This is a note to let you know that I've just added the patch titled ALSA: usb-audio: Less restriction for low-latency playback mode 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-less-restriction-for-low-latency-playback-mode.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 53451b6da8271905941eb1eb369db152c4bd92f2 Mon Sep 17 00:00:00 2001 From: Takashi Iwai <tiwai@xxxxxxx> Date: Mon, 11 Oct 2021 12:36:50 +0200 Subject: ALSA: usb-audio: Less restriction for low-latency playback mode From: Takashi Iwai <tiwai@xxxxxxx> commit 53451b6da8271905941eb1eb369db152c4bd92f2 upstream. The recent support for the improved low-latency playback mode applied the SNDRV_PCM_INFO_EXPLICIT_SYNC flag for the target streams, but this was a slight overkill. The use of the flag above disables effectively both PCM status and control mmaps, while basically what we want to track is only about the appl_ptr update. For less restriction, use a more proper flag, SNDRV_PCM_INFO_SYNC_APPLPTR instead, which disables only the control mmap. Fixes: d5f871f89e21 ("ALSA: usb-audio: Improved lowlatency playback support") Link: https://lore.kernel.org/r/20211011103650.10182-1-tiwai@xxxxxxx Signed-off-by: Takashi Iwai <tiwai@xxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- sound/usb/pcm.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/sound/usb/pcm.c +++ b/sound/usb/pcm.c @@ -1095,7 +1095,7 @@ static int snd_usb_pcm_open(struct snd_p /* need an explicit sync to catch applptr update in low-latency mode */ if (direction == SNDRV_PCM_STREAM_PLAYBACK && as->chip->lowlatency) - runtime->hw.info |= SNDRV_PCM_INFO_EXPLICIT_SYNC; + runtime->hw.info |= SNDRV_PCM_INFO_SYNC_APPLPTR; runtime->private_data = subs; subs->pcm_substream = substream; /* runtime PM is also done there */ 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