kern/58026: amdgpu suspend/resume almost works

[mrg%eterna23.net@localhost]

>Number:         58026
>Category:       kern
>Synopsis:       amdgpu suspend/resume almost works
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sun Mar 10 08:50:02 +0000 2024
>Originator:     matthew green
>Release:        -current
>Organization:
>Environment:
amd64, thinkpad A475
>Description:
after suspend/resume cycle where X11 was the active console, the display
shows a blank screen with a cursor in the top-left, and requires switching
the vt away from X and then back to it, where it works fine.  it seems like the display is left in "text" mode at this point..

on half-generation earlier amd HP system, which has radeon for drm not
amdgpu (but are both 4-gen bulldozer APU systems), this works fine and it
resumes into X no problem, so something about amdgpu vs radeon may be the
problem here...
>How-To-Repeat:
run X on thinkpad A475 and suspend/resume.
>Fix: