LG UltraFine 5k monitor in Linux

Smaryus · 08-06-2023, 08:27 PM

Hi,
At the moment I am working with apple devices, because of this I’ve brought LG UltraFine 5k monitor. Now I will switch to work on Linux. Does anyone know how does this monitor works lately with Linux, since it has only a USB-C/TB connection? Found on some older forums different hacks to make it work, but they a bit older, like this http://johnwilger.com/2019/01/27/lg-...ome3-gdm3.html.

Thank you for any advice.

Emerson · 08-07-2023, 03:58 PM

Does your Linux machine have proper hardware for this?

Quote:

First check that you have a quality cable that complies with the USB-C and DisplayPort specifications. I know you said you tested this cable on another computer and it works there but that may simply mean the other computer isn't following the spec and/or is more forgiving of cables that violate the spect as written. The people that make these cables pay a lot of money for getting their cables tested, and with this money cones the right to put on their cables the USB "trident" icon, the Thunderbolt "spark", or the DisplayPort stylized "DP". Don't go running out a buy a new cable if you don't see any of these icons, just keep that in mind as a possibility as you check other possible problems.

Even if your cable meets USB-C and DisplayPort specifications there's also more than one specification. USB-C is required to supply a minimum of 7.5 watts, it's possible there's some electronics in the cable that needs more than this and that the port doesn't supply the required power. Theres more than one grade of DisplayPort cable, and your setup may require a higher grade of cable than you have. One way to grade them is RBR (reduced bit rate, supports 1080i), standard (supports 4K though perhaps at low refresh rates), and DP8K (tested to support 8K resolution). Another is to rate them by the version of DisplayPort they support, which can be 1.0, 1.2, 1.3, 1.4, or 2.0. Another is by the data rate they support, which can be anywhere from 5 to 80 Gbps. To confuse things further is that there's at least one more standard to indicate the bandwidth of the cable.

It's hard to say what kind of cable you need but if you are using USB-C to DisplayPort then the cable should have some indication of meeting the DP 1.2 spec or newer.

A second thing I suggest to check is the BIOS settings on the computer. Reading the forum link you gave would suggest that some computers will not output DisplayPort to USB-C unless explicitly enabled. Enabling DP output on USB-C could come with disabling any HDMI port the computer might have (which is not likely a concern for you). Enabling DP output on USB-C might come with losing USB 3.0 on the port, because DisplayPort and USB 3.0 use the same "superspeed" wires on the connector and only one of them can use those wires at a time. Most computers will make this switch between USB 3.0 and DisplayPort automatically depending on which kind of cable the computer detects, which I suspect the Dell computer does that you tested the cable with. This lack of automatic switching appears to be most common on computers with Intel graphics. You can speculate as well as I can on why this is.

I suggest looking in the BIOS for some setting to enable DP output to the USB-C port. I suggest checking that the cable is up to spec, and testing with another cable if possible. If you don't see an option for DP output in the BIOS, and the cable appears to be up to spec, then it's possible the computer simply does not support DisplayPort video output.

Copied from https://unix.stackexchange.com/quest...d-in-xrandr-ub

Smaryus · 10-05-2023, 03:24 AM

@Emerson, yes I've got from work a Lenovo with TB.
Ubuntu is able to detect the monitor and it detects that it has 2 monitors. I didn't spent time yet to combine into a single screen to have 5k.
The most annoying problem is the initial detection. It is not able to establish the connection, just after some time. in dmesg I see a lot of:
```
new retimer found, vendor...
retimer disconnected
```
this can go for a few seconds or minutes. In this time LG is not found, but eventually it works, also the laptop is charging on/off until the connection is made.

I'll need to find out why is the error message.

Smaryus · 01-18-2024, 05:51 AM

Just an update, maybe helps someone else.
I've managed to run the use the monitor, but:
* the laptop must always be connected to the external power source or it must have the battery over ~80%, otherwise it will enter into the connect/disconnect continuous loop.
* since I have Ubuntu on my laptop with wayland, I need to disable one of the 2 monitors detected for LG, and make the first monitor to cover the entire screen. This is because as far as I saw wayland doesn't support at this time "virtual display", to combine multiple screens into a single monitor(xorg has this feature).
* it happened once that I needed to shutdown the laptop and restart it(reboot didn't helped), because the display was not found, only the audio and the camera.