R9-270 has no video output when underclocked
Submitted by Mario Wenzel
Assigned to Default DRI bug account
I have a Radeon R9-270 and I am running Fedora 23 with the default OpenSource drivers supplied with the repository.
Yesterday I did an Update from Kernel 4.3.3-300 to 4.4.3-300 and I started seeing some issues. When I do nothing for about 12 seconds the screens (dual head) turn blank. Moving the mouse makes the screen go back on again. Sometimes the login-screen of the gnome-shell or chrome are frozen but the system as a whole seems fine.
During normal operations /sys/kernel/debug/dri/0/radeon_pm_info is the following:
power level 0 sclk: 30000 mclk: 120000 vddc: 950 vddci: 1000 pcie gen: 2
When the screen is still for a bit (exactly when it turns blank) the output is
power level 0 sclk: 30000 mclk: 15000 vddc: 900 vddci: 850 pcie gen: 2
So apparently, when the video card is clocked down, the output is deactivated.
My current "workaround" is running videos on the side - not an ideal solution.