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authorJani Nikula <jani.nikula@intel.com>2013-01-17 10:24:09 +0200
committerDaniel Vetter <daniel.vetter@ffwll.ch>2013-01-17 11:09:25 +0100
commitb514407547890686572606c9dfa4b7f832db9958 (patch)
treebfb885d0f62a121b91e6f4947d3d82e2846f71f8
parent262b6d363fcff16359c93bd58c297f961f6e6273 (diff)
downloadlinaro-lsk-b514407547890686572606c9dfa4b7f832db9958.tar.gz
drm/i915: fix FORCEWAKE posting reads
We stopped reading FORCEWAKE for posting reads in commit 8dee3eea3ccd3b6c00a8d3a08dd715d6adf737dd 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>
-rw-r--r--drivers/gpu/drm/i915/intel_pm.c17
1 files changed, 12 insertions, 5 deletions
diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index e83a1179417..3280cffe50f 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -4250,7 +4250,8 @@ static void __gen6_gt_force_wake_get(struct drm_i915_private *dev_priv)
static void __gen6_gt_force_wake_mt_reset(struct drm_i915_private *dev_priv)
{
I915_WRITE_NOTRACE(FORCEWAKE_MT, _MASKED_BIT_DISABLE(0xffff));
- POSTING_READ(ECOBUS); /* something from same cacheline, but !FORCEWAKE */
+ /* something from same cacheline, but !FORCEWAKE_MT */
+ POSTING_READ(ECOBUS);
}
static void __gen6_gt_force_wake_mt_get(struct drm_i915_private *dev_priv)
@@ -4267,7 +4268,8 @@ static void __gen6_gt_force_wake_mt_get(struct drm_i915_private *dev_priv)
DRM_ERROR("Timed out waiting for forcewake old ack to clear.\n");
I915_WRITE_NOTRACE(FORCEWAKE_MT, _MASKED_BIT_ENABLE(FORCEWAKE_KERNEL));
- POSTING_READ(ECOBUS); /* something from same cacheline, but !FORCEWAKE */
+ /* something from same cacheline, but !FORCEWAKE_MT */
+ POSTING_READ(ECOBUS);
if (wait_for_atomic((I915_READ_NOTRACE(forcewake_ack) & 1),
FORCEWAKE_ACK_TIMEOUT_MS))
@@ -4304,14 +4306,16 @@ void gen6_gt_check_fifodbg(struct drm_i915_private *dev_priv)
static void __gen6_gt_force_wake_put(struct drm_i915_private *dev_priv)
{
I915_WRITE_NOTRACE(FORCEWAKE, 0);
- /* gen6_gt_check_fifodbg doubles as the POSTING_READ */
+ /* something from same cacheline, but !FORCEWAKE */
+ POSTING_READ(ECOBUS);
gen6_gt_check_fifodbg(dev_priv);
}
static void __gen6_gt_force_wake_mt_put(struct drm_i915_private *dev_priv)
{
I915_WRITE_NOTRACE(FORCEWAKE_MT, _MASKED_BIT_DISABLE(FORCEWAKE_KERNEL));
- /* gen6_gt_check_fifodbg doubles as the POSTING_READ */
+ /* something from same cacheline, but !FORCEWAKE_MT */
+ POSTING_READ(ECOBUS);
gen6_gt_check_fifodbg(dev_priv);
}
@@ -4351,6 +4355,8 @@ int __gen6_gt_wait_for_fifo(struct drm_i915_private *dev_priv)
static void vlv_force_wake_reset(struct drm_i915_private *dev_priv)
{
I915_WRITE_NOTRACE(FORCEWAKE_VLV, _MASKED_BIT_DISABLE(0xffff));
+ /* something from same cacheline, but !FORCEWAKE_VLV */
+ POSTING_READ(FORCEWAKE_ACK_VLV);
}
static void vlv_force_wake_get(struct drm_i915_private *dev_priv)
@@ -4371,7 +4377,8 @@ static void vlv_force_wake_get(struct drm_i915_private *dev_priv)
static void vlv_force_wake_put(struct drm_i915_private *dev_priv)
{
I915_WRITE_NOTRACE(FORCEWAKE_VLV, _MASKED_BIT_DISABLE(FORCEWAKE_KERNEL));
- /* The below doubles as a POSTING_READ */
+ /* something from same cacheline, but !FORCEWAKE_VLV */
+ POSTING_READ(FORCEWAKE_ACK_VLV);
gen6_gt_check_fifodbg(dev_priv);
}