Incomplete stable drm/ast backport - screen freeze on boot

[Keno Fischer]

Greetings,

When connected to a remote machine via the BMC KVM functionality,
I am experiencing screen freezes on boot when using 6.5 stable,
but not master.

The BMC on the machine in question is an ASpeed AST2600.
A quick bisect shows the problematic commit to be 2fb9667
("drm/ast: report connection status on Display Port.").
This is commit f81bb0ac upstream.

I believe the problem is that the previous commit in the series
e329cb5 ("drm/ast: Add BMC virtual connector")
was not backported to the stable branch.
As a consequence, it appears that the more accurate DP state detection
is causing the kernel to believe that no display is connected,
even when the BMC's virtual display is in fact in use.
A cherry-pick of e329cb5 onto the stable branch resolves the issue.

Cheers,
Keno