From: Sinan Kaya <okaya@codeaurora.org>
Date: Mon, 19 Mar 2018 22:47:44 -0400
Subject: IB/mlx4: Eliminate duplicate barriers on weakly-ordered archs
Patch-mainline: v4.17-rc1
Git-commit: 97d82a48d7a7eca6f20b100ae19811134509406e
References: bsc#1103988 FATE#326003

Code includes wmb() followed by writel(). writel() already has a barrier on
some architectures like arm64.

This ends up CPU observing two barriers back to back before executing the
register write.

Since code already has an explicit barrier call, changing writel() to
writel_relaxed().

Signed-off-by: Sinan Kaya <okaya@codeaurora.org>
Reviewed-by: Jason Gunthorpe <jgg@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 drivers/infiniband/hw/mlx4/qp.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/drivers/infiniband/hw/mlx4/qp.c
+++ b/drivers/infiniband/hw/mlx4/qp.c
@@ -3894,8 +3894,8 @@ out:
 		 */
 		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