4.18.0-rc6 amdgpu framebuffer problems with DisplayPort

Submitted by LD @lkd-fdo

Assigned to Default DRI bug account

Link to original bug (#107393)

Description

Created attachment 140848
combined kernel dmesg for two boot sessions, one in 4.17.0 and the other in 4.18.0-rc6

On kernel 4.17.0, amdgpudrmfb functions correctly; taking the fb from efifb

On kernel 4.18.0-rc6 (and previous), the framebuffer proper doesn't start; monitor doesn't get a valid display signal. If I log in and blind-start a Wayland compositor (sway in my case), the display gets a desktop and things work normally. Once I exit out back to FB, the display is blanked.

Everything works normally if I connect the monitor with HDMI instead.

This was a problem with 4.18.0-rc5 as well. I was pointed to the patch at https://lists.freedesktop.org/archives/amd-gfx/2018-July/023920.html and applied it to 4.18.0-rc5, but it had no effect on behavior.

GPU: Vega64
Monitor: Acer XR341CK

Attachment 140848, "combined kernel dmesg for two boot sessions, one in 4.17.0 and the other in 4.18.0-rc6":
kernel-dmesg.out