Black screen on boot for Fedora 28 with 4.17 kernel (i.e. with amdgpu.dc defaulted)

Submitted by Simon Geard

Assigned to Default DRI bug account

Description

Created attachment 141422
Contents of /proc/cpuinfo on successful boot

My Fedora 28 desktop stopped booting up cleanly after switching to the 4.17 kernel where amdgpu.dc became the default... the system seems to be working (e.g when installing updates, it automatically reboots once done), but the screen goes black immediately after grub loads the kernel, and it remains that way indefinitely. Passing "amdgpu.dc=0" on the kernel command line resolves the problem.

The active graphics card is an AMD RX-470, the CPU is an AMD A10-7850k (with unused onboard graphics).

This was logged on the RedHat bugzilla, but after receiving no response in over a month, I've opted to log it here instead. Here's the link to the downstream bug:

https://bugzilla.redhat.com/show_bug.cgi?id=1601812

I've re-attached the same files provided there – the output of lspci, dmesg, and /proc/cpuinfo for a successful boot – but if you need anything else to track this down, let me know.

Attachment 141422, "Contents of /proc/cpuinfo on successful boot":
cpuinfo.txt