Linux 7.2 has been released, bringing another Asahi Linux progress report for Apple Silicon. The team tackles CPU core power management, a major obstacle to battery life. Apple cores feature a "deep" WFI mode shutting down more core components, but the downstream cpuidle driver cannot be upstreamed due to kernel mandates requiring PSCI (Power State Coordination Interface) for all arm64 hardware.

PSCI calls require yielding to EL3 firmware via SMC or HVC instructions, but Apple Silicon lacks EL3 implementation. With the kernel at EL2 and no EL3 firmware, PSCI is unusable. Moving the kernel to EL1 would break virtualization, so the team explored using m1n1 — their custom bootloader — as a firmware-like layer.

m1n1 loads U-Boot for UEFI support, enabling standard bootloaders like GRUB. UEFI Runtime Services provide a mechanism for OS-to-firmware calls. The team is investigating implementing PSCI via UEFI Runtime Services, allowing the kernel to manage CPU power states through m1n1 without architectural compromises. This approach could finally enable proper upstream power management for Apple Silicon.