Comment 22 for bug 761065

i'm having similar issues...and it most certainly seems to be originating from the kernel and not from the X server, as i've run through three different versions of both the kernel and the X server while holding one fixed and changing the other and changing the X server didn't affect the problem at all, but changing the kernels did.

not sure what debugging information might be helpful in helping to shed light on my particular config, but would be happy to post some, just let me know what to post. for now, i'll just attach an lspci and give a bit of a description:

(1) started with "latest version" of ubuntu iso on thinkpad x220 with corei7-2620m and intel HD3000. the iso at the time provided me with kernel and headers version 2.6.38-8.42. aside from some thinkpad-tinkering, everything pretty much worked "out of the box", as others have reported.

(2) then, connected to dell u2711 via displayport and got a desktop that was seemingly split between two windows, and everything on the u2711 was blacked out except for the top menu and a square sitting on the lower left corner of the panel the size of the thinkpad's display. thinkpad display unresponsive during this time (but not black). rebooted with display connected and both screens black (and unusable).

(3) tried to upgrade to kernel 2.6.39-1.6, which had the same outcome as kernel 2.6.39-2.7. upon reboot, monitors set to mirror same image with 1024x768 resolution. i know this is unrelated, but here and with the 2.6.38-8.42 kernel, the Fn-F7 worked for switching between resolutions. anyway, upon switching between resolutions i got the same outcome as in (2), except that now i could use the Fn-F7 to switch between non-working full-resolutions and working (mirrored) 1024x768 resolutions.

(4) after a bit of digging around, found a recommendation to try kernel 2.6.38-996-generic #201103251543 SMP Fri Mar 25 15:47:37 UTC 2011 x86_64 x86_64 x86_64 GNU/Linux, and accompanying headers, which worked properly. currently using xorg-server 2:1.10.1+git20110429+server-1.10-branch.b4455b11-0ubuntu0sarvatt, but switching to 2.14.0ubuntu7.1 from the natty updates, as well as using 2.14-0-4ubuntu7 (natty) made absolutely no difference. these three xorg versions were used in all my testing.

At (4) both displays are function properly. however, i cannot switch between monitors without rebooting. whatever monitor i boot in works, but if that's the u2711 fed through the display port, then if i unplug the display port cable, the thinkpad LCD is not switched to automatically (and remains off, not just black). likewise, if i boot with the thinkpad display active, plugging in the u2711 9-times-out-of-10 causes both screens to go black, the Fn-F7 doesn't work, and to fix the problem i have to hard-reboot. it's interesting to note that in the gnome monitors panel, only the active display shows. in other words, if i boot while connected to the u2711, it shows (but the built-in laptop screen doesn't), and if i boot without the external display connected, the thinkpad LCD shows, but once i plug in the u2711 (without rebooting) the 1 time out of 10 the display doesn't go nuts on me, it only shows the u2711 and not both the u2711 and the thinkpad LCD, as i would expect. a strange aside, the "thinkvantage" button works for every kernel change except (4), the one in which both displays work properly. additionally, i had to recompile the r8192ce_pci wireless module from the DKMS package to get it to work with each kernel change as this driver was not included in the newer kernels.