https://bugs.freedesktop.org/show_bug.cgi?id=104300

            Bug ID: 104300
           Summary: Kernel 4.15-rc2 on Polaris RX 480 with amdgpu.dc=1 has
                    trouble waking up displays after suspend
           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: toni.spets@iki.fi
                CC: mariusz.g.mazur@gmail.com
                CC: mariusz.g.mazur@gmail.com

When resuming from suspend on 4.15-rc2 the DC stack *usually* wakes up displays
after some waiting on this Polaris card compared to non-DC code which flips
them on instantly.

I've encountered the following issues with my dual head setup (native DVI and
HDMI->DVI adapter):

 - it takes long (2-5 seconds) for the outputs to come up
 - Xfce thinks both of the display were hotplugged causing all kinds of
desktop/windowing related issues
 - sometimes corrupted image on both outputs and the outputs are reset after
waiting for 20 seconds or so, sometimes they come up, sometimes the corruption
stays, the system is unresponsive to input while that's going on

I have zero issues without DC. Waking up works 100% of the time and Xfce never
thinks the displays were hotplugged.

Currently I have no logs from kernel from that time. Hope this description is
enough.

--- Comment #1 from Mariusz Mazur <mariusz.g.mazur@gmail.com> ---
I'm reliably getting monitors waking up be treated as hotplugged on ubuntu
18.04's 4.15 kernels and a build of 4.16.7. More info:
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1770836

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