mtd: nand: mxc: oobfree layout?

mtd: nand: mxc: oobfree layout?

[Benoît Thébaudeau]

Dear Sascha Hauer,

I've seen in the history of mxc_nand.c that you have worked on the
nand_ecclayout structs. The following things look abnormal. Can you confirm?
 - nandv1_hw_eccoob_smallpage and nandv2_hw_eccoob_smallpage:
    * Why are bytes 0 and 1 in oobfree? These bytes are used for bad block
      information on the 16-bit variants of these 512-byte-page NANDs.
 - nandv1_hw_eccoob_largepage:
    * According to the i.MX31 reference manual, the BI bytes of the spare area
      buffers are not free to use. So why are bytes 5, 11, 27, 43 and 59 in
      oobfree? On the contrary, if this note is a mistake in the RM, then why
      are bytes 21, 37 and 53 not in oobfree?
 - nandv2_hw_eccoob_smallpage, nandv2_hw_eccoob_largepage and
   nandv2_hw_eccoob_4k:
    * Why is byte 6 not in oobfree?

Best regards,
Benoît

Re: mtd: nand: mxc: oobfree layout?

[Sascha Hauer]

On Tue, Nov 20, 2012 at 09:05:18PM +0100, Benoît Thébaudeau wrote:
> Dear Sascha Hauer,
> 
> I've seen in the history of mxc_nand.c that you have worked on the
> nand_ecclayout structs. The following things look abnormal. Can you confirm?
>  - nandv1_hw_eccoob_smallpage and nandv2_hw_eccoob_smallpage:
>     * Why are bytes 0 and 1 in oobfree? These bytes are used for bad block
>       information on the 16-bit variants of these 512-byte-page NANDs.

This is probably a bug. Very few people seem to use 16bit flashes.

>  - nandv1_hw_eccoob_largepage:
>     * According to the i.MX31 reference manual, the BI bytes of the spare area
>       buffers are not free to use. So why are bytes 5, 11, 27, 43 and 59 in
>       oobfree? On the contrary, if this note is a mistake in the RM, then why
>       are bytes 21, 37 and 53 not in oobfree?
>  - nandv2_hw_eccoob_smallpage, nandv2_hw_eccoob_largepage and
>    nandv2_hw_eccoob_4k:
>     * Why is byte 6 not in oobfree?

Probably bugs aswell. Most people do not use filesystems requiring OOB
data anymore, so bugs may stay uncovered for longer.

Sascha


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