Hello Jaehoon, Per
I have experimented with eMMC v4.41 card and BKOPS feature and want to add
info on EXT_CSD_BKOPS_EN[163] field. See below.
> Hi Per
>
>>>>>>>
>>>>>>> if (card->ext_csd.rev >= 5) {
>>>>>>> + /* check whether the eMMC card support BKOPS */
>>>>>>> + if (ext_csd[EXT_CSD_BKOPS_SUPPORT] & 0x1) {
>>>>>>> + card->ext_csd.bkops = 1;
>>>>>>> + card->ext_csd.bkops_en = 1;
>>>>>> What if the card has not enabled bkops? This bit could be unset.
>>>>>> card->ext_csd.bkops_en = ext_csd[EXT_CSD_BKOPS_EN];
>>>>> When card is supported the bkops, bkops_en bit is set by default...
>>>>>
>>>> How do you know if the bkops_en is really enabled in th ext_csd?
>>>> It could be unset in the ext_csd, right?
>>>
>>> In emmc4.5 spec, if card is supported the bkops, bkops_en is set by
>>> default.
>> If bkops_en is set by default it should be in the the ext_csd too,
>> right?
>> It should be safer to trust the value of ext_csd[EXT_CSD_BKOPS_EN] in
>> this case I think.
>
> If we want to ensure whether bkops_en bit is set or not, your approach is
> right.
>
> Best Regards,
> Jaehoon Chung
First of all protocol state:
------------------------------
7.4.57 BKOPS_EN [163]
This field allows the _host_ to indicate to the device if it is expected
to periodically manually start background operations by writing to the
BKOPS_START field.
...In order for the device to know if host is going to periodically start
background operations, host shall set bit 0 of BKOPS_EN (EXT_CSD byte
[163]) to indicate that it is going to write to BKOPS_START periodically.
The device may then delay some of its maintenance operations to when host
writes to BKOPS_START.
------------------------------
My card supports BKOPS (by reading Bit 0 of BKOPS_SUPPORT (EXT_CSD byte
[502]), but BKOPS_EN[163] is not set. So I suppose, original code to set
BKOPS_EN[163] is needed, otherwise card will never delay its maintenance
operations.
Thanks,
Kostya
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