Linux Picking Up A Driver For Checking If Thunderbolt/USB4 Ports Are Functional
The DMA Traffic Test Driver does just that and is used for sending and receiving a specified number of packets on a loopback connection to see whether a port is functioning, primarily for testing purposes during hardware manufacturing.
Besides needing this new Thunderbolt/USB4 driver, a Thunderbolt/USB4 cable needs to be connected back to the host router port or making use of a special loopback dongle where the RX and TX lines are crossed.
The USB4_DMA_TEST driver (thunderbolt_dma_test kernel module) exposes its send/receive tunables via DebugFS and for initiating the test and reading back the status.
More details on this pending Intel Linux driver for USB4/Thunderbolt port testing via dma-test on Thunderbolt.git that will then likely be mainlined for Linux 5.11 if wanting to verify working functionality for a given port.
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