Created attachment 143104 [details]
Xorg.0.log using xf86-video-modesetting

Michel has suggested trying xf86-video-modesetting. A difference from user
perspective is minimal.

1) With both drivers I can use HDMI output port just fine after booting
(without a docking station)

2) After that I connect docking station, connect DP, disconnect DP, disconnect
docking station

3) Finally I try connecting monitor to the HDMI output again:
a) With xorg-xf86-video-amdgpu I get "Output DisplayPort-0 is not disconnected
but has no modes"
b) With xf86-video-modesetting I get "xrandr: Configure crtc 1 failed"