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

[Andrea Scian <rnd4@dave-tech.it>]

Sorry for the later feedback, but unfortunately I had to move to other
stuff before coming back to this topic

Il 15/03/2015 10:07, Boris Brezillon ha scritto:
> Hi Andrea,
> 
> On Fri,  6 Mar 2015 13:12:17 +0100
> rnd4@dave-tech.it wrote:
> 
>> From: Andrea Scian <andrea.scian@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 agree

> I know there is currently no way to retrieve this information,

For this reason I just put a hardcoded value.

> 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

I'll try to figure out how to solve this
Any suggestion is welcome!

Regards,

-- 

Andrea SCIAN

DAVE Embedded Systems