AArch64 has support for PSCI. This is especially useful for SMP because
PSCI is used to power on the secordary cores.
When the PSCI driver was introduced in Zephyr it was designed to rely on
a very PSCI-centric subsystem / interface.
There are two kinds of problems with this choice:
1. PSCI is only defined for the non-secure world and it is designed to
boot CPU cores into non-secure state (that means that PSCI is only
supposed to work if Zephyr is running in non-secure state)
2. There can be other ways or standards used to start / stop a core
different from PSCI
This patch is trying to fix the original wrong assumption by making the
interface / subsystem a generic one, called 'pm_cpu_ops', and using PSCI
only as an actual driver that is a user of this new interface /
subsystem.
For now the new subsystem is only exposing two methods: cpu_on and
cpu_off, others will probably follow according to the needs.
Signed-off-by: Carlo Caione <ccaione@baylibre.com>
Flavio Ceolin