i915kms kernel module causing freezes on FreeBSD 13.0-RELEASE

[Matt K]

Hello,

After upgrading from FreeBSD 12.2-p6 to FreeBSD 13.0 I started encountering
freezes using the i915kms kernel module and starting X. Here's what I tried
and what I found out:

- Loading the module via rc.conf and kld_list="${kld_list} i915kms" causes
freezes 100% of the time when starting X (tty is fine). Does not matter if
I start X by "startx" command or by some login manager like XDM. It also
does not matter if I use the "modesetting" driver in xorg.conf or if I use
xf86-video-intel "intel" driver in xorg.conf. Freezes happen certainly.
- I tried both the pkg version of drm-fbsd13-kmod and the ports version.
- I tried various combinations of loading the i915kms manually with kldload
and starting X with modesetting, loading it automatically via rc.conf with
"intel" driver, loading it automatically via rc.conf with "modesetting"
driver, using XDM, not using XDM.
- These are the possibilities to have a stable usable system with X:
1. not mentioning i915kms in rc.conf is a must. Then I can load X with XDM
and it automatically pulls i915kms by specifying "Driver" "intel" in
xorg.conf.
2. not mentioning i915kms in rc.conf is a must. Then I have to "kldload
i915kms" and then I can "startx" and it works. In this case It does not
matter if I have "modesetting" or "intel" in xorg.conf, both work.

- Sometimes the freezes are so drastic, that not even pressing the power
button works, I've also had a few freezes, where also the reset button on
the PC case did not work (first time I've seen that happen in my entire
life) and I had to turn off the power supply by a mechanical switch.
- When the freezes happen, these messages appear in /var/log/messages
(during some of the softer freezes, when the computer even has a chance to
write something to logs):

May  2 16:34:15 fbsd kernel: drmn0: GPU HANG: ecode 7:1:0xdfffbe76, in
MainThread [101358], hang on rcs0
May  2 16:34:15 fbsd kernel: drmn0: Resetting chip for hang on rcs0

May  7 19:28:59 fbsd kernel: drmn0: GPU HANG: ecode 7:1:0xccfac4e0, in
MainThread [101334], hang on rcs0
May  7 19:28:59 fbsd kernel: drmn0: Resetting chip for hang on rcs0

Here is my original thread on FreeBSD forums
https://forums.freebsd.org/threads/i915-driver-causing-freezes-on-freebsd-13-0.80016/

What caused me to ask for your generous advice here is the fact that other
FreeBSD users chimed in with similar/identical problems with various other
intel CPUs, their problems, too, started after upgrading to 13.0.

user#1: CPU: Intel(R) Xeon(R) CPU E3-1225 v3 @ 3.20GHz (3192.68-MHz
K8-class CPU)
user#2: i5-3570K
me: i5-4690

Any advice is appreciated in advance,

MK