Linux Kernel Patches Out For Review To Enable USB4/Thunderbolt For Apple M1 / M2 / M3

The Linux kernel recently released patches for review, enabling USB4 and Thunderbolt support for Apple's M1, M2, and M3 processors. Each USB4 capable Type-C port features an Apple Converged I/O (ACIO) block, which houses a Cortex-M3 co-processor and the hardware responsible for managing the USB4 router. This ACIO block is not treated as separate devices but rather shares a 16 MiB window within the main SoC bus MMIO space, with the co-processor running independently.

The main driver initiates the ACIO, boots the co-processor, populates the DART (Device Assignment and Resource Translation) and NHI (Next-Generation Hub Interface) components once their MMIO regions are accessible, and registers the NHI with the software connection manager. The final three patches will introduce device tree nodes for the M1 and M2 processors, with M3 nodes expected to follow once the rest of the stack is integrated into the mainline kernel.

Currently, XDomain connections and USB3 via USB4 tunnels are supported, with PCIe and DisplayPort tunnels expected to arrive later as additional work and reverse engineering are required. Suspend functionality is also pending, as suspending while an active connection is present would lead to an SError. Michael Larabel, the principal author of Phoronix.com and its founder, contributed extensively to the patches, which are now available for review.