This is a note to let you know that I've just added the patch titled
ALSA: snd-usb: restore delay information
to the 3.5-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
alsa-snd-usb-restore-delay-information.patch
and it can be found in the queue-3.5 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <[email protected]> know about it.
>From fbcfbf5f673847657ccd98afb4d8e13af7fdc372 Mon Sep 17 00:00:00 2001
From: Daniel Mack <[email protected]>
Date: Thu, 30 Aug 2012 18:52:29 +0200
Subject: ALSA: snd-usb: restore delay information
From: Daniel Mack <[email protected]>
commit fbcfbf5f673847657ccd98afb4d8e13af7fdc372 upstream.
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: Daniel Mack <[email protected]>
Cc: Pierre-Louis Bossart <[email protected]>
Signed-off-by: Takashi Iwai <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
sound/usb/pcm.c | 29 ++++++++++++++++++++++++++---
1 file changed, 26 insertions(+), 3 deletions(-)
--- a/sound/usb/pcm.c
+++ b/sound/usb/pcm.c
@@ -1091,7 +1091,16 @@ static void prepare_playback_urb(struct
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 s
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);
}
Patches currently in stable-queue which might be from [email protected] are
queue-3.5/alsa-snd-usb-fix-urb-cancellation-at-stream-start.patch
queue-3.5/alsa-snd-usb-fix-calls-to-next_packet_size.patch
queue-3.5/alsa-snd-usb-fix-cross-interface-streaming-devices.patch
queue-3.5/alsa-snd-usb-restore-delay-information.patch
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