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From: Sinan Kaya <okaya@codeaurora.org>
To: linux-scsi@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>,
	James Smart <james.smart@broadcom.com>,
	Dick Kennedy <dick.kennedy@broadcom.com>,
	"James E.J. Bottomley" <jejb@linux.vnet.ibm.com>,
	"Martin K. Petersen" <martin.petersen@oracle.com>,
	linux-kernel@vger.kernel.org
Subject: [PATCH v4 4/7] scsi: lpfc: Eliminate duplicate barriers on weakly-ordered archs
Date: Mon, 19 Mar 2018 22:50:04 -0400	[thread overview]
Message-ID: <1521514207-10695-5-git-send-email-okaya@codeaurora.org> (raw)
In-Reply-To: <1521514207-10695-1-git-send-email-okaya@codeaurora.org>

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@codeaurora.org>
---
 drivers/scsi/lpfc/lpfc_sli.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/scsi/lpfc/lpfc_sli.c b/drivers/scsi/lpfc/lpfc_sli.c
index 5f5528a..7dae7d3 100644
--- a/drivers/scsi/lpfc/lpfc_sli.c
+++ b/drivers/scsi/lpfc/lpfc_sli.c
@@ -1647,7 +1647,7 @@ lpfc_sli_update_full_ring(struct lpfc_hba *phba, struct lpfc_sli_ring *pring)
 	 * Set ring 'ringno' to SET R0CE_REQ in Chip Att register.
 	 * The HBA will tell us when an IOCB entry is available.
 	 */
-	writel((CA_R0ATT|CA_R0CE_REQ) << (ringno*4), phba->CAregaddr);
+	writel_relaxed((CA_R0ATT|CA_R0CE_REQ) << (ringno*4), phba->CAregaddr);
 	readl(phba->CAregaddr); /* flush */
 
 	pring->stats.iocb_cmd_full++;
@@ -1672,7 +1672,7 @@ lpfc_sli_update_ring(struct lpfc_hba *phba, struct lpfc_sli_ring *pring)
 	 */
 	if (!(phba->sli3_options & LPFC_SLI3_CRP_ENABLED)) {
 		wmb();
-		writel(CA_R0ATT << (ringno * 4), phba->CAregaddr);
+		writel_relaxed(CA_R0ATT << (ringno * 4), phba->CAregaddr);
 		readl(phba->CAregaddr); /* flush */
 	}
 }
-- 
2.7.4

WARNING: multiple messages have this Message-ID (diff)
From: okaya@codeaurora.org (Sinan Kaya)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH v4 4/7] scsi: lpfc: Eliminate duplicate barriers on weakly-ordered archs
Date: Mon, 19 Mar 2018 22:50:04 -0400	[thread overview]
Message-ID: <1521514207-10695-5-git-send-email-okaya@codeaurora.org> (raw)
In-Reply-To: <1521514207-10695-1-git-send-email-okaya@codeaurora.org>

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@codeaurora.org>
---
 drivers/scsi/lpfc/lpfc_sli.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/scsi/lpfc/lpfc_sli.c b/drivers/scsi/lpfc/lpfc_sli.c
index 5f5528a..7dae7d3 100644
--- a/drivers/scsi/lpfc/lpfc_sli.c
+++ b/drivers/scsi/lpfc/lpfc_sli.c
@@ -1647,7 +1647,7 @@ lpfc_sli_update_full_ring(struct lpfc_hba *phba, struct lpfc_sli_ring *pring)
 	 * Set ring 'ringno' to SET R0CE_REQ in Chip Att register.
 	 * The HBA will tell us when an IOCB entry is available.
 	 */
-	writel((CA_R0ATT|CA_R0CE_REQ) << (ringno*4), phba->CAregaddr);
+	writel_relaxed((CA_R0ATT|CA_R0CE_REQ) << (ringno*4), phba->CAregaddr);
 	readl(phba->CAregaddr); /* flush */
 
 	pring->stats.iocb_cmd_full++;
@@ -1672,7 +1672,7 @@ lpfc_sli_update_ring(struct lpfc_hba *phba, struct lpfc_sli_ring *pring)
 	 */
 	if (!(phba->sli3_options & LPFC_SLI3_CRP_ENABLED)) {
 		wmb();
-		writel(CA_R0ATT << (ringno * 4), phba->CAregaddr);
+		writel_relaxed(CA_R0ATT << (ringno * 4), phba->CAregaddr);
 		readl(phba->CAregaddr); /* flush */
 	}
 }
-- 
2.7.4

  parent reply	other threads:[~2018-03-20  2:50 UTC|newest]

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-03-20  2:50 [PATCH v4 0/7] scsi: Eliminate duplicate barriers on weakly-ordered archs Sinan Kaya
2018-03-20  2:50 ` Sinan Kaya
2018-03-20  2:50 ` [PATCH v4 1/7] scsi: hpsa: " Sinan Kaya
2018-03-20  2:50   ` Sinan Kaya
2018-03-20 14:01   ` Don Brace
2018-03-20 14:01     ` Don Brace
2018-03-20 16:51   ` Laurence Oberman
2018-03-20 16:51     ` Laurence Oberman
2018-03-20  2:50 ` [PATCH v4 2/7] scsi: megaraid: eliminate " Sinan Kaya
2018-03-20  2:50   ` Sinan Kaya
2018-03-20  2:50 ` [PATCH v4 3/7] scsi: dpt_i2o: " Sinan Kaya
2018-03-20  2:50   ` Sinan Kaya
2018-03-20 10:23   ` Christoph Hellwig
2018-03-20 10:23     ` Christoph Hellwig
2018-03-20 12:13     ` okaya
2018-03-20 12:13       ` okaya at codeaurora.org
2018-03-20  2:50 ` Sinan Kaya [this message]
2018-03-20  2:50   ` [PATCH v4 4/7] scsi: lpfc: Eliminate " Sinan Kaya
2018-03-20  2:50 ` [PATCH v4 5/7] scsi: ipr: " Sinan Kaya
2018-03-20  2:50   ` Sinan Kaya
2018-05-29 20:45   ` Brian King
2018-05-29 20:45     ` Brian King
2018-03-20  2:50 ` [PATCH v4 6/7] scsi: bnx2i: " Sinan Kaya
2018-03-20  2:50   ` Sinan Kaya
2018-03-20  2:50 ` [PATCH v4 7/7] scsi: csiostor: " Sinan Kaya
2018-03-20  2:50   ` Sinan Kaya

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