drm/i915: Provide a fastpath for waiting on vma bindings

Before we can execute a request, we must wait for all of its vma to be
bound. This is a frequent operation for which we can optimise away a
few atomic operations (notably a cmpxchg) in lieu of the RCU protection.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Thomas Hellström <thomas.hellstrom@intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200731085015.32368-7-chris@chris-wilson.co.uk
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>

diff --git a/drivers/gpu/drm/i915/i915_active.h b/drivers/gpu/drm/i915/i915_active.h
index b9e0394..fb165d3 100644 (file)
--- a/drivers/gpu/drm/i915/i915_active.h
+++ b/drivers/gpu/drm/i915/i915_active.h
@@ -231,4 +231,19 @@ struct i915_active *i915_active_create(void);
 struct i915_active *i915_active_get(struct i915_active *ref);
 void i915_active_put(struct i915_active *ref);
 
+static inline int __i915_request_await_exclusive(struct i915_request *rq,
+                                                struct i915_active *active)
+{
+       struct dma_fence *fence;
+       int err = 0;
+
+       fence = i915_active_fence_get(&active->excl);
+       if (fence) {
+               err = i915_request_await_dma_fence(rq, fence);
+               dma_fence_put(fence);
+       }
+
+       return err;
+}
+
 #endif /* _I915_ACTIVE_H_ */

diff --git a/drivers/gpu/drm/i915/i915_vma.c b/drivers/gpu/drm/i915/i915_vma.c
index bc64f77..cd12047 100644 (file)
--- a/drivers/gpu/drm/i915/i915_vma.c
+++ b/drivers/gpu/drm/i915/i915_vma.c
@@ -1167,6 +1167,12 @@ void i915_vma_revoke_mmap(struct i915_vma *vma)
                list_del(&vma->obj->userfault_link);
 }
 
+static int
+__i915_request_await_bind(struct i915_request *rq, struct i915_vma *vma)
+{
+       return __i915_request_await_exclusive(rq, &vma->active);
+}
+
 int __i915_vma_move_to_active(struct i915_vma *vma, struct i915_request *rq)
 {
        int err;
@@ -1174,8 +1180,7 @@ int __i915_vma_move_to_active(struct i915_vma *vma, struct i915_request *rq)
        GEM_BUG_ON(!i915_vma_is_pinned(vma));
 
        /* Wait for the vma to be bound before we start! */
-       err = i915_request_await_active(rq, &vma->active,
-                                       I915_ACTIVE_AWAIT_EXCL);
+       err = __i915_request_await_bind(rq, vma);
        if (err)
                return err;