ALSA: usbaudio - Add delay account

Manage the PCM delay account based on the queued URBs.

Signed-off-by: Takashi Iwai <tiwai@suse.de>

1 files changed, 13 insertions, 1 deletions

diff --git a/sound/usb/usbaudio.c b/sound/usb/usbaudio.c
index 823296d7d578..6c25fa23f702 100644
--- a/sound/usb/usbaudio.c
+++ b/sound/usb/usbaudio.c
@@ -627,6 +627,7 @@ static int prepare_playback_urb(struct snd_usb_substream *subs,
         subs->hwptr_done += offs;
         if (subs->hwptr_done >= runtime->buffer_size)
                 subs->hwptr_done -= runtime->buffer_size;
+        runtime->delay += offs;
         spin_unlock_irqrestore(&subs->lock, flags);
         urb->transfer_buffer_length = offs * stride;
         if (period_elapsed)
@@ -636,12 +637,22 @@ static int prepare_playback_urb(struct snd_usb_substream *subs,
 
 /*
  * process after playback data complete
- * - nothing to do
+ * - decrease the delay count again
  */
 static int retire_playback_urb(struct snd_usb_substream *subs,
                                struct snd_pcm_runtime *runtime,
                                struct urb *urb)
 {
+        unsigned long flags;
+        int stride = runtime->frame_bits >> 3;
+        int processed = urb->transfer_buffer_length / stride;
+
+        spin_lock_irqsave(&subs->lock, flags);
+        if (processed > runtime->delay)
+                runtime->delay = 0;
+        else
+                runtime->delay -= processed;
+        spin_unlock_irqrestore(&subs->lock, flags);
         return 0;
 }
 
@@ -1520,6 +1531,7 @@ static int snd_usb_pcm_prepare(struct snd_pcm_substream *substream)
         subs->hwptr_done = 0;
         subs->transfer_done = 0;
         subs->phase = 0;
+        runtime->delay = 0;
 
         /* clear urbs (to be sure) */
         deactivate_urbs(subs, 0, 1);