No USB from Lenovo Thunderbolt dock 40AC0135

A nice new bit of issued kit not working in the way I wanted it to - namely that USB ports seemed to give power, but now show up as devices. Most confusing for things like backlit keyboards, or microphones. They seem to work from a power point of view - but no function - and not showing up as USB devices. With only two USB3 sockets in the laptop, this is a proper issue.

The dock in question is the Thunderbolt 3 USBC connected (issued with a comedically short lead - I mean - really?) 40AC dock. It supplies power to the laptop, powers two Display Ports (VGA and HDMI) a selection of high power / USB3 / USB2 sockets, USB C sockets, external 3.5mm sound output, and an RJ45 for a wired gigabit connection.

Following this resolution - everything is working except the RJ45 (which shows link light, but does not show up under ip addr) - I will update this post if I get that working.

The fix resolved both the USB sockets and the 3.5mm sound jack that was in the dock conveniently... just that RJ45 to resolve now (update: resolved in Fedora 30 install - see comment update below).

// USB sockets in Lenovo 40AC thunderbolt dock not working

With the thunderbolt connector in the correct port (not the one at the back) - the monitors function fine, there is power to the USB sockets, but they are not enumerating any devices.

// Environment

   - Lenovo T480 and other units that make use of the 40AC dock.
   - RHEL 7.
   - Likely other Linux.

// Resolution

Ensure that your USB C Thunderbolt cable is NOT plugged into the power socket at the back (shown with a plug to the left of it) but is plugged into the USB C socket that is closer to yourself - to the right of the Thunderbolt logo. This is the wonder of a standard that can be used over other sockets. #win. Without this step - the rest are pointless.

Shut down the machine. Starting the machine into the BIOS setup.

Under peripherals or similar - look for THUNDERBOLT SECURITY.  Make note the security setting currently.
Reduce the security setting for this device, save the settings, restart the machine. Test.
If this does not resolve the issue - repeat - reducing the security setting further.

// Root Cause

Thunderbolt has its own security that can is set initially at boot time, and is not changeable by the OS.

// Diagnostic Steps

Using boltctl list shows the dock is attached and functioning. However boltctl enrole (followed by the UUID for the dock as displayed previously) gained from the list does not cause lsusb to start finding those devices.
lsusb is not showing devices that are plugged into the dock unit. Plugging the same device into the laptop directly, it is enumerated, and shows in lsusb. In both cases any power lights, backlights, or similar are illuminated.
It is likely that the Security setting for this Thunderbolt connection is set too high for what you are trying to do.

One Response to “No USB from Lenovo Thunderbolt dock 40AC0135


    The NIC in the dock I was unable to get to work with RHEL7.

    On switching to Fedora 30 however, the device became visible and useable.

    The device enumerated as:

    ens1u1: connected to Wired connection 1
    “Lenovo ThinkPad TBT3”

    The GUI shows it as a “USB Network Card” – and the MAC address vendor looks to be allocated to the delightfully named, and particularly unknown Good Way Industrial Co. .

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