[RyanTheTide]

After some reboots of the M1 Pro (T6000) and the M2 (T8112), U-Boot cannot bring the NVMe up, so the Mac cannot boot Linux. Retrying from the U-Boot prompt fails the same way.

Cause

aura Stage 1 hands the ANS over by asking it to sleep, stopping its CPU and resetting it. Since aura 1.0.0b1, the sleep request sometimes runs past its 1 s bound. The firmware finishes its GC bitmap rebuild and saves its context first, which takes 0.4 to 0.55 s on the M2 by its own log. When the request runs over, Stage 1 logs rtkit(nvme): IOP power transition timed out and resets the ANS with CPU_CTRL.RUN still set. The late answer may still be queued in the mailbox.

apple_nvme_boot() then sets RUN on a CPU that is already running and sends INIT. apple_rtkit_boot() requires HELLO as the first message, so it fails, and every later probe does the same. The aura side is fixed in aurora-silicon/aura (fix/ans-shutdown-handoff). This PR lets U-Boot recover with the Stage 1 that is already installed, which needs a 1TR visit to replace on these machines.

Change

This is the same recovery Linux's apple-nvme runs before it restarts the coprocessor:

• If RUN is already set at probe, drop queued messages, clear RUN, wait 1 ms, drop anything that arrived meanwhile, then reset the block with its PMGR reset (resets in the DT).
• If RUN is clear, still drop stale messages.
• If the firmware still does not start (no HELLO, or no boot status), stop and reset once more and retry before giving up.
• A clean handoff takes the same path as before.
• Post-M4 (adopt/wake) is untouched.

Tests

• test/py/tests/test_apple_nvme_restart.py runs on the host with --noconftest. It builds the driver's real apple_nvme_boot() against a model ANS that sends HELLO only after a fresh start and keeps its last message in the FIFO. It covers a clean handoff, a timed-out sleep with RUN set, a stale message, one failed start and a dead firmware. If the stop is removed from either path, the timed-out case fails.
• Host build (aarch64-elf-gcc 16.2, the review-fix .config): clean, u-boot-nodtb.bin 701,720 B.
• Not yet run on hardware. The Neo only exercises the unchanged post-M4 path. The real check is an M1 Pro or M2 reboot loop, and that test plan is with the lead.

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