Bug 628906

Description of problem:
(Not sure if this is the right component.) After F12 -> F13 upgrade, external monitor no longer works in "mirror screens" configuration.  Having two different virtual desktops works OK. VGA output works fine until some time after GDM login.

In messages log this results in the following errors:
Aug 31 13:45:20 lapps kernel: [drm:intel_lvds_mode_fixup] *ERROR* Can't enable LVDS and another encoder on the same pipe
Aug 31 13:45:20 lapps kernel: [drm:drm_crtc_helper_set_config] *ERROR* failed to set mode on crtc f657c000

Version-Release number of selected component (if applicable):

control-center-2.30.1-3.fc13.i686
kernel-2.6.34.6-47.fc13.i686 (all of these kernel versions tested)
kernel-2.6.33.8-149.fc13.i686
kernel-2.6.33.3-85.fc13.i686
xorg-x11-drv-intel-2.11.0-5.fc13.i686
gnome-settings-daemon-2.30.1-7.fc13.i686

How reproducible:
100%.

Steps to Reproduce:
1. Boot up with external screen attached to VGA1. (Press Fn-F7 as needed.) You see everything outputted to both screens up until some time after GDM login screen.
2. Then login either switches to multi-screen (and on VGA you get the Fedora background image), or continue in semi-crippled fashion as before (e.g. mouse movement doesn't show on VGA).
3. In gnome-settings-display, re-enabling mirror screens results in the complete loss of VGA (e.g. crippled no longer works either) except for multi-screen.
 
Actual results:
Mirror screens works in a crippled fashion after a reboot only, and gets lost if you switch modes afterwards.

Expected results:
Mirror screens works and reflects what's on the screen.

Additional info:

Booting with "nomodeset" doesn't boot in init 5; prefdm seems to crash somehow.

Failure to change VGA mode results in the following kind of syslog:

Aug 31 13:45:20 lapps kernel: [drm:intel_lvds_mode_fixup] *ERROR* Can't enable LVDS and another encoder on the same pipe
Aug 31 13:45:20 lapps kernel: [drm:drm_crtc_helper_set_config] *ERROR* failed to set mode on crtc f657c000

Using Lenovo X61s with Intel 965GM card:

00:02.0 VGA compatible controller: Intel Corporation Mobile GM965/GL960 Integrated Graphics Controller (rev 0c)

'Xrandr' output when mirror screens is enabled and VGA is hooked up is as follows:

Screen 0: minimum 320 x 200, current 1024 x 768, maximum 8192 x 8192
LVDS1 connected 1024x768+0+0 (normal left inverted right x axis y axis) 246mm x 185mm
   1024x768       60.0*+
   800x600        60.3     56.2
   640x480        60.0     59.9
VGA1 connected 1024x768+0+0 (normal left inverted right x axis y axis) 886mm x 498mm
   1024x768       75.1 +   70.1     60.0*
   1920x1080      60.0 +
   1600x1200      60.0
   1280x1024      75.0     60.0
   1280x960       60.0
   1360x768       60.0
   1152x864       75.0
   832x624        74.6
   800x600        72.2     75.0     60.3     56.2
   640x480        72.8     75.0     66.7     60.0
   720x400        70.1

There seems to be some similarity to bug #623824.