[Bug 105971] DVI port is not detecting connected monitor with 4.16.0+ kernel and amdgpu.dc=1 set

[bugzilla-daemon@freedesktop.org]

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https://bugs.freedesktop.org/show_bug.cgi?id=105971

            Bug ID: 105971
           Summary: DVI port is not detecting connected monitor with
                    4.16.0+ kernel and amdgpu.dc=1 set
           Product: DRI
           Version: unspecified
          Hardware: x86-64 (AMD64)
                OS: Linux (All)
            Status: NEW
          Severity: normal
          Priority: medium
         Component: DRM/AMDgpu
          Assignee: dri-devel@lists.freedesktop.org
          Reporter: sass.joel@gmail.com

Created attachment 138731
  --> https://bugs.freedesktop.org/attachment.cgi?id=138731&action=edit
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.

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