Pinebook Pro not detecting Dell U2720Q USB-C external display

ARM Technical Assistance
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1

I have a new Pinebook Pro running Manjaro 5.7.19-1-MANJARO-ARM #1 SMP Wed Sep 2 20:43:09 +03 2020 aarch64 GNU/Linux. I am unable to get it to detect a Dell UltraSharp 27 4K USB-C Monitor - U2720Q external display plugged in via the included USB-C cable. Charging works, but video out does not.

The user manual says the monitor supports: 1 x USB Type-C (Alternate mode with DisplayPort 1.4, USB 3.0 upstream port, Power Delivery PD up to 90 W).

When I plug the cable into the Pinebook Pro, dmesg shows the following:

[Mon Sep 21 10:39:06 2020] usb 7-1.5: USB disconnect, device number 11
[Mon Sep 21 10:39:06 2020] cdn-dp fec00000.dp: [drm:cdn_dp_pd_event_work [rockchipdrm]] Not connected. Disabling cdn
[Mon Sep 21 10:39:06 2020] cdn-dp fec00000.dp: [drm:cdn_dp_pd_event_work [rockchipdrm]] Not connected. Disabling cdn
[Mon Sep 21 10:39:30 2020] cdn-dp fec00000.dp: [drm:cdn_dp_pd_event_work [rockchipdrm]] Not connected. Disabling cdn
[Mon Sep 21 10:39:30 2020] cdn-dp fec00000.dp: [drm:cdn_dp_pd_event_work [rockchipdrm]] Not connected. Disabling cdn
[Mon Sep 21 10:39:30 2020] typec_displayport port0-partner.0: No compatible pin configuration found:0000 -> 0014, 001c <- 0000
[Mon Sep 21 10:39:30 2020] usb 7-1: new high-speed USB device number 12 using xhci-hcd
[Mon Sep 21 10:39:30 2020] usb 7-1: New USB device found, idVendor=0451, idProduct=8442, bcdDevice= 1.00
[Mon Sep 21 10:39:30 2020] usb 7-1: New USB device strings: Mfr=0, Product=0, SerialNumber=1
[Mon Sep 21 10:39:30 2020] usb 7-1: SerialNumber: 52010851800D
[Mon Sep 21 10:39:30 2020] hub 7-1:1.0: USB hub found
[Mon Sep 21 10:39:30 2020] hub 7-1:1.0: 6 ports detected
[Mon Sep 21 10:39:30 2020] usb 8-1: new SuperSpeed Gen 1 USB device number 6 using xhci-hcd
[Mon Sep 21 10:39:30 2020] usb 8-1: New USB device found, idVendor=0451, idProduct=8440, bcdDevice= 1.10
[Mon Sep 21 10:39:30 2020] usb 8-1: New USB device strings: Mfr=0, Product=0, SerialNumber=0
[Mon Sep 21 10:39:30 2020] hub 8-1:1.0: USB hub found
[Mon Sep 21 10:39:30 2020] hub 8-1:1.0: 4 ports detected
[Mon Sep 21 10:39:31 2020] usb 7-1.5: new high-speed USB device number 13 using xhci-hcd
[Mon Sep 21 10:39:31 2020] usb 7-1.5: New USB device found, idVendor=0451, idProduct=82ff, bcdDevice= 2.00
[Mon Sep 21 10:39:31 2020] usb 7-1.5: New USB device strings: Mfr=0, Product=0, SerialNumber=0
[Mon Sep 21 10:39:31 2020] hid-generic 0003:0451:82FF.000A: hiddev97,hidraw2: USB HID v1.11 Device [HID 0451:82ff] on usb-xhci-hcd.1.auto-1.5/input0

I have seen the post about the 5.8 kernel issue with DP-Alt on the Pinebook Pro but this seems to be related to the 5.8 kernel, and I am on 5.7. Any suggestions for how to debug this?

2

Is the screen not detected at all?

Try turning the USB-C plug upside down.

3

Nothing seems to be detected. Same thing either way the USB is plugged in.

4

Got any phone’s that have USB C? So you can plug in the display…

:rofl:
I was about to add an meme but went Na,

5

The display works fine - I can plug it into a Macbook Air (2018) via USB-C without any issues.

6

have you try to boot pinebook Pro and switch on Screen Dell with USB-c ?

7

Some USB-C displays simply don’t work with the Pinebook Pro. There’s a reason there are compatability lists around.

8

Yeah, rebooting with it connected makes no difference.

9

Fine, but there must be a reason. What steps do you suggest to try and debug it?

10

To be honest I dont know.
The hack we had placed in kernel 5.7 was just that. A hack. And it even stopped working, for no apparent reason, in 5.8.

11

usb 3.x ( stack) has been rebuild in this version linux ( for securities reasons )

12

I’ve posted this over on the Pine64 forums as several people are also having the same problem.

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