Comment 0 for bug 1968235

I recently started using a Cable-Matters-201355 with my XPS 9380 (8th Gen TB3). The dock supports dual 4K DP @ 60Hz via thunderbolt with PD input. (HBR3 compliant USB-C Dock (DSC/DP1.4 support) that uses all 4 high speed lanes to get dual 60Hz)

Both displays boot mirrored when powered up (Dell Logo, Grub, Kernel output) however go blank just as wayland starts up.

Unplugging one of them allows the other to appear at 3840x2160@60Hz, after which I have to execute the following process to get both up and running.

1) Change the refresh rate of the active display to 30Hz, apply in Screen Display settings dialog
2) Plug the 2nd monitor in; At this point both appear in Screen Display dialog @60Hz, but the 2nd remains blank
3) Change both to 30Hz, apply; At this point the 2nd screen turns on
4) Change both to 60Hz, apply; At this point both are working at 60Hz, my desired end state

Inspection of edid seems fine (below), other than the DisplaySize showing 27" instead of 32"

Previously, I might be able to script my steps above using xrandr, but that seems to no longer be the case with 21.10 and wayland. I seem to be limited to the Screen Display dialog.

Since I can fix by simply re-applying the settings, it seems like a bug on startup. If I could find a CLI option to allow me to script this somehow, that workaround would be just fine for myself.

Lid open/closed, power via the 201344 or direct via other TB-PD port has no impact.

Here's hoping for a bugfix in 22.04 or at least a way to script the display configuration.

$ cat /sys/class/drm/card0-DP-4/edid | parse-edid
Checksum Correct

Section "Monitor"
 Identifier "LG HDR 4K"
 ModelName "LG HDR 4K"
 VendorName "GSM"
 # Monitor Manufactured week 5 of 2021
 # EDID version 1.4
 # Digital Display
 DisplaySize 600 340
 Gamma 2.20
 Option "DPMS" "true"
 Horizsync 30-135
 VertRefresh 56-61
 # Maximum pixel clock is 560MHz
 #Not giving standard mode: 1152x864, 60Hz
 #Not giving standard mode: 1280x1024, 60Hz
 #Not giving standard mode: 1280x720, 60Hz
 #Not giving standard mode: 1600x900, 60Hz
 #Not giving standard mode: 1920x1080, 60Hz
 #Not giving standard mode: 1280x800, 60Hz

 #Extension block found. Parsing...
 Modeline "Mode 6" 148.50 1920 2008 2052 2200 1080 1084 1089 1125 +hsync +vsync
 Modeline "Mode 0" 519.38 3840 3864 3880 3896 2160 2214 2219 2222 +hsync -vsync
 Modeline "Mode 1" 266.64 3840 3848 3992 4000 2160 2214 2219 2222 +hsync -vsync
 Modeline "Mode 2" 148.500 1920 2008 2052 2200 1080 1084 1089 1125 +hsync +vsync
 Modeline "Mode 3" 74.250 1280 1390 1420 1650 720 725 730 750 +hsync +vsync
 Modeline "Mode 4" 27.027 720 736 798 858 480 489 495 525 -hsync -vsync
 Modeline "Mode 5" 25.200 640 656 752 800 480 490 492 525 -hsync -vsync
 Modeline "Mode 7" 241.50 2560 2608 2640 2720 1440 1443 1448 1481 +hsync -vsync
 Option "PreferredMode" "Mode 6"
EndSection