amdgpu with mst WARNING and Kernel Oops on blanking/resume

[Tuomas Heino]

HWE kernel appears to get more amdgpu MST related WARNINGs and Oopses than non-HWE, mostly after resume from blanking or suspend.
Kernel logs for most recent one attached.

$ journalctl -b -1 -k | egrep -v 'audit|dbus-daemon' > oops20210428.txt
$ fgrep RIP oops20210428.txt | cut -c 31-
RIP: 0010:dcn20_validate_bandwidth_fp+0x9d/0xf0 [amdgpu]
RIP: 0010:dcn10_get_dig_frontend+0x93/0xc0 [amdgpu]
RIP: 0010:dc_link_allocate_mst_payload+0x1c9/0x1e0 [amdgpu]
RIP: 0033:0x7fe6953a550b
RIP: 0010:dc_link_add_remote_sink+0x65/0x110 [amdgpu]
RIP: 0033:0x7fe6953a550b
RIP: 0010:dm_dp_mst_get_modes+0xd9/0x210 [amdgpu]
RIP: 0033:0x7fe6953a550b
RIP: 0010:dm_dp_mst_get_modes+0xd9/0x210 [amdgpu]

ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: linux-image-5.8.0-50-generic 5.8.0-50.56~20.04.1
ProcVersionSignature: Ubuntu 5.8.0-50.56~20.04.1-generic 5.8.18
Uname: Linux 5.8.0-50-generic x86_64
ApportVersion: 2.20.11-0ubuntu27.16
Architecture: amd64
CasperMD5CheckResult: skip
CurrentDesktop: ubuntu:GNOME
Date: Wed Apr 28 08:43:08 2021
InstallationDate: Installed on 2020-04-10 (382 days ago)
InstallationMedia: Ubuntu 20.04 LTS "Focal Fossa" - Beta amd64 (20200402)
SourcePackage: linux-signed-hwe-5.8
UpgradeStatus: No upgrade log present (probably fresh install)

[Tuomas Heino (iheino+ub)]

Similar symptoms to https://gitlab.freedesktop.org/drm/amd/-/issues/1406 and repeats in some form most of the time when unlocking screen after screen blanking.

After suspend somewhat more random behaviour (works more often than after blanking).