Commit 561e5d48 authored Mar 13, 2018 by Sinan Kaya Committed by Jason Gunthorpe Mar 15, 2018

RDMA/qedr: eliminate duplicate barriers on weakly-ordered archs



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 <okaya@codeaurora.org>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

parent 7b48221c

drivers/infiniband/hw/qedr/verbs.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -1870,7 +1870,7 @@ static int qedr_update_qp_state(struct qedr_dev *dev,

		if (rdma_protocol_roce(&dev->ibdev, 1)) {
		wmb();
		writel(qp->rq.db_data.raw, qp->rq.db);
		writel_relaxed(qp->rq.db_data.raw, qp->rq.db);
		/* Make sure write takes effect */
		mmiowb();
		}
		@@ -3257,7 +3257,7 @@ int qedr_post_send(struct ib_qp ibqp, struct ib_send_wr wr,
		* redundant doorbell.
		*/
		wmb();
		writel(qp->sq.db_data.raw, qp->sq.db);
		writel_relaxed(qp->sq.db_data.raw, qp->sq.db);

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