drm/i915: Never read FORCEWAKE
authorBen Widawsky <ben@bwidawsk.net>
Sun, 2 Sep 2012 05:59:50 +0000 (22:59 -0700)
committerDaniel Vetter <daniel.vetter@ffwll.ch>
Mon, 3 Sep 2012 08:28:32 +0000 (10:28 +0200)
commit8dee3eea3ccd3b6c00a8d3a08dd715d6adf737dd
tree8a31d9d71d99ad8bf73267aac1b833108122c4f8
parent057d3860613813b2e8507bb932f9a523ad2cca2f
drm/i915: Never read FORCEWAKE

The same designer from the previous patch has told us to never read
FORCEWAKE. We only do this for the POSTING_READ(), so simply change that
to something within the same cacheline (for no reason in particular
other than it sounds nice). In the _mt case we can leverage
the gtfifodbg check for the POSTING_READ.

This partially reverts
commit 6af2d180f82151cf3d58952e35a4f96e45bc453a
Author: Daniel Vetter <daniel.vetter@ffwll.ch>
Date:   Thu Jul 26 16:24:50 2012 +0200

    drm/i915: fix forcewake related hangs on snb

v2: commit message, comments about posting read from (Daniel)

Note: vlv forcewake doesn't need any changes for this special
treatment since FORCEWAKE_VLV is in a totally different register
range, and the readback FORCEWAKE_ACK_VLV readback that follows is in
the same range.

Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
Acked-by: Chris Wilson <chris@chris-wilson.co.uk>
[danvet: Added note.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
drivers/gpu/drm/i915/intel_pm.c