Problem with dual monitor config in Ubuntu 18.04

Question

I have a really annoying problem after a clean installation of Ubuntu 18.04.

Setup

A 24" monitor connected to a Dell XPS 13 (9365 2-in-1) laptop via a Dell dock connected to the ThunderBolt port. From the dock I use a mini-display port to display-port to connect the dock to the monitor.

Problem

When I turn on the laptop, the monitor works, and I can see the startup information (BIOS) and the password prompt for the encrypted drive. When the login (gnome) screen is about to be displayed, the monitor turns off and does not recover from that state. I have to disconnect the laptop from the dock, log in, then plug the dock/monitor back in. Sometimes both screens are purple, mouse pointer moves in the screen but nothing else happens.

Driver info

WARNING: you should run this program as super-user.
*-display                 
   description: VGA compatible controller
   product: Intel Corporation
   vendor: Intel Corporation
   physical id: 2
   bus info: pci@0000:00:02.0
   version: 02
   width: 64 bits
   clock: 33MHz
   capabilities: vga_controller bus_master cap_list rom
   configuration: driver=i915 latency=0

lspci output

00:00.0 Host bridge: Intel Corporation Device 590c (rev 02)
00:02.0 VGA compatible controller: Intel Corporation Device 591e 
(rev02)
00:04.0 Signal processing controller: Intel Corporation Skylake          
Processor Thermal Subsystem (rev 02)
00:13.0 Non-VGA unclassified device: Intel Corporation Sunrise Point-LP 
Integrated Sensor Hub (rev 21)
00:14.0 USB controller: Intel Corporation Sunrise Point-LP USB 3.0 xHCI Controller (rev 21)
00:14.2 Signal processing controller: Intel Corporation Sunrise Point- LP Thermal subsystem (rev 21)
00:15.0 Signal processing controller: Intel Corporation Sunrise Point- LP Serial IO I2C Controller #0 (rev 21)
00:15.1 Signal processing controller: Intel Corporation Sunrise Point- LP Serial IO I2C Controller #1 (rev 21)
00:16.0 Communication controller: Intel Corporation Sunrise Point-LP CSME HECI #1 (rev 21)
00:16.3 Serial controller: Intel Corporation Device 9d3d (rev 21)
00:1c.0 PCI bridge: Intel Corporation Sunrise Point-LP PCI Express Root Port (rev f1)
00:1c.4 PCI bridge: Intel Corporation Sunrise Point-LP PCI Express Root Port #5 (rev f1)
00:1d.0 PCI bridge: Intel Corporation Sunrise Point-LP PCI Express Root Port #9 (rev f1)
00:1d.1 PCI bridge: Intel Corporation Sunrise Point-LP PCI Express Root Port (rev f1)
00:1f.0 ISA bridge: Intel Corporation Device 9d4b (rev 21)
00:1f.2 Memory controller: Intel Corporation Sunrise Point-LP PMC (rev 21)
00:1f.3 Audio device: Intel Corporation Sunrise Point-LP HD Audio (rev 21)
00:1f.4 SMBus: Intel Corporation Sunrise Point-LP SMBus (rev 21)
01:00.0 PCI bridge: Intel Corporation JHL6340 Thunderbolt 3 Bridge (C step) [Alpine Ridge 2C 2016] (rev 02)
02:00.0 PCI bridge: Intel Corporation JHL6340 Thunderbolt 3 Bridge (C step) [Alpine Ridge 2C 2016] (rev 02)
02:01.0 PCI bridge: Intel Corporation JHL6340 Thunderbolt 3 Bridge (C step) [Alpine Ridge 2C 2016] (rev 02)
02:02.0 PCI bridge: Intel Corporation JHL6340 Thunderbolt 3 Bridge (C step) [Alpine Ridge 2C 2016] (rev 02)
39:00.0 USB controller: Intel Corporation Device 15db (rev 02)
3a:00.0 Non-Volatile memory controller: Sandisk Corp WD Black NVMe SSD
3b:00.0 Unassigned class [ff00]: Realtek Semiconductor Co., Ltd. RTS525A PCI Express Card Reader (rev 01)
3c:00.0 Network controller: Intel Corporation Wireless 8265 / 8275 (rev 78)

Any ideas on what to check or what to do?

Thanks in advance.

Answer 1

Your dock is probably not supported in linux unless its a true thunderbolt dock or has its own driver.

Please update your question with the full lspci output.

Thunderbolt 2 is the same physical connector as mini displayport , on a true thunderbolt dock the displayport is just another socket for the display card. I use an OWC thunderbolt dock this way , its almost invisible to the computer as its basically pci-e hotlpug.

If your dock is made by dell it almost certainly uses a displaylink chipset it will need a driver for it to work properly, you can get one here. It will be laggy and slow , these are barely usable in linux. http://www.displaylink.com/downloads/ubuntu

Unless you need the dock for the other ports i would just plug the monitor directly in to the thunderbolt socket, you might need an adapter.

Answer 2

This could be related to gdm3 using wayland. Please try disabling wayland for gdm3.

In order to make gdm3 use xorg instead of wayland, edit the file /etc/gdm3/custom.conf, find the line containing WaylandEnable=false and remove the comment sign (#). After you made the change, reboot and test if your problem still persists.

Answer 3

I seem to have a issue which is very similar...

I had issues with Ubuntu 18.04 totally locking up when I had my laptop closed into the docking station for some reason.

I couldn't fix the issue so I updated with in mind that it might have been an update of 18.04 that messed it up.

This seemed to have solved the lockup issue for me, but now when docked the second screen isn't begin detected from the login screen on, unless my laptop is open or when i switch up the monitor cables in the docking to make screen 1, screen 2 en screen 2, screen 1. No idea why this helps, but it does work...

Maybe this helps in your case too...