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

Can Guo
2021-03-23T06:48:22Z

On 2021-03-23 14:37, Daejun Park wrote:
>> On 2021-03-23 14:19, Daejun Park wrote:
>>>> 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.
>>>
>>> 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.
>>>
>>> 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’s HPB READ command.
>>>
>>> If some UFS builds L2P map data from the host's HPB READ commands, we
>>> don't
>>> have to discard HPB entries in the host.
>>>
>>> So I thinks there is nothing to do when it receives 0x2.
>>
>> But in HPB2.0, if we do nothing to active regions in host side, host
>> can
>> write
>> HPB entries (which host thinks valid, but actually invalid in device
>> side since
>> reset happened) back to device through HPB Write Buffer cmds (BUFFER
>> ID
>> = 0x2).
>> My question is that are all UFSs OK with this?
>
> Yes, it must be OK.
>
> Please refer the following the HPB 2.0 spec:
>
> If the HPB Entries sent by HPB WRITE BUFFER are removed by the device,
> for example, because they are not consumed for a long enough period of
> time,
> then the HPB READ command for the removed HPB entries shall be handled
> as a
> normal READ command.
>

No, it is talking about the subsequent HPB READ cmd sent after a HPB
WRITE BUFFER cmd,
but not the HPB WRITE BUFFER cmd itself...

Thanks,
Can Guo.

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