On Tue, Apr 23, 2024 at 07:35:32PM +0200, Uwe Kleine-König wrote:
> From: Uwe Kleine-König <u.kleine-koenig@xxxxxxxxxxxxxx>
>
> To better describe why the BBM is at offset 2000 describe the full
> misinterpretation^Wmapping of the NAND memory that the i.MX hardware
> implements.
>
> Also adapt the comment to reality: A BBT is created automatically since
> commit 2ad441bb7e78 ("mtd: nand-imx: Create BBT automatically when
> necessary") which was included in v2020.03.0.
>
> Signed-off-by: Uwe Kleine-König <u.kleine-koenig@xxxxxxxxxxxxxx>
> ---
> drivers/mtd/nand/nand_imx.c | 30 +++++++++++++++++++++---------
> 1 file changed, 21 insertions(+), 9 deletions(-)
As the driver has been abandoned in favour for the Kernel driver I can't
apply this one.
Sascha
>
> diff --git a/drivers/mtd/nand/nand_imx.c b/drivers/mtd/nand/nand_imx.c
> index 23b9c52e0f76..77655daa4efe 100644
> --- a/drivers/mtd/nand/nand_imx.c
> +++ b/drivers/mtd/nand/nand_imx.c
> @@ -1139,20 +1139,32 @@ static int __init mxcnd_probe_dt(struct imx_nand_host *host)
> * 512b data + 16b OOB +
> * 512b data + 16b OOB
> *
> + * So the mapping between original NAND addressing (as intended by the chip
> + * vendor) and interpretation when accessed via the i.MX NAND controller is as
> + * follows:
> + *
> + * original | i.MX
> + * ---------------------+---------------------
> + * data 0x0000 - 0x0200 | data 0x0000 - 0x0200
> + * data 0x0200 - 0x0210 | oob 0x0000 - 0x0010
> + * data 0x0210 - 0x0410 | data 0x0200 - 0x0400
> + * data 0x0410 - 0x0420 | oob 0x0010 - 0x0020
> + * data 0x0420 - 0x0620 | data 0x0400 - 0x0600
> + * data 0x0620 - 0x0630 | oob 0x0020 - 0x0030
> + * data 0x0630 - 0x0800 | data 0x0600 - 0x07d0
> + * oob 0x0000 - 0x0030 | data 0x07d0 - 0x0800
> + * oob 0x0030 - 0x0040 | oob 0x0030 - 0x0040
> + *
> * This means that the factory provided bad block marker ends up
> - * in the page data at offset 2000 instead of in the OOB data.
> + * in the page data at offset 2000 = 0x7d0 instead of in the OOB data.
> *
> - * To preserve the factory bad block information we take the following
> - * strategy:
> - *
> - * - If the NAND driver detects that no flash BBT is present on 2k NAND
> - * chips it will not create one because it would do so based on the wrong
> - * BBM position
> - * - This command is used to create a flash BBT then.
> + * If the NAND driver detects that no flash BBT is present on a 2k NAND
> + * chip it will create one automatically in the assumption that the NAND is
> + * pristine (that is completely erased with only vendor BBMs in the OOB) to
> + * preserve factory bad block information.
> *
> * From this point on we can forget about the BBMs and rely completely
> * on the flash BBT.
> - *
> */
> static int checkbad(struct nand_chip *chip, loff_t ofs)
> {
>
> base-commit: f40319c8e157c90117d32aed1dae5549a723c63e
> --
> 2.43.0
>
>
>
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