linux-kernel - Re: [PATCH V2] scsi: mpt3sas: remove redundant wmb

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Date:   Fri, 21 Apr 2017 10:10:57 -0500
From:   Brian King <brking@...ux.vnet.ibm.com>
To:     Sreekanth Reddy <sreekanth.reddy@...adcom.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>
Cc:     Sinan Kaya <okaya@...eaurora.org>,
        "linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>,
        timur@...eaurora.org, linux-arm-msm@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        Sathya Prakash <sathya.prakash@...adcom.com>,
        Chaitra P B <chaitra.basappa@...adcom.com>,
        Suganath Prabu Subramani 
        <suganath-prabu.subramani@...adcom.com>,
        "James E.J. Bottomley" <jejb@...ux.vnet.ibm.com>,
        "open list:LSILOGIC MPT FUSION DRIVERS (FC/SAS/SPI)" 
        <MPT-FusionLinux.pdl@...adcom.com>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH V2] scsi: mpt3sas: remove redundant wmb

On 04/21/2017 02:56 AM, Sreekanth Reddy wrote:
> On Thu, Apr 20, 2017 at 7:58 AM, Martin K. Petersen
> <martin.petersen@...cle.com> wrote:
>> Sinan Kaya <okaya@...eaurora.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 is also true for Power. 

Reviewed-by: Brian King <brking@...ux.vnet.ibm.com>

-Brian

-- 
Brian King
Power Linux I/O
IBM Linux Technology Center