Kernel 4.15-rc2 on Polaris RX 480 with amdgpu.dc=1 has trouble waking up displays after suspend

Submitted by Toni Spets

Assigned to Default DRI bug account

Link to original bug (#104300)

Description

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.