When booting kernel 4.17 or 4.18-pre on Power9 machine with Radeon Pro WX 4100 I get no output on a monitor connected thru DisplayPort, the monitor is not detected by the driver and a "PowerPlay" error appears in the kernel log. When booting 4.16 kernel (kernel-4.16.16-300.fc28.ppc64le), all is OK. See attached dmesg (resp. journalctl -k -b) outputs.
Created attachment 140359 [details]
boot log for 4.18.0-0.rc2.git2.1.fc29
Created attachment 140360 [details]
boot log for 4.16.16-300.fc28
No output is for the host OS (kernel), that's kexec-ed from the bootloader. I see the petitboot output.
amdgpu.dc=0 on the kernel command line might serve as a workaround for now.
(In reply to Michel Dänzer from comment #4)
> amdgpu.dc=0 on the kernel command line might serve as a workaround for now.
Thanks, it helps.
Could you please also post the respective /var/log/Xorg.* logs?
Created attachment 140364 [details]
Xorg log for 4.18.0-0.rc2.git2.1.fc29
Created attachment 140365 [details]
Xorg log for 4.17.2-200.fc28 with amdgpu.dc=0
Probably a good news, the amdgpu.dc=0 workaround isn't needed with 5.1-rc7 (haven't checked previous kernels yet).
and the dc=0 was still required for 5.0, so sound like an improvement in 5.1
(In reply to Dan Horák from comment #10)
> and the dc=0 was still required for 5.0, so sound like an improvement in 5.1
Glad to hear it's fixed in 5.1! Thanks for the follow-ups, resolving accordingly.