DeviceTree

Minimal code to deal with Apple's DeviceTree format.

The Makefile builds dt and pmgr binaries, but you should also be able to use dt.c + dt.h as a library of sorts.

Usage

dt ./DeviceTree                     # Print all properties of all nodes
dt ./DeviceTree cpu0                # Print all properties of node "cpu0"
dt ./DeviceTree cpu0 reg-private    # Print property "reg-private" of node "cpu0"
dt ./DeviceTree +cpus               # Print all properties of node "cpus" and all its child nodes
dt ./DeviceTree +cpus reg-private   # Print property "reg-private" of node "cpus" and all its child nodes
dt ./DeviceTree -4                  # Do hexdumps as uint32
dt ./DeviceTree cpu0 reg-private -8 # Do hexdumps as uint64

pmgr ./DeviceTree                   # Print MMIO addresses of all devices in the power manager

Notes

1. The addresses given by pmgr can be used to turn on various SoC components and possibly more.
   Bits 0xf are the "wanted mode" and can be used to turn on or off with value 0x0 being off and 0xf being on. There seem to be exceptions to this though, e.g. cpu0 doesn't let itself be turned off at boot. States between 0x0 and 0xf supposedly control clocking or smth like that.
   Bits 0xf0 are the "actual mode" of the component.
   Higher bits exist, but for most their meaning is unknown and might change between chip generations.

2. The reg-private property of cpu<N> nodes in the DeviceTree gives you their CoreSight debugbase address. Relative to those are other potentially interesting things:

   +0x00000 DBG - CoreSight / External debug interface
   +0x10000 CTI - Cross-Trigger Interface
   +0x20000 PMU - Performance monitors
   +0x30000 TRC - Custom Apple "trace" registers
   +0x40000 SYS - Custom Apple "implementation specific" registers
   

   The first three should be roughly as in the ARM spec.
   TRC has a register at 0x0 that can halt, resume, catch-on-reset, etc.
   SYS has IORVBAR at 0x0.

License

MPL2 with Exhibit B.