Dell XPS15 L502x Mini Display Port not working Ubuntu 13.04

Before i had Ubuntu 12.10 running on this laptop and the mini display port worked. Now i have Ubuntu 13.04 and the mini display port does not work anymore. If i connect my external monitor using a vga to mini display port adapter (as i did with ubuntu 12.10 too) nothing at all happens. Not even a flicker. I have bumblebee installed.

lspci | grep VGA
00:02.0 VGA compatible controller: Intel Corporation 2nd Generation Core Processor Family Integrated Graphics Controller (rev 09)
01:00.0 VGA compatible controller: NVIDIA Corporation GF108M [GeForce GT 540M] (rev ff)

xrandr -q
Screen 0: minimum 320 x 200, current 1920 x 1080, maximum 32767 x 32767
LVDS1 connected 1920x1080+0+0 (normal left inverted right x axis y axis) 344mm x 193mm
   1920x1080      60.0*+   59.9  
   1680x1050      60.0     59.9  
   1600x1024      60.2  
   1400x1050      60.0  
   1280x1024      60.0  
   1440x900       59.9  
   1280x960       60.0  
   1360x768       59.8     60.0  
   1152x864       60.0  
   1024x768       60.0  
   800x600        60.3     56.2  
   640x480        59.9  
VGA1 disconnected (normal left inverted right x axis y axis)
HDMI1 disconnected (normal left inverted right x axis y axis)
DP1 disconnected (normal left inverted right x axis y axis)

What can i try to make it work? As far as i know, the mini display port is connected to the intel graphics card.

Solution 1:

Found the solution:

xrandr --addmode DP1 1920x1080
xrandr --output DP1 --mode 1920x1080 --right-of LVDS1

works like a charm