[Intel-gfx] [BUG - BISECTED] display not detected anymore

[Heiko Carstens]

Hello,

I have Fedora 33 running, and with the Fedore kernel update from 5.11
series to 5.12 my external monitor was not detected anymore. Same is
true with the Fedora supplied 5.13 kernel version.

So I tried with vanilla kernel 5.11 and latest git head from Linus'
tree. 5.11 works while latest git head does not. Bisecting the problem
points to commit 32c3d9b0f51e ("Merge tag 'drm-intel-next-2021-01-27'
of git://anongit.freedesktop.org/drm/drm-intel into drm-next").

Unfortunately it is a merge commit, so it looks like conflicting
changes have been made in the parent branches.

Hardware in use:

- ThinkPad X1 Yoga 4th / Carbon 7th
- Intel(R) Core(TM) i5-8265U CPU @ 1.60GHz

The Thinkpad is connected to a ThinkPad Thunderbolt 3 Dock with a
Thunderbolt cable and a monitor (Eizo EV3285) is connected via
Displayport to the docking station.

The monitor is detected and works without any problems (4k at 60HZ)
before the above mentioned merge commit. With the commit and
afterwards it is not detected anymore and only the Thinkpad builtin
display can be used.

Any idea what went wrong? I can provide more information, or test
debug patches if wanted. Just let me know.

Thanks,
Heiko