ARM: 7161/1: errata: no automatic store buffer drain
commit11ed0ba1754841316d4095478944300acf19acc3
authorWill Deacon <will.deacon@arm.com>
Mon, 14 Nov 2011 16:24:58 +0000 (14 17:24 +0100)
committerRussell King <rmk+kernel@arm.linux.org.uk>
Mon, 21 Nov 2011 13:12:18 +0000 (21 13:12 +0000)
tree2b7b1002398ca3bd035ec69fbec92ac6648fadf6
parent6fe4c6d466e95d31164f14b1ac4aefb51f0f4f82
ARM: 7161/1: errata: no automatic store buffer drain

This patch implements a workaround for PL310 erratum 769419. On
revisions of the PL310 prior to r3p2, the Store Buffer does not
automatically drain. This can cause normal, non-cacheable writes to be
retained when the memory system is idle, leading to suboptimal I/O
performance for drivers using coherent DMA.

This patch adds an optional wmb() call to the cpu_idle loop. On systems
with an outer cache, this causes an explicit flush of the store buffer.

Cc: stable@vger.kernel.org
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Tested-by: Marc Zyngier <marc.zyngier@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/kernel/process.c