Comment # 8 on bug 100745 from Benjamin Bellec

I hit the same problem today after enabling amdgpu.dc=1
The screen doesn't light up at all if I boot the kernel with amdgpu.dc=1

Config is:
Fedora 27 + kernel 4.15.0-0.rc0.git7.1.fc28.x86_64
Radeon R9 380X
Dell U2414H


dmesg error is:
kernel: [drm:dm_logger_write [amdgpu]] *ERROR* perform_clock_recovery_sequence:
Link Training Error, could not                          get CR after 100 tries.