I'm using a Lenovo ThinkPad T440s with the latest BIOS installed (and the latest firmware applied to the UltraDock). When I put the laptop in the Ultradock with a monitor connected (DVI), the kernel starts to boot, but freezes hard very early in the process. No errors are shown, even with drm.debug=6. If I boot without the laptop in the dock, it boots up fine. If I put the booted laptop in the dock, the system freezes and the laptop panel goes dark. If I then undock the laptop, it resumes normal operation. If I disconnect the external monitor from the UltraDock, then boot with the laptop docked, it works properly. I had this issue back in Fedora 20, until I updated the firmware on the UltraDock. This all was working fine from then. through Fedora 21 and 22, but stopped working with Fedora 23 (in fact, if I boot into the rescue kernel from 22, it works again). Kernels where I see this failure are: 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 Let me know what I can do to help debug this issue, it's really annoying. Internal GPU: 0:02.0 VGA compatible controller: Intel Corporation Haswell-ULT Integrated Graphics Controller (rev 0b) External monitor is an Acer AL2223W.
Please attach the dmesg with drm.debug=14 all the way from early boot.
The good news is that it no longer hard locks the machine as of kernel-4.2.0-0.rc6.git0.2.fc23.x86_64. The bad news is that it definitely isn't working right. I get text console on the monitor connected to the ultradock (at the wrong resolution), but if I start X, it goes very slow and eventually locks up, while only outputting to the laptop panel.
Created attachment 117897 [details] dmesg log with drm.debug=14
Created attachment 118522 [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.
This is now working as expected in Fedora kernel 4.2.3-300.fc23.x86_64
(In reply to Tom Callaway from comment #5) > This is now working as expected in Fedora kernel 4.2.3-300.fc23.x86_64 Thanks the report, and for following up.
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