Bug 107393

Summary: 4.18.0-rc6 amdgpu framebuffer problems with DisplayPort
Product: DRI Reporter: lkd-fdo
Component: DRM/AMDgpuAssignee: Default DRI bug account <dri-devel>
Status: RESOLVED MOVED QA Contact:
Severity: normal    
Priority: medium CC: harry.wentland, pmenzel+bugs.freedesktop.org
Version: unspecified   
Hardware: x86-64 (AMD64)   
OS: Linux (All)   
Whiteboard:
i915 platform: i915 features:
Attachments:
Description Flags
combined kernel dmesg for two boot sessions, one in 4.17.0 and the other in 4.18.0-rc6 none

Description lkd-fdo 2018-07-27 07:48:45 UTC 
Created attachment 140848 [details]
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
Comment 1 lkd-fdo 2018-11-25 19:21:02 UTC 
Additional new wrinkle (old bug but just for completeness)

The monitor I use (Acer XR341CK) evidently has a built-in DisplayPort MST, and it's controllable for either extending the display or cloning it to the other DP connector.

All the issues from this bug report disappear provided the MST mode is set to clone the incoming signal.
Comment 2 Martin Peres 2019-11-19 08:45:54 UTC 
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