https://bugs.freedesktop.org/show_bug.cgi?id=79806
--- Comment #3 from Chernovsky Oleg adonai@xaker.ru ---
Workaround: when resume, execute "echo auto > /sys/class/drm/card0/device/power_dpm_force_performance_level".
How did you do that? It gives me "echo: write error: Invalid argument" on kernel 3.15