https://bugs.freedesktop.org/show_bug.cgi?id=79980
--- Comment #16 from Andy Furniss adf.lists@gmail.com --- (In reply to comment #15)
This bug is caused by TAHITI_mc2.bin firmware. The old firmware works good.
Well I haven't tried without it, but I have so far failed to reproduce this bug on a slightly older 3.15 drm fixes also using TAHITI_mc2.bin.