[U-Boot-Users] skipping bad blocks when erasing nand

[Stefan Roese <sr@denx.de>]

Hello Wolfgang,

On Friday 14 July 2006 10:28, Wolfgang Denk wrote:
> in message <200607140914.07427.sr@denx.de> you wrote:
> > I am "voting" for David's implementation, since bad blocks are "normal"
> > on NAND chips. And if I remember correctly, the "old" U-Boot NAND driver
> > also just skipped the bad block upon erasing without reproting them.
>
> I'm sorry, but I disagree. This code is not coming out of  thin  air.
> It is a more or less vrbatim copy of the corresponding Linux MTD NAND
> code, see "drivers/mtd/nand/nand_base.c" in your Linux kernel tree.
>
> In U-Boot, we have the additional #define NAND_ALLOW_ERASE_ALL  which
> can be enabled if you don't like this behaviour.
>
> If you believe that the U-Boot behavious is wrong, then the Linux MTD
> driver would be wrong, too. In this case discussion  should  continue
> on the MTD mailing list.

I find it hard to believe that a linux NAND erase operation will stop upon 
reaching a bad block. But you are right: the code in question is the same in 
the current linux mtd driver. From my experience, I never had problems 
erasing NAND flash devices (from U-Boot & linux) which had bad blocks.

> As long as I don't see any changes to the current MTD Linux code  you
> will  need  really good arguments to talk me into changing the U-Boot
> code.

I see. You have a good point here. This needs some testing on a device with 
bad blocks. "Unfortunately" the device on my desk has no bad blocks at all:

=> nand bad

Device 0 bad blocks:

Perhaps somebody else can jump in here and test the current linux mtd driver 
behavior on a device with bad blocks. Thanks.

Best regards,
Stefan