[U-Boot] u-boot NAND memory use

[Scott Wood]

On Mon, 4 Oct 2010 14:41:55 -0400
Michael Galime <mgalime at datacomsystems.com> wrote:

> Hi.
> 
>  
> 
> I have a board which I am using Uboot on.  Arm9, nand flash, etc.  
> 
>  
> 
> Currently the board has the uboot image and the ENV in one partition,
> size 0x00200000.
> 
>  
> 
> I would like to make another partition for the ENV so that if I have to
> upgrade Uboot I don't lose my ENV.
> 
>  
> 
> What size does the partition have to be?  

At a minimum, one block, so you can erase it independently of
everything else.

You may want to use CONFIG_ENV_RANGE to assign multiple blocks in case
one of the blocks is bad, or you may want to use the env.oob mechanism
to dynamically choose a good block for the environment when each
board's NAND is first programmed (but be aware that you'll have to
run "nand env.oob" again whenever you reflash block zero).

> And where in the Uboot code do I change the memory location and size for
> the env so I can rebuild Uboot and start using a new ENV partition?

Assuming you mean the location in NAND flash, and not in memory, look
in your board config header file.  You should find CONFIG_ENV_OFFSET,
CONFIG_ENV_SIZE, etc.

-Scott