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

Miquel Raynal
2023-08-23T08:46:43Z

Hi Martin,

mmkurbanov@sberdevices.ru wrote on Tue, 22 Aug 2023 19:57:11 +0300:

> Hi Miquel,
>
> On 22.08.2023 16:35, Miquel Raynal wrote:
> > Hi Martin,
> >
> > mmkurbanov@sberdevices.ru wrote on Tue, 22 Aug 2023 15:25:34 +0300:
> >
> >> The first 4 bytes are reserved for bad block data.
> >
> > Are you sure about that? I've never seen 4-bytes BBM.
>
> Yes, I'm sure. I have checked in all the relevant datasheets:
> ----------------------------------------------------------------------------------
> | Name | Max Byte | Min Byte | Area | Description |
> | | Address | Address | | |
> |--------------------+----------+----------+---------+---------------------------|
> | MT29F2G01ABAGD [1] | | | | |
> |--------------------| | | | |
> | MT29F2G01ABBGD [2] | | | | |
> |--------------------| 803h | 800h | | |
> | MT29F1G01ABAFD [3] | | | | |
> |--------------------| | | | |
> | MT29F4G01ADAGD [4] | | | | |
> |--------------------+----------+----------| Spare 0 | Reserved (bad block data) |
> | MT29F4G01ABAFD [5] | | | | |
> |--------------------| | | | |
> | MT29F4G01ABBFD [6] | | | | |
> |--------------------| 1003h | 1000h | | |
> | MT29F8G01ADAFD [7] | | | | |
> |--------------------| | | | |
> | MT29F8G01ADBFD [8] | | | | |
> ----------------------------------------------------------------------------------
>
> Note: to view the datasheet on the Micron (https://www.micron.com/) website, you need
> to register.

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.

> Links:
> [1] https://datasheet.lcsc.com/lcsc/1912111437_Micron-Tech-MT29F2G01ABAGDWB-IT-G_C410863.pdf - page 45
> [2] https://www.micron.com/-/media/client/global/documents/products/data-sheet/nand-flash/70-series/m79a_2gb_1_8v_nand_spi.pdf - page 46
> [3] https://datasheet.lcsc.com/lcsc/2209201030_Micron-Tech-MT29F1G01ABAFDWB-IT-F_C2905686.pdf - page 46
> [4] https://www.micron.com/-/media/client/global/documents/products/data-sheet/nand-flash/70-series/m79a_ddp_4gb_3v_nand_spi.pdf - page 46
> [5] https://www.micron.com/-/media/client/global/documents/products/data-sheet/nand-flash/70-series/m70a_4gb_3v_nand_spi.pdf - page 47
> [6] https://www.micron.com/-/media/client/global/documents/products/data-sheet/nand-flash/70-series/m70a_4gb_1_8v_nand_spi.pdf - page 49
> [7] https://www.micron.com/-/media/client/global/documents/products/data-sheet/nand-flash/70-series/m70a_ddp_8gb_3v_nand_spi.pdf - page 48
> [8] https://www.micron.com/-/media/client/global/documents/products/data-sheet/nand-flash/70-series/m70a_ddp_8gb_1_8v_nand_spi.pdf - page 48
>

Thanks,
Miquèl