drm-kmod kills FreeBSD

[Chris Hill]

Hello, list.

This is a head-scratcher for me; any help or clues will be most welcome.

I had been running xorg on 12.2-R [1], but recently had a disk failure 
and had to reinstall. Although I (thought I had!) kept meticulous notes, 
the onboard Intel UHD 630 graphics are just not happening. [2] Note, I'm 
not even to the point of attempting to start X; I'm just trying to get 
the system to boot and recognize the onboard graphics.

I've installed both drm-kmod-g20190710 and 
drm-fbsd12.0-kmod-4.16.g20201016 (not at the same time) [3], and put 
kld_list="/boot/modules/i915kms.ko" in /etc/rc.conf, as instructed.

When I boot the system like that, it appears to hang partway through the 
console boot messages. The screen goes blank, and the network interface 
becomes unresponsive. The remedy is a hard shutdown from the power 
button, boot from a memstick and remove the offending line from rc.conf. 
I get the same result from `kldload /boot/modules/i915kms.ko`.

I *think* it's hanging in the neighborhood of loading drm; a dmesg I 
saved from a pre-failure successful boot has lines like
drmn0: <drmn> on vgapci0
  and
[drm] Connector DP-1: get mode from tunables:
  ...where we currently see none of that.

Thanks very much.


[1] The hardware is a Dell Precision 3630 tower workstation. The OS is a 
fresh install, with freebsd-update applied just after.
$ uname -mvU
FreeBSD 12.2-RELEASE-p1 GENERIC  amd64 1202000

[2] The graphics system appears thus in the output of `pciconf -lv`:
vgapci0 at pci0:0:2:0:     class=0x030000 card=0x08711028 chip=0x3e928086
rev=0x00 hdr=0x00
     vendor     = 'Intel Corporation'
     device     = 'UHD Graphics 630 (Desktop)'
     class      = display
     subclass   = VGA

[3] As of this writing, I have
$ pkg info
drm-fbsd12.0-kmod-4.16.g20201016 DRM modules for the linuxkpi-based KMS components
gpu-firmware-kmod-g20201213    Firmware modules for the linuxkpi-based KMS components
pkg-1.16.1                     Package manager

-- 
Chris Hill               chris at monochrome.org