This is a note to let you know that I've just added the patch titled
ALSA: usb-audio: Disable low-latency mode for implicit feedback sync
to the 5.15-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-usb-audio-disable-low-latency-mode-for-implicit-feedback-sync.patch
and it can be found in the queue-5.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From bceee75387554f682638e719d1ea60125ea78cea Mon Sep 17 00:00:00 2001
From: Takashi Iwai <tiwai@xxxxxxx>
Date: Wed, 29 Sep 2021 10:08:40 +0200
Subject: ALSA: usb-audio: Disable low-latency mode for implicit feedback sync
From: Takashi Iwai <tiwai@xxxxxxx>
commit bceee75387554f682638e719d1ea60125ea78cea upstream.
When a playback stream runs in the implicit feedback mode, its
operation is passive and won't start unless the capture packet is
received. This behavior contradicts with the low-latency playback
mode, and we should turn off lowlatency_playback flag accordingly.
In theory, we may take the low-latency mode when the playback-first
quirk is set, but it still conflicts with the later operation with the
fixed packet numbers, so it's disabled all together for now.
Link: https://lore.kernel.org/r/20210929080844.11583-6-tiwai@xxxxxxx
Signed-off-by: Takashi Iwai <tiwai@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
sound/usb/pcm.c | 3 +++
1 file changed, 3 insertions(+)
--- a/sound/usb/pcm.c
+++ b/sound/usb/pcm.c
@@ -595,6 +595,9 @@ static int lowlatency_playback_available
/* free-wheeling mode? (e.g. dmix) */
if (runtime->stop_threshold > runtime->buffer_size)
return false;
+ /* implicit feedback mode has own operation mode */
+ if (snd_usb_endpoint_implicit_feedback_sink(subs->data_endpoint))
+ return false;
/* too short periods? */
if (subs->data_endpoint->nominal_queue_size >= subs->buffer_bytes)
return false;
Patches currently in stable-queue which might be from tiwai@xxxxxxx are
queue-5.15/alsa-usb-audio-rename-early_playback_start-flag-with-lowlatency_playback.patch
queue-5.15/alsa-usb-audio-disable-low-latency-playback-for-free-wheel-mode.patch
queue-5.15/alsa-usb-audio-avoid-killing-in-flight-urbs-during-draining.patch
queue-5.15/alsa-usb-audio-less-restriction-for-low-latency-playback-mode.patch
queue-5.15/alsa-usb-audio-improved-lowlatency-playback-support.patch
queue-5.15/alsa-usb-audio-check-available-frames-for-the-next-packet-size.patch
queue-5.15/alsa-usb-audio-switch-back-to-non-latency-mode-at-a-later-point.patch
queue-5.15/alsa-usb-audio-fix-packet-size-calculation-regression.patch
queue-5.15/alsa-usb-audio-don-t-start-stream-for-capture-at-prepare.patch
queue-5.15/alsa-usb-audio-disable-low-latency-mode-for-implicit-feedback-sync.patch
queue-5.15/alsa-usb-audio-add-spinlock-to-stop_urbs.patch
queue-5.15/alsa-usb-audio-restrict-rates-for-the-shared-clocks.patch
