[Bug 101462] New: External monitor shows no signal after unplugging and plugging the cable back into dock

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=101462

            Bug ID: 101462
           Summary: External monitor shows no signal after unplugging and
                    plugging the cable back into dock
           Product: DRI
           Version: XOrg git
          Hardware: Other
                OS: All
            Status: NEW
          Severity: normal
          Priority: medium
         Component: DRM/Intel
          Assignee: intel-gfx-bugs at lists.freedesktop.org
          Reporter: ethan.hsieh at canonical.com
        QA Contact: intel-gfx-bugs at lists.freedesktop.org
                CC: intel-gfx-bugs at lists.freedesktop.org

Created attachment 131993
  --> https://bugs.freedesktop.org/attachment.cgi?id=131993&action=edit
kernel log (drm.debug=0xe), Xorg.0.log, and xrandr

External monitor shows no signal after unplugging and plugging the cable back
into dock

Reproduction steps:
1. The external monitor with DP/mDP/HDMI cable connected to Dell Dock.
All two displays: Built-in LCD and external DP/mDP/HDMI monitor
2. Boot to Ubuntu Desktop
3. See two displays (extend mode)
4. Unplug the DP/mDP/HDMI cable from dock
5. wait for at least 30 seconds
6. Plug the cable back into dock
7. Check if the external monitor displays well

Additional information:
1. Kernel: 4.12.0-994-generic x86_64
2. Linux distribution: Ubuntu 16.04.2 LTS
3. Laptop: Dell Precision 5520
4. Dell Business Thunderbolt Dock - TB16
https://goo.gl/vFDjpi
5. Connector (kernel log):
[CONNECTOR:48:eDP-1]: Bulit-in LCD
[CONNECTOR:74:DP-4]: The external monitor
After unplugging and plugging in the cable back
[CONNECTOR:48:eDP-1]: Bulit-in LCD
[CONNECTOR:84:DP-5]: The external monitor

How to recover:
1. Go to [All Settings] => [Displays], Press [Detect Displays]
2. Run xrandr to resize the screen

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