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Thunderbolt

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Thunderbolt (including Thunderbolt security) is supported out of the box by the Linux kernel.

Obtain firmware updates

Some vendors use fwupd to push firmware updates on Linux. For others, browsing on their website will usually allow access to the needed files.

User device authorization

Modern Thunderbolt devices implement security modes that require user authorization when connecting devices - this is to protect from malicious devices performing DMA attacks or otherwise interfering with the hardware (see Thunderstrike 2).

The modes currently supported on Linux are:

  • none - No security, all devices are connected and initialized by default. In BIOS settings this is typically called Legacy mode.
  • user - User authorization is required every time a device is connected. In BIOS settings this is typically called Unique ID.
  • secure - User authorization is required, but the device is then remembered and does not require re-authorization. In BIOS settings this is typically called One time saved key.
  • dponly - DisplayPort functionality only, no other devices are allowed. In BIOS settings this is typically called Display Port Only.

The security level is normally configured at firmware level; it is recommended to set it to at least secure. The state of this setting can be queried with: 

$ cat /sys/bus/thunderbolt/devices/domain0/security
Tip User-space solutions are available such as bolt or tbtAUR to authorize devices.

Graphical front-ends

Automatically connect any device

Users who just want to connect any device without any sort of manual work can create a udev rule as in 99-removable.rules: 

/etc/udev/rules.d/99-removable.rules
ACTION=="add", SUBSYSTEM=="thunderbolt", ATTR{authorized}=="0", ATTR{authorized}="1"

Forcing power

Many OEMs include a method that can be used to force the power of a Thunderbolt controller to an On state. If supported by the machine this will be exposed by the WMI bus with a sysfs attribute called force_power [1].

Forcing power may especially be useful when a connected device loses connection or the controller that switches itself off.

To force the power to be on/off, write 1 or 0 to this attribute, e.g. to force power: 

# echo 1 > /sys/bus/wmi/devices/86CCFD48-205E-4A77-9C48-2021CBEDE341/force_power
Note It is not possible to query the current force_power state.

Troubleshooting

PCI buses are not registered

Sometimes when connecting a Thunderbolt device PCI buses might not be registered. This is apparent by having screens working while USB devices fail to register on your computer. This can be solved by issuing a PCI rescan: 

# echo 1 > /sys/bus/pci/rescan

Automatic PCI bus rescan

For persistent issues with PCI buses not being registered, an automatic rescan can be configured using udev rules. This will trigger a rescan whenever a Thunderbolt device is connected.

Create the PCI rescan bash script: 

/usr/local/bin/thunderbolt-rescan.sh
#!/bin/bash
echo 1 > /sys/bus/pci/rescan

Make it executable, then create a udev rule that triggers on thunderbolt connection: 

/etc/udev/rules.d/98-thunderbolt-rescan.rules
ACTION=="change", SUBSYSTEM=="thunderbolt", ATTR{authorized}=="1", RUN+="/usr/local/bin/thunderbolt-rescan.sh"

Increasing hot-plug bus size and memory

Some motherboards' firmware does not report enough bus and memory sizes to the kernel, causing drivers loading to fail. Add the following to kernel command line to manually set the size. 

pci=hpbussize=0x33,hpmemsize=256M

Display issues on a Thunderbolt dock

If you have a monitor connected to a Thunderbolt docking station and your system does not detect it, the station may require DisplayLink to work properly. For some docking stations this might also work better than alternative modes of connection.

Notebook Thunderbolt issues: EC/power reset

Try an EC/power reset (steps vary by notebook model) to clear a temporary embedded-controller or power-state:

  1. Shut down the notebook completely.
  2. Unplug the charger and disconnect all peripherals.
  3. If the battery is removable, remove it. If it is not removable, the BIOS likely has a maintenance mode feature along with instructions.
  4. Follow the manufacturer’s instructions for an EC or power reset. Some models use a specific power-button hold; the required time varies.
  5. Reconnect the battery, if removed, and the charger, then start the notebook.

This may clear a Thunderbolt power-state issue. It will not necessarily fix Thunderbolt firmware, BIOS, driver, cable, or dock problems.

Thunderbolt not working during boot

You need to make the thunderbolt module to your initramfs. See Kernel module#Automatic module loading.

See also