AMDGPU doesn't detect monitor 90% of the time
So I recently built a new computer with an AMD Radeon RX 570 graphics card in it. Unfortunately, I have been struggling quite considerably with getting it to work. 90% of the time, when I boot up Linux, the GPU doesn't detect the monitor at all and I have no clue what's going on. The BIOS is always visible, as is the GRUB menu, but after that point it just sorta stops. Fortunately, SSH access is enabled, so I have managed to hack away at the issue.
After troubleshooting on the Arch forums (link), we're pretty sure that this appears to be a kernel issue, unfortunately. When the boot option
amdgpu.dc=0 is enabled, I am always able to boot fine, with no issues whatsoever. When it's not enabled, the issue is extremely prevalent, so we can assume this is a DisplayCore problem. The issue appears to be from at least 4.19 (Debian Stable), but I have confirmed it still occurs on 5.5-rc2.
Attached are two dmesg logs, taken after just having boot up. Both include
drm.debug=0x1e log_buf_len=2M as options, but one includes
amdgpu.dc=0 and the other does not. I'm still crossing my fingers that this is just me being very stupid with a config problem, but I'm not holding out too much hope for that.