[U-Boot] How to boot a newer version of u-boot from a older one?

[Scott Wood]

On Sun, 5 Jun 2011 14:54:06 +0800
Lingfeng Xiong <xionglingfeng at gmail.com> wrote:

> hi there,
> I bought a Freescale MPC8313E-RDB some days before. The version of 
> u-boot on that board is quite old and I wanna run a newer one. I have 
> already built the latest git version of u-boot for that board. But I 
> found there are several configuration files:
> > MPC8313ERDB_33               powerpc     mpc83xx     mpc8313erdb         freescale      -           MPC8313ERDB:SYS_33MHZ
> > MPC8313ERDB_66               powerpc     mpc83xx     mpc8313erdb         freescale      -           MPC8313ERDB:SYS_66MHZ
> > MPC8313ERDB_NAND_33          powerpc     mpc83xx     mpc8313erdb         freescale      -           MPC8313ERDB:SYS_33MHZ,NAND_U_BOOT
> > MPC8313ERDB_NAND_66          powerpc     mpc83xx     mpc8313erdb         freescale      -           MPC8313ERDB:SYS_66MHZ,NAND_U_BOOT
> 
> My board is Rev C and all switches are in factory default, could you 
> tell me which configuration should I use?

MPC8313ERDB_33 is for booting from NOR, which is the default.

The "66" targets are for an earlier version of the board that had a 66MHz
crystal rather than 33MHz.

> For I have no USBTAP, there are no way for me to flush either NOR Flash 
> or NAND Flash, so I am afraid if I install my u-boot to NOR Flash and 
> that u-boot cannot run correctly, my board would be unavailable.

Your best option is probably to build MPC8313ERDB_NAND_33, and put it in
NAND flash.  Then you can change the board switches to boot from NAND, and
if it doesn't work, switch them back to NOR which you've left unmodified.

Once you have a working NAND, you can replace the NOR image, switching
back to NAND if the new NOR image is broken.

And of course be careful not to write to the wrong flash, and destroy your
backup boot source.

-Scott