The kernel already has the responsibility to handle resources such as the

CCI when hotplugging CPUs, during the booting of secondary CPUs, and when
resuming from suspend/idle.  It would be more coherent and less confusing
if the CCI for the boot CPU (or cluster)  was also initialized by the
kernel rather than expecting the firmware/bootloader to do it and only in
that case. After all, the kernel has all the necessary code already and
the bootloader shouldn't have to care at all.

The CCI may be turned on only when the cache is off. Leveraging the CPU
suspend code to loop back through the low-level MCPM entry point is all
that is needed to properly turn on the CCI from the kernel by using the
same code as during secondary boot.

Let's provide a generic MCPM loopback function that can be invoked by
backend initialization code to set things (CCI or similar) on the boot
CPU just as it is done for the other CPUs.

Signed-off-by: Nicolas Pitre <nico@linaro.org>
Reviewed-by: Kevin Hilman <khilman@linaro.org>
Tested-by: Kevin Hilman <khilman@linaro.org>
Tested-by: Doug Anderson <dianders@chromium.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

The name "power_down_finish" seems to be causing some confusion,
because it suggests that this function is responsible for taking
some action to cause the specified CPU to complete its power down.

This patch renames the affected functions to "wait_for_powerdown"
and similar, since this function's intended purpose is just to wait
for the hardware to finish a powerdown initiated by a previous
cpu_power_down.

Signed-off-by: Dave Martin <Dave.Martin@arm.com>
Acked-by: Nicolas Pitre <nico@linaro.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

The switcher should not depend on MAX_CLUSTER to determine ifit should
be activated or not. In a multiplatform kernel binary it is possible to
have dual-cluster and quad-cluster platforms configured in. In that case
MAX_CLUSTER which is a build time limit should be 4 and that shouldn't
prevent the switcher from working if the kernel is booted on a b.L
dual-cluster system.

In bL_switcher_halve_cpus() we already have a runtime validation check
to make sure we're dealing with only two clusters, so booting on a quad
cluster system will be caught and switcher activation aborted.

However, the b.L switcher must ensure the MCPM layer is initialized on
the booted hardware before doing anything.  The mcpm_is_available()
function is added to that effect.

Signed-off-by: Nicolas Pitre <nico@linaro.org>
Tested-by: Abhilash Kesavan <kesavan.abhilash@gmail.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

sync_cache_w already includes a dsb, so we can just use sev() directly
then following a cache-sync.

Acked-by: Dave Martin <Dave.Martin@arm.com>
Acked-by: Nicolas Pitre <nico@linaro.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

We have a handy macro to replace open coded __cpuc_flush_dcache_area(()
and outer_clean_range() sequences. Let's use it. No functional change.

Signed-off-by: Nicolas Pitre <nico@linaro.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

Conflicts:
	arch/arm/include/asm/atomic.h
	arch/arm/include/asm/hardirq.h
	arch/arm/kernel/smp.c

CPU hotplug and kexec rely on smp_ops.cpu_kill(), which is supposed
to wait for the CPU to park or power down, and perform the last
rites (such as disabling clocks etc., where the platform doesn't do
this automatically).

kexec in particular is unsafe without performing this
synchronisation to park secondaries.  Without it, the secondaries
might not be parked when kexec trashes the kernel.

There is no generic way to do this synchronisation, so a new mcpm
platform_ops method power_down_finish() is added by this patch.

The new method is mandatory.  A platform which provides no way to
detect when CPUs are parked is likely broken.

Signed-off-by: Dave Martin <Dave.Martin@arm.com>
Reviewed-by: Nicolas Pitre <nico@linaro.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

Currently mcpm_cpu_power_down() and mcpm_cpu_suspend() trigger BUG()
if mcpm_platform_register() is not called beforehand.  This may occur
for many reasons such as some incomplete device tree passed to the kernel
or the like.

Let's be nicer to users and avoid killing the kernel if that happens by
logging a warning and returning to the caller.  The mcpm_cpu_suspend()
user is already set to deal with this situation, and so is cpu_die()
invoking mcpm_cpu_die().

The problematic case would have been the B.L switcher's usage of
mcpm_cpu_power_down(), however it has to call mcpm_cpu_power_up() first
which is already set to catch an error resulting from a missing
mcpm_platform_register() call.

Signed-off-by: Nicolas Pitre <nico@linaro.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

This allows to poke a predetermined value into a specific address
upon entering the early boot code in bL_head.S.

Signed-off-by: Nicolas Pitre <nico@linaro.org>