0

I'm running Ubuntu 20.10 with the latest updates on an LG Gram 17" laptop. I'm also using an LG 32UN880 monitor, which comes with a USB 3.0 hub that somehow is detected as a USB 2.0 hub:

lsusb output

How can I make Ubuntu correctly detect the hub?

On another thread someone suggested adding iommu=soft to the GRUB options. I tried that, but all it did was to make the USB hub show up as two entries rather than one on lsusb, one showing as 2.0 and another as 2.1. So it was useless.

I appreciate any help and tips on solving this, as it is slowing down a lot my USB Ethernet adapter as well as my webcam that are both connected to this USB hub.

BeastOfCaerbannog
  • 14,585
Libre
  • 31
  • 1
  • 6

1 Answers1

1

Are you using the USB-C port for DP video? That would explain why you are not seeing a USB 3.x hub.

USB-C has three relatively independent connections within it, there's power, USB 2.0, and the four "superspeed" data lanes. The four superspeed data lanes can be split into two pairs for USB 3.x and DP video or, if more bandwidth is needed than two superspeed data lanes can provide then all four can be used for DP video. If all four superspeed data lanes are used for video then... no USB 3.x for you.

If you need that USB 3.x hub in the display to work then maybe lowering the resolution can get it to work. I doubt it since once it detects use of USB-C for video it likely switches all USB-C superspeed lanes for video use. Another way that is far more likely to work is to use a separate cable for video, using the DP or HDMI ports for video instead of USB-C. By using a separate cable for video the display should switch the USB-C port into USB 3.x mode and enable the USB hub in the display to bring USB 3.x signals to the USB-A ports.

It is pretty standard from what I've seen for 4K displays to not offer USB 3.x data on any downstream USB ports if connected by USB-C. There's only so much bandwidth on USB-C cables and 4K video takes a lot of bandwidth, there's likely not enough room for both 4K video and USB 3.x. Close examination of the user manual should prove or disprove my theory.

MacGuffin
  • 377