screen flickers indefinitely when connecting a display via USB-C

[Tamas Papp]

Dell XPS 13 Skylake laptop, only external display port is adapter is via USB-C. When connecting any of the adapters I have (eg USB-C to VGA, HDMI, DisplayPort, I tried all and the behavior is the same), the screen starts flickering as if trying to detect something, and then keeps doing this indefinitely. Mouse moves but windows don't react. Can switch to terminal and back with Ctrl-Alt-F1 etc.

This only happens with Unity/Gnome. KDE and XFCE4 work fine, just detect the display.

It would help greatly as a workaround if I could just disable the part of unity/gnome which tries to detect the new display and use xrandr instead (which, again, works fine with other desktops), but I could not figure out which program that is, or where it writes its logfiles.

Using latest xenial packages.

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: unity 7.4.0+16.04.20160401.1-0ubuntu1
Uname: Linux 4.4.6-040406-generic x86_64
.tmp.unity.support.test.0:

ApportVersion: 2.20.1-0ubuntu1
Architecture: amd64
CompizPlugins: No value set for `/apps/compiz-1/general/screen0/options/active_plugins'
CompositorRunning: compiz
CompositorUnredirectDriverBlacklist: '(nouveau|Intel).*Mesa 8.0'
CompositorUnredirectFSW: true
CurrentDesktop: Unity
Date: Tue Apr 5 18:06:36 2016
DistUpgraded: 2016-02-27 15:22:35,661 DEBUG enabling apt cron job
DistroCodename: xenial
DistroVariant: ubuntu
DkmsStatus:
 virtualbox, 5.0.16, 4.4.0-16-generic, x86_64: installed
 virtualbox, 5.0.16, 4.4.6-040406-generic, x86_64: installed
 virtualbox, 5.0.16, 4.5.0-040500-generic, x86_64: installed
GraphicsCard:
 Intel Corporation Sky Lake Integrated Graphics [8086:1926] (rev 0a) (prog-if 00 [VGA controller])
   Subsystem: Dell Skylake Integrated Graphics [1028:0704]
InstallationDate: Installed on 2016-02-26 (39 days ago)
InstallationMedia: Ubuntu 15.10 "Wily Werewolf" - Release amd64 (20151021)
Lsusb:
 Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
 Bus 001 Device 004: ID 0bda:5682 Realtek Semiconductor Corp.
 Bus 001 Device 003: ID 04f3:20d0 Elan Microelectronics Corp.
 Bus 001 Device 002: ID 0a5c:6412 Broadcom Corp.
 Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
MachineType: Dell Inc. XPS 13 9350
ProcEnviron:
 LANGUAGE=en_US
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=en_US.UTF-8
 SHELL=/bin/bash
ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-4.4.6-040406-generic root=/dev/mapper/ubuntu--vg-root ro quiet splash i915.enable_rc6=0 vt.handoff=7
SourcePackage: unity
UpgradeStatus: Upgraded to xenial on 2016-02-27 (38 days ago)
dmi.bios.date: 03/01/2016
dmi.bios.vendor: Dell Inc.
dmi.bios.version: 1.3.3
dmi.board.name: 09JHRY
dmi.board.vendor: Dell Inc.
dmi.board.version: A00
dmi.chassis.type: 9
dmi.chassis.vendor: Dell Inc.
dmi.modalias: dmi:bvnDellInc.:bvr1.3.3:bd03/01/2016:svnDellInc.:pnXPS139350:pvr:rvnDellInc.:rn09JHRY:rvrA00:cvnDellInc.:ct9:cvr:
dmi.product.name: XPS 13 9350
dmi.sys.vendor: Dell Inc.
upstart.unity-panel-service.log: (unity-panel-service:1483): Indicator-Appmenu-WARNING **: Already have a menu for window ID 71303388 with path /com/canonical/menu/44000DC from :1.72, unregistering that one
version.compiz: compiz 1:0.9.12.2+16.04.20160331-0ubuntu1
version.ia32-libs: ia32-libs N/A
version.libdrm2: libdrm2 2.4.67-1
version.libgl1-mesa-dri: libgl1-mesa-dri 11.1.2-1ubuntu2
version.libgl1-mesa-dri-experimental: libgl1-mesa-dri-experimental N/A
version.libgl1-mesa-glx: libgl1-mesa-glx 11.1.2-1ubuntu2
version.xserver-xorg-core: xserver-xorg-core 2:1.18.1-1ubuntu4
version.xserver-xorg-input-evdev: xserver-xorg-input-evdev 1:2.10.1-1ubuntu2
version.xserver-xorg-video-ati: xserver-xorg-video-ati 1:7.6.1-1ubuntu2
version.xserver-xorg-video-intel: xserver-xorg-video-intel 2:2.99.917+git20160218-1ubuntu3
version.xserver-xorg-video-nouveau: xserver-xorg-video-nouveau 1:1.0.12-1build2
xserver.bootTime: Tue Apr 5 18:03:49 2016
xserver.configfile: default
xserver.errors:

xserver.logfile: /var/log/Xorg.0.log
xserver.outputs:
 product id 5194
 vendor SHP
xserver.version: 2:1.18.1-1ubuntu4

[Brad Figg (brad-figg)]

This change was made by a bot.

[Iyad Kandalaft (iyadkandalaft)]

I get the same behavior when connecting a new display via display link. then I realised that the flickering occurs when changing resolution on the built-in display without any external monitor. do you have the same issue.

I had everything working without problems a week ago but I'm not sure what I've changed since.