https://bugs.freedesktop.org/show_bug.cgi?id=91880
--- Comment #155 from john@dev1ce.com --- Running a gigabyte AMD R9 380 card and getting similar problems.
the system boots, loads the driver and the fans briefly spin to 100% before the video goes completely dark and the monitor turns off. the card is detected as a Tonga PRO 285/380.
this issue is going to become much more critical in the next week, as SteamOS just switched their AMD proprietary drivers for amdgpu open source drivers.