Re: [microblaze-uclinux] Question related to u-boot

[Michal Simek <michal.simek@xxxxxxxxxxxxx>]

John Williams wrote:
> On Thu, Jul 23, 2009 at 6:46 PM, Kulkarni, Mayuri
> <Mayuri.Kulkarni@xxxxxxx <mailto:Mayuri.Kulkarni@xxxxxxx>> wrote:
> 
>     Hi,
>     I have the following problem definition for u-boot usage for
>     Petalinux running on Microblaze soft CPU:
>      
>     - I have a system without flash wherein I am copying the Petelinux
>     kernel image.ub into memory through xmd and then invoking u-boot.
>     Now if I have another kernel image at a second location in memory, I
>     want u-boot to let me choose which image to boot.
> 
> 
> u-boot can boot an image from any address - you just change the value
> passed to the "bootm" command.

but you can't rewrite u-boot

> 
> How that value is derived is up to you.  u-boot has some basic scripting
> and conditional execution capabilities - see the manual at www.denx.com
> <http://www.denx.com>

Just minor fixup denx.de.




>  
> 
>      
>     - After this stage, is it possible to programmatically change the
>     default image from which u-boot can boot? I want to be able to copy
>     an upgraded kernel image either into the flash or memory and make
>     u-boot use the upgraded image the next time the system reboots.
> 
> 
> I thought you just said you have a system without flash?
> 
> Anyway, with flash, you could adjust the uboot environment with
> "setenv", then use "saveenv" to save it to flash.  Next time u-boot
> starts, it gets the saved environment.
> 
> Without flash, you'll need something like a DIP switch on the board, and
> have u-boot query that to make its decision about which image to boot.
>  
> 
>     I have checked the auto-boot script but don’t see how we can change
>     the script or issue a u-boot setenv-like command through another
>     process in a running system.
> 
> 
> The problem seems to be your lack of persistent storage more than
> anything else.  We've configured u-boot in PetaLinux to cover the most
> standard situations - what you are describing is far from standard, but
> likely to be achievable in some way.
> 
> It would help to know more about what you are trying to achieve, in the
> broader sense.  There is almost certainly an easier way to do whatever
> it is you are trying to achieve.

This was discussed many times on u-boot mailing list. You should look there.

Regards,
Michal

> 
> Regards,
> 
> John
> -- 
> John Williams, PhD, B.Eng, B.IT <http://B.IT>
> PetaLogix - Linux Solutions for a Reconfigurable World
> w: www.petalogix.com <http://www.petalogix.com>  p: +61-7-30090663  f:
> +61-7-30090663

-- 
Michal Simek, Ing. (M.Eng)
PetaLogix - Linux Solutions for a Reconfigurable World
w: www.petalogix.com p: +61-7-30090663,+42-0-721842854 f: +61-7-30090663
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