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From: Sinan Kaya <okaya@codeaurora.org>
To: linux-scsi@vger.kernel.org, timur@codeaurora.org
Cc: linux-arm-msm@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	Sinan Kaya <okaya@codeaurora.org>,
	Sathya Prakash <sathya.prakash@broadcom.com>,
	Chaitra P B <chaitra.basappa@broadcom.com>,
	Suganath Prabu Subramani  <suganath-prabu.subramani@broadcom.com>,
	"James E.J. Bottomley" <jejb@linux.vnet.ibm.com>,
	"Martin K. Petersen" <martin.petersen@oracle.com>,
	MPT-FusionLinux.pdl@broadcom.com (open list:LSILOGIC MPT FUSION
	DRIVERS (FC/SAS/SPI)), linux-kernel@vger.kernel.org (open list)
Subject: [PATCH V2] scsi: mpt3sas: remove redundant wmb
Date: Fri,  7 Apr 2017 15:06:18 -0400	[thread overview]
Message-ID: <1491591978-17880-1-git-send-email-okaya@codeaurora.org> (raw)

Due to relaxed ordering requirements on multiple architectures,
drivers are required to use wmb/rmb/mb combinations when they
need to guarantee observability between the memory and the HW.

The mpt3sas driver is already using wmb() for this purpose.
However, it issues a writel following wmb(). writel() function
on arm/arm64 arhictectures have an embedded wmb() call inside.

This results in unnecessary performance loss and code duplication.

writel already guarantees ordering for both cpu and bus. we don't need
additional wmb()

Signed-off-by: Sinan Kaya <okaya@codeaurora.org>
---
 drivers/scsi/mpt3sas/mpt3sas_base.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/drivers/scsi/mpt3sas/mpt3sas_base.c b/drivers/scsi/mpt3sas/mpt3sas_base.c
index 5b7aec5..18039bb 100644
--- a/drivers/scsi/mpt3sas/mpt3sas_base.c
+++ b/drivers/scsi/mpt3sas/mpt3sas_base.c
@@ -1025,7 +1025,6 @@ static int mpt3sas_remove_dead_ioc_func(void *arg)
 				    0 : ioc->reply_free_host_index + 1;
 				ioc->reply_free[ioc->reply_free_host_index] =
 				    cpu_to_le32(reply);
-				wmb();
 				writel(ioc->reply_free_host_index,
 				    &ioc->chip->ReplyFreeHostIndex);
 			}
@@ -1074,7 +1073,6 @@ static int mpt3sas_remove_dead_ioc_func(void *arg)
 		return IRQ_NONE;
 	}
 
-	wmb();
 	if (ioc->is_warpdrive) {
 		writel(reply_q->reply_post_host_index,
 		ioc->reply_post_host_index[msix_index]);
-- 
1.9.1

             reply	other threads:[~2017-04-07 19:06 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-04-07 19:06 Sinan Kaya [this message]
2017-04-20  2:28 ` Martin K. Petersen
2017-04-21  7:56   ` Sreekanth Reddy
2017-04-21 13:47     ` Sinan Kaya
2017-04-21 15:10     ` Brian King
2017-04-24 22:32 ` Martin K. Petersen

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