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

[Bear]

hi,
> 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.

Thanks for your help. Now I have already wrote the newer version of 
u-boot into NAND Flash and boot from it!
Do you mind me to ask some more questions?
Where is environment stored? If I save the NAND-version u-boot's 
environment, will it overwrite the one of NOR-version u-boot?

Thanks.


On 100/6/7 上午 02:50, Scott Wood wrote:
> 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
>
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