USB-C port doesn't work if nothing is connected at boot

User Support Hardware Issues
1

Thinkpad P51, which has one USB-C 3.1 port (Thunderbolt 3).
Qubes OS 4.2 fresh install.

If no device is connected to the USB-C port at the time of boot, then a flash drive or USB-C hub is not discovered when connecting it after the OS has started.

However, if a flash drive is connected at the time of boot, then it is shown in the list of devices, then it works fine, and I can attach it do individual VMs.

The following surprises me most: If an USB-C hub was connected to USB-C at the time of boot, then it works to hot-plug flash drives at Qubes runtime.

I wonder if there is a plausible explanation of this behavior, or if it seems like a hardware/BIOS bug.

I haven’t yet tried to boot a live USB system on that laptop, to check whether the behavior is the same with other Linux flavors.

2

Check the BIOS settings, there may be an option to only init the USB devices on boot time.

3

USB-A ports already work fine.
Only USB-C has that behavior.

4

Are there any options in BIOS related to Thunderbolt or USB-C specifically?

5

USB-A and USB-C are controlled independently. Read user manual. Snippet below . . .

After you install another operating system, you can enable the Thunderbolt 3 technology in ThinkPad Setup by doing the following:

1. Restart the computer and press F1 when the logo screen is displayed.
2. Select Config ➙ Thunderbolt™ 3 ➙ Security level.
3. Change the settings from Display Port and USB to any other selection.

6

Trying different related BIOS options didn’t have any impact on the reported behavior.

However, I noticed one more interesting detail.

It isn’t necessary to do a full reboot to get Qubes to discover the device connected to the USB-C port.

It is sufficient to restart the qube that handles the USB devices. (In my scenario, it’s sys-net which handles USB, too.)

So it doesn’t look like a BIOS issue, but rather an issue at the Qubes level? Is it possible that Qubes doesn’t re-scan the USB-C port during runtime, but only scans it on initial startup of the respective USB qube?

7

Do you need to have USB device connected during sys-usb restart?
Or if you restart sys-usb without USB device connected and connect USB device after sys-usb is started then it’ll work?

8

It must be connected at the time sys-usb starts.

If the port is empty at the time sys-usb starts, then no devices are detected for the remaining runtime of sys-usb.

(Or, it works, if a hub is connected at the time sys-usb starts. Then, devices connected to the hub at a later time will also be detected.)

9

Do you see anything in sys-usb log when you connect the USB device and it’s not recognized?
Restart sys-usb without USB device connected.
Run in sys-usb terminal:

sudo journalctl -f -n0

And connect the USB device.
Check the log.