From: Will Deacon <will.deacon@arm.com>
Date: Wed, 4 Sep 2013 11:30:08 +0000 (+0100)
Subject: documentation: memory-barriers: clarify relaxed io accessor semantics
X-Git-Tag: omap-for-v3.19/fixes-for-merge-window~8^2~2^2
X-Git-Url: https://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=a8e0aead70b4af957e6b27b82fba849c6179b707;p=pandora-kernel.git

documentation: memory-barriers: clarify relaxed io accessor semantics

This patch extends the paragraph describing the relaxed read io accessors
so that the relaxed accessors are defined to be:

 - Ordered with respect to each other if accessing the same peripheral

 - Unordered with respect to normal memory accesses

 - Unordered with respect to LOCK/UNLOCK operations

Whilst many architectures will provide stricter semantics, ARM, Alpha and
PPC can achieve significant performance gains by taking advantage of some
or all of the above relaxations.

Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: David Howells <dhowells@redhat.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
---

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