Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
DMARC-Filter: OpenDMARC Filter v1.3.2 smtp.codeaurora.org 1BF3460C64
From:   Sinan Kaya <okaya@codeaurora.org>
To:     linux-rdma@vger.kernel.org, timur@codeaurora.org,
        sulrich@codeaurora.org
Cc:     linux-arm-msm@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org,
        Sinan Kaya <okaya@codeaurora.org>,
        Selvin Xavier <selvin.xavier@broadcom.com>,
        Devesh Sharma <devesh.sharma@broadcom.com>,
        Somnath Kotur <somnath.kotur@broadcom.com>,
        Sriharsha Basavapatna <sriharsha.basavapatna@broadcom.com>,
        Doug Ledford <dledford@redhat.com>,
        Jason Gunthorpe <jgg@ziepe.ca>, linux-kernel@vger.kernel.org
Subject: [PATCH v5 1/3] RDMA/bnxt_re: Eliminate duplicate barriers on weakly-ordered archs
Date:   Thu, 22 Mar 2018 12:26:47 -0400
Message-Id: <1521736009-23387-2-git-send-email-okaya@codeaurora.org>
In-Reply-To: <1521736009-23387-1-git-send-email-okaya@codeaurora.org>
References: <1521736009-23387-1-git-send-email-okaya@codeaurora.org>
MIME-Version: 1.0
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

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/bnxt_re/qplib_rcfw.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/drivers/infiniband/hw/bnxt_re/qplib_rcfw.c b/drivers/infiniband/hw/bnxt_re/qplib_rcfw.c
index 8329ec6..10f9a26 100644
--- a/drivers/infiniband/hw/bnxt_re/qplib_rcfw.c
+++ b/drivers/infiniband/hw/bnxt_re/qplib_rcfw.c
@@ -181,10 +181,11 @@ static int __send_message(struct bnxt_qplib_rcfw *rcfw, struct cmdq_base *req,
 
 	/* ring CMDQ DB */
 	wmb();
-	writel(cmdq_prod, rcfw->cmdq_bar_reg_iomem +
-	       rcfw->cmdq_bar_reg_prod_off);
-	writel(RCFW_CMDQ_TRIG_VAL, rcfw->cmdq_bar_reg_iomem +
-	       rcfw->cmdq_bar_reg_trig_off);
+	writel_relaxed(cmdq_prod, rcfw->cmdq_bar_reg_iomem +
+		       rcfw->cmdq_bar_reg_prod_off);
+	writel_relaxed(RCFW_CMDQ_TRIG_VAL, rcfw->cmdq_bar_reg_iomem +
+		       rcfw->cmdq_bar_reg_trig_off);
+	mmiowb();
 done:
 	spin_unlock_irqrestore(&cmdq->lock, flags);
 	/* Return the CREQ response pointer */
-- 
2.7.4