drm/xe: Add xe_exec_queue_last_fence_test_dep

Helpful to determine if a bind can immediately use CPU or needs to be
deferred a drm scheduler job.

v7:
- Better wording in kernel doc (Matthew Auld)

Signed-off-by: Matthew Brost <[e-mail]>
Reviewed-by: Matthew Auld <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]

drivers/gpu/drm/xe/xe_exec_queue.c

···
 	xe_exec_queue_last_fence_put(q, vm);
 	q->last_fence = dma_fence_get(fence);
 }
+
+/**
+ * xe_exec_queue_last_fence_test_dep - Test last fence dependency of queue
+ * @q: The exec queue
+ * @vm: The VM the engine does a bind or exec for
+ *
+ * Returns:
+ * -ETIME if there exists an unsignalled last fence dependency, zero otherwise.
+ */
+int xe_exec_queue_last_fence_test_dep(struct xe_exec_queue *q, struct xe_vm *vm)
+{
+	struct dma_fence *fence;
+	int err = 0;
+
+	fence = xe_exec_queue_last_fence_get(q, vm);
+	if (fence) {
+		err = test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags) ?
+			0 : -ETIME;
+		dma_fence_put(fence);
+	}
+
+	return err;
+}

drivers/gpu/drm/xe/xe_exec_queue.h

···
 					       struct xe_vm *vm);
 void xe_exec_queue_last_fence_set(struct xe_exec_queue *e, struct xe_vm *vm,
 				  struct dma_fence *fence);
+int xe_exec_queue_last_fence_test_dep(struct xe_exec_queue *q,
+				      struct xe_vm *vm);
 void xe_exec_queue_update_run_ticks(struct xe_exec_queue *q);
 
 #endif