Comment 42 for bug 749817

It's a bit more complicated: when I reconnected and tried to use the external monitor, it was back to the original behaviour of showing just black on both panels. With the monitor connected by vga over either the ultrabase or built in vga port, I get the flickering red/black display. Unplugging the monitor puts things back to a working built in display. I have some more kernel log messages:

pr 12 12:15:32 joy kernel: [ 2022.623546] [drm:i915_gem_do_execbuffer] *ERROR* Object ffff88022e695e00 [handle 618, index 1] appears more than once in object list
Apr 12 12:15:33 joy kernel: [ 2023.296025] [drm:intel_dp_complete_link_train] *ERROR* failed to train DP, aborting
Apr 12 12:15:34 joy kernel: [ 2024.153864] [drm:intel_dp_complete_link_train] *ERROR* failed to train DP, aborting
Apr 12 12:15:35 joy kernel: [ 2025.011692] [drm:intel_dp_complete_link_train] *ERROR* failed to train DP, aborting
Apr 12 12:15:36 joy kernel: [ 2025.859615] [drm:intel_dp_complete_link_train] *ERROR* failed to train DP, aborting
Apr 12 12:15:36 joy kernel: [ 2026.697493] [drm:intel_dp_complete_link_train] *ERROR* failed to train DP, aborting
Apr 12 12:15:37 joy kernel: [ 2027.545447] [drm:intel_dp_complete_link_train] *ERROR* failed to train DP, aborting