[U-Boot] NAND flash question

[ANDY KENNEDY]

> -----Original Message-----
> From: u-boot-bounces at lists.denx.de [mailto:u-boot-bounces at lists.denx.de] On Behalf Of Peter Barada
> Sent: Thursday, September 19, 2013 3:26 PM
> To: u-boot at lists.denx.de; Peter Barada
> Subject: Re: [U-Boot] NAND flash question
> 
> On 09/19/2013 04:04 PM, ANDY KENNEDY wrote:
> > All,
> >
> > We have a design that has NAND as a secondary device (not the boot
> > device).  The last four pages of the NAND flash are reported as bad.
> > Should this be true for all NAND flash devices we have?
> >
> >
> No, I wouldn't think so.  Manufacturers qualify their parts and mark bad
> blocks found during qualification testing.  Most data sheets indicate
> that the number of bad blocks marked bad during manufacturer is below a
> set percentage(if above thent he part is rejected).  Some parts that are
> meant to be used during boot (such as NAND meant for OMAP parts) will
> have certain blocks that are guaranteed good (i.e. the boot blocks).
> Past that bad blocks could be anywhere in a particular device.
> 

Okay, well, next question:  So on EVERY unit we have designed with a
NAND flash, when u-Boot reads the NAND flash it reports that it couldn't
locate a bad block table and states that it cannot read the last four
pages of the flash.  Next, when one does a 'nand bad' on these boards,
these last four pages are reported by u-Boot as bad.  Looking at the
code, we believe that this is by design.  Is that correct?  Has anyone
else done a 'nand bad' on a board and seen the same information?

Thanks again for any information you can provide,

Andy