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

Daejun Park
2021-03-23T06:38:30Z

>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.

Thanks,
Daejun

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