Disabling DisplayPort hot plug detect
Displayport 1.1 and 1.2 both provide for a 3.3V power pin. Standard Displayport Cables for 1.2 do not wire the pin, but there are cables that do. Regardless of the wiring, if the PIN is present, you can hack the cable:

DP_PWR 3.3V+/-10% / 500mA max, available both on upstream/downstream device connectors
Mainly intended for powering cable adaptors
Standard DisplayPort cable does not have wire connected on DP_PWR pin

Cut the HDP from the downstream device (Monitor), and wire a typical pull-up resistor (4.7k ~ 60k, try experimenting) between the upstream DP_Pwr pin and the upstream HDP pin will work. Of course, this does break some features, as the HDP pin is also used as a signal from the downstream device to the upstream device:

Asserted by a downstream device when it is ready for AUX transaction
HPD line also used for an IRQ assertion by a downstream device

Info gathered from http://www.vesa.org/wp-content/uploads/2010/12/DisplayPort-DevCon-Presentation-DP-1.2-Dec-2010-rev-2b.pdf