1 files changed, 72 insertions, 33 deletions

diff --git a/sound/core/pcm_lib.c b/sound/core/pcm_lib.c
index d21c73944efd..9c121a921b04 100644
--- a/sound/core/pcm_lib.c
+++ b/sound/core/pcm_lib.c
@@ -33,6 +33,25 @@
 static int fill_silence_frames(struct snd_pcm_substream *substream,
 			       snd_pcm_uframes_t off, snd_pcm_uframes_t frames);
 
+
+static inline void update_silence_vars(struct snd_pcm_runtime *runtime,
+				       snd_pcm_uframes_t ptr,
+				       snd_pcm_uframes_t new_ptr)
+{
+	snd_pcm_sframes_t delta;
+
+	delta = new_ptr - ptr;
+	if (delta == 0)
+		return;
+	if (delta < 0)
+		delta += runtime->boundary;
+	if ((snd_pcm_uframes_t)delta < runtime->silence_filled)
+		runtime->silence_filled -= delta;
+	else
+		runtime->silence_filled = 0;
+	runtime->silence_start = new_ptr;
+}
+
 /*
  * fill ring buffer with silence
  * runtime->silence_start: starting pointer to silence area
@@ -42,47 +61,67 @@ static int fill_silence_frames(struct snd_pcm_substream *substream,
  *
  * when runtime->silence_size >= runtime->boundary - fill processed area with silence immediately
  */
-void snd_pcm_playback_silence(struct snd_pcm_substream *substream)
+void snd_pcm_playback_silence(struct snd_pcm_substream *substream, snd_pcm_uframes_t new_hw_ptr)
 {
 	struct snd_pcm_runtime *runtime = substream->runtime;
-	snd_pcm_uframes_t appl_ptr = READ_ONCE(runtime->control->appl_ptr);
-	snd_pcm_sframes_t added, hw_avail, frames;
-	snd_pcm_uframes_t noise_dist, ofs, transfer;
+	snd_pcm_uframes_t frames, ofs, transfer;
 	int err;
 
-	added = appl_ptr - runtime->silence_start;
-	if (added) {
-		if (added < 0)
-			added += runtime->boundary;
-		if (added < runtime->silence_filled)
-			runtime->silence_filled -= added;
-		else
-			runtime->silence_filled = 0;
-		runtime->silence_start = appl_ptr;
-	}
-
-	// This will "legitimately" turn negative on underrun, and will be mangled
-	// into a huge number by the boundary crossing handling. The initial state
-	// might also be not quite sane. The code below MUST account for these cases.
-	hw_avail = appl_ptr - runtime->status->hw_ptr;
-	if (hw_avail < 0)
-		hw_avail += runtime->boundary;
-
-	noise_dist = hw_avail + runtime->silence_filled;
 	if (runtime->silence_size < runtime->boundary) {
-		frames = runtime->silence_threshold - noise_dist;
-		if (frames <= 0)
+		snd_pcm_sframes_t noise_dist;
+		snd_pcm_uframes_t appl_ptr = READ_ONCE(runtime->control->appl_ptr);
+		update_silence_vars(runtime, runtime->silence_start, appl_ptr);
+		/* initialization outside pointer updates */
+		if (new_hw_ptr == ULONG_MAX)
+			new_hw_ptr = runtime->status->hw_ptr;
+		/* get hw_avail with the boundary crossing */
+		noise_dist = appl_ptr - new_hw_ptr;
+		if (noise_dist < 0)
+			noise_dist += runtime->boundary;
+		/* total noise distance */
+		noise_dist += runtime->silence_filled;
+		if (noise_dist >= (snd_pcm_sframes_t) runtime->silence_threshold)
 			return;
+		frames = runtime->silence_threshold - noise_dist;
 		if (frames > runtime->silence_size)
 			frames = runtime->silence_size;
 	} else {
-		frames = runtime->buffer_size - noise_dist;
-		if (frames <= 0)
-			return;
+		/*
+		 * This filling mode aims at free-running mode (used for example by dmix),
+		 * which doesn't update the application pointer.
+		 */
+		snd_pcm_uframes_t hw_ptr = runtime->status->hw_ptr;
+		if (new_hw_ptr == ULONG_MAX) {
+			/*
+			 * Initialization, fill the whole unused buffer with silence.
+			 *
+			 * Usually, this is entered while stopped, before data is queued,
+			 * so both pointers are expected to be zero.
+			 */
+			snd_pcm_sframes_t avail = runtime->control->appl_ptr - hw_ptr;
+			if (avail < 0)
+				avail += runtime->boundary;
+			/*
+			 * In free-running mode, appl_ptr will be zero even while running,
+			 * so we end up with a huge number. There is no useful way to
+			 * handle this, so we just clear the whole buffer.
+			 */
+			runtime->silence_filled = avail > runtime->buffer_size ? 0 : avail;
+			runtime->silence_start = hw_ptr;
+		} else {
+			/* Silence the just played area immediately */
+			update_silence_vars(runtime, hw_ptr, new_hw_ptr);
+		}
+		/*
+		 * In this mode, silence_filled actually includes the valid
+		 * sample data from the user.
+		 */
+		frames = runtime->buffer_size - runtime->silence_filled;
 	}
-
 	if (snd_BUG_ON(frames > runtime->buffer_size))
 		return;
+	if (frames == 0)
+		return;
 	ofs = (runtime->silence_start + runtime->silence_filled) % runtime->buffer_size;
 	do {
 		transfer = ofs + frames > runtime->buffer_size ? runtime->buffer_size - ofs : frames;
@@ -425,6 +464,10 @@ static int snd_pcm_update_hw_ptr0(struct snd_pcm_substream *substream,
 		return 0;
 	}
 
+	if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK &&
+	    runtime->silence_size > 0)
+		snd_pcm_playback_silence(substream, new_hw_ptr);
+
 	if (in_interrupt) {
 		delta = new_hw_ptr - runtime->hw_ptr_interrupt;
 		if (delta < 0)
@@ -442,10 +485,6 @@ static int snd_pcm_update_hw_ptr0(struct snd_pcm_substream *substream,
 		runtime->hw_ptr_wrap += runtime->boundary;
 	}
 
-	if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK &&
-	    runtime->silence_size > 0)
-		snd_pcm_playback_silence(substream);
-
 	update_audio_tstamp(substream, &curr_tstamp, &audio_tstamp);
 
 	return snd_pcm_update_state(substream, runtime);