[Bug 95498] New: T460s (Skylake): System freeze when attaching a monitor to a Ultra Dock DP connector

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=95498

            Bug ID: 95498
           Summary: T460s (Skylake): System freeze when attaching a
                    monitor to a Ultra Dock DP connector
           Product: DRI
           Version: DRI git
          Hardware: Other
                OS: All
            Status: NEW
          Severity: normal
          Priority: medium
         Component: DRM/Intel
          Assignee: intel-gfx-bugs at lists.freedesktop.org
          Reporter: kaon at posteo.de
        QA Contact: intel-gfx-bugs at lists.freedesktop.org
                CC: intel-gfx-bugs at lists.freedesktop.org

Created attachment 123925
  --> https://bugs.freedesktop.org/attachment.cgi?id=123925&action=edit
dmes

Kernel version: drm-intel-nightly @ c6740c9c9e914742fd2ec159142c40701f7df966
(2016-05-18)

Everything else is a stock Fedora 24 install running stock GNOME.

Devices involved:

  - Thinkpad T460s (i5-6200U)
  - Thinkpad Ultra Dock (latest firmware)
  - LG 27MU67-B (3840x2160, DP1.2)

Whenever I connect a monitor to the DP connector on the dock, the system
freezes. I captured the last kmsgs before the freeze using netconsole, see
attachment (drm.debug=0x1e).

A similar issue (probably the same) occurred when I attached a Dell full HD
screen to the DVI port next to the DP connector (they somehow belong together
according to the marking on the dock). System would freeze a few seconds after
attaching the monitor, but the screen would sometimes work before the crash. No
logs though for that, can acquire them if necessary.

Works fine with stock Windows 10 (full resolution, 60hz).

Problem seems to affect other users too:

  -
https://www.reddit.com/r/thinkpad/comments/4c6fea/my_t460s_after_two_weeks_a_heavily_biased/
("The display connectors are currently unusable with Linux and crash the
kernel. This might be addressed with updated Intel drivers, I'm to lazy to
fiddle around with it - so my external monitor runs with an adapter on the
Mini-DP port, which fills up the desk. (Windows handles the connectors without
problems.)")

  - https://bbs.archlinux.org/viewtopic.php?id=210229

Any help would be greatly appreciated. I have a working kernel development
setup here and will do whatever is necessary to help with debugging.

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