HW:SMP spin up - AsahiLinux/docs GitHub Wiki

SMP spin-up

From the ADT:

• /arm-io/pmgr[reg] power manager registers
  • CPU start block is at a device-dependent offset to this register
    • 0x30000 for A7-A8(X)
    • 0xd4000 for A9(X)-A11
    • 0x54000 for M1 series
    • 0x34000 for M2 and M3
    • 0x28000 for M2 Pro/Max
    • 0x88000 for M3 Pro/Max
  • For multi-die systems, each die has its own power manager registers. The power manager registers for each die is at offset die * 0x2000000000 from the registers of die 0.
• /cpus/cpu<n>[cpu-impl-reg] CPU implementation registers
• /cpus/cpu<n>[reg] CPU startup information
  • Bits [0:7] holds the core id
  • Bits [8:10] holds the cluster id
  • Bits [11:14] holds the die id

The cluster id in the /cpus/cpu<n>[reg] is possibly only for CPU start purposes. On A11 the cluster id field is both 0 for P and E CPUs, which conflicted with the /cpus/cpu<n>[cluster-id] property in the ADT.

For old firmwares, /cpus/cpu<n>[cpu-impl-reg] may not exist, in this case /arm-io/reg[2*n+2] can be used to find the location to write the start address.

CPU start registers in PMGR:

offset + 0x4: System-wide CPU core startup/active bitmask
offset + 0x8: Cluster 0 (e) CPU core startup
offset + 0xc: Cluster 1 (p) CPU core startup

Startup sequence

• Write start address to RVBAR at cpu-impl-reg + 0x00
  • This is locked for cpu0 by iBoot, other CPUs are free to change
• Set (1 << cpu) in pmgr[offset + 0x4]
  • This seems to be some kind of system-wide "core alive" signal. It is not required for the core to spin up, but without it AIC interrupts won't work, and probably other things.
• Set (1 << core) in pmgr[(offset + 0x8) + 4*cluster] (that's core from 0-3, cluster 0-1)
  • This starts up the core itself.

Core starts up at RVBAR. Chicken bits / etc must be applied as usual.