There is two year bug causing white screen, when running a game on dedicated graphics.
I (probably) found an solution here:
https://bugs.freedesktop.org/show_bug.cgi?id=69101
Which is inserting
radeon.runpm=0
Onto kernel command line and launching a game with DRI_PRIME=1 and LIBGL_DRI3_DISABLE=1. Author of this solution wrote, that it will raises power consumption.
Is there a better idea? I uses my laptop on school and for entertainment, so I need good performance and low power consumption (not always I can connect laptop to power input),