I am using an HP Elitebook 2560p which has an integrated Intel video card. I use two external monitors, one connected on the DisplayPort as primary and one on the VGA port as secondary. I am not using the built-in display.

I use x11 with xfce. It all works fine, except that the the primary monitor (on the DisplayPort) goes black at random times. Once black, the monitor reports no signal and goes on stand by. It does not resume working if I move the mouse or type on the keyboard. One way I managed to recover it is to turn the display off with xrandr and then back on, like this:

  xrandr --output DP1 --off ; xrandr --output DP1 --auto --rotate normal --pos 0x0 --output VGA1 --auto --rotate left --right-of DP1


On the system console I get a lot of messages like:

  error: [drm:pid4802:gen6_sanitize_pm] *ERROR* Power management discrepancy: GEN6_RP_INTERRUPT_LIMITS expected 1a0d0000, was 1a000000

and from time to time I get:

  error: [drm:pid4802:drm_edid_block_valid] *ERROR* EDID checksum is invalid, remainder is 160


On the terminal where I run "startx" I get:

  (xfwm4:4825): xfwm4-WARNING **: output size (1200x1920) and logical screen size (3760x1920) do not match
  (xfdesktop:4835): GdkPixbuf-CRITICAL **: gdk_pixbuf_new: assertion 'width > 0' failed
  (xfdesktop:4835): GdkPixbuf-CRITICAL **: gdk_pixbuf_fill: assertion 'GDK_IS_PIXBUF (pixbuf)' failed
  (xfdesktop:4835): GdkPixbuf-CRITICAL **: gdk_pixbuf_composite: assertion 'GDK_IS_PIXBUF (dest)' failed


In console mode, the monitors work fine. The problem manifests only in x11.


Conf info:

  > cat /boot/loader.conf
  ...
  i915kms_load="YES"
  kern.vty="vt"
  kern.vt.fb.default_mode="1366x768"


  > cat /usr/local/etc/X11/xorg.conf.d/driver-intel.conf
  Section "Device"
          Identifier "Card0"
          Driver     "intel"
          # BusID    "PCI:1:0:0"
  EndSection


  > xrandr
  Screen 0: minimum 320 x 200, current 3760 x 1920, maximum 8192 x 8192
  LVDS1 connected (normal left inverted right x axis y axis)
     1366x768      60.10 +  40.07  
     1024x768      60.00  
     800x600       60.32    56.25  
     640x480       59.94  
  VGA1 connected 1200x1920+2560+0 left (normal left inverted right x axis y axis) 518mm x 324mm
     1920x1200     59.95*+
     1920x1080     59.99  
     1600x1200     60.00  
     1680x1050     59.95  
     1280x1024     60.02  
     1440x900      59.89  
     1280x960      60.00  
     1024x768      60.00  
     800x600       60.32  
     640x480       60.00  
  HDMI1 disconnected (normal left inverted right x axis y axis)
  DP1 connected 2560x1600+0+0 (normal left inverted right x axis y axis) 641mm x 400mm
     2560x1600     59.97*+
     1920x1200     59.88  
     1920x1080     60.00    50.00  
     1600x1200     60.00  
     1680x1050     59.95  
     1280x1024     60.02  
     1440x900      59.89  
     1280x800      59.81  
     1280x720      60.00    50.00  
     1024x768      60.00  
     800x600       60.32  
     720x576       50.00  
     720x480       59.94  
     640x480       60.00    59.94  
     720x400       70.08  
  HDMI2 disconnected (normal left inverted right x axis y axis)
  DP2 disconnected (normal left inverted right x axis y axis)


  > cat .xinitrc
  xrandr --output DP1 --auto --rotate normal --pos 0x0 --output VGA1 --auto --rotate left --right-of DP1 &
  ...


Hardware info:

  > pciconf -lv | grep -B3 display
  vgapci0@pci0:0:2:0:	class=0x030000 card=0x162b103c chip=0x01268086 rev=0x09 hdr=0x00
      vendor     = 'Intel Corporation'
      device     = '2nd Generation Core Processor Family Integrated Graphics Controller'
      class      = display


Version info (all software installed with pkg):

  # pkg show xf86-video-intel
  xf86-video-intel-2.21.15_9
  Name           : xf86-video-intel
  Version        : 2.21.15_9
  Installed on   : Thu Jul  7 08:47:45 2016 PDT
  Origin         : x11-drivers/xf86-video-intel
  Architecture   : freebsd:10:x86:64


  # pkg show xorg
  xorg-7.7_2
  Name           : xorg
  Version        : 7.7_2
  Installed on   : Thu Jul  7 08:47:48 2016 PDT
  Origin         : x11/xorg
  Architecture   : freebsd:10:*


  # pkg show xfce
  xfce-4.12_1
  Name           : xfce
  Version        : 4.12_1
  Installed on   : Thu Jul  7 13:22:20 2016 PDT
  Origin         : x11-wm/xfce4
  Architecture   : freebsd:10:*