Re: [PATCH v2 2/2] mtd: spinand: micron: fixing the offset for OOB

Martin Kurbanov
2023-08-24T09:36:54Z

On 23.08.2023 14:39, Miquel Raynal wrote:
> Hi Martin,
>
> mmkurbanov@sberdevices.ru wrote on Wed, 23 Aug 2023 14:33:57 +0300:
>
>> Hi Miquel,
>>
>> On 23.08.2023 11:41, Miquel Raynal wrote:
>>> Hi Martin,
>>>
>>> I don't think the four bytes have any "bad block specific" meaning. In
>>> practice, the datasheet states:
>>>
>>> Value programmed for bad block at the first byte of spare
>>> area: 00h
>>>
>>> So only the first byte is used to mark the block bad, the rest is
>>> probably marked "reserved" for simplicity. I believe we should keep the
>>> current layout because it would otherwise break users for no real
>>> reason.
>>
>> I agree with you that this can break the work of users who use OOB.
>> However, I believe it would be more appropriate to use an offset of 4,
>> as the micron chip can use all 4 bytes for additional data about the
>> bad block. So, there is a non-zero probability of losing OOB data in
>> the reserved area (2 bytes) when the hardware chip attempts to mark
>> the block as bad.
>
> Is this really a process the chip can do? Aren't bad blocks factory
> marked only?

Actually, there is my understanding, I’m not sure exactly.

--
Best Regards,
Martin Kurbanov