ARM: mvebu: synchronize secondary CPU clocks on resume

ARM: mvebu: synchronize secondary CPU clocks on resume

The Armada XP has multiple cores clocked by independent clocks. The
SMP startup code contains a function called set_secondary_cpus_clock()
called in armada_xp_smp_prepare_cpus() to ensure the clocks of the
secondary CPUs match the clock of the boot CPU.

With the introduction of suspend/resume, this operation is no longer
needed when booting the system, but also when existing the suspend to
RAM state. Therefore this commit reworks a bit the logic: instead of
configuring the clock of all secondary CPUs in
armada_xp_smp_prepare_cpus(), we do it on a per-secondary CPU basis in
armada_xp_boot_secondary(), as this function gets called when existing
suspend to RAM for each secondary CPU.

Since the function now only takes care of one CPU, we rename it from
set_secondary_cpus_clock() to set_secondary_cpu_clock(), and it looses
its __init marker, as it is now used beyond the system initialization.

Note that we can't use smp_processor_id() directly, because when
exiting from suspend to RAM, the code is apparently executed with
preemption enabled, so smp_processor_id() is not happy (prints a
warning). We therefore switch to using get_cpu()/put_cpu(), even
though we pretty much have the guarantee that the code starting the
secondary CPUs is going to run on the boot CPU and will not be
migrated.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Acked-by: Gregory CLEMENT <gregory.clement@free-electrons.com>
Link: https://lkml.kernel.org/r/1416585613-2113-14-git-send-email-thomas.petazzoni@free-electrons.com
Signed-off-by: Jason Cooper <jason@lakedaemon.net>