https://bugzilla.kernel.org/show_bug.cgi?id=200531
--- Comment #5 from Aleksandr Mezin (mezin.alexander@gmail.com) --- "REG_WAIT timeout" doesn't occur with kernel built from "amd-staging-drm-next" branch from https://cgit.freedesktop.org/~agd5f/linux/. I can't find the exact commit because after some commits the system just doesn't boot.