[PATCH 2/2] NAND on DM355: Add 4-bit ECC support for large page NAND chips

[David Brownell]

On Thursday 07 May 2009, vimal singh wrote:
> >> How about leaving bytes '4' and '5' for bad block marker, to support 16-bit
> >> NAND parts too.
> >
> > This 4-bit ECC engine only works for 8-bit wide parts ...
> > or are you suggesting that in case TI re-engineers that
> > engine in the future?
>
> I am omap guy and was not aware of that. In omap HW BCH
> ECC (4- or 8- bit correction)can work both kind of memories.

I'm somewhat more of an OMAP guy too -- just got sucked in to
trying to get a dm355 board to run off NAND in mainline-bound
code, and you can see where that landed me!

Last I looked at the OMAP2/OMAP3 NAND controller driver, it
didn't yet support most fancy hardware features, like ECC
using more than one bit or the prefetch/postwrite logic. 

One nice feature of that OMAP2/OMAP3 controller, beyond the
support for 8 bit ECC, is that it buffers the ECC syndrome
data so that it doesn't need NAND_ECC_HW_OOB_FIRST logic to
prevent trashing the manufacturer OOB markers.  The limit
of max 4K pages seems like not a big worry for now.

- Dave