[U-Boot] NAND flash - bad blocks

[Scott Wood]

On 01/10/2013 01:56:30 AM, Dimitar Penev wrote:
> Hello,
> 
> First of all sorry if this question was already answered here.
> 
> We are sourcing some K9F8G08U0M-PIB0 NAND flash devices.
> On the first erase in uboot 2011.09 I got bunch of mostly consecutive  
> bad blocks.
> According to the datasheet we should get not more then 80 bad blocks  
> for our chip
> but I get something like 240 bad blocks for most of the NAND chips.
> 
> I seems to be able to fix this using the following procedure:

Call your NAND vendor and complain?

After making sure that there's nothing wrong with your NAND driver or  
controller that causes the OOB to be read incorrectly.  Did you do  
anything to the NAND chip prior to this "first erase"?  In particular,  
did you write to the OOB?

> In uboot
> uboot>nand scrub.chip
> 
> In uboot
> uboot>nand erase.chip clean
> at this point I get usually 1,2 bad blocks which looks normal to me.

You're not fixing anything -- you're wiping out all bad block  
information.  Those "1,2 bad blocks" are not actually bad blocks, but  
are the bad block table which appears "bad" to reserve it.  These  
should be at the end of flash.  Or, possibly, they're blocks that  
happen to be damaged in a way that prevents the bad block marker from  
becoming 0xff.

> In Linux we have few mtd partitions on this NAND chip.
> Unmount all of them and for all of them :
> linux>nandtest -m /dev/mtdx
> Usually this doesn't add any new badblocks on top of what I get on  
> nand erase in uboot,
> but I really haven't tested that much device to say.
> 
> After this procedure the NAND flash seems to work fine.
> Do you think this is reliable way?

No.

-Scott