arm64: Implement PSCI command support

Provide support for SoCs to participate in PSCI commands.
There are 2 steps to a command:
1. prepare() - look at request and adjust state accordingly
2. commit() - take action on the command

The prepare() function is called with psci locks held while
the commit() function is called with the locks dropped.
No SoC implements the appropriate logic yet.

TEST=Booted PSCI kernel -- no SMP because cmd_prepare()
     knowingly fails. Spintable kernel still brings up both

Change-Id: I2ae4d1c3f3eac4d1060c1b41472909933815d078
Signed-off-by: Patrick Georgi <>
Original-Commit-Id: 698d38b53bbc2bc043548792cea7219542b5fe6b
Original-Change-Id: I0821dc2ee8dc6bd1e8bc1c10f8b98b10e24fc97e
Original-Signed-off-by: Aaron Durbin <>
Original-Reviewed-by: Furquan Shaikh <>
Reviewed-by: Stefan Reinauer <>
Tested-by: build bot (Jenkins)
3 files changed