[Bug 77137] New: drm/i915: VGA cannot be turned on

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=77137

          Priority: medium
            Bug ID: 77137
                CC: intel-gfx-bugs at lists.freedesktop.org
          Assignee: intel-gfx-bugs at lists.freedesktop.org
           Summary: drm/i915: VGA cannot be turned on
        QA Contact: intel-gfx-bugs at lists.freedesktop.org
          Severity: normal
    Classification: Unclassified
                OS: Linux (All)
          Reporter: bugs-freedesktop-ugeuder at snkmail.com
          Hardware: x86 (IA32)
            Status: NEW
           Version: DRI CVS
         Component: DRM/Intel
           Product: DRI

Created attachment 97039
  --> https://bugs.freedesktop.org/attachment.cgi?id=97039&action=edit
kernel log for mode switch on VGA

When trying to turn on VGA output using command

xrandr --output VGA1 --mode 800x600 

nothing happens. (Expected result: VGA display turned on)

This was first observed using a 3.11 distro kernel, but it is 100% repeatable
using the 3.14 mainline kernel and also the drm-intel-next/2014-04-05-trusty
kernel from the Ubuntu kernel team.

Observation: Changing mode on LVDS1 is successful, but a kernel warning is
produced.

[   87.540325] [drm:intel_pipe_config_compare] *ERROR* mismatch in
gmch_pfit.lvds_border_bits (expected 32768, found 0)
[   87.540334] ------------[ cut here ]------------
[   87.540441] WARNING: CPU: 1 PID: 934 at
/home/apw/COD/linux/drivers/gpu/drm/i915/intel_display.c:9813
check_crtc_state+0x26b/0x360 [i915]()
[   87.540447] pipe state doesn't match!

I don't know whether the warning for LVDS1 is in any way related to
non-functional VGA. For LVDS1 everything seems to work fine but a kernel
warning is produced. For VGA1 nothing visible works, but no warning is produced
either. 

Attached kernel log dmesg-994-vga.txt has been produced the following way

1.) Boot kernel drm-intel-next/2014-04-05-trusty as built by Ubuntu kernel team
    with extra command line parameter drm.debug=0x

2.) attach VGA display

3.) run script

#!/bin/sh
cmd="xrandr --output VGA1 --mode 800x600"
echo "*** calling $cmd" | sudo tee /dev/kmsg
$cmd
echo "*** returned from $cmd" | sudo tee /dev/kmsg



Attached kernel log dmesg-994-lvds.txt has been produced the following way

1.) Boot kernel drm-intel-next/2014-04-05-trusty as built by Ubuntu kernel team
    with extra command line parameter drm.debug=0x

2.) run script

#!/bin/sh
cmd="xrandr --output LVDS1 --mode 800x600"
echo "*** calling $cmd" | sudo tee /dev/kmsg
$cmd
echo "*** returned from $cmd" | sudo tee /dev/kmsg

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