drm/i915: reuse i915_gem_object_put_fence_reg for fence stealing code

This has a few functional changes against the old code:

* a few more unnecessary loads and stores to the drm_i915_fence_reg
  objects. Also an unnecessary store to the hw fence register.

* zaps any userspace mappings before doing other flushes. Only changes
  anything when userspace does racy stuff against itself.

* also flush GTT domain. This is a noop, but still try to keep the
  bookkeeping correct.

Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Eric Anholt <eric@anholt.net>

1 files changed, 3 insertions, 26 deletions

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index c73da4049c81..302e096c3ca0 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -2460,39 +2460,16 @@ i915_gem_object_get_fence_reg(struct drm_gem_object *obj)
                          */
                         drm_gem_object_reference(old_obj);
 
-                        /* i915 uses fences for GPU access to tiled buffers */
-                        if (IS_I965G(dev) || !old_obj_priv->active)
-                                break;
-
-                        /* This brings the object to the head of the LRU if it
-                         * had been written to.  The only way this should
-                         * result in us waiting longer than the expected
-                         * optimal amount of time is if there was a
-                         * fence-using buffer later that was read-only.
-                         */
-                        i915_gem_object_flush_gpu_write_domain(old_obj);
-                        ret = i915_gem_object_wait_rendering(old_obj);
-                        if (ret != 0) {
-                                drm_gem_object_unreference(old_obj);
-                                return ret;
-                        }
-
                         break;
                 }
 
-                /*
-                 * Zap this virtual mapping so we can set up a fence again
-                 * for this object next time we need it.
-                 */
-                i915_gem_release_mmap(old_obj);
-
                 i = old_obj_priv->fence_reg;
                 reg = &dev_priv->fence_regs[i];
 
-                old_obj_priv->fence_reg = I915_FENCE_REG_NONE;
-                list_del_init(&old_obj_priv->fence_list);
-
+                ret = i915_gem_object_put_fence_reg(old_obj);
                 drm_gem_object_unreference(old_obj);
+                if (ret != 0) 
+                        return ret;
         }
 
         obj_priv->fence_reg = i;