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

[Bean Huo 霍斌斌 (beanhuo)]

> >> Hi, Andrea and Boris
> >> This is a historical subject, and talked before.
> >>  From our field issues, 8 bits of bad block mark for MLC NAND is not
> reasonable.
> >> Because of bitflip on bad block mark, regard one good block as a bad
> >> block is common Issue. Especially first time boot after reflow. The
> >> solution is modified this value to 4 for MLC NAND by hand, and the factory
> BB mark is “0x00”.
> >> I think, 4 bits for MLC NAND make sense.
> >
> >
> > I'm tempted to say "let's start with this value and see what happens
> > in real world". If we want to be a bit more conservative we could
> > decide to chose 2, which should address most problems too (during my
> > tests, I never seen such a huge concentration of bitflips in the same byte).
> >
> > Brian, Andrea, what do you think?
> >
> 
> I'm currently using 4 on my custom kernel.
> On all datasheet I've seen factory bad block marker is 0x00 and the same is
> (AFAIK) used by MTD to mark bad blocks.
> 
> Kind Regards,
> 
> --
> 
> Andrea SCIAN
> 
> DAVE Embedded Systems
Micron factory bad block marker of all NAND is 0x00.
But for good bad, after reflow, most good block will be
made mistake of think bad block just Because of bitflips 
on marker bytes. I want to clarify this is first time boot.
Currently no bad block table.