Jani Nikula b514407547 drm/i915: fix FORCEWAKE posting reads ... We stopped reading FORCEWAKE for posting reads in commit 8dee3eea3c Author: Ben Widawsky <ben@bwidawsk.net> Date: Sat Sep 1 22:59:50 2012 -0700 drm/i915: Never read FORCEWAKE and started using something from the same cacheline instead. On the bug reporter's machine this broke entering rc6 states after a suspend/resume cycle. It turns out reading ECOBUS as posting read worked fine, while GTFIFODBG did not, preventing RC6 states after suspend/resume per the bug report referenced below. It's not entirely clear why, but clearly GTFIFODBG was nowhere near the same cacheline or address range as FORCEWAKE. Trying out various registers for posting reads showed that all tested registers for which NEEDS_FORCE_WAKE() (in i915_drv.c) returns true work. Conversely, most (but not quite all) registers for which NEEDS_FORCE_WAKE() returns false do not work. Details in the referenced bug. Based on the above, add posting reads on ECOBUS where GTFIFODBG was previously relied on. In true cargo cult spirit, add posting reads for FORCEWAKE_VLV writes as well, but instead of ECOBUS, use FORCEWAKE_ACK_VLV which is in the same address range as FORCEWAKE_VLV. v2: Add more details to the commit message. No functional changes. Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=52411 Reported-and-tested-by: Alexander Bersenev <bay@hackerdom.ru> CC: Ben Widawsky <ben@bwidawsk.net> Signed-off-by: Jani Nikula <jani.nikula@intel.com> Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk> Cc: stable@vger.kernel.org [danvet: add cc: stable and make the commit message a bit clearer that this is a regression fix and what exactly broke.] Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>		2013-01-17 11:09:25 +01:00
..
drm	drm/i915: fix FORCEWAKE posting reads	2013-01-17 11:09:25 +01:00
stub	i915: select VIDEO_OUTPUT_CONTROL for ACPI_VIDEO	2011-04-13 09:10:25 +10:00
vga	Merge branch 'drm-next' of git://people.freedesktop.org/~airlied/linux	2012-12-17 08:26:17 -08:00
Makefile	gpu: Add Intel GMA500(Poulsbo) Stub Driver	2010-10-26 11:00:13 +10:00