Re: [PATCH v6] mmc: support BKOPS feature for eMMC

[Jaehoon Chung <jh80.chung@samsung.com>]

On 01/20/2012 04:31 PM, Adrian Hunter wrote:

> On 19/01/12 17:32, S, Venkatraman wrote:
>> On Thu, Jan 19, 2012 at 5:14 PM, Adrian Hunter <adrian.hunter@intel.com> wrote:
>>> On 19/01/12 13:33, Jaehoon Chung wrote:
>>>> Hi Adrian.
>>>>
>>>> On 01/19/2012 07:21 PM, Adrian Hunter wrote:
>>>>
>>>>> On 19/01/12 07:29, Jaehoon Chung wrote:
>>>>>> Enable eMMC background operations (BKOPS) feature.
>>>>>>
>>>>>> If URGENT_BKOPS is set after a response, note that BKOPS
>>>>>> are required. After all I/O requests are finished, run
>>>>>> BKOPS if required. Should read/write operations be requested
>>>>>> during BKOPS, first issue HPI to interrupt the ongoing BKOPS
>>>>>> and then service the request.
>>>>>
>>>>> This still does not seem to address my earlier comment which was:
>>>>>
>>>>> The main problem with bkops is:
>>>>>
>>>>>      If the status is at level 3 ("critical"), some operations
>>>>>      may extend beyond their original timeouts due to maintenance
>>>>>      operations which cannot be delayed anymore.
>>>>>
>>>>> This means:
>>>>>
>>>>>      1. at level 3 either bkops are run or the timeout of the next
>>>>>      (data?) operation is extended
>>>>>
>>>>>      2. at level 3 either the bkops must not be interrupted or the
>>>>>      level must be rechecked after interruption and bkops run again
>>>>>      if the level is still 3, or the timeout of the next (data?)
>>>>>      operation is extended
>>>>>
>>>>
>>>> This patch didn't issue the HPI when bkops-status is level2-3
>>>> (URGENT_BKOPS case).
>>>> I didn't understand that must be recheck?? it's case of using HPI..?
>>>> If HPI didn't issue,though must be recheck bkops status?
>>>> And level-1 control should be considered for future-work.
>>>> I will also modify the patch comment..it's confused something.
>>>
>>> 1. Say there are 2 write requests queued and after the first write request
>>> the bkops level is 3.  That means the 2nd write request may timeout because
>>> the normal timeout rules do not apply.
>>>
>>> Thus:
>>>        1. at level 3 either bkops are run or the timeout of the next
>>>        (data?) operation is extended
>>>
>>> 2. Say you are running bkops because the level was 3 and a write request
>>> arrives.  You use HPI to interrupt the bkops, but the bkops level may still
>>> be 3, so the write request may timeout.  Hence:
>>>
>>>        2. at level 3 either the bkops must not be interrupted or the
>>>        level must be rechecked after interruption and bkops run again
>>>        if the level is still 3, or the timeout of the next (data?)
>>>        operation is extended
>>>
>>
>> A naive question perhaps, but don't the current timeout values include
>> sufficient
>> buffer to do implicit garbage collection anyways ?
> 
> Maybe, but the problem is the JEDEC specification says otherwise.  This bit
> is a quote:
> 
> 	If the status is at level 3 ("critical"), some operations
> 	may extend beyond their original timeouts due to maintenance
> 	operations which cannot be delayed anymore.
> 
> I think level 3 is a very rare case so I would just run bkops and wait for
> it to finish without interruption.

Yes..JEDEC spec say those..but I think not bad that wait for bkops-done..
actually i didn't know how long time run the bkops...
so i think the use the hpi command..then re-check the bkops-status until clear status.
(i think the request's priority is higher than any bkops status)

it would be open to interpretation that sentence.

Best Regards,
Jaehoon Chung

> --
> To unsubscribe from this list: send the line "unsubscribe linux-mmc" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>