linux-kernel - [PATCH v4 6/7] scsi: bnx2i: Eliminate duplicate barriers on weakly-ordered archs

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Message-Id: <1521514207-10695-7-git-send-email-okaya@codeaurora.org>
Date:   Mon, 19 Mar 2018 22:50:06 -0400
From:   Sinan Kaya <okaya@...eaurora.org>
To:     linux-scsi@...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>,
        QLogic-Storage-Upstream@...gic.com,
        "James E.J. Bottomley" <jejb@...ux.vnet.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        linux-kernel@...r.kernel.org
Subject: [PATCH v4 6/7] scsi: bnx2i: Eliminate duplicate barriers on weakly-ordered archs

Code includes barrier() 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/scsi/bnx2i/bnx2i_hwi.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/scsi/bnx2i/bnx2i_hwi.c b/drivers/scsi/bnx2i/bnx2i_hwi.c
index 8f03a86..075735b 100644
--- a/drivers/scsi/bnx2i/bnx2i_hwi.c
+++ b/drivers/scsi/bnx2i/bnx2i_hwi.c
@@ -278,7 +278,7 @@ static void bnx2i_ring_sq_dbell(struct bnx2i_conn *bnx2i_conn, int count)
 		sq_db->prod_idx = ep->qp.sq_prod_idx;
 		bnx2i_ring_577xx_doorbell(bnx2i_conn);
 	} else
-		writew(count, ep->qp.ctx_base + CNIC_SEND_DOORBELL);
+		writew_relaxed(count, ep->qp.ctx_base + CNIC_SEND_DOORBELL);
 
 	mmiowb(); /* flush posted PCI writes */
 }
-- 
2.7.4