External Monitor not Working
Hello forum,

This thread looks like the right place to report this, but feel free to redirect me if needed.

I received my brand new PBP a couple days ago and I am happy with it overall. I am test driving it with the default desktop environment (Manjaro KDE plasma). One unfortunate thing that I've found is that (contrary to my expectations) my external screen does not work via USB-C.

The screen is a Dell UltraSharp U3818DW with a native resolution of 3840x1600 at 60Hz and its USB-C input is spec'd as: Alternate mode with DP1.2, Power Delivery, and USB2.0. So judging from the specs, it should be compatible with the PBP video output. Also, this is a professional grade monitor and I expect that things are correctly implemented on its side (but you can never be sure, can you?). I am driving this monitor every day via its HDMI input, but sadly I haven't been able to test its USB-C input with a different computer.

Anyway, when I connect the monitor to the PBP with a direct USB-C to USB-C cable:
- The monitor's OSD displays "USB Type-C Plugged", which is good.
- The PBP starts charging the battery, which is good.
- Nothing else directly visible happens, but this appears in dmesg:

[ 1643.685532] cdn-dp fec00000.dp: [drm:cdn_dp_pd_event_work [rockchipdrm]] Not connected. Disabling cdn
[ 1643.929266] cdn-dp fec00000.dp: [drm:cdn_dp_pd_event_work [rockchipdrm]] Not connected. Disabling cdn
[ 1643.984981] typec_displayport port0-partner.0: No compatible pin configuration found:0000 -> 001c, 001c <- 0000
[ 1645.315793] usb 7-1: new high-speed USB device number 2 using xhci-hcd
[ 1645.506446] usb 7-1: New USB device found, idVendor=0451, idProduct=8442, bcdDevice= 1.00
[ 1645.506494] usb 7-1: New USB device strings: Mfr=0, Product=0, SerialNumber=1
[ 1645.506516] usb 7-1: SerialNumber: B1050089D092
[ 1645.560481] hub 7-1:1.0: USB hub found
[ 1645.560617] hub 7-1:1.0: 6 ports detected
[ 1645.965773] usb 7-1.5: new high-speed USB device number 3 using xhci-hcd
[ 1646.106643] usb 7-1.5: New USB device found, idVendor=0451, idProduct=82ff, bcdDevice= 1.00
[ 1646.106674] usb 7-1.5: New USB device strings: Mfr=0, Product=0, SerialNumber=1
[ 1646.106685] usb 7-1.5: SerialNumber: B1050089D092
[ 1646.169149] hid-generic 0003:0451:82FF.0003: hiddev97,hidraw2: USB HID v1.11 Device [HID 0451:82ff] on usb-xhci-hcd.1.auto-1.5/input0
[ 1646.265782] usb 7-1.6: new high-speed USB device number 4 using xhci-hcd
[ 1646.396762] usb 7-1.6: New USB device found, idVendor=0451, idProduct=82ee, bcdDevice= 1.00
[ 1646.396810] usb 7-1.6: New USB device strings: Mfr=0, Product=0, SerialNumber=3
[ 1646.396832] usb 7-1.6: SerialNumber: B1050089D092

- If I then press Fn+F3 to change the video output (to, let's say, "Switch to external screen"), nothing visible happens. And nothing else appears in dmesg either.

- I have tried flipping the USB-C connector (plugging it in the other way) and there is no difference, the same things happen as above.

- The cable is (I believe) from Apple; it has been used to drive a display in another setting (MacBook Pro with a different monitor by LG), so I believe it is good. I also tested with a different USB-C cable, the one that was supplied with the Dell monitor. It is much more stiff, so my preference is the Apple cable, but I don't think any of the cables are faulty.

Not surprisingly, if I look at System settings -> Display configuration, the screen does not show up (only the internal laptop screen is present).

Maybe the screen resolution is too high? I don't believe so, because I have an Asus TinkerBoard (RockChip RK3288, with a lower-end ARM Mali T760) that drives this screen via HDMI at its native resolution (@30Hz).

# uname -a
Linux xyz 5.11.16-1-MANJARO-ARM #1 SMP Wed Apr 21 12:27:08 UTC 2021 aarch64 GNU/Linux

Please let me know if there is any other diagnostics I can supply, or things I could try to troubleshoot this.

And thanks for making the PBP, it is a great piece of kit!

Messages In This Thread
External Monitor not Working - by sciolus - 03-12-2021, 07:45 AM
RE: External Monitor not Working - by Arwen - 03-14-2021, 02:05 PM
RE: External Monitor not Working - by sciolus - 03-18-2021, 03:00 PM
RE: External Monitor not Working - by Arwen - 03-19-2021, 07:27 AM
RE: External Monitor not Working - by mspohr - 03-20-2021, 08:17 AM
RE: External Monitor not Working - by aurora.borealis - 05-05-2021, 02:05 AM

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