ALSA: usbaudio - Add delay account

Manage the PCM delay account based on the queued URBs.

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

diff --git a/sound/usb/usbaudio.c b/sound/usb/usbaudio.c
index 823296d7d5781cbebb7d2ff4ab37cb8ecfefe74c..6c25fa23f702acb8fe8b0975af5c50cec969270c 100644 (file)
--- 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);