ALSA: pcm: fix playback silence - use the actual new_hw_ptr for the threshold mode

The snd_pcm_playback_hw_avail() function uses runtime->status->hw_ptr.
Unfortunately, in case when we call this function from snd_pcm_update_hw_ptr0(),
this variable contains the previous hardware pointer. Use the new_hw_ptr
argument to calculate hw_avail (filled samples by the user space) to
correct the threshold comparison.

The new_hw_ptr argument may also be set to ULONG_MAX which means the
initialization phase. In this case, use runtime->status->hw_ptr.

Suggested-by: Oswald Buddenhagen <oswald.buddenhagen@gmx.de>
Signed-off-by: Jaroslav Kysela <perex@perex.cz>
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@gmx.de>
Link: https://lore.kernel.org/r/20230505155244.2312199-2-oswald.buddenhagen@gmx.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>

Author: perexg

sound/core/pcm_lib.c

@@ -63,7 +63,15 @@ void snd_pcm_playback_silence(struct snd_pcm_substream *substream, snd_pcm_ufram
 		}
 		if (runtime->silence_filled >= runtime->buffer_size)
 			return;
-		noise_dist = snd_pcm_playback_hw_avail(runtime) + runtime->silence_filled;
+		/* 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;