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

Miquel Raynal
2023-08-23T11:40:06Z

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?

Then it's mtd's duty to manage them.

Thanks,
Miquèl