https://bugs.freedesktop.org/show_bug.cgi?id=97179
--- Comment #1 from Michel Dänzer michel@daenzer.net --- (In reply to russianneuromancer from comment #0)
Most of the time I launch games via DRI_PRIME, but issue is also reproducible when game is launched on iGPU.
It can't be an r600 driver bug then.
Are you sure it's not a kwin bug?