Commit fbcfbf5f authored by Daniel Mack's avatar Daniel Mack Committed by Takashi Iwai
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ALSA: snd-usb: restore delay information 



Parts of commit 294c4fb8 ("ALSA: usb: refine delay information with USB
frame counter") were unfortunately lost during the refactoring of the
snd-usb driver in 3.5.

This patch adds them back, restoring the correct delay information
behaviour.

Signed-off-by: default avatarDaniel Mack <zonque@gmail.com>
Cc: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Cc: stable@kernel.org [3.5+]
Signed-off-by: default avatarTakashi Iwai <tiwai@suse.de>
parent 03d2f44e

sound/usb/pcm.c

+26 −3
Original line number Diff line number Diff line
@@ -1091,7 +1091,16 @@ static void prepare_playback_urb(struct snd_usb_substream *subs, 
	subs->hwptr_done += bytes;

	if (subs->hwptr_done >= runtime->buffer_size * stride)

		subs->hwptr_done -= runtime->buffer_size * stride;



	/* update delay with exact number of samples queued */

	runtime->delay = subs->last_delay;

	runtime->delay += frames;

	subs->last_delay = runtime->delay;



	/* realign last_frame_number */

	subs->last_frame_number = usb_get_current_frame_number(subs->dev);

	subs->last_frame_number &= 0xFF; /* keep 8 LSBs */



	spin_unlock_irqrestore(&subs->lock, flags);

	urb->transfer_buffer_length = bytes;

	if (period_elapsed)
@@ -1109,12 +1118,26 @@ static void retire_playback_urb(struct snd_usb_substream *subs, 
	struct snd_pcm_runtime *runtime = subs->pcm_substream->runtime;

	int stride = runtime->frame_bits >> 3;

	int processed = urb->transfer_buffer_length / stride;

	int est_delay;



	spin_lock_irqsave(&subs->lock, flags);

	if (processed > runtime->delay)

		runtime->delay = 0;

	est_delay = snd_usb_pcm_delay(subs, runtime->rate);

	/* update delay with exact number of samples played */

	if (processed > subs->last_delay)

		subs->last_delay = 0;

	else

		runtime->delay -= processed;

		subs->last_delay -= processed;

	runtime->delay = subs->last_delay;



	/*

	 * Report when delay estimate is off by more than 2ms.

	 * The error should be lower than 2ms since the estimate relies

	 * on two reads of a counter updated every ms.

	 */

	if (abs(est_delay - subs->last_delay) * 1000 > runtime->rate * 2)

		snd_printk(KERN_DEBUG "delay: estimated %d, actual %d\n",

			est_delay, subs->last_delay);



	spin_unlock_irqrestore(&subs->lock, flags);

}

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