USB Audio Xruns/Backport USB Audio Kernel Fixes

[djhardrich]

Great work, and thank you as always! I’ve been getting xruns with usb audio (tested with no MiSTer process running), pretty sure they’re related to the problems with/overhaul the usb audio stack has gotten between kernel 5.10 and 5.16. The author has a list of commits that fix the problems for 5.15 here: https://www.spinics.net/lists/stable/msg518525.html

Thanks again!!

[amstan]

Darn, not so easy, merge conflicts (click the one line to expand):

alex@alex-desktop:/tmp/Linux-Kernel_MiSTer (MiSTer-v5.15)% git cherry-pick 4e7cf1fbb3 9c9a3b9da8 e581f1cec4 bceee75387 d215f63d49 0ef74366bc d5f871f89e 813a17cab9 23939115be 53451b6da8 eee5d6f135 83de8f8381

[MiSTer-v5.15 3e9a0b15815a] ALSA: usb-audio: Restrict rates for the shared clocks
 Author: Takashi Iwai <[email protected]>
 Date: Wed Sep 29 10:08:36 2021 +0200
 4 files changed, 32 insertions(+)
Auto-merging sound/usb/card.h
Auto-merging sound/usb/endpoint.c
[MiSTer-v5.15 7d04573d3863] ALSA: usb-audio: Rename early_playback_start flag with lowlatency_playback
 Author: Takashi Iwai <[email protected]>
 Date: Wed Sep 29 10:08:38 2021 +0200
 3 files changed, 26 insertions(+), 10 deletions(-)
[MiSTer-v5.15 20191bf0ee39] ALSA: usb-audio: Disable low-latency playback for free-wheel mode
 Author: Takashi Iwai <[email protected]>
 Date: Wed Sep 29 10:08:39 2021 +0200
 1 file changed, 6 insertions(+), 2 deletions(-)
[MiSTer-v5.15 5f2887a0728c] ALSA: usb-audio: Disable low-latency mode for implicit feedback sync
 Author: Takashi Iwai <[email protected]>
 Date: Wed Sep 29 10:08:40 2021 +0200
 1 file changed, 3 insertions(+)
Auto-merging sound/usb/endpoint.c
[MiSTer-v5.15 7fb5dd34f3ee] ALSA: usb-audio: Check available frames for the next packet size
 Author: Takashi Iwai <[email protected]>
 Date: Wed Sep 29 10:08:41 2021 +0200
 3 files changed, 39 insertions(+), 17 deletions(-)
Auto-merging sound/usb/endpoint.c
[MiSTer-v5.15 ca0e2bcc7a6c] ALSA: usb-audio: Add spinlock to stop_urbs()
 Author: Takashi Iwai <[email protected]>
 Date: Wed Sep 29 10:08:42 2021 +0200
 1 file changed, 3 insertions(+)
Auto-merging sound/usb/card.h
Auto-merging sound/usb/endpoint.c
CONFLICT (content): Merge conflict in sound/usb/endpoint.c
error: could not apply d5f871f89e21... ALSA: usb-audio: Improved lowlatency playback support
hint: After resolving the conflicts, mark them with
hint: "git add/rm <pathspec>", then run
hint: "git cherry-pick --continue".
hint: You can instead skip this commit with "git cherry-pick --skip".
hint: To abort and get back to the state before "git cherry-pick",
hint: run "git cherry-pick --abort".

The keyword from that thread is "they can be applied and built cleanly on 5.15.5.", Mister's kernel is a little behind that :D
So we either need to update the whole kernel to 5.15.whateverit'snow and hope Sorg's modifications don't conflict, or we need to find the individual audio patches (present in 5.15.5) that are requirements of the other patches above.

[amstan]

I already mentioned on discord: I did a rebase, try using linux-misterarch-5.15.25-1. It's an experiment based on the work at https://github.com/MiSTerArch/linux