From: Will Deacon <will.deacon@arm.com>
Date: Fri, 4 Mar 2011 11:38:54 +0000 (+0100)
Subject: ARM: 6784/1: errata: no automatic Store Buffer drain on Cortex-A9
X-Git-Tag: v2.6.39-rc1~463^2~3^3
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=5dab26af1bacad9a7189d904fbc8b4fe8e95dd81;p=pandora-kernel.git

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>
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