drmkms solid hang on T200 laptop booting GENERIC amd64

[Dave Tyson <dtyson%anduin.org.uk@localhost>]

I have been testing current on a Lenovo T200 (type 2504) on and off for 
a while. I think the last successful boot of current was GENERIC from 
29th October before the KMS code was add the the GENERIC config. IIRC 
the DRMKMS kernel from that base would hang.

With GENERIC (AMD64) CVS'ed and compiled from a couple of days ago the 
system boots and then hangs in the KMS code. kernel messages just before 
hang:

wsmouse0 at pms0 mux 0
pci0 at mainbus0 bus0: configuaration mode 1
pchb0 at pci0 dev 0 function 0: vendor 8086 product 2a40 (rev. 0x07)
agp0 at pchb0: G4X-family chipset
agp0: detected 32252k stolen memory
agp0: aperture at 0xd0000000, size 0x10000000
i915drmkms0 at pci0 dev 2 function 0: vendor 8086 product 2a42 (rev. 0x07)
drm: Memory usable by graphics device = 512M
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 error in init_ring_common: render ring initialization failed ctl 
0001f001 head 0543b084 tail 00000000 start 00003000
warning: /usr/src/sys/external/bsd/drm2/dist/drm/i915/intel_pm.c:5734: 
!power_domains->domain_use_count[domain]

I am happy to turn on/add debugging code to help pin this down as I 
really want this laptop to work!

Cheers,
Dave




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