[PATCH] ALSA: aloop: Fix random zeros in capture data when using jiffies timer

From: Pattara Teerapong
Date: Thu Sep 01 2022 - 10:42:49 EST


In loopback_jiffies_timer_pos_update(), we are getting jiffies twice.
First time for playback, second time for capture. Jiffies can be updated
between these two calls and if the capture jiffies is larger, extra zeros
will be filled in the capture buffer.

Change to get jiffies once and use it for both playback and capture.

Signed-off-by: Pattara Teerapong <pteerapong@xxxxxxxxxxxx>
---

sound/drivers/aloop.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/sound/drivers/aloop.c b/sound/drivers/aloop.c
index 9b4a7cdb103a..12f12a294df5 100644
--- a/sound/drivers/aloop.c
+++ b/sound/drivers/aloop.c
@@ -605,17 +605,18 @@ static unsigned int loopback_jiffies_timer_pos_update
cable->streams[SNDRV_PCM_STREAM_PLAYBACK];
struct loopback_pcm *dpcm_capt =
cable->streams[SNDRV_PCM_STREAM_CAPTURE];
- unsigned long delta_play = 0, delta_capt = 0;
+ unsigned long delta_play = 0, delta_capt = 0, cur_jiffies;
unsigned int running, count1, count2;

+ cur_jiffies = jiffies;
running = cable->running ^ cable->pause;
if (running & (1 << SNDRV_PCM_STREAM_PLAYBACK)) {
- delta_play = jiffies - dpcm_play->last_jiffies;
+ delta_play = cur_jiffies - dpcm_play->last_jiffies;
dpcm_play->last_jiffies += delta_play;
}

if (running & (1 << SNDRV_PCM_STREAM_CAPTURE)) {
- delta_capt = jiffies - dpcm_capt->last_jiffies;
+ delta_capt = cur_jiffies - dpcm_capt->last_jiffies;
dpcm_capt->last_jiffies += delta_capt;
}

--
2.37.2.789.g6183377224-goog