Dear Maintainer,

Unfortunately, the bug #1108250 re-occurred after a reboot. Since Ben
Hutchings indicated that this is probably not related to
firmware-intel-graphics, I am filing directly against the kernel.

Starting in 6.12.30+bpo-amd64 I noticed syslog errors from the i915
module. The screen flickers or stays completely black, even VTs are not
working. X11 sometimes hangs in an uninterruptible sleep, so I can only
reboot to restart it. In the syslog I found messages like:

[   38.701277] i915 0000:00:02.0: [drm] *ERROR* flip_done timed out
[   38.701311] i915 0000:00:02.0: [drm] *ERROR* [CRTC:53:pipe A] commit
wait timed out
[   48.942077] i915 0000:00:02.0: [drm] *ERROR* flip_done timed out
[   48.942106] i915 0000:00:02.0: [drm] *ERROR* [CONNECTOR:86:HDMI-A-1]
commit wait timed out

I tested a bit further and realized that there is a certain chance that
the graphics works normally after a boot. I observed the same behavior
on kernel 6.12.38+deb12-amd64. I also tried a fresh install on a new SSD
and memtest'd the RAM.

I then attached a serial console to get all messages during reboot and
realized that there is indeed a crash in the i915 module, specifically
with a "vblank wait timed out on crtc 0" message.

Please find attached a full dmesg, a full `lspci -nnnvv`, and the
recorded serial log during reboot.

Unfortunately, my research on the error messages did not reveal much. I
experimented with some kernel options without success.

Do you have any idea for further analysis?

Best,
Maximilian