Asahi Linux ships first Thunderbolt support and submits macaudio and AVD drivers upstream

Asahi Linux has published its progress report for the Linux 7.3 cycle, and it covers a lot of ground: the project's audio and video decoder drivers are on their way upstream, M3-series Macs are now supported without installation caveats, and Thunderbolt support — promised back in January 2024 — has finally started shipping to users.

Drivers head upstream

According to the report, two substantial drivers were submitted for upstream review this cycle: macaudio and AVD. Preparing macaudio was difficult because Apple Silicon's audio subsystem is unusual enough to require changes to core ALSA code, and Apple ships special variants of speaker and headset amplifiers whose existing upstream drivers needed significant rework. The driver and its Devicetree changes total roughly 3,100 lines.

AVD moved much faster, spending barely three months in Asahi's downstream tree before submission. The report calls this the shortest turnaround yet for a major SoC component and a good omen for a future transition to upstream-first development. AVD and its Devicetree changes span about 13,000 lines.

Initial Devicetrees for M4 Pro, M4 Max and M5 devices, credited to contributor Yureka, also landed this cycle. They are deliberately minimal — just enough to boot the SoC to a text console — with fuller enablement in progress. Meanwhile, changes to the TI USB-PD and SPMI drivers required by new devices, along with initial Thunderbolt support, were developed upstream-first from the start, an approach the project says is starting to pay off.

M3 support goes generally available

Having introduced M3 support behind the installer's EXPERT flag in the previous report, Asahi says early adopters reported almost no issues, so the flag requirement has been removed. M3 machines also gained DCP, the display driver, bringing performance and battery-life improvements, enabling sleep, and making the screen area around the notch usable on MacBooks. m1n1 and kernel updates were said to be arriving within days.

Thunderbolt arrives, partially

The project promised Thunderbolt within 2024; after two years of near-silence, the patchset has now been sent upstream first and is shipping in the downstream kernel. The report explains the delay: since Intel built effectively every Thunderbolt controller on the market, the kernel's Thunderbolt subsystem assumes Intel's hardware topology and register access patterns. Apple, pushing to insource silicon IP, designed its own controller — a Cortex-M3 core running RTKit paired with a bespoke Thunderbolt/USB4 router, one per Thunderbolt-enabled USB-C port — which breaks many of those assumptions. The controller is also oddly coupled to PMGR, with reset lines toggled by writing bits in the middle of PMGR's MMIO range, behaviour the team initially mistook for noise.

For now, only USB3, XDomain and Thunderbolt Networking work: USB devices function and two Thunderbolt computers can be linked, but PCIe and DisplayPort tunnelling — required by most docks — is not yet supported. The report credits Sven with nearly five years of work on the feature.

Three VMs under m1n1

m1n1, Asahi's bootloader and hypervisor, can now virtualise SPTM-enabled macOS, enabling reverse engineering on M4 machines. M5 raises the stakes: every macOS version that supports it requires Exclaves, small applications running in an isolated environment controlled by the Secure Kernel, such as the camera-in-use indicator. XNU reaches them over SPTM using another IPC protocol, Tightbeam, an arrangement the report compares to Arm's TrustZone. Some Exclaves can be bypassed via command-line settings, but Asahi expects that will not last. Sven's solution was to run the Secure Kernel and Exclave userspace in an additional VM beside SPTM and macOS, which worked immediately — m1n1 now spawns three VMs in EL1, making virtualisation and reverse engineering of macOS possible on both M4 and M5.

The M3 GPU draws a triangle

M3 machines are otherwise near feature parity with M1 and M2, except for the GPU, which the report describes as a significant architectural departure within Apple's apparent tick-tock cadence. At XDC, Alyssa Millburn, Anna Maniscalco and TellowKrinkle presented their reverse-engineering progress: m1n1 can now initialise the M3 GPU and render a triangle. Apple's design choices will still demand considerable engineering to integrate into upstream Mesa.

Why it matters

Each of these items narrows the gap between a new Apple Silicon Mac shipping and Linux running well on it. Submitting more than 16,000 lines of driver and Devicetree changes upstream means future kernel releases should carry Apple Silicon audio and video decode natively, reducing Asahi's reliance on a downstream patch pile, while barebones M4 and M5 Devicetrees show enablement of the newest hardware has already begun. Shipping Thunderbolt, even without PCIe or DisplayPort tunnelling, closes one of the most visible gaps versus macOS. And the ability to virtualise current macOS versions on M4 and M5 keeps the reverse-engineering pipeline open as Apple layers on SPTM, Exclaves and other security machinery.