From: Andres Salomon <dilinger@queued.net>
Date: Thu, 2 Dec 2010 22:31:17 +0000 (-0800)
Subject: cs5535-gpio: apply CS5536 errata workaround for GPIOs
X-Git-Tag: v2.6.37-rc5~22
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=853ff88324a248a9f5da6e110850223db353ec07;p=pandora-kernel.git

cs5535-gpio: apply CS5536 errata workaround for GPIOs

The AMD Geode CS5536 Companion Device Silicon Revision B1 Specification
Update mentions the follow as issue #36:

 "Atomic write transactions to the atomic GPIO High Bank Feature Bit
  registers should only affect the bits selected [...]"

 "after Suspend, an atomic write transaction [...] will clear all
  non-selected bits of the accessed register."

In other words, writing to the high bank for a single GPIO bit will
clear every other GPIO bit (but only sometimes after a suspend).

The workaround described is obvious and simple; do a read-modify-write.
This patch does that, and documents why we're doing it.

Signed-off-by: Andres Salomon <dilinger@queued.net>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---

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