https://bugs.freedesktop.org/show_bug.cgi?id=73378
--- Comment #33 from Chernovsky Oleg adonai@xaker.ru --- Yep, I rechecked it and it seems set to 1 always...
Anyway I gathered around 18 Mb of mmiotrace logs to investigate. Now digging through divider and clock registers.
P.S. I only fear that maybe I launched mmiotrace too late, I did rmmod and then modprobe fglrx again. Could it setup any registers at the first run? Because at second it touched UVD only when I launched mpv.