NAND OOB data.

[Atlant Schmidt]

Andy:

> All the other boards apparently are all good
> (is that normal?),

  It happens; we're in the midst of switching from
  MLC to SLC flash and while I'd never expect that
  from our MLC parts, it seems to be pretty-commonly
  true for our SLC parts.


> Okay, so how do I (without the luxury of u-boot), in user or
> kernel space, wipe the OOB data?  I'm looking at the code for
> u-boot nand_erase_nand right now.  I mean, I'm not above writing
> an userspace app that will do kernel level work for me.  I'm okay
> with using /dev/mem and screwing with stuff.  Am I on the right
> track?  I mean, I hate to go down this road if I'm just heading
> for a dead-end.

  I think there's enough "stuff" available simply through
  /dev/mtd... to let you do any of this. I do a lot of
  Flash manipulation simply using Perl, mtdinfo, ubinfo
  and the /dev/mtd... and /dev/ubi... devices.

  (Unfortunately, I can't share any of that code.)

                               Atlant

-----Original Message-----
From: ANDY KENNEDY [mailto:ANDY.KENNEDY at adtran.com]
Sent: Monday, June 20, 2011 13:54
To: Atlant Schmidt; linux-mtd at lists.infradead.org
Subject: RE: NAND OOB data.

> -----Original Message-----
> From: Atlant Schmidt [mailto:aschmidt at dekaresearch.com]
> Sent: Monday, June 20, 2011 6:14 AM
> To: ANDY KENNEDY; linux-mtd at lists.infradead.org
> Subject: RE: NAND OOB data.
>
> Andy:
>
>   If you don't have the old bad block information saved
>   away somewhere (a bad block table, a scrap of paper,
>   etc.), then you *CAN'T* completely recover from this
>   situation; the original bad block data for that chip
>   is probably irretrievably lost.*

All the other boards apparently are all good (is that normal?), but,
I'm not worried about the NAND having KNOWN bad blocks as this board
is supposed to be mine.

>
>   You can mark all the blocks as "good", of course, and
>   then exercise the chip a bit, marking bad blocks as you
>   go. You'll probably never achieve the same depth of
>   testing that the factory was able to achieve using
>   voltage, temperature, and timing margining, of course,
>   but the results may be "good enough".
>
>                           Atlant

Okay, so how do I (without the luxury of u-boot), in user or
kernel space, wipe the OOB data?  I'm looking at the code for
u-boot nand_erase_nand right now.  I mean, I'm not above writing
an userspace app that will do kernel level work for me.  I'm okay
with using /dev/mem and screwing with stuff.  Am I on the right
track?  I mean, I hate to go down this road if I'm just heading
for a dead-end.

Andy


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