I have a Fiji card 01:00.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI] Fiji [Radeon R9 FURY / NANO Series] (rev ca) with two LG DisplayPort 27" 4K monitors. If one of the displays is powered off, but connected, dmesg shows error messages [drm:drm_crtc_helper_set_config [drm_kms_helper]] *ERROR* failed to set mode on [CRTC:34:crtc-1] and GDM/X will refuse to run.
Please attach your dmesg output and xorg log.
Created attachment 243531 [details] xorg log
Created attachment 243541 [details] dmesg