ARM: mutex: use generic atomic_dec-based implementation for ARMv6+

Commit a76d7bd96d65 ("ARM: 7467/1: mutex: use generic xchg-based
implementation for ARMv6+") removed the barrier-less, ARM-specific
mutex implementation in favour of the generic xchg-based code.

Since then, a bug was uncovered in the xchg code when running on SMP
platforms, due to interactions between the locking paths and the
MUTEX_SPIN_ON_OWNER code. This was fixed in 0bce9c46bf3b ("mutex: place
lock in contended state after fastpath_lock failure"), however, the
atomic_dec-based mutex algorithm is now marginally more efficient for
ARM (~0.5% improvement in hackbench scores on dual A15).

This patch moves ARMv6+ platforms to the atomic_dec-based mutex code.

Cc: Nicolas Pitre <nico@fluxnic.net>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Acked-by: Nicolas Pitre <nico@linaro.org>
Reviewed-on: http://git-master/r/130941
Reviewed-by: Automatic_Commit_Validation_User
Reviewed-by: Bharat Nihalani <bnihalani@nvidia.com>
Tested-by: Bharat Nihalani <bnihalani@nvidia.com>

Conflicts:
	arch/arm/include/asm/mutex.h

Change-Id: I8f64e98ccb61cc1cb9cb68ee15e55d8a792792f5
ARM: 7583/1: decompressor: Enable unaligned memory access
 for v6 and above

Modern GCC can generate code which makes use of the CPU's native
unaligned memory access capabilities.  This is useful for the C
decompressor implementations used for unpacking compressed kernels.

This patch disables alignment faults and enables the v6 unaligned
access model on CPUs which support these features (i.e., v6 and
later), allowing full unaligned access support for C code in the
decompressor.

The decompressor C code must not be built to assume that unaligned
access works if support for v5 or older platforms is included in
the kernel.

For correct code generation, C decompressor code must always use
the get_unaligned and put_unaligned accessors when dealing with
unaligned pointers, regardless of this patch.

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

Change-Id: I802b95835b45f077716cb9114ebe0f28ace52fba
Merge "ARM: mutex: use generic atomic_dec-based implementation for ARMv6+" into cm-10.2
Merge "ARM: 7583/1: decompressor: Enable unaligned memory access  for v6 and above" into cm-10.2