This is a note to let you know that I've just added the patch titled
ALSA: usb-audio: Workaround for XRUN at prepare
to the 6.1-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-workaround-for-xrun-at-prepare.patch
and it can be found in the queue-6.1 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 198dde085ecc0138e4f0b0b69d18a0c870f2dea6 Mon Sep 17 00:00:00 2001
From: Takashi Iwai <tiwai@xxxxxxx>
Date: Mon, 5 Dec 2022 14:21:24 +0100
Subject: ALSA: usb-audio: Workaround for XRUN at prepare
From: Takashi Iwai <tiwai@xxxxxxx>
commit 198dde085ecc0138e4f0b0b69d18a0c870f2dea6 upstream.
Under certain situations (typically in the implicit feedback mode),
USB-audio driver starts a playback stream already at PCM prepare call
even before the actual PCM trigger-START call. For implicit feedback
mode, this effectively starts two streams for data and sync
endpoints, and if a coupled sync stream gets XRUN at this point, it
results in an error -EPIPE.
The problem is that currently we return -EPIPE error as is from the
prepare. Then application tries to recover again via the prepare
call, but it'll fail again because the sync-stop is missing. The
sync-stop is missing because it's an internal trigger call (hence the
PCM core isn't involved).
Since we'll need to re-issue the prepare in anyway when trapped into
this pitfall, this patch attempts to address it in a bit different
way; namely, the driver tries to prepare once again after syncing the
stop manually by itself -- so applications don't see the internal
error. At the second failure, we report the error as is, but this
shouldn't happen in normal situations.
Reported-and-tested-by: Carl Hetherington <lists@xxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/b4e71631-4a94-613-27b2-fb595792630@xxxxxxxxx
Link: https://lore.kernel.org/r/20221205132124.11585-4-tiwai@xxxxxxx
Signed-off-by: Takashi Iwai <tiwai@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
sound/usb/pcm.c | 13 +++++++++++--
1 file changed, 11 insertions(+), 2 deletions(-)
--- a/sound/usb/pcm.c
+++ b/sound/usb/pcm.c
@@ -604,6 +604,7 @@ static int snd_usb_pcm_prepare(struct sn
struct snd_pcm_runtime *runtime = substream->runtime;
struct snd_usb_substream *subs = runtime->private_data;
struct snd_usb_audio *chip = subs->stream->chip;
+ int retry = 0;
int ret;
ret = snd_usb_lock_shutdown(chip);
@@ -614,6 +615,7 @@ static int snd_usb_pcm_prepare(struct sn
goto unlock;
}
+ again:
if (subs->sync_endpoint) {
ret = snd_usb_endpoint_prepare(chip, subs->sync_endpoint);
if (ret < 0)
@@ -638,9 +640,16 @@ static int snd_usb_pcm_prepare(struct sn
subs->lowlatency_playback = lowlatency_playback_available(runtime, subs);
if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK &&
- !subs->lowlatency_playback)
+ !subs->lowlatency_playback) {
ret = start_endpoints(subs);
-
+ /* if XRUN happens at starting streams (possibly with implicit
+ * fb case), restart again, but only try once.
+ */
+ if (ret == -EPIPE && !retry++) {
+ sync_pending_stops(subs);
+ goto again;
+ }
+ }
unlock:
snd_usb_unlock_shutdown(chip);
return ret;
Patches currently in stable-queue which might be from tiwai@xxxxxxx are
queue-6.1/alsa-pcm-fix-undefined-behavior-in-bit-shift-for-snd.patch
queue-6.1/alsa-seq-fix-undefined-behavior-in-bit-shift-for-snd.patch
queue-6.1/alsa-hda-hdmi-set-default-audio-parameters-for-kae-s.patch
queue-6.1/alsa-asihpi-fix-missing-pci_disable_device.patch
queue-6.1/alsa-mts64-fix-possible-null-ptr-defer-in-snd_mts64_.patch
queue-6.1/alsa-pcm-set-missing-stop_operating-flag-at-undoing-.patch
queue-6.1/alsa-hda-hdmi-fix-stream-id-config-keep-alive-for-rt.patch
queue-6.1/alsa-hda-hdmi-add-hp-device-0x8711-to-force-connect-list.patch
queue-6.1/alsa-usb-audio-add-the-quirk-for-kt0206-device.patch
queue-6.1/alsa-usb-audio-add-quirk-for-tascam-model-12.patch
queue-6.1/alsa-hda-hdmi-fix-i915-silent-stream-programming-flo.patch
queue-6.1/alsa-usb-audio-workaround-for-xrun-at-prepare.patch
queue-6.1/alsa-hda-realtek-add-quirk-for-lenovo-tianyi510pro-14iob.patch
queue-6.1/alsa-memalloc-allocate-more-contiguous-pages-for-fal.patch
