Earlier this year, Linux 5.6 brought the original form of USB4 support by leveraging Intel's existing thunderbolt kernel support, and the updated USB specification is based on this.The subsequent kernel continues to mature with the USB4 implementation, which continues in Linux 5.10.
Around tiger lake, the kernel has also carried out a lot of work on optimizing thunderbolt, including the repair and improvement of runtime power management in CM mode, optimization of strong power logic, and debugfs interface for thunderbolt debugging.
As early as the development of Linux 5.9, the original tiger Lake thunderbolt / USB4 code has been implemented and improved in the subsequent kernel.
Other parts also include small work on USB type-C update and PHY driver. Another notable addition is USB 3 PHY support for Intel lightning mountain SOC.