This reverts commit 25ff119 and the follow on for Valleyview commit 2dc8aae.
commit 25ff1195f8a0b3724541ae7bbe331b4296de9c06
Author: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Date: Thu Apr 4 21:31:03 2013 +0100
drm/i915: Workaround incoherence between fences and LLC across multiple CPUs
commit 2dc8aae06d53458dd3624dc0accd4f81100ee631
Author: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Date: Wed May 22 17:08:06 2013 +0100
drm/i915: Workaround incoherence with fence updates on Valleyview
Jon Bloomfield came up with a plausible explanation and cheap fix
(drm/i915: Fix incoherence with fence updates on Sandybridge+) for the
race condition, so lets run with it.
This is a candidate for stable as the old workaround incurs a
significant cost (calling wbinvd on all CPUs before performing the
register write) for some workloads as noted by Carsten Ede.
Link: http://lists.freedesktop.org/archives/intel-gfx/2013-June/028819.html
References: https://www.osadl.org/?id=1543#c7602
References: https://bugs.freedesktop.org/show_bug.cgi?id=63825
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Daniel Vetter <daniel.vetter@xxxxxxxx>
Cc: Jon Bloomfield <jon.bloomfield@xxxxxxxxx>
Cc: Carsten Emde<C.Emde@xxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
---
drivers/gpu/drm/i915/i915_gem.c | 47 ++++-------------------------------------
1 file changed, 4 insertions(+), 43 deletions(-)
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index d9d664d..861bb11 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -2938,56 +2938,17 @@ static inline int fence_number(struct drm_i915_private *dev_priv,
return fence - dev_priv->fence_regs;
}
-struct write_fence {
- struct drm_device *dev;
- struct drm_i915_gem_object *obj;
- int fence;
-};
-
-static void i915_gem_write_fence__ipi(void *data)
-{
- struct write_fence *args = data;
-
- /* Required for SNB+ with LLC */
- wbinvd();
-
- /* Required for VLV */
- i915_gem_write_fence(args->dev, args->fence, args->obj);
-}
-
static void i915_gem_object_update_fence(struct drm_i915_gem_object *obj,
struct drm_i915_fence_reg *fence,
bool enable)
{
struct drm_i915_private *dev_priv = obj->base.dev->dev_private;
- struct write_fence args = {
- .dev = obj->base.dev,
- .fence = fence_number(dev_priv, fence),
- .obj = enable ? obj : NULL,
- };
-
- /* In order to fully serialize access to the fenced region and
- * the update to the fence register we need to take extreme
- * measures on SNB+. In theory, the write to the fence register
- * flushes all memory transactions before, and coupled with the
- * mb() placed around the register write we serialise all memory
- * operations with respect to the changes in the tiler. Yet, on
- * SNB+ we need to take a step further and emit an explicit wbinvd()
- * on each processor in order to manually flush all memory
- * transactions before updating the fence register.
- *
- * However, Valleyview complicates matter. There the wbinvd is
- * insufficient and unlike SNB/IVB requires the serialising
- * register write. (Note that that register write by itself is
- * conversely not sufficient for SNB+.) To compromise, we do both.
- */
- if (INTEL_INFO(args.dev)->gen >= 6)
- on_each_cpu(i915_gem_write_fence__ipi, &args, 1);
- else
- i915_gem_write_fence(args.dev, args.fence, args.obj);
+ int reg = fence_number(dev_priv, fence);
+
+ i915_gem_write_fence(obj->base.dev, reg, enable ? obj : NULL);
if (enable) {
- obj->fence_reg = args.fence;
+ obj->fence_reg = reg;
fence->obj = obj;
list_move_tail(&fence->lru_list, &dev_priv->mm.fence_list);
} else {
--
1.8.3.2
--
To unsubscribe from this list: send the line "unsubscribe stable" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html