[PATCH 2/2] ALSA: pcm: auto-fill buffer with silence when draining playback

[Oswald Buddenhagen <oswald.buddenhagen@gmx.de>]

Draining will always playback somewhat beyond the end of the filled
buffer. This would produce artifacts if the user did not set up the
auto-silencing machinery. This patch makes it work out of the box.

Rather than figuring out the right threshold (which is one period plus
the card-specific FIFO size plus some IRQ jitter), we use "top-up" mode.

Signed-off-by: Oswald Buddenhagen <oswald.buddenhagen@gmx.de>
---
 sound/core/pcm_lib.c    | 5 +++--
 sound/core/pcm_native.c | 3 ++-
 2 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/sound/core/pcm_lib.c b/sound/core/pcm_lib.c
index b074c5b926db..1dd870a2093d 100644
--- a/sound/core/pcm_lib.c
+++ b/sound/core/pcm_lib.c
@@ -71,7 +71,8 @@ void snd_pcm_playback_silence(struct snd_pcm_substream *substream)
 	}
 
 	noise_dist = hw_avail + runtime->silence_filled;
-	if (runtime->silence_size < runtime->boundary) {
+	if (runtime->silence_size < runtime->boundary &&
+	    runtime->state != SNDRV_PCM_STATE_DRAINING) {
 		frames = runtime->silence_threshold - noise_dist;
 		if ((snd_pcm_sframes_t) frames <= 0)
 			return;
@@ -445,7 +446,7 @@ static int snd_pcm_update_hw_ptr0(struct snd_pcm_substream *substream,
 	}
 
 	if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK &&
-	    runtime->silence_size > 0)
+	    (runtime->silence_size > 0 || runtime->state == SNDRV_PCM_STATE_DRAINING))
 		snd_pcm_playback_silence(substream);
 
 	update_audio_tstamp(substream, &curr_tstamp, &audio_tstamp);
diff --git a/sound/core/pcm_native.c b/sound/core/pcm_native.c
index 0e3e7997dc58..6ecb6a733606 100644
--- a/sound/core/pcm_native.c
+++ b/sound/core/pcm_native.c
@@ -1454,7 +1454,7 @@ static void snd_pcm_post_start(struct snd_pcm_substream *substream,
 							    runtime->rate;
 	__snd_pcm_set_state(runtime, state);
 	if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK &&
-	    runtime->silence_size > 0)
+	    (runtime->silence_size > 0 || state == SNDRV_PCM_STATE_DRAINING))
 		snd_pcm_playback_silence(substream);
 	snd_pcm_timer_notify(substream, SNDRV_TIMER_EVENT_MSTART);
 }
@@ -2045,6 +2045,7 @@ static int snd_pcm_do_drain_init(struct snd_pcm_substream *substream,
 			break;
 		case SNDRV_PCM_STATE_RUNNING:
 			__snd_pcm_set_state(runtime, SNDRV_PCM_STATE_DRAINING);
+			snd_pcm_playback_silence(substream);
 			break;
 		case SNDRV_PCM_STATE_XRUN:
 			__snd_pcm_set_state(runtime, SNDRV_PCM_STATE_SETUP);
-- 
2.40.0.152.g15d061e6df