kern/49751: With DRMKMS (i915GM), console gets rainbow stripes while loading drm

[makoto%ki.nu@localhost]

>Number:         49751
>Category:       kern
>Synopsis:       With DRMKMS, LVDS1 (LCD display) gets rainbow stripes while loading drm
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Mon Mar 16 13:35:00 +0000 2015
>Originator:     Makoto Fujiwara
>Release:        NetBSD 7.99.6
>Organization:
KINU Corporation
>Environment:
        
        
System: NetBSD cf-r4.i.ki.nu 7.99.6 NetBSD 7.99.6 (GENERIC) #38: Mon Mar 16 21:26:45 JST 2015 root@h87:/export/O-i386/sys/arch/i386/compile/GENERIC i386
Architecture: i386
Machine: i386
>Description:
	On Lets' Note CF-R4, i386 machine with i915GM graphics, 
	when booting above kernel,
	LVDS1 (LCD display) BIOS console will once blanked, and then shows
	changing rainbow color vertical stripes:
	  https://www.youtube.com/watch?v=tUgjEBBXIaE&feature=youtu.be
	The machine can accept ssh login (if network is properly set), and
	if drm_debug = 1; set in sys/external/bsd/drm2/dist/drm/drm_stub.c,
	(suggested by riastradh@)
	dmesg looks like:
   	  http://www.ki.nu/~makoto/NetBSD/i915drm/7.99.6-drm_debug_1
	mlelstv@ suggested to connect external VGA. It works. X11 works.
	with some trial and error, xrandr shows
   	  http://www.ki.nu/~makoto/NetBSD/i915drm/xrandr
	(OR)
	---------------------------
	Screen 0: minimum 320 x 200, current 1024 x 768, maximum 32767 x 32767
	LVDS1 connected 640x480+0+0 (normal left inverted right x axis y axis) 0mm x 0mm
	   640x480      155.10*+  85.01    72.81    75.00    59.94  
	   640x400       85.08  
	   640x350       85.08  
	VGA1 connected 1024x768+0+0 (normal left inverted right x axis y axis) 304mm x 228mm
	   1024x768      75.03*+  75.08    70.07    60.00  
	   832x624       74.55  
	   800x600       72.19    75.00    60.32    56.25  
	   640x480       75.00    72.81    66.67    60.00  
	   720x400       70.08  
	TV1 unknown connection (normal left inverted right x axis y axis)
	   848x480       59.94 +
	   640x480       59.94 +
	   1024x768      59.94  
	   800x600       59.94
	---------------------------   
	Implying internal LVDS1 is recognized as 640x480, which should be 1024x768.
	One suspect is following line
	  'drm: failed to find VBIOS tables' in dmesg comes from
	sys/external/bsd/drm2/dist/drm/i915/i915_dma.c
	which may be because failing following function call 
	   bios = pci_map_rom(pdev, &size);	
	at 
	sys/external/bsd/drm2/dist/drm/i915/intel_bios.c

	For the reference, following output is also at the directory:
   	  http://www.ki.nu/~makoto/NetBSD/i915drm/	
	acpidump -dt
	pcictl pci0 dump -b 0 -d 2
	Xorg.0.log   (external VGA only)
	Xorg.0.log-2 (plus internal LVDS1)
	  -- above switching is done at BIOS setting --

>How-To-Repeat:
	Lets' Note CF-R4, i386 machine with i915GM graphics
	boot DRMKMS kernel, for example 7.99.6.
	Just looking at LCD. You will got above.
>Fix:
	Not known. 

>Unformatted: