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Subject: RE: Re: [PATCH v31 2/4] scsi: ufs: L2P map management for HPB read
Reply-To: daejun7.park@samsung.com
Sender: Daejun Park <daejun7.park@samsung.com>
From:   Daejun Park <daejun7.park@samsung.com>
To:     Can Guo <cang@codeaurora.org>,
        Daejun Park <daejun7.park@samsung.com>
CC:     Bean Huo <huobean@gmail.com>, Greg KH <gregkh@linuxfoundation.org>,
        "avri.altman@wdc.com" <avri.altman@wdc.com>,
        "jejb@linux.ibm.com" <jejb@linux.ibm.com>,
        "martin.petersen@oracle.com" <martin.petersen@oracle.com>,
        "asutoshd@codeaurora.org" <asutoshd@codeaurora.org>,
        "stanley.chu@mediatek.com" <stanley.chu@mediatek.com>,
        "bvanassche@acm.org" <bvanassche@acm.org>,
        "linux-scsi@vger.kernel.org" <linux-scsi@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        ALIM AKHTAR <alim.akhtar@samsung.com>,
        JinHwan Park <jh.i.park@samsung.com>,
        Javier Gonzalez <javier.gonz@samsung.com>,
        Sung-Jun Park <sungjun07.park@samsung.com>,
        Jinyoung CHOI <j-young.choi@samsung.com>,
        Dukhyun Kwon <d_hyun.kwon@samsung.com>,
        Keoseong Park <keosung.park@samsung.com>,
        Jaemyung Lee <jaemyung.lee@samsung.com>,
        Jieon Seol <jieon.seol@samsung.com>
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Message-ID: <20210323061922epcms2p739666492ebb458d70deab026d074caf4@epcms2p7>
Date:   Tue, 23 Mar 2021 15:19:22 +0900
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>On 2021-03-23 13:37, Daejun Park wrote:
>>> On 2021-03-23 12:22, Can Guo wrote:
>>>> On 2021-03-22 17:11, Bean Huo wrote:
>>>>> On Mon, 2021-03-22 at 15:54 +0900, Daejun Park wrote:
>>>>>> +       switch (rsp_field->hpb_op) =7B
>>>>>>=20
>>>>>> +       case HPB_RSP_REQ_REGION_UPDATE:
>>>>>>=20
>>>>>> +               if (data_seg_len =21=3D DEV_DATA_SEG_LEN)
>>>>>>=20
>>>>>> +                       dev_warn(&hpb->sdev_ufs_lu->sdev_dev,
>>>>>>=20
>>>>>> +                                =22%s: data seg length is not
>>>>>> same.=5Cn=22,
>>>>>>=20
>>>>>> +                                __func__);
>>>>>>=20
>>>>>> +               ufshpb_rsp_req_region_update(hpb, rsp_field);
>>>>>>=20
>>>>>> +               break;
>>>>>>=20
>>>>>> +       case HPB_RSP_DEV_RESET:
>>>>>>=20
>>>>>> +               dev_warn(&hpb->sdev_ufs_lu->sdev_dev,
>>>>>>=20
>>>>>> +                        =22UFS device lost HPB information during
>>>>>> PM.=5Cn=22);
>>>>>>=20
>>>>>> +               break;
>>>>>=20
>>>>> Hi Deajun,
>>>>> This series looks good to me. Just here I have one question. You
>>>>> didn't
>>>>> handle HPB_RSP_DEV_RESET, just a warning.  Based on your SS UFS, how
>>>>> to
>>>>> handle HPB_RSP_DEV_RESET from the host side? Do you think we shoud
>>>>> reset host side HPB entry as well or what else?
>>>>>=20
>>>>>=20
>>>>> Bean
>>>>=20
>>>> Same question here - I am still collecting feedbacks from flash=20
>>>> vendors
>>>> about
>>>> what is recommanded host behavior on reception of HPB Op code 0x2,
>>>> since it
>>>> is not cleared defined in HPB2.0 specs.
>>>>=20
>>>> Can Guo.
>>>=20
>>> I think the question should be asked in the HPB2.0 patch, since in
>>> HPB1.0 device
>>> control mode, a HPB reset in device side does not impact anything in
>>> host side -
>>> host is not writing back any HPB entries to device anyways and HPB=20
>>> Read
>>> cmd with
>>> invalid HPB entries shall be treated as normal Read(10) cmd without=20
>>> any
>>> problems.
>>=20
>> Yes, UFS device will process read command even the HPB entries are=20
>> valid or
>> not. So it is warning about read performance drop by dev reset.
>=20
>Yeah, but still I am 100% sure about what should host do in case of=20
>HPB2.0
>when it receives HPB Op code 0x2, I am waiting for feedbacks.

I think the host has two choices when it receives 0x2.
One is nothing on host.
The other is discarding all HPB entries in the host.=20

In the JEDEC HPB spec, it as follows:
When the device is powered off by the host, the device may restore L2P map
data upon power up or build from the host=E2=80=99s=20HPB=20READ=20command.=
=0D=0A=0D=0AIf=20some=20UFS=20builds=20L2P=20map=20data=20from=20the=20host=
's=20HPB=20READ=20commands,=20we=20don't=0D=0Ahave=20to=20discard=20HPB=20e=
ntries=20in=20the=20host.=0D=0A=0D=0ASo=20I=20thinks=20there=20is=20nothing=
=20to=20do=20when=20it=20receives=200x2.=0D=0A=0D=0AThanks,=0D=0ADaejun=0D=
=0A=0D=0A>Thanks,=0D=0A>Can=20Guo.=0D=0A>=20=0D=0A>>=20=0D=0A>>=20Thanks,=
=0D=0A>>=20Daejun=0D=0A>>=20=0D=0A>>>=20Please=20correct=20me=20if=20I=20am=
=20wrong.=0D=0A>>=20=0D=0A>>=20=0D=0A>>=20=0D=0A>>>=20Thanks,=0D=0A>>>=20Ca=
n=20Guo.=0D=0A>>>=20=0D=0A>>>=20=0D=0A>>>=20=0D=0A>=20=0D=0A>=20=0D=0A>=20=
=20