[Intel-gfx] [PATCH] drm/i915: Relinquish any fence when changing cache levels

[Chris Wilson]

This is vital to maintain our contract with the hw for not using fences
on snooped memory for older chipsets. It should have no impact
other than clearing the fence register (and updating the fence
bookkeeping) as any future IO access (page faults or pwrite/pread) will
go through the cached CPU domain for older chipsets. On SandyBridge, we
incur an extra get_fence() on the rare path that we need to perform
detiling through a pagefault (i.e. texture transfers).

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/i915_gem.c |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 6ca026d..2d16a23 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -3355,6 +3355,10 @@ int i915_gem_object_set_cache_level(struct drm_i915_gem_object *obj,
 		if (ret)
 			return ret;
 
+		ret = i915_gem_object_put_fence(obj);
+		if (ret)
+			return ret;
+
 		ret = i915_gem_gtt_bind_object(obj, cache_level);
 		if (ret)
 			return ret;
-- 
1.7.4.1