[PATCH 1/2] mtd: nand: use a lower value for badblockbits when working with MLC NAND

[Boris Brezillon]

Hi Andrea,

On Fri,  6 Mar 2015 13:12:17 +0100
rnd4 at dave-tech.it wrote:

> From: Andrea Scian <andrea.scian at dave.eu>
> 
> MLC NANDs have more bit flips that SLC. When looking for bad block
> marker we have a lot of false positive if we check for the whole byte. To
> avoid this tolerate a few (4 here) bit flips for byte.

I'm not sure sure we want to accept 4 bitflips for all MLC NANDs. IMHO
this value should be chip dependent.
I know there is currently no way to retrieve this information, so here
are two suggestions:

1/ make this value depend on the required NAND ecc strength
(badblockbits = ecc_strength / 10 ?)
2/ let each controller change this value after nand_scan_ident
depending on the detected chip until we find a generic solution to
select this value

Best Regards,

Boris

-- 
Boris Brezillon, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com