Thank you for the response. I think these might fall into the third category of 'VESA is its own special story' ?
I bought both the adapters from the dell configurator at the time I bought the machine. This is the part that flakes: https://www.dell.com/en-us/shop/accessories/apd/470-acfc The other part, that works fine It is advertised as suitable for 4K 60hz, which as you note exceeds USB3.1, but see the link from the dell site - https://www.usb.org/sites/default/files/D2T1-4%20-%20VESA%20DP%20Alt%20Mode%20over%20USB%20Type-C.pdf - it is not being carried over USB, but over alt-mode DP as far as I can tell, which should have plenty of bandwidth. The monitors are, from memory DP 1.2, requiring MST to operate - https://downloads.dell.com/manuals/all- products/esuprt_display_projector/esuprt_display/dell-up2414q_user%27s %20guide_en-us.pdf confirms this. However, the mystery deepens. There are two USB-C/thunderbolt connectors on the laptop. My initial report had the combined-power-HDMI-DP one in the left connector, and the DP only one in the right connector. On a lets-be-pedantic hunch I just plugged them in on the opposite sides. With the DP only adapter plugged in on the left side, it: - reports both the MST panels - both panels autoconfigure for a combined 4k 60hz - yay! """ DP-1-8 connected 1920x2160+5760+0 (normal left inverted right x axis y axis) 527mm x 296mm 1920x2160 59.99*+ DP-1-9 connected 1920x2160+3840+0 (normal left inverted right x axis y axis) 527mm x 296mm 1920x2160 59.99*+ 1920x1200 59.88 """ With both adapters plugged in, the DP only one still on the left side, the behaviour that I originally filed the bug because of returns: """ xrandr --output DP-3 --auto --output DP-1-8 --auto --output DP-1-9 --auto xrandr: cannot find crtc for output DP-1-9 """ If I turn DP-3 off I can run the single DP monitor fine even though the adapter is plugged in. This behaviour is also consistent if I switch the power/hdmi/dp adapter to use HDMI rather than DP. What I had hoped to do is to use - ideally - all three outputs, or at worst, two external outputs and have my laptop folded flat and out of the way while I use my clicky-clacky keyboard and real mouse at my desk; being able to use either adapter, one at a time, is a dissapointment. What I think this shows so far: - each adapter works independently, with either adapter, from either USB-C port. - something I don't know enough about yet causes some resource constraint or conflict when both external screens are in use. ** Changed in: xorg-server (Ubuntu) Status: Incomplete => New -- You received this bug notification because you are a member of Desktop Packages, which is subscribed to xorg-server in Ubuntu. https://bugs.launchpad.net/bugs/1886729 Title: Dell displayport YJ3Y6 adapter doesn't drive 4K screen properly Status in xorg-server package in Ubuntu: New Bug description: I have some early dell 4k 60hz screens - the ones which report 2 panels internally for DP 60Hz - horrid hack I know; I recently got a new XPS laptop and put Ubuntu on it. That XPS laptop has two USB-C/thunderbolt ports, so to drive the screens I bought two slightly different DP adapters - one with power passthrough, and a cheaper one that only does DP. The more expensive one 'USB-C to HDMI/DP' drives the monitor happily over DP, though sadly only at 30Hz - can't have everything :/. It reports one monitor as one output: DP-1 in the attached information: DP-1 connected 3840x2160+0+0 (normal left inverted right x axis y axis) 527mm x 296mm 3840x2160 29.98*+ 30.00 29.97 1920x1200 59.88 ... The cheaper one reports the single monitor as two distinct outputs, at 60hz interestingly - DP-3-8 connected (normal left inverted right x axis y axis) 1920x2160 59.99 + DP-3-9 connected 1920x2160+7680+0 (normal left inverted right x axis y axis) 527mm x 296mm 1920x2160 59.99*+ 1920x1200 59.88 which in theory if summed together would be one whole screen. But attempting to configure the output results in an error: xrandr --output DP-1 --auto --left-of eDP-1 --output DP-3-9 --auto --right-of DP-3-8 --output DP-3-8 --auto --right-of eDP-1 xrandr: cannot find crtc for output DP-3-8 I'm not sure if this is an intrinsic limitation of the USB-C->DP dongle, or whether there is something that can be done in the software to deal with this 10 year old hardware hack I have sitting on my desktop. ProblemType: Bug DistroRelease: Ubuntu 20.04 Package: xorg 1:7.7+19ubuntu14 ProcVersionSignature: Ubuntu 5.4.0-40.44-generic 5.4.44 Uname: Linux 5.4.0-40-generic x86_64 ApportVersion: 2.20.11-0ubuntu27.3 Architecture: amd64 BootLog: Error: [Errno 13] Permission denied: '/var/log/boot.log' CasperMD5CheckResult: skip CompositorRunning: None CurrentDesktop: ubuntu:GNOME Date: Wed Jul 8 11:20:17 2020 DistUpgraded: Fresh install DistroCodename: focal DistroVariant: ubuntu ExtraDebuggingInterest: Yes, including running git bisection searches GraphicsCard: Intel Corporation Iris Plus Graphics G7 [8086:8a52] (rev 07) (prog-if 00 [VGA controller]) Subsystem: Dell Iris Plus Graphics G7 [1028:096d] InstallationDate: Installed on 2020-07-07 (0 days ago) InstallationMedia: Ubuntu 20.04 LTS "Focal Fossa" - Release amd64 (20200423) MachineType: Dell Inc. XPS 13 9300 ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-5.4.0-40-generic root=/dev/mapper/vgubuntu-root ro quiet splash vt.handoff=7 SourcePackage: xorg Symptom: display UpgradeStatus: No upgrade log present (probably fresh install) dmi.bios.date: 05/08/2020 dmi.bios.vendor: Dell Inc. dmi.bios.version: 1.0.11 dmi.board.name: 0WX9VX dmi.board.vendor: Dell Inc. dmi.board.version: A00 dmi.chassis.type: 10 dmi.chassis.vendor: Dell Inc. dmi.modalias: dmi:bvnDellInc.:bvr1.0.11:bd05/08/2020:svnDellInc.:pnXPS139300:pvr:rvnDellInc.:rn0WX9VX:rvrA00:cvnDellInc.:ct10:cvr: dmi.product.family: XPS dmi.product.name: XPS 13 9300 dmi.product.sku: 096D dmi.sys.vendor: Dell Inc. version.compiz: compiz N/A version.libdrm2: libdrm2 2.4.101-2 version.libgl1-mesa-dri: libgl1-mesa-dri 20.0.8-0ubuntu1~20.04.1 version.libgl1-mesa-glx: libgl1-mesa-glx N/A version.xserver-xorg-core: xserver-xorg-core 2:1.20.8-2ubuntu2.1 version.xserver-xorg-input-evdev: xserver-xorg-input-evdev N/A version.xserver-xorg-video-ati: xserver-xorg-video-ati 1:19.1.0-1 version.xserver-xorg-video-intel: xserver-xorg-video-intel 2:2.99.917+git20200226-1 version.xserver-xorg-video-nouveau: xserver-xorg-video-nouveau 1:1.0.16-1 To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/xorg-server/+bug/1886729/+subscriptions -- Mailing list: https://launchpad.net/~desktop-packages Post to : [email protected] Unsubscribe : https://launchpad.net/~desktop-packages More help : https://help.launchpad.net/ListHelp
