Comment # 7 on bug 95308 from Marek Olšák

Can you please do this:
- Disable GPU reset by adding this kernel parameter: radeon.lockup_timeout=0
- Reproduce the GPU hang.
- CTRL+F1. This should switch to text mode successfully if you've disabled GPU
reset. You can't got back to X now.
- Save the contents of dmesg.
- Reboot

Attach dmesg here.

If dmesg doesn't contain a VM fault, you don't have to do anything else for
now.

If dmesg contains a VM fault, set this environment variable and start the game:
R600_DEBUG=check_vm

(If it's a steam game, you must get the correct steam run command, which can be
obtained from the desktop shortcut. For me, it looks like this: steam
steam://rungameid/440 ; Make sure Steam isn't running, then run
"R600_DEBUG=check_vm steam steam://rungameid/$number" where $number is the game
number)

After you reproduce the hang again, reboot and attach the new files located in
~/ddebug_dumps/. Those should be records of VM faults created by
R600_DEBUG=check_vm.

I can't promise I will be able to fix this. The issue is kinda random and it
may be fixed by a later kernel or Mesa release.