[PATCH v4 6/6] RDMA/qedr: eliminate duplicate barriers on weakly-ordered archs #2

From: Sinan Kaya [mailto:okaya at codeaurora.org]
Sent: Tuesday, March 20, 2018 4:48 AM

Code includes wmb() followed by writel() in multiple places. 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 <redacted>
---
 drivers/infiniband/hw/qedr/verbs.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/infiniband/hw/qedr/verbs.c

b/drivers/infiniband/hw/qedr/verbs.c
index ccd55f4..db60360 100644

--- a/drivers/infiniband/hw/qedr/verbs.c
+++ b/drivers/infiniband/hw/qedr/verbs.c

@@ -860,7 +860,7 @@ static void doorbell_cq(struct qedr_cq *cq, u32 cons,

u8 flags)
 	wmb();
 	cq->db.data.agg_flags = flags;
 	cq->db.data.value = cpu_to_le32(cons);
-	writeq(cq->db.raw, cq->db_addr);
+	writeq_relaxed(cq->db.raw, cq->db_addr);

 	/* Make sure write would stick */
 	mmiowb();

@@ -3338,7 +3338,7 @@ int qedr_post_recv(struct ib_qp *ibqp, struct

ib_recv_wr *wr,

 		qp->rq.db_data.data.value++;

-		writel(qp->rq.db_data.raw, qp->rq.db);
+		writel_relaxed(qp->rq.db_data.raw, qp->rq.db);

 		/* Make sure write sticks */
 		mmiowb();
--
2.7.4