From: "Martin K. Petersen" <martin.petersen@oracle.com>
To: Sinan Kaya <okaya@codeaurora.org>
Cc: linux-scsi@vger.kernel.org, timur@codeaurora.org,
linux-arm-msm@vger.kernel.org,
linux-arm-kernel@lists.infradead.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>,
"open list:LSILOGIC MPT FUSION DRIVERS FC/SAS/SPI"
<MPT-FusionLinux.pdl@broadcom.com>,
open list <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH V2] scsi: mpt3sas: remove redundant wmb
Date: Wed, 19 Apr 2017 22:28:30 -0400 [thread overview]
Message-ID: <yq1y3uvq0c1.fsf@oracle.com> (raw)
In-Reply-To: <1491591978-17880-1-git-send-email-okaya@codeaurora.org> (Sinan Kaya's message of "Fri, 7 Apr 2017 15:06:18 -0400")
Sinan Kaya <okaya@codeaurora.org> writes:
> 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()
Broadcom folks, please review!
--
Martin K. Petersen Oracle Linux Engineering
WARNING: multiple messages have this Message-ID (diff)
From: martin.petersen@oracle.com (Martin K. Petersen)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH V2] scsi: mpt3sas: remove redundant wmb
Date: Wed, 19 Apr 2017 22:28:30 -0400 [thread overview]
Message-ID: <yq1y3uvq0c1.fsf@oracle.com> (raw)
In-Reply-To: <1491591978-17880-1-git-send-email-okaya@codeaurora.org> (Sinan Kaya's message of "Fri, 7 Apr 2017 15:06:18 -0400")
Sinan Kaya <okaya@codeaurora.org> writes:
> 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()
Broadcom folks, please review!
--
Martin K. Petersen Oracle Linux Engineering
WARNING: multiple messages have this Message-ID (diff)
From: "Martin K. Petersen" <martin.petersen@oracle.com>
To: Sinan Kaya <okaya@codeaurora.org>
Cc: linux-scsi@vger.kernel.org, timur@codeaurora.org,
linux-arm-msm@vger.kernel.org,
linux-arm-kernel@lists.infradead.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: Re: [PATCH V2] scsi: mpt3sas: remove redundant wmb
Date: Wed, 19 Apr 2017 22:28:30 -0400 [thread overview]
Message-ID: <yq1y3uvq0c1.fsf@oracle.com> (raw)
In-Reply-To: <1491591978-17880-1-git-send-email-okaya@codeaurora.org> (Sinan Kaya's message of "Fri, 7 Apr 2017 15:06:18 -0400")
Sinan Kaya <okaya@codeaurora.org> writes:
> 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()
Broadcom folks, please review!
--
Martin K. Petersen Oracle Linux Engineering
next prev parent reply other threads:[~2017-04-20 2:28 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-04-07 19:06 [PATCH V2] scsi: mpt3sas: remove redundant wmb Sinan Kaya
2017-04-07 19:06 ` Sinan Kaya
2017-04-07 19:06 ` Sinan Kaya
2017-04-20 2:28 ` Martin K. Petersen [this message]
2017-04-20 2:28 ` Martin K. Petersen
2017-04-20 2:28 ` Martin K. Petersen
2017-04-21 7:56 ` Sreekanth Reddy
2017-04-21 7:56 ` Sreekanth Reddy
2017-04-21 7:56 ` Sreekanth Reddy
2017-04-21 13:47 ` Sinan Kaya
2017-04-21 13:47 ` Sinan Kaya
2017-04-21 15:10 ` Brian King
2017-04-21 15:10 ` Brian King
2017-04-21 15:10 ` Brian King
2017-04-24 22:32 ` Martin K. Petersen
2017-04-24 22:32 ` Martin K. Petersen
2017-04-24 22:32 ` Martin K. Petersen
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