Librem 14 display over USB-C

Hardware
1

Hello,

Apologies for another post on the topic, but information is hard to distill from other posts.

I have a new Librem 14 and am having issues connecting it to my monitor via USB-C. I can connect it via HDMI, which works fine, but the monitor has an integrated USB hub, sound, and ethernet that I’d like to take advantage of (only sound is recognized over HDMI).

With my work laptop (a Dell XPS running Ubuntu), I can connect to a USB-C port and it recognizes all the above attached devices. When I connect it to the Librem 14, I get nothing. However, if I attach a USB-C to HDMI adapter to the Librem 14 USB-C port, the display works, but none of the network, sound, or USB devices attached to the monitor are recognized. I’d really like to just swap the USB-C cable between my work and personal laptop to keep things simple. If I can do this over HDMI, this would work as well, but the HDMI port only recognizes sound and no ethernet or USB devices.

Interestingly, the left port (which I know is data-only) recognizes USB devices and the ethernet connection, but no sound or display. Here are the USB-C specs for my monitor:

image
image981×235 31.4 KB

The monitor has a setting for DisplayPort 1.1 or 1.2: neither seem to change the outcome. Any advice or things for me to try here?

2

Can you boot with a Ubuntu live USB on the L14 to try and narrow down if its a hardware incompatibility or a software issue?

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3

What are the display specs of the monitor (resolution and frame rate)?

Have you tried lsusb and lsusb -s xxx -v and/or looked in system logs to see what the laptop thinks when it is connected to the monitor via USB-C? (Building on what @lo0 suggests, you could compare output in the three scenarios: Ubuntu on Dell laptop, Ubuntu on Librem 14, PureOS on Librem 14.)

Since the USB-C is optimistically described in your post as a “reversible plug connector” :wink:, have you tried all four orientations of the USB-C cable?

“Sound” is complicated because normally sound is part of the HDMI data itself i.e. not a separate USB device even when DisplayPort altmode USB is working as intended, I would guess. So it would depend on the details of exactly how the monitor is handling “sound”. Hence:

sound ought to work in this scenario provided that you configure Linux to output sound via HDMI.

(As of HDMI 1.4 there is ethernet-over-HDMI but I have never done it or even ever seen it in use. I don’t know what the level of support is in Linux or in hardware on which and with which Linux is typically used. It is reportedly Fast Ethernet only i.e. 100 Mbit/s, hence many people would find that unappealing.)

4

Hi everyone,

I’m not sure whether I should create a separate post or not, but I do have a similar issue with my Librem 14 in that my USB-C monitor (Dell P3421W) does not work (exact same setup works for other devices).

For the left USB-C port, USB devices work but the display doesn’t, as expected. For the right USB-C port, the display and all USB devices connect and disconnect repeatedly. I first suspected insufficient power delivery, but the behavior remains when the notebook is connected to the power adapter additionally. It was reproducible for both a current Qubes 4.1 RC and a Ubuntu 21.10 Desktop (Kernel 5.13.0-19).

Any ideas? Might it be related to OP’s issue?

Cheers!

1 Like
5

Thanks for the suggestion! I booted into a live USB running Ubuntu 21.10 and got similar behaviour: HDMI port works as expected, USB-C is not recognized. Interestingly, connecting the USB-C to HDMI adapter to the L14 running Ubuntu did not recognize the monitor as PureOS did.

6

I appreciate the thorough reply! Here is a screenshot of some specs:

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…and a link to the full manual if you’re interested:

lsusb on my Dell laptop shows the USB hub and the ethernet connection (the Realtek entries), but I don’t know if I should expect anything indicating there is a monitor:

$ lsusb
Bus 004 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
Bus 003 Device 016: ID 046d:c539 Logitech, Inc. USB Receiver
Bus 003 Device 015: ID 0bda:5420 Realtek Semiconductor Corp. 4-Port USB 2.0 Hub
Bus 003 Device 004: ID 0c45:672a Microdia Integrated_Webcam_HD
Bus 003 Device 002: ID 27c6:533c Shenzhen Goodix Technology Co.,Ltd. FingerPrint
Bus 003 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 002 Device 013: ID 0bda:8153 Realtek Semiconductor Corp. RTL8153 Gigabit Ethernet Adapter
Bus 002 Device 012: ID 0bda:0420 Realtek Semiconductor Corp. 4-Port USB 3.0 Hub
Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub

On the L14, I noticed something where the devices would disappear and reappear from one run to the next with different device numbers. Ethernet never showed up in the results. For example (the monitor was plugged in after the first run):

$ lsusb
Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
Bus 001 Device 003: ID 04ca:3006 Lite-On Technology Corp.
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
$ lsusb
Bus 001 Device 039: ID 0bda:5420 Realtek Semiconductor Corp. 4-Port USB 2.0 Hub
Bus 002 Device 034: ID 0bda:0420 Realtek Semiconductor Corp. 4-Port USB 3.0 Hub
Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
Bus 001 Device 003: ID 04ca:3006 Lite-On Technology Corp.
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
$ lsusb
Bus 002 Device 041: ID 0bda:0420 Realtek Semiconductor Corp. 4-Port USB 3.0 Hub
Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
Bus 001 Device 050: ID 0bda:5420 Realtek Semiconductor Corp. 4-Port USB 2.0 Hub
Bus 001 Device 003: ID 04ca:3006 Lite-On Technology Corp.
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
$ lsusb
Bus 002 Device 082: ID 0bda:0420 Realtek Semiconductor Corp. 4-Port USB 3.0 Hub
Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
Bus 001 Device 003: ID 04ca:3006 Lite-On Technology Corp.
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
$ lsusb
Bus 001 Device 049: ID 0bda:5420 Realtek Semiconductor Corp. 4-Port USB 2.0 Hub
Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
Bus 001 Device 003: ID 04ca:3006 Lite-On Technology Corp.
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub

So, aside from the ethernet, the two computers seem to recognize the hubs as the same, but something odd is going on with the L14 where it doesn’t seem to maintain connection (?) with the monitor’s USB.

Since the USB-C is optimistically described in your post as a “reversible plug connector” :wink:, have you tried all four orientations of the USB-C cable?

Tried this, but I didn’t notice any difference.

sound ought to work in this scenario provided that you configure Linux to output sound via HDMI.

To clarify, I was indeed mistaken in my original post: sounds was working via HDMI through the USB-C to HDMI adapter.

Again, I appreciate the response! Let me know if anything else would help.

7

For you and those who happen to have a Dell monitor, go through your monitor settings and try to find MST (Multi-Stream Transport) and turn it ON, this helped with my unit.

For others I don’t think you will be getting DP over usb-c working unless you go with a dongle (usb-c to hdmi or something else). Librem 14’s usb-c chip that handles DP over usb-c, PD over usb-c etc. doesn’t seem to be USB-IF certified or at least doesn’t meet their standards.

8

For you and those who happen to have a Dell monitor, go through your monitor settings and try to find MST (Multi-Stream Transport) and turn it ON, this helped with my unit.

Thanks for the hint, unfortunately I didn’t find that option on my monitor.

For others I don’t think you will be getting DP over usb-c working unless you go with a dongle (usb-c to hdmi or something else). Librem 14’s usb-c chip that handles DP over usb-c, PD over usb-c etc. doesn’t seem to be USB-IF certified or at least doesn’t meet their standards.

I’m afraid it might be something like this. Might be totally unrelated, but I already had the notebook repaired since power control seemed to be broken after playing around with various combinations of USB-C monitor and power adapter (doesn’t necessarily mean it was caused by that of course).

9

Thanks for the input. I need help clarifying, though. Are you saying that it is not possible to successfully connect a monitor with integrated USB hub via the USB-C port? I’m flexible in terms of solutions here since I can get a different monitor or USB hub if needed, but my ideal solution is to simply connect one USB-C cable to the L14 and have display, Ethernet, sound, keyboard, and mouse all run through it like I’ve done with other laptops. If that’s not possible with any monitor and the L14, it would be good to know so I can stop chasing that solution and move to using HDMI with a separate USB hub.

10

You definitely can use a USB-C hub/dock for this. But there is basically no guarantee that the dock/hub will work with L14, this guy has had a few docks that didn’t work on L14 and found one that worked:
https://ajmartinez.com/tech/posts/202152-001-librem14

Also I can tell that Dell P2720DC works properly when MST is enabled (otherwise most resolutions are not available).

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11

I know this is probably getting a little beyond what you can reasonably confirm, but do you have any idea of compatibility beyond this morning as far as “MST” goes? I’m curious if I could search Dell for monitors with this option (feature?). I’ve heard the advice of making sure there is a good return policy when shopping for L14 peripherals, so I’m not looking to hold anyone to account, just curious if I can make my search easier.

Curious if there’s some consolidated thread on confirmed working devices. I followed through the link you posted on the USB-C hub and it was no longer available.

12

Even Dell displays that have MST are not guaranteed to work, I can only confirm that Dell P2720DC work when it is enabled (it might switch to another USB-C controller, no other ideas why it works). Mr Chromebox has Dell 34UW19 and it’s working with L14 according to him. I don’t think there is a list of confirmed to work docks/displays for L14.

You might be able to find that same dock from local stores or some online resellers. For example Proshop still has the dock https://www.proshop.de/Dockingstationen/Lenovo-ThinkPad-USB-C-Dock-Gen2-90W-EU-40AS0090EU/2744782