kern/53795: i915drmkms causes crash on boot with Atom N270/945GSE netbook

[elliott1787%gmail.com@localhost]

>Number:         53795
>Category:       kern
>Synopsis:       i915drmkms causes crash on boot with Atom N270/945GSE netbook
>Confidential:   no
>Severity:       critical
>Priority:       high
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sun Dec 16 23:50:00 +0000 2018
>Originator:     Elliott Shue
>Release:        NetBSD/i386-8.0
>Organization:
>Environment:
>Description:
I have an Atom N270 powered netbook with an Intel 945GSE chipset. It is a re-branded ECS E09EI6. It works fine in OpenBSD and Linux.

If I boot the GENERIC NetBSD kernel with i915drmkms enabled I get a hang with garbage on the screen right when intelfb should be initialized. 

If I disable i915drmkms in userconf I can get the system to boot and complete the install. I've built a kernel without i915drmkms for now to play around. It runs, but X falls back to vesa.

The last lines before the screen goes blank and displays garbage are:
i915drmkms0: interrupting at ioapic0 pin 16 (i915)  
drm: initialized overlay support                  
drm: GMBUS [i915 gmbus vga] timed out, falling back to bit-banging on pin 2


I had to take a video of the screen since a serial console is not possible. Here is a snapshot of the last frame before it goes black:

https://i.imgur.com/xnvurv3.jpg

I built a kernel with the legacy i915drm, it boots, but I don't get a proper framebuffer and also am stuck with vesa for X.

The problem exists in 7.x as well.
>How-To-Repeat:
Boot this netbook with i915drmkms enabled.
>Fix: