linux-kernel - Re: [PATCH v31 2/4] scsi: ufs: L2P map management for HPB read

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Date:   Tue, 23 Mar 2021 14:07:00 +0800
From:   Can Guo <cang@...eaurora.org>
To:     daejun7.park@...sung.com
Cc:     Bean Huo <huobean@...il.com>, Greg KH <gregkh@...uxfoundation.org>,
        avri.altman@....com, jejb@...ux.ibm.com,
        martin.petersen@...cle.com, asutoshd@...eaurora.org,
        stanley.chu@...iatek.com, bvanassche@....org,
        linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org,
        ALIM AKHTAR <alim.akhtar@...sung.com>,
        JinHwan Park <jh.i.park@...sung.com>,
        Javier Gonzalez <javier.gonz@...sung.com>,
        Sung-Jun Park <sungjun07.park@...sung.com>,
        Jinyoung CHOI <j-young.choi@...sung.com>,
        Dukhyun Kwon <d_hyun.kwon@...sung.com>,
        Keoseong Park <keosung.park@...sung.com>,
        Jaemyung Lee <jaemyung.lee@...sung.com>,
        Jieon Seol <jieon.seol@...sung.com>
Subject: Re: [PATCH v31 2/4] scsi: ufs: L2P map management for HPB read

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) {
>>>>> 
>>>>> +       case HPB_RSP_REQ_REGION_UPDATE:
>>>>> 
>>>>> +               if (data_seg_len != DEV_DATA_SEG_LEN)
>>>>> 
>>>>> +                       dev_warn(&hpb->sdev_ufs_lu->sdev_dev,
>>>>> 
>>>>> +                                "%s: data seg length is not
>>>>> same.\n",
>>>>> 
>>>>> +                                __func__);
>>>>> 
>>>>> +               ufshpb_rsp_req_region_update(hpb, rsp_field);
>>>>> 
>>>>> +               break;
>>>>> 
>>>>> +       case HPB_RSP_DEV_RESET:
>>>>> 
>>>>> +               dev_warn(&hpb->sdev_ufs_lu->sdev_dev,
>>>>> 
>>>>> +                        "UFS device lost HPB information during
>>>>> PM.\n");
>>>>> 
>>>>> +               break;
>>>> 
>>>> 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?
>>>> 
>>>> 
>>>> Bean
>>> 
>>> Same question here - I am still collecting feedbacks from flash 
>>> vendors
>>> about
>>> what is recommanded host behavior on reception of HPB Op code 0x2,
>>> since it
>>> is not cleared defined in HPB2.0 specs.
>>> 
>>> Can Guo.
>> 
>> 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 
>> Read
>> cmd with
>> invalid HPB entries shall be treated as normal Read(10) cmd without 
>> any
>> problems.
> 
> Yes, UFS device will process read command even the HPB entries are 
> valid or
> not. So it is warning about read performance drop by dev reset.

Yeah, but still I am 100% sure about what should host do in case of 
HPB2.0
when it receives HPB Op code 0x2, I am waiting for feedbacks.

Thanks,
Can Guo.

> 
> Thanks,
> Daejun
> 
>> Please correct me if I am wrong.
> 
> 
> 
>> Thanks,
>> Can Guo.
>> 
>> 
>>