[U-Boot] booting from half of NAND, and mounting jffs on other half of NAND

[John Stile <john@stilen.com>]

On Fri, 2013-02-01 at 12:47 -0800, John Stile wrote:
> Using uboot 2013.01, booting from NAND, I am having difficulty
> understanding how partitions (areas of NAND) work.
> 
> I have written to NAND in the following layout:
> 0x0000000 at91bootstrap1
> 0x0020000 uboot1
> 0x0060000 uboot-env1
> 0x0200000 kernel1
> 0x0400000 rootfs1
> 0x8000000 at91bootstrap2
> 0x8020000 uboot2
> 0x8060000 uboot-env2
> 0x8200000 kernel
> 0x8400000 rootfs2
> 
> I hacked at91bootstrap to load into ram a uboot and an environment, and
> I can stop uboot and 'env print' to see that the proper environment was
> loaded.
> 
> While booted into linux on one rootfs I would like to access the other
> rootfs. 
> 
> I try tried to use the mtdparts parameter that describes the partitions
> of NAND, but this isn't working, and I don't think I understand what it
> should be.
> 
> First problem, or signs that I'm doing something wrong is my mtdparts
> parameter.  If I try to edit on the interactive uboot shell, the line is
> too long to change, so I have to write flash for each test.  That can't
> be correct?  Regardless of which uboot environemnt I use, this is what I
> am trying to use to describe my NAND layout:
> mtdparts=at91_nand:128k(bootstrap1)ro,256k(uboot1)ro,128k(env1)ro,1536K(unused),2M(linux1),124M(rootfs1),128k(bootstrap2)ro,256k(uboot2)ro,128k(env2)ro,1536k(unused2),2M(linux2),124M(rootfs2)
> What should I use here?
> 
> Second problem is what to use for root=/dev/mtdblock*.  I have tried
> many things, but most lead to an inability to find the file system, and
> since each test requires re-writing NAND flash it takes a really long
> time to debug.  What should I use here?

I solved my own problem.
bootargs  mtdparts= addressed the wrong name for nand.  
I had at91_nand.
The kernel messages said, "Creating 3 MTD partitions on "atmel_nand":".
Changing at91_nand to atmel_nand, my partitions are visible.