i.MX21 ADS NAND flash bad blocks scan. Barebox vs Linux

[Sascha Hauer]

On Thu, Mar 13, 2014 at 08:44:08PM +0000, Cristiano De Alti wrote:
> Hi,
>   I'm probably posting to the wrong list since this is Linux issue.
> I'm still trying to revive this old board.
> 
> This board has a 64MBi Samsung NAND flash that is detected both by Barebox
> (recent snapshot) and Linux 3.4.77.
> 
> The issue is that, while the bad blocks scan takes a negligible time on
> Barebox, it takes 10 minutes to complete on Linux.
> They both detect block 0 as a bad block. This is strange since it is
> guaranteed to be good by the manufacturer but I've read the OOB data with
> barebox and it's marked ad bad. I found this board in the lab and don't know
> how it was used before.
> 
> Barebox code, nand_imx.c, and Linux code, mxc_nand.c, are similar but not
> identical of course. I also think that Linux code was contributed by
> Pengutronix so this is the reason I'm asking here.
> 
> I've enabled debug statements in Linux code and added my own statements.
> As said, scan completes, everything looks OK but it is very slow.

I assume this is a 512 byte page Nand, right? In this case you shouldn't
have any issues with bad block marker swapping.
An issue could be that one party uses a bad block table wereas the other
scans each time. I recommend using a bad block table for barebox and the
kernel.
Maybe somebody has marked block 0 as bad to see whether the ROM Code
handles this properly.

Sascha

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