https://bugzilla.kernel.org/show_bug.cgi?id=66871
--- Comment #9 from Erik Edwards erik@emedwards.info --- (In reply to Alex Deucher from comment #8)
Can you use git to bisect what commit caused the regression? Google for git bisect howto.
3.12.5
Found a workaround:
Allow nromal boot to graphical environment with all monitors powered on. After GUI login is displayed and DVI connected monitor is blank do <ctrl><alt>F2 to switch to text console. Wait until all working displayas are stable then power off and power on non-fucntional display via its power button. Wait until all displays are stable then return to GUI.