Linux 6.19 Kernel Fixes USB Detection Issues on Apple Silicon Macs

The upcoming Linux 6.19-rc6 kernel release includes two significant fixes addressing USB compatibility issues on Apple Silicon Macs. These patches specifically target problems affecting USB 2.0 and USB 3.x device detection on M1 and M2 series devices running mainline Linux kernels.

Core Fixes Explained

1. USB-C Role Switch Handling The first patch resolves USB detection failures on M2 and M1/M2 Pro/Max/Ultra devices by modifying how the kernel interacts with the USB-C port controller. Previously, unnecessary role switches triggered by the hardware would reset the USB controller, leaving attached devices in an undetectable state. The fix ignores redundant role-switch requests when the controller is already in the correct configuration, maintaining stable device enumeration. This matches the dwc3 controller's internal role management logic.

2. USB2 PHY Initialization Timing The second patch changes the sequence of USB controller initialization. By configuring the USB2 PHY mode before initializing the DWC3 controller core, Linux avoids state conflicts that occurred when USB2 devices were connected during boot. Apple's hardware requires this precise initialization order because role transitions (host↔device) fail if the PHY is reconfigured after DWC3 activation. This timing issue didn't affect USB3 PHY operations.

Background and Impact

These patches cap a multi-year effort to refine Apple Silicon support. The foundational USB DWC3 driver was upstreamed during the Linux 6.19 merge window after extensive testing in Asahi Linux's downstream kernel. Both fixes will be backported to stable kernel branches (5.15+), benefiting current Linux-on-Mac users.

The USB pull request also includes minor enhancements:

• Added PICAXE AXE027 cable support to FTDI SIO driver
• Elgato 4K X device quirk
• Miscellaneous driver corrections

Maintainers expect these changes to resolve long-standing USB reliability complaints on Apple hardware when Linux 6.19 releases in July 2026. Users can test the fixes immediately in rc6 or upcoming stable backports.