https://bugzilla.kernel.org/show_bug.cgi?id=199749
--- Comment #31 from James Le Cuirot (chewi@gentoo.org) --- (In reply to notsyncing from comment #30)
Finally got logs from serial port when freezed. Seems my problem has nothing to do with amdgpu. Maybe I should file a new bug.
I may be off the mark but that looks more like bug #196683. Have you tried adjusting "Power Supply Idle Control" in the BIOS (if you have it) or using zenstates.py to disable the C6 package state?