Bug#645983: 2560x1440 60Hz not working (Dell U2711)

[Martin Monperrus <martin.monperrus@gmail.com>]

Package: xserver-xorg-video-intel
Version:2:2.16.0-1

I connect a Dell U2711 to the docking station using the display port
interface (DP2 in xrandr, see below) and a diplayport cable. Then, the
maximum resolution of 2560x1440 at 60.0 Hz does not work, the screen
is black. The lower resolutions (e.g. 1920x1200) work.

As suggested in http://rndhero.org/cms/index.php?id=10 a workaround
consists of manually setting the refresh rate to 35 Hz.

Regards, --Martin


[ 52045.402] (II) intel(0): Integrated Graphics Chipset: Intel(R) GM45
[ 52045.402] (--) intel(0): Chipset: "GM45"


DP2 connected 2560x1440+0+0 (normal left inverted right x axis y axis)
597mm x 336mm
   2560x1440      60.0 +
   1920x1200      59.9
   1920x1080      60.0
   1600x1200      60.0
   1680x1050      60.0
   1280x1024      75.0     60.0
   1280x800       59.8
   1152x864       75.0
   1024x768       75.1     60.0
   800x600        75.0     60.3
   640x480        75.0     60.0
   720x400        70.1
   2560x1         35.0*