diff --git a/drivers/infiniband/hw/mlx4/qp.c b/drivers/infiniband/hw/mlx4/qp.c
index 04efc05fb5313de0359d13f7605e9acc95b237f1..523028e944ed2dd87862c9093c26d995f6f29d59 100644
--- a/drivers/infiniband/hw/mlx4/qp.c
+++ b/drivers/infiniband/hw/mlx4/qp.c
@@ -3894,8 +3894,8 @@ int mlx4_ib_post_send(struct ib_qp *ibqp, struct ib_send_wr *wr,
 		 */
 		wmb();
 
-		writel(qp->doorbell_qpn,
-		       to_mdev(ibqp->device)->uar_map + MLX4_SEND_DOORBELL);
+		writel_relaxed(qp->doorbell_qpn,
+			to_mdev(ibqp->device)->uar_map + MLX4_SEND_DOORBELL);
 
 		/*
 		 * Make sure doorbells don't leak out of SQ spinlock