From: jgg@ziepe•ca (Jason Gunthorpe)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH v4 6/6] RDMA/qedr: eliminate duplicate barriers on weakly-ordered archs #2
Date: Tue, 20 Mar 2018 08:55:26 -0600 [thread overview]
Message-ID: <20180320145526.GI19744@ziepe.ca> (raw)
In-Reply-To: <1521514068-8856-7-git-send-email-okaya@codeaurora.org>
On Mon, Mar 19, 2018 at 10:47:48PM -0400, Sinan Kaya wrote:
> 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>
> 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
> +++ 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();
Looks fine, but the next lines should be relaxed too:
/* Make sure write sticks */
mmiowb();
if (rdma_protocol_iwarp(&dev->ibdev, 1)) {
writel(qp->rq.iwarp_db2_data.raw, qp->rq.iwarp_db2);
mmiowb(); /* for second doorbell */
}
mmiowb() is strong enough to order writel, IIRC.
Jason
next prev parent reply other threads:[~2018-03-20 14:55 UTC|newest]
Thread overview: 47+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-03-20 2:47 [PATCH v4 0/6] ib: Eliminate duplicate barriers on weakly-ordered archs Sinan Kaya
2018-03-20 2:47 ` [PATCH v4 1/6] RDMA/bnxt_re: " Sinan Kaya
2018-03-20 14:48 ` Jason Gunthorpe
2018-03-20 15:00 ` Sinan Kaya
2018-03-20 15:08 ` Sinan Kaya
2018-03-20 15:23 ` Jason Gunthorpe
2018-03-20 15:20 ` Jason Gunthorpe
2018-03-20 15:30 ` Sinan Kaya
2018-03-20 16:02 ` Jason Gunthorpe
2018-03-20 2:47 ` [PATCH v4 2/6] IB/mlx4: " Sinan Kaya
2018-03-20 14:48 ` Jason Gunthorpe
2018-03-20 2:47 ` [PATCH v4 3/6] RDMA/i40iw: " Sinan Kaya
2018-03-20 14:56 ` Jason Gunthorpe
2018-03-21 13:38 ` Shiraz Saleem
2018-03-21 20:02 ` Jason Gunthorpe
2018-03-21 21:01 ` Sinan Kaya
2018-03-20 2:47 ` [PATCH v4 4/6] infiniband: cxgb4: " Sinan Kaya
2018-03-20 14:51 ` Jason Gunthorpe
2018-03-20 15:10 ` Steve Wise
2018-03-20 15:38 ` Steve Wise
2018-03-22 6:44 ` kbuild test robot
2018-03-22 12:24 ` okaya at codeaurora.org
2018-03-22 12:48 ` okaya at codeaurora.org
2018-03-22 14:33 ` Sinan Kaya
2018-03-22 14:40 ` Steve Wise
2018-03-22 14:52 ` Sinan Kaya
2018-03-22 16:28 ` Steve Wise
2018-03-22 19:44 ` Casey Leedom
2018-03-22 20:16 ` Jason Gunthorpe
2018-03-22 20:45 ` Casey Leedom
2018-03-22 21:25 ` Jason Gunthorpe
2018-03-22 21:27 ` Sinan Kaya
2018-03-22 22:02 ` Casey Leedom
[not found] ` <437ab002-b8db-24aa-583e-0e61d61aaa97@codeaurora.org>
2018-03-22 18:46 ` Jason Gunthorpe
2018-03-22 18:48 ` Jason Gunthorpe
2018-03-22 18:58 ` Sinan Kaya
2018-03-23 4:14 ` kbuild test robot
2018-03-20 2:47 ` [PATCH v4 5/6] IB/nes: " Sinan Kaya
2018-03-20 14:54 ` Jason Gunthorpe
2018-03-20 15:23 ` Sinan Kaya
2018-03-20 16:01 ` Jason Gunthorpe
2018-03-20 16:08 ` Sinan Kaya
2018-03-20 16:29 ` Jason Gunthorpe
2018-03-20 2:47 ` [PATCH v4 6/6] RDMA/qedr: eliminate duplicate barriers on weakly-ordered archs #2 Sinan Kaya
2018-03-20 7:38 ` Kalderon, Michal
2018-03-20 14:55 ` Jason Gunthorpe [this message]
2018-03-21 20:08 ` [PATCH v4 0/6] ib: Eliminate duplicate barriers on weakly-ordered archs Jason Gunthorpe
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