Since the update from 2.21.15 (with kernel/xorg staying the same, since I also
tried 2.99.917-1~exp1 before the xorg api breakage), I noticed that the video
output is occasionally corrupted, with horizontal banding being visible, like
for a miscalculated stride offset.

I'm also experiencing stalls of 1-2 seconds, independently of the output
corruption.

Nothing is being written in dmesg/xorg logs when any of the above happens.

This also seems to happen irregardless if there's one single output or a second
monitor is also connected to the system.

Unfortunately hard to reproduce reliably.

Please file this upstream at
https://bugs.freedesktop.org/enter_bug.cgi?product=xorg&component=Driver/intel

Thanks,
Julien

	There is a bug fix out for Fedora that
fixes what looks like a similar issue for
V2.99.917-9 (https://bugzilla.redhat.com/show_bug.cgi?id=1226531).
Apparently DRI3 (which was enabled on 917-2) was disabled in
917-9.  It would be nice to have a later version available
in Debian to test out DRI3 and whether this bug is fixed.