+++ This bug was initially created as a clone of Bug #1036974 +++ Description of problem: The Ultradock bug is back! Essentailly, this is the same problem as reported in the past on Bug #1036974 and Bug #1035448. I have a Lenovo T440s, running BIOS GJET84WW (2.34 ). I have an Ultradock for it. When I have a monitor connected to the Ultradock, Linux freezes. This happens very early if I try to boot on the dock, and if I boot undocked, then dock the laptop, it freezes. Disconnecting the monitor from the Ultradock resolves this issue. Lenovo released a firmware update for the Ultradock which I applied a long time ago. (You can only apply this from Windows, I borrowed a windows T440s to update the ultradock firmware). Since then, Fedora 21 and 22 have been working perfectly, but on Fedora 23 kernels, it has broken again. Tested: kernel-4.2.0-0.rc2.git1.1.fc23.x86_64 kernel-4.2.0-0.rc3.git2.1.fc23.x86_64 kernel-4.2.0-0.rc3.git4.1.fc23.x86_64
I'm wondering if a patch got lost somewhere in the 4.2 cycle.
Created attachment 1078383 [details] dmesg log with drm.debug=14 on kernel 4.2.1-300.fc23 This continues to be broken with current kernels. I put the Thinkpad in the dock, booted up with drm.debug=14. Plymouth (the graphical boot screen in Fedora) loads up properly on both monitors, but when it drops to the gdm login screen, it only shows up on the laptop panel (the external monitor is black). GNOME slowly loads, but when I bring up the display control panel, it seems to freeze but eventually shows me that it can see the external display, but no matter what I do, it cannot output to it. As a reminder, when I undock the laptop and connect the external monitor to the VGA port, it works as expected. I had to gz the dmesg log file due to its size, there is a LOT of noise in there.
I believe this has been fixed with kernel 4.2.2-300. Would you mind testing and letting me know?
Confirmed as fixed. Sorry it took so long to test this, but I have been away from my desk (where the dock lives).