Comment # 6 on bug 105619 from Michael Lange

Running in the same problem, same error in dmesg.
I have two monitors (AOG AG272FCX), one connected via hdmi to the discrete gpu
(HD 8800) and the second one connected via hdmi to the integrated gpu (KAVERI).
On Windows 10 both working as expected, but in linux only the first monitor
(connected to HD8800) works. 

Mainbord: Gigabyte G1.Sniper A88X-CF
CPU: A10-7850K

linux: 4.16.2

The dmesg and Xorg.0.log are attached