     "old_hw_ptr=%ld)\n",
+			     in_interrupt ? "[Q] " : "",
 			     substream->stream, (long)delta,
-			     (long)hw_ptr_interrupt);
-		/* rebase hw_ptr_interrupt */
-		hw_ptr_interrupt =
-			new_hw_ptr - new_hw_ptr % runtime->period_size;
+			     (long)new_hw_ptr,
+			     (long)old_hw_ptr);
 	}
-	runtime->hw_ptr_interrupt = hw_ptr_interrupt;
+
+	if (runtime->status->hw_ptr == new_hw_ptr)
+		return 0;
 
 	if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK &&
 	    runtime->silence_size > 0)
 		snd_pcm_playback_silence(substream, new_hw_ptr);
 
-	if (runtime->status->hw_ptr == new_hw_ptr)
-		return 0;
-
 	runtime->hw_ptr_base = hw_base;
 	runtime->status->hw_ptr = new_hw_ptr;
 	runtime->hw_ptr_jiffies = jiffies;
@@ -456,83 +447,7 @@ static int snd_pcm_update_hw_ptr_interrupt(struct snd_pcm_substream *substream)
 /* CAUTION: call it with irq disabled */
 int snd_pcm_update_hw_ptr(struct snd_pcm_substream *substream)
 {
-	struct snd_pcm_runtime *runtime = substream->runtime;
-	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);
-	if (pos == SNDRV_PCM_POS_XRUN) {
-		xrun(substream);
-		return -EPIPE;
-	}
-	if (xrun_debug(substream, XRUN_DEBUG_HWPTRUPDATE)) {
-		char name[16];
-		pcm_debug_name(substream, name, sizeof(name));
-		snd_printd("hw_update: %s: pos=0x%x/0x%x/0x%x, "
-			   "hwptr=0x%lx, hw_base=0x%lx, hw_intr=0x%lx\n",
-			   name, (unsigned int)pos,
-			   (unsigned int)runtime->period_size,
-			   (unsigned int)runtime->buffer_size,
-			   (unsigned long)old_hw_ptr,
-			   (unsigned long)runtime->hw_ptr_base,
-			   (unsigned long)runtime->hw_ptr_interrupt);
-	}
-
-	hw_base = runtime->hw_ptr_base;
-	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) {
-			xrun_log_show(substream);
-			hw_ptr_error(substream, 
-				     "Unexpected hw_pointer value [2] "
-				     "(stream=%i, pos=%ld, old_ptr=%ld, jdelta=%li)\n",
-				     substream->stream, (long)pos,
-				     (long)old_hw_ptr, jdelta);
-			return 0;
-		}
-		hw_base += runtime->buffer_size;
-		if (hw_base >= runtime->boundary)
-			hw_base = 0;
-		new_hw_ptr = hw_base + pos;
-	}
-	/* Do jiffies check only in xrun_debug mode */
-	if (!xrun_debug(substream, XRUN_DEBUG_JIFFIESCHECK))
-		goto no_jiffies_check;
-	if (delta < runtime->delay)
-		goto no_jiffies_check;
-	delta -= runtime->delay;
-	if (((delta * HZ) / runtime->rate) > jdelta + HZ/100) {
-		xrun_log_show(substream);
-		hw_ptr_error(substream,
-			     "hw_ptr skipping! "
-			     "(pos=%ld, delta=%ld, period=%ld, jdelta=%lu/%lu)\n",
-			     (long)pos, (long)delta,
-			     (long)runtime->period_size, jdelta,
-			     ((delta * HZ) / runtime->rate));
-		return 0;
-	}
- no_jiffies_check:
-	if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK &&
-	    runtime->silence_size > 0)
-		snd_pcm_playback_silence(substream, new_hw_ptr);
-
-	if (runtime->status->hw_ptr == new_hw_ptr)
-		return 0;
-
-	runtime->hw_ptr_base = hw_base;
-	runtime->status->hw_ptr = new_hw_ptr;
-	runtime->hw_ptr_jiffies = jiffies;
-	if (runtime->tstamp_mode == SNDRV_PCM_TSTAMP_ENABLE)
-		snd_pcm_gettime(runtime, (struct timespec *)&runtime->status->tstamp);
-
-	return snd_pcm_update_hw_ptr_post(substream, runtime);
+	return snd_pcm_update_hw_ptr0(substream, 0);
 }
 
 /**
@@ -1744,7 +1659,7 @@ void snd_pcm_period_elapsed(struct snd_pcm_substream *substream)
 
 	snd_pcm_stream_lock_irqsave(substream, flags);
 	if (!snd_pcm_running(substream) ||
-	    snd_pcm_update_hw_ptr_interrupt(substream) < 0)
+	    snd_pcm_update_hw_ptr0(substream, 1) < 0)
 		goto _end;
 
 	if (substream->timer_running)