i915 DRMKMS GPU hang

["John D. Baker" <jdbaker%mylinuxisp.com@localhost>]

On an IBM ThinkCentre S51:

$ uname -a
NetBSD thinkcentre.technoskunk.fur 7.0_STABLE NetBSD 7.0_STABLE (GX260A) #5: Thu Jan 28 10:44:14 CST 2016  sysop%x3650.technoskunk.fur@localhost:/r0/build/netbsd-7/obj/i386/sys/arch/i386/compile/GX260A i386

with:

[...]
pchb0 at pci0 dev 0 function 0: Intel 82915P/G/GL Host (rev. 0x04)
agp0 at pchb0: i915-family chipset
agp0: detected 7932k stolen memory
agp0: aperture at 0xc0000000, size 0x10000000
i915drmkms0 at pci0 dev 2 function 0: Intel 82915G/GL Integrated Graphics Device (rev. 0x04)
drm: Memory usable by graphics device = 256M
drm: Supports vblank timestamp caching Rev 2 (21.10.2013).
drm: Driver supports precise vblank timestamp query.
i915drmkms0: interrupting at ioapic0 pin 16 (i915)
drm: initialized overlay support
intelfb0 at i915drmkms0
i915drmkms0: info: registered panic notifier
intelfb0: framebuffer at 0xda5a4000, size 1280x1024, depth 32, stride 5120
wsdisplay0 at intelfb0 kbdmux 1: console (default, vt100 emulation), using wskbd[...]

the display freezes for a couple of minutes shortly after starting X
following a reboot--usually a couple of minutes after logging in via
'xdm'.  I then see the following in 'dmesg' and XConsole.  It seems only
to occur once.  If it happened more than once in a session, it's been
too long ago for me to remember.

drm: stuck on render ring
drm: GPU HANG: ecode 0:0x3c8160c1, reason: Ring hung, action: reset
drm: GPU hangs can indicate a bug anywhere in the entire gfx stack, including userspace.
drm: Please file a _new_ bug report on bugs.freedesktop.org against DRI -> DRM/Intel
drm: drm/i915 developers can then reassign to the right component if it's not a kernel issue.
drm: The gpu crash dump is required to analyze gpu hangs, so please always attach it.
drm: GPU crash dump saved to /sys/class/drm/card0/error
DRM error in i915_reset: Failed to reset chip: -19

After this, it seems to operate normally essentially indefinitely.

Of course, the reported GPU crash dump does not exist.  Does our flavor
of DRMKMS try to save the GPU crash dump someplace?  Perhaps the reported
path is expected to exist first?  I'll try creating it and see if
something is saved there the next time it happens.

-- 
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