Kernel 5.14-rc4 and -rc5 give the following message on boot:

[    2.533418] i915 0000:00:02.0: Device initialization failed (-19)
[    2.533472] i915 0000:00:02.0: Please file a bug on drm/i915; see
https://gitlab.freedesktop.org/drm/intel/-/wikis/How-to-file-i915-bugs
for details.

And when I suspend the machine, the screen stays dark when resuming.

Bisected to the following commit:

commit 69de4421bb4c103ef42a32bafc596e23918c106f
Author: Jason Ekstrand <jason@jlekstrand.net>
Date:   Wed Jul 21 10:23:57 2021 -0500

    drm/ttm: Initialize debugfs from ttm_global_init()

And reverting this fixes the problem.

This is on a Thinkpad T520, and "lspci" tells me the following about the
graphics card:

00:02.0 VGA compatible controller: Intel Corporation 2nd Generation Core
Processor Family Integrated Graphics Controller (rev 09)

.config is attached
-- 
Hilsen Harald