amdgpu: Wrong screen resolution after monitor power cycle

[Lothar Paltins]

Hi,

I've got a system with an AMD Ryzen 5 2400G with Radeon Vega Graphics 
that is connected to a Dell U3011 Monitor with a native resolution of 
2560x1600 via DisplayPort. The OS is OpenSuse Tumbleweed with Kernel 
4.16.12. I was used to switch off the monitor with the power button when 
I'm not using the system. But now when I switch the monitor on again, 
the screen resolution is often only 1920x1200 and I've found no way to 
set it back to 2560x1600 without rebooting the system. This happens not 
always, but very often. And it doesn't happen in DPMS standby mode, only 
after a power cycle of the monitor. Does anybody know, why this happens 
and how it could be fixed?

Best regards
Lothar