https://bugs.freedesktop.org/show_bug.cgi?id=100364
--- Comment #4 from John Brooks bugs.freedesktop@fastquake.com --- It's possible that I just didn't leave it alone for long enough after it turned off (or after I turned it off with xset dpms force off). Maybe after a period of time with no signal, the monitor itself goes into its own sleep state that affects the DisplayPort connection in a way similar to turning it off completely. If it's important I can test it further.