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

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Message-ID: <ccf3099f-0e10-a87c-be83-4a414f01dca7@sberdevices.ru>
Date:   Thu, 24 Aug 2023 12:35:46 +0300
From:   Martin Kurbanov <mmkurbanov@...rdevices.ru>
To:     Miquel Raynal <miquel.raynal@...tlin.com>
CC:     Richard Weinberger <richard@....at>,
        Vignesh Raghavendra <vigneshr@...com>,
        <linux-kernel@...r.kernel.org>, <linux-mtd@...ts.infradead.org>,
        <kernel@...rdevices.ru>
Subject: Re: [PATCH v2 2/2] mtd: spinand: micron: fixing the offset for OOB



On 23.08.2023 14:39, Miquel Raynal wrote:
> Hi Martin,
> 
> mmkurbanov@...rdevices.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