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scotchie
June 14th, 2012, 04:49 PM
After upgrade from 11.10 to 12.04, my laptop freezes whenever I plug it into the docking station. When I boot it from inside the docking station, the login screen works fine, but it freezes after logon. This all worked fine with 11.10.

I have a Lenovo T420 (Intel integrated graphics) with 2 external Acer V233H monitors connected to the docking station, one connected via a DVI cable and the other via a VGA cable.

When it freezes, I either get a purple Ubuntu 12.04 LTS splash screen with no mouse pointer, or else I get a black screen with a mouse pointer near the left side of the VGA monitor. In either case, none of the keyboard/mouse inputs works - neither the external ones connected to the dock nor the built-in input devices. Only hard-shutdown via the laptop's power button seems to do anything.

I've found a strange workaround.


Boot it outside of the docking station,
Remove ~/.config/monitors.xml
Plug it into the docking station. Neither of the monitors automatically comes on.
Open the "Displays" dialog. Automatically, the DVI monitor is detected, but not the VGA monitor. Pressing "Detect Displays" does not detect the VGA monitor.
Enable the DVI monitor at the default (maximum - 1920x1080) resolution and click "Apply". Instantly, the VGA monitor is automatically detected as soon as the DVI monitor is enabled.
Change the VGA monitor to the 2nd-step-down resolution (1680x1050), disable the laptop display, enable the VGA monitor, and click "Apply". After this point, I get both monitors enabled and working.
Note that if I enable both monitors at the default/maximum 1920x1080 resolution, then the screen freezes as described above.

Although I have a workaround, I would prefer something that "just plain works". Does anyone have any ideas on how I can troubleshoot this?

I do believe it has something to do with enabling both monitors at the maximum 1920x1080 resolution, as the login screen works and that seems to be at a lower resolution. However, monitors.xml is remembering my choice of resolutions, yet I have to remove it to prevent the problem.

Any help greatly appreciated!!!

Thanks,
Scott

scotchie
July 9th, 2012, 05:26 PM
The solution to bug 992778 has solved my problem.
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/992778

Only problem is that this bug fix has not been included in the Ubuntu standard distribution. Now every time upgrade manager runs, it suggests that I "upgrade" back to the broken version.

Does anyone know how to get this fix included in the standard Ubuntu packages so that other users can benefit without any workarounds?