AMD GPU Wake from sleep intermittent issue (unresponsive, related to vblank)

Had an interesting wake from sleep this morning. Symptoms included: kscreenlocker wasn’t engaged (though might be unrelated), mouse was extremely slow and stuttery, keyboard entirely unresponsive. I forced a hard reboot and investigated.

Journal revealed these items, spammed several times:
[drm:dc_dmub_srv_wait_idle [amdgpu]] *ERROR* Error waiting for DMUB idle: status=3
[drm:dc_dmub_srv_cmd_queue [amdgpu]] *ERROR* Error queuing DMUB command: status=2

I’ve not had this issue before, and can only assume that the bug that caused it was included in the latest stable update. The problem seems intermittent as well, as this is the first time it has happened, and a couple of sleep tests have not caused it to reoccur (as yet).

I did some digging, and found that others with AMD 6000 series GPUs (6700XT, 6600XT, 6500XT) are affected and it seems to be caused by a commit which was intended to save power by disabling vblank IRQs aggressively (so says the comment in the commit). A solution I found on the gitlab forum was to revert the change, and a patch was provided by an amd dev. Another quick solution was adding the kernel parameter drm.vblankoffdelay=0. (see links below)

I have several questions I hope someone here can shed some light on:

  • was this commit part of the latest stable update?
  • are there any side-effects/downsides to enabling the kernel parameter drm.vblankoffdelay=0?
  • did the last stable update include grub that had the issue with fwsetup that would obliterate my bootloader if I updated my grub config?
  • is this patch included in a future amd driver update that is coming in the next stable update?

Thank you for any insights! I like to learn about a problem as much as I can.

the offending commit :
the apparent solution (scroll down to Alex Deucher’s response and Red Squid’s explanation) :

My system info:
CPU: AMD Ryzen 7 3700X
Kernel: 5.15.65
DE: KDE 5.25.5
(can’t think of anything else that might be relevant. display drivers are as per stable update 2022-09-12)