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I'm running Xubuntu 20.04 on an HP Elitebook 845 G7 which has an AMD Ryzen 7 PRO 4750U with Radeon Graphics. I've been trying to use two daisy-chained DisplayPort monitors (Dell P2421DC) connected via the laptop's USB-C port. The first monitor is detected and works correctly, however the second monitor (daisy-chained from the first) is detected but cannot be enabled either via the Display settings or xrandr. Attempting to enable the second display gives me the following output in dmesg:

[drm] Failed to add display topology, DTM TA is not initialized.

I've enabled the HWE stack for 20.04 so I'm currently running kernel 5.8.0-49 which looks like it's correctly using the amdgpu module for the GPU:

$ inxi -G
Graphics:  Device-1: Advanced Micro Devices [AMD/ATI] Renoir driver: amdgpu v: kernel 
           Display: x11 server: X.Org 1.20.9 driver: amdgpu,ati unloaded: fbdev,modesetting,vesa resolution: 2560x1440~60Hz 
           OpenGL: renderer: AMD RENOIR (DRM 3.38.0 5.8.0-49-generic LLVM 11.0.0) v: 4.6 Mesa 20.2.6 

xrandr correctly detects the daisy-chained second monitor (DisplayPort-3) along with its resolutions:

$ xrandr --query
Screen 0: minimum 320 x 200, current 2560 x 1440, maximum 16384 x 16384
eDP connected (normal left inverted right x axis y axis)
   1920x1080     60.02 +  39.98  
   1680x1050     60.02  
   1280x1024     60.02  
   1440x900      60.02  
   1280x800      60.02  
   1280x720      60.02  
   1024x768      60.02  
   800x600       60.02  
   640x480       60.02  
HDMI-A-0 disconnected (normal left inverted right x axis y axis)
DisplayPort-0 disconnected (normal left inverted right x axis y axis)
DisplayPort-1 disconnected (normal left inverted right x axis y axis)
DisplayPort-2 connected primary 2560x1440+0+0 (normal left inverted right x axis y axis) 527mm x 296mm
   2560x1440     59.95*+
   1920x1200     59.88  
   2048x1080     60.00  
   1920x1080     60.00    50.00    59.94  
   1600x1200     60.00  
   1680x1050     59.95  
   1280x1024     75.02    60.02  
   1280x800      59.81  
   1152x864      75.00  
   1280x720      60.00    50.00    59.94  
   1024x768      75.03    60.00  
   800x600       75.00    60.32  
   720x576       50.00  
   720x480       60.00    59.94  
   640x480       75.00    60.00    59.94  
   720x400       70.08  
DisplayPort-3 connected (normal left inverted right x axis y axis)
   2560x1440     59.95 +
   1920x1200     59.88  
   2048x1080     60.00  
   1920x1080     60.00    50.00    59.94  
   1600x1200     60.00  
   1680x1050     59.95  
   1280x1024     75.02    60.02  
   1280x800      59.81  
   1152x864      75.00  
   1280x720      60.00    50.00    59.94  
   1024x768      75.03    60.00  
   800x600       75.00    60.32  
   720x576       50.00  
   720x480       60.00    59.94  
   640x480       75.00    60.00    59.94  
   720x400       70.08  

When I attempt to enable the monitor via xrandr or the Display configuration of XFCE it doesn't get enabled. xrandr gives the following output:

$ xrandr -d :0 --output DisplayPort-3 --auto
xrandr: Configure crtc 1 failed

and I get the dmesg output about DTM TA is not initialized

Any ideas about how to resolve this or further diagnose the issue would be most welcome.

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  • It is not entirely clear that your monitors support using USB-C for daisy-chaining, versus using displayport cables. Additionally, you do need to enable DisplayPort 1.2 MST on the monitor in the middle of the chain (but not the one on the end of the chain) Dell Document Apr 14, 2021 at 17:24
  • In addition to above, many laptops are incapable of running any more than the native display +1
    – Nmath
    Apr 14, 2021 at 17:34
  • I've just installed Windows 10 to verify and can confirm that out of the box Windows will drive both displays over USB-C at 1920x1080. If I install the AMD Radeon software it can drive both displays at 2560x1440 over USB-C. So the hardware definitely supports it. Apr 14, 2021 at 20:41
  • Same issue with HP EliteBook 830 G7 when using the HP travel usb-c multi-port hub. I ended up connecting the USB-C multi-port hub on the second thunderbolt port with one screen connected on there. The other screen is connected on the laptop's HDMI port.
    – Stelios
    Jul 25, 2021 at 11:42

3 Answers 3

1

I just hit same (or at least similar) issue with Dell P2723DE.


TLDR: with USB-C connected open monitor menu, find USB-C Prioritization and switch it to High resolution.

enter image description here

Little more details...

xrandr: Configure crtc 1 failed

From my past experiences with daisy chain and different hubs and graphic cards, I know this means (simplified) that there aren't enough lanes to push your data through.

But, from technical specifications, this didn't seem right. Monitor should be able to use daisy chain on two 2k monitors.

I tried to go through menu and found USB-C Prioritization and when switched it to High resolution, it processed the change for a while and than voilá, xrandr now works without any issue.

Btw. from manual to your monitor (P2421DC) it looks like this happens only when you have USB-C Charging set to On During Power Off or is at least related to that setting.

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  • This works brilliantly. As the monitor was also charging the laptop I had to follow the steps in the Setting USB-C Prioritization when USB-C Charging is set to On During Power Off instructions in the user guide. Apr 13, 2022 at 19:38
0

This worked for me: Enable MST on the first monitor connected to your Laptop and disable MST on the chained monitor. Sometimes If the chained monitor is only mirroring the first monitor then try enabling DisplayPort 1.1 on the chained monitor (and make sure the first monitor has at least DisplayPort 1.2 enabled).

Optionally: Once this works you can try re-enabling DisplayPort 1.2 (or above) on the chained monitor and it still works sometimes.

0

I ran into the same issue as Kepi, the dell laptop owner, I am using an hp elitebook. Updated the bios setting like suggested, no luck.

As I was using an anker dongle/dock, I had the power feed attached to the dock. My 3rd display was not detected. Moved the power from the dongle to the laptop like suggested, and viola, 3rd display sprung into action.

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