[Regression] Tonga can't bring up > 1 display since DC enablement

Submitted by Lyude Paul @lyudess

Assigned to Default DRI bug account

Link to original bug (#107066)

Description

Created attachment 140384
Aforementioned dmesg

Since DC got enabled for my GPU (R9 380 Tonga from Gigabyte, 22:00.0 VGA compatible controller [0300]: Advanced Micro Devices, Inc. [AMD/ATI] Tonga PRO [Radeon R9 285/380] [1002:6939] (rev f1)) I haven't been able to bring up more then a single display at a time. More then one display usually results in at least one display turning on, one other display possibly turning on but only showing purple and another not turning on, or one display works and the other two just don't come up at all. Additionally, my dmesg is filled with spam from amdgpu (see attachment).

I've confirmed this still seems to be present in amdgpu's drm-next-4.19, and it seems to be caused by the fact that none of the dc_states in the function mentioned in the WARN_ON() actually have a stream assigned to them. I'm currently swimming in a sea of bugs though, so any help would be appreciated :).

Attachment 140384, "Aforementioned dmesg":
dmesg.log