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From: Suganath Prabu Subramani <suganath-prabu.subramani@broadcom.com>
Date: Fri, 1 Sep 2017 14:09:54 +0530
Message-ID: <CA+RiK667V9nDEr7RywED2_RoSq97m511HZTpGqPbij9-=vADvQ@mail.gmail.com>
Subject: Re: [PATCH v4 00/14] mpt3sas driver NVMe support:
To: "Martin K. Petersen" <martin.petersen@oracle.com>
Cc: linux-scsi@vger.kernel.org,
        Sathya Prakash <Sathya.Prakash@broadcom.com>,
        Kashyap Desai <kashyap.desai@broadcom.com>,
        linux-kernel@vger.kernel.org,
        Chaitra Basappa <chaitra.basappa@broadcom.com>,
        Sreekanth Reddy <sreekanth.reddy@broadcom.com>,
        linux-nvme@lists.infradead.org
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Hi Martin,

On Fri, Sep 1, 2017 at 8:52 AM, Martin K. Petersen
<martin.petersen@oracle.com> wrote:
>
> Hi Suganath,
>
>> Let me explain - NVME device fast path is possible in two ways.  IEEE
>> SGL and PRP SGL. Due to h/w constraint we choose IEEE SGL only for
>> smaller IO size.  Both above is true h/w Fast Path and no firmware
>> involvement.
>
>> Agree with you. We are planning to see if we can keep only simple Fast
>> Path using only PRP.
>
> That would be great, thank you!
>
>> Currently there is no performance issue for UNMAP translation in FW.
>
> Good!
>
>>> And yet patch 4 circumvents that statement by adding support for
>>> encapsulated commands to bypass the FW translation...
>>
>> This path is not due to performance reason. User wants to interact
>> with NVME drive in native NVME command for management.
>
> Patch 4 states:
>
> "This encapsulated NVMe command is used by applications to send direct
> NVMe commands to NVMe drives or for handling unmap where the translation
> at controller/firmware level is having performance issues."
>
> --

The statement in description of patch 4 is added by mistake, We ll
correct the description and re sending that.

> Martin K. Petersen      Oracle Linux Engineering

Thanks,
Suganath Prabu S