[Bug 94930] New: Freeze during activation of external display on Lenovo X260

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=94930

            Bug ID: 94930
           Summary: Freeze during activation of external display on Lenovo
                    X260
           Product: DRI
           Version: unspecified
          Hardware: x86-64 (AMD64)
                OS: Linux (All)
            Status: NEW
          Severity: normal
          Priority: medium
         Component: DRM/Intel
          Assignee: intel-gfx-bugs at lists.freedesktop.org
          Reporter: dennis.wassenberg at secunet.com
        QA Contact: intel-gfx-bugs at lists.freedesktop.org
                CC: intel-gfx-bugs at lists.freedesktop.org

Created attachment 122921
  --> https://bugs.freedesktop.org/attachment.cgi?id=122921&action=edit
dmesg drm.debug=1

Hi all,

I tried to connect an external display to a Lenovo X260. It doen't matter if it
is connected via HDMI or m-DP. Every time I activate the connected display
(e.g. Xubuntu - Settings->Display->Select External Display->Use this output)
the system will freeze completely. A reboot is possible by holding the power
button for 4 seconds only.

It is not possible to get a dmesg output which shows a kernel oops / panic
because the cpu seems to stop working completely. I will attach a default dmesg
output and a dmesg output with drm.debug=1. Even trying to create a crash dump
via pstore efi backend creates no crash dumps.

To make sure that this issue is not associated with
https://bugzilla.kernel.org/show_bug.cgi?id=110941 I added intel_pstate=no_hwp
to kernel command line.

This freeze will not occur with Ubuntu wily kernel <= 4.4.6. It starts freezing
with Ubuntu wily kernel >= 4.5. So maybe it looks like a regression? Using
Ubuntu xenial it freezes not dependent on the kernel version. I checked it with
default kernel of beta2 (Ubuntu-4.4.0-15) and the latest kernel
Ubuntu-4.4.0-18.34.

I dont't know if this is related to
https://bugs.freedesktop.org/show_bug.cgi?id=94534 but there a Haswell CPU is
involved (Skylake here).

I have also reported this bug on bugzilla.kernel.org
(https://bugzilla.kernel.org/show_bug.cgi?id=116201), not sure where the best
place to report this is.

Best regards,
Dennis

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