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[v3,16/18] IB/mlx4: Eliminate duplicate barriers on weakly-ordered archs

Message ID 1521216991-28706-17-git-send-email-okaya@codeaurora.org (mailing list archive)
State New, archived
Headers show

Commit Message

Sinan Kaya March 16, 2018, 4:16 p.m. UTC 
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>
---
 drivers/infiniband/hw/mlx4/qp.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
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Patch

diff --git a/drivers/infiniband/hw/mlx4/qp.c b/drivers/infiniband/hw/mlx4/qp.c
index f045491..74b27b0 100644
--- a/drivers/infiniband/hw/mlx4/qp.c
+++ b/drivers/infiniband/hw/mlx4/qp.c
@@ -3880,8 +3880,8 @@  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