linux-kernel - [PATCH v4 09/17] net: qla3xxx: Eliminate duplicate barriers on weakly-ordered archs

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Message-Id: <1521513753-7325-10-git-send-email-okaya@codeaurora.org>
Date:   Mon, 19 Mar 2018 22:42:24 -0400
From:   Sinan Kaya <okaya@...eaurora.org>
To:     netdev@...r.kernel.org, timur@...eaurora.org,
        sulrich@...eaurora.org
Cc:     linux-arm-msm@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        Sinan Kaya <okaya@...eaurora.org>,
        Dept-GELinuxNICDev@...ium.com, linux-kernel@...r.kernel.org
Subject: [PATCH v4 09/17] net: qla3xxx: Eliminate duplicate barriers on weakly-ordered archs

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@...eaurora.org>
---
 drivers/net/ethernet/qlogic/qla3xxx.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/qlogic/qla3xxx.c b/drivers/net/ethernet/qlogic/qla3xxx.c
index 9e5264d..0e71b74 100644
--- a/drivers/net/ethernet/qlogic/qla3xxx.c
+++ b/drivers/net/ethernet/qlogic/qla3xxx.c
@@ -1858,8 +1858,8 @@ static void ql_update_small_bufq_prod_index(struct ql3_adapter *qdev)
 			qdev->small_buf_release_cnt -= 8;
 		}
 		wmb();
-		writel(qdev->small_buf_q_producer_index,
-			&port_regs->CommonRegs.rxSmallQProducerIndex);
+		writel_relaxed(qdev->small_buf_q_producer_index,
+			       &port_regs->CommonRegs.rxSmallQProducerIndex);
 	}
 }
 
-- 
2.7.4