linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Sreekanth Reddy <sreekanth.reddy@broadcom.com>
To: "Martin K. Petersen" <martin.petersen@oracle.com>
Cc: Sinan Kaya <okaya@codeaurora.org>,
	"linux-scsi@vger.kernel.org" <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>,
	"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: Fri, 21 Apr 2017 13:26:29 +0530	[thread overview]
Message-ID: <CAK=zhgpmcmq-CnWuU9=WRJpAaEduw63LSPLE9yZzF_sUHkM4AA@mail.gmail.com> (raw)
In-Reply-To: <yq1y3uvq0c1.fsf@oracle.com>

On Thu, Apr 20, 2017 at 7:58 AM, Martin K. Petersen
<martin.petersen@oracle.com> wrote:
> 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.

[Sreekanth] Whether same thing applicable for SPARC & POWER
architectures. If yes then we are fine with this patch changes.

>>
>> 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

  reply	other threads:[~2017-04-21  7:56 UTC|newest]

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

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to='CAK=zhgpmcmq-CnWuU9=WRJpAaEduw63LSPLE9yZzF_sUHkM4AA@mail.gmail.com' \
    --to=sreekanth.reddy@broadcom.com \
    --cc=MPT-FusionLinux.pdl@broadcom.com \
    --cc=chaitra.basappa@broadcom.com \
    --cc=jejb@linux.vnet.ibm.com \
    --cc=linux-arm-kernel@lists.infradead.org \
    --cc=linux-arm-msm@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-scsi@vger.kernel.org \
    --cc=martin.petersen@oracle.com \
    --cc=okaya@codeaurora.org \
    --cc=sathya.prakash@broadcom.com \
    --cc=suganath-prabu.subramani@broadcom.com \
    --cc=timur@codeaurora.org \
    --subject='Re: [PATCH V2] scsi: mpt3sas: remove redundant wmb' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).