Created attachment 138731 [details] dmesg output from amdgpu.dc=0 switch Hello. I'm trying to get 4 monitors working on the same desktop. Video card is a Radeon RX560. root@nope:/tmp# lsb_release -a LSB Version: core-9.20160110ubuntu0.2-amd64:core-9.20160110ubuntu0.2-noarch:security-9.20160110ubuntu0.2-amd64:security-9.20160110ubuntu0.2-noarch Distributor ID: Ubuntu Description: Ubuntu 16.04.4 LTS Release: 16.04 Codename: xenial root@nope:/tmp# uname -a Linux nope 4.16.0+ #1 SMP Mon Apr 2 15:52:14 CEST 2018 x86_64 x86_64 x86_64 GNU/Linux With kernel switch amdgpu.dc=1, DVI port doesn't detected connected monitor, but displayport MST is detected and utilized properly, allowing me to output video to three monitors from a single displayport. With kernel switch amdgpu.dc=0, DVI port properly detects connected monitor, but displayport MST is not detected. Instead, displayport MST acts as a single output, and video output is mirrored to all three connected monitors. This appears to be a kernel issue. Kernel was retrieved from git repo github.com/M-Bab/linux-kernel-amdgpu-binaries I'm running the AMDGPU.UBUNTU kernel on that repo. I'll attach dmesg, xrandr and Xorg.0.log output from both kernel switches. I'm running amdgpu.dc_log=1 kernel switch for verbose logging.
Created attachment 138732 [details] Xorg.0.log with amdgpu.dc=0
Created attachment 138733 [details] xrandr with amdgpu.dc=0
Created attachment 138734 [details] lshw output
Created attachment 138735 [details] Xorg.0.log with amdgpu.dc=1
Created attachment 138736 [details] dmesg output with amdgpu.dc=1 switch
Created attachment 138737 [details] xrandr with amdgpu.dc=1 switch
A note about the Xorg.0.log with amdgpu.dc=0, I see that the amdgpu module doesn't appear to be loaded. X came up just fine without the driver being loaded, and GPU desktop acceleration still worked just fine with compiz in gnome-flashback.
Update: looks like the DVI output detection of the monitor has been fixed in drm-fixes-4.17 from agd5f here: https://cgit.freedesktop.org/~agd5f/linux/?h=drm-fixes-4.17 had to compile it myself, but works relatively well. When plugging in a new monitor, the size was not properly detected, but it's better than freezing. Thanks!
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