port-amd64/50651: i915drmkms/xf86-video-intel: black screen switching X -> ttyEx

[is%netbsd.org@localhost]

>Number:         50651
>Category:       port-amd64
>Synopsis:       i915drmkms/xf86-video-intel: black screen switching X -> ttyEx
>Confidential:   no
>Severity:       serious
>Priority:       low
>Responsible:    port-amd64-maintainer
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Tue Jan 12 19:55:00 +0000 2016
>Originator:     Ignatios Souvatzis
>Release:        NetBSD 7.0_STABLE
>Organization:
	private machine
>Environment:
System: NetBSD henrietta 7.0_STABLE NetBSD 7.0_STABLE (GENERIC) #2: Sat Jan 9 15:39:43 CET 2016 is@henrietta:/var/itch/sources/7/obj.amd64/sys/arch/amd64/compile/GENERIC amd64
Architecture: x86_64
Machine: amd64

userland: NetBSD-6.1.5_PATCH as of late December 2015
	
X11: pkgsrc-2015Q2 X; en detail:

modular-xorg-server-1.17.1;Modular X11 server from modular X.org
xf86-input-keyboard-1.8.1nb1;Modular Xorg keyboard driver
xf86-input-mouse-1.9.1nb2;Modular Xorg mouse driver
xf86-input-void-1.4.1;Modular Xorg dummy input driver
xf86-video-intel-2.99.917nb3;Modular Xorg Intel video driver
xf86-video-vesa-2.3.3nb3;Modular Xorg VESA video driver
xf86-video-wsfb-0.4.0nb1;Modular Xorg wsdisplay framebuffer video driver

dmesg.boot excerpt:

pci0 at mainbus0 bus 0: configuration mode 1
pci0: i/o space, memory space enabled, rd/line, rd/mult, wr/inv ok
pchb0 at pci0 dev 0 function 0: vendor 0x8086 product 0x2a00 (rev. 0x0c)
agp0 at pchb0: i965-family chipset
agp0: detected 7676k stolen memory
agp0: aperture at 0xe0000000, size 0x20000000
i915drmkms0 at pci0 dev 2 function 0: vendor 0x8086 product 0x2a02 (rev. 0x0c)
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: initialized overlay support
intelfb0 at i915drmkms0
i915drmkms0: info: registered panic notifier
intelfb0: framebuffer at 0xffff8000477f8000, size 1280x800, depth 32, stride 5120
wsdisplay0 at intelfb0 kbdmux 1: console (default, vt100 emulation), using wskbd0
wsmux1: connecting to wsdisplay0
vendor 0x8086 product 0x2a03 (miscellaneous display, revision 0x0c) at pci0 dev 2 function 1 not configured

Xorg.0.log excerpt:

[    35.531] (II) Loading /usr/pkg/lib/xorg/modules/drivers/intel_drv.so
[    35.587] (II) Loading /usr/pkg/lib/xorg/modules/input/mouse_drv.so
[    35.588] (II) Loading /usr/pkg/lib/xorg/modules/input/kbd_drv.so
...
[    37.616] (II) XINPUT: Adding extended input device "Keyboard0" (type: KEYBOARD, id 7)
[  1517.127] (II) AIGLX: Suspending AIGLX clients for VT switch
[  1523.172] (II) AIGLX: Resuming AIGLX clients after VT switch
[  1523.173] (II) intel(0): switch to mode 1280x800@60.0 on LVDS1 using pipe 1, position (0, 0), rotation normal, reflection none


>Description:
When booting the -7 kernel, the machine switches to the intelfb wscons 
(still with green kernel/white userland text on black as per default).

Loading X with xf86-video-intel works, e.g. mplayer -vo xv needs only
some 2.5% cpu for a scaled-to-fullscreen video.

Switching to a text screen (e.g. ctrl-alt-F2) shows only a black screen.
I can log in blindly and check this (from X11) with "who" or by running
"echo ctrl-g"

Switching back to a working X11 with ctrl-alt-F5 works.


>How-To-Repeat:
	ctrl-alt-F1 or ctrl-alt-F2 or ctrl-alt-F3 or ctrl-alt-F4
>Fix:
	workaround: type blindly or use xterm in X11.

>Unformatted:
 	<Please check that the above is correct for the bug being reported,>
 	<and append source date of snapshot, if applicable (one line).>
 	20160109T1530