drm/i915: Forgo last_fence active request tracking

We were using the last_fence to track the last request that used this
vma that might be interpreted by a fence register and forced ourselves
to wait for this request before modifying any fence register that
overlapped our vma. Due to requirement that we need to track any XY_BLT
command, linear or tiled, this in effect meant that we have to track the
vma for its active lifespan anyway, so we can forgo the explicit
last_fence tracking and just use the whole vma->active.

Another solution would be to pipeline the register updates, and would
help resolve some long running stalls for gen3 (but only gen 2 and 3!)

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190812174804.26180-1-chris@chris-wilson.co.uk

1 files changed, 2 insertions, 4 deletions

diff --git a/drivers/gpu/drm/i915/i915_gem_fence_reg.c b/drivers/gpu/drm/i915/i915_gem_fence_reg.c
index bcac359ec661..c9654f1a468f 100644
--- a/drivers/gpu/drm/i915/i915_gem_fence_reg.c
+++ b/drivers/gpu/drm/i915/i915_gem_fence_reg.c
@@ -230,16 +230,14 @@ static int fence_update(struct i915_fence_reg *fence,
 			 i915_gem_object_get_tiling(vma->obj)))
 			return -EINVAL;
 
-		ret = i915_active_request_retire(&vma->last_fence,
-					     &vma->obj->base.dev->struct_mutex);
+		ret = i915_active_wait(&vma->active);
 		if (ret)
 			return ret;
 	}
 
 	old = xchg(&fence->vma, NULL);
 	if (old) {
-		ret = i915_active_request_retire(&old->last_fence,
-					     &old->obj->base.dev->struct_mutex);
+		ret = i915_active_wait(&old->active);
 		if (ret) {
 			fence->vma = old;
 			return ret;