ARM: 6784/1: errata: no automatic Store Buffer drain on Cortex-A9
authorWill Deacon <will.deacon@arm.com>
Fri, 4 Mar 2011 11:38:54 +0000 (12:38 +0100)
committerRussell King <rmk+kernel@arm.linux.org.uk>
Wed, 9 Mar 2011 21:40:18 +0000 (21:40 +0000)
commit5dab26af1bacad9a7189d904fbc8b4fe8e95dd81
tree246c70038035ee4a0505f2b043ecb3c73018b01b
parentfcbdc5fe6ebe07d502c9b652cb63376bcc4227ac
ARM: 6784/1: errata: no automatic Store Buffer drain on Cortex-A9

On revisions of the Cortex-A9 prior to r2p0, the Store Buffer does not
have any automatic draining mechanism and therefore a livelock may occur
if an external agent continuously polls a memory location waiting to
observe an update.

This workaround defines cpu_relax() as smp_mb(), preventing correctly
written polling loops from denying visibility of updates to memory.

Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
arch/arm/Kconfig
arch/arm/include/asm/processor.h