From: Zou Nan hai <nanhai.zou@intel.com>
Date: Tue, 9 Nov 2010 09:17:32 +0000 (+0800)
Subject: drm/i915/ringbuffer: set FORCE_WAKE bit before reading ring register
X-Git-Tag: v2.6.38-rc1~419^2~23^2~109
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=cae5852dcaa1139b198e13ebd3aeb7f3c065f875;p=pandora-kernel.git

drm/i915/ringbuffer: set FORCE_WAKE bit before reading ring register

Before reading ring register, set FORCE_WAKE bit to prevent GT core
power down to low power state, otherwise we may read stale values.

Signed-off-by: Zou Nan hai <nanhai.zou@intel.com>
[ickle: added a udelay which seemed to do the trick on my SNB]
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
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