This is the basic API used to handle the powering up/down of individual
CPUs in a (multi-)cluster system.  The platform specific backend
implementation has the responsibility to also handle the cluster level
power as well when the first/last CPU in a cluster is brought up/down.
Signed-off-by: NNicolas Pitre <nico@linaro.org>
Reviewed-by: NSantosh Shilimkar <santosh.shilimkar@ti.com>
Reviewed-by: NWill Deacon <will.deacon@arm.com>

CPUs in cluster based systems, such as big.LITTLE, have special needs
when entering the kernel due to a hotplug event, or when resuming from
a deep sleep mode.

This is vectorized so multiple CPUs can enter the kernel in parallel
without serialization.

The mcpm prefix stands for "multi cluster power management", however
this is usable on single cluster systems as well.  Only the basic
structure is introduced here.  This will be extended with later patches.

In order not to complexify things more than they currently have to,
the planned work to make runtime adjusted MPIDR based indexing and
dynamic memory allocation for cluster states is postponed to a later
cycle. The MAX_NR_CLUSTERS and MAX_CPUS_PER_CLUSTER static definitions
should be sufficient for those systems expected to be available in the
near future.
Signed-off-by: NNicolas Pitre <nico@linaro.org>
Reviewed-by: NSantosh Shilimkar <santosh.shilimkar@ti.com>
Reviewed-by: NWill Deacon <will.deacon@arm.com>