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Re: in mips how to change the start address to the new second boot load

To: nagalakshmi veeramallu <lucky.veeramallu@gmail.com>
Subject: Re: in mips how to change the start address to the new second boot loader ?
From: Florian Fainelli <florian@openwrt.org>
Date: Thu, 23 Apr 2009 11:01:25 +0200
Cc: Geert Uytterhoeven <geert@linux-m68k.org>, "Kevin D. Kissell" <kevink@paralogos.com>, "M. Warner Losh" <imp@bsdimp.com>, linux-mips@linux-mips.org
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Hi,

Le Tuesday 21 April 2009 16:20:48 nagalakshmi veeramallu, vous avez écrit :
> Hi,
> will this approach work? if i used "start" environmental variable will it
> go to new boot loader address directly.

Yamon also has a start environnment variable which is used to do something 
without user-intervention. I do not know cmon, but assuming it behaves 
similarly, you might want to set the start variable to something like: "go 
0xdeadbeef". And make sure your code starts at 0xdeadbeef for instance.

That way, you keep cmon on the flash and use it to jump to an arbitrary 
location, which is anyway, what would be done if you used cmon to boot Linux 
for instance.

>
> Regards,
> Lucky
>
> On Tue, Apr 21, 2009 at 7:40 PM, Geert Uytterhoeven 
<geert@linux-m68k.org>wrote:
> > On Tue, Apr 21, 2009 at 15:46, nagalakshmi veeramallu
> >
> > <lucky.veeramallu@gmail.com> wrote:
> > > hi,
> > >          --          if we set environmental variable “start” as “go
> > > new_address”, will it go directly to the new bootloader in the next
> > > power-on.
> > > what about using system environmental "start" ,can you tell me at which
> > > context after power on environmental variables come onto picture.
> >
> > Environment variables are parsed by the boot loader, whose code resides
> > at, guess what, 0x1fc00000...
> >
> > > On Tue, Apr 21, 2009 at 6:55 PM, Kevin D. Kissell
> > > <kevink@paralogos.com>
> > >
> > > wrote:
> > >> nagalakshmi veeramallu wrote:
> > >>
> > >> -           Mips atlas board has jumper  which will redirect accesses
> >
> > from
> >
> > >> “Bootcode” range to either “Monitor flash” (0x1e000000) or the upper
> > >> 4MB
> >
> > of
> >
> > >> “System flash” (0x1dc00000) based on jumper settings. if my kmc board
> >
> > have
> >
> > >> some jumper like this, can I redirect the start address.
> > >>
> > >> Of course, what is really happening there is that the Atlas boot ROM
> > >> has
> >
> > a
> >
> > >> vector at 0x1fc00000 which reads the jumper and jumps to one address
> > >> or
> >
> > the
> >
> > >> other depending on the jumper setting. If you control what is in ROM
> > >> at 0x1fc00000 and you have a software-readable jumper on your KMC
> > >> board,
> >
> > you
> >
> > >> can do the same thing.
> > >>
> > >>           Regards,
> > >>
> > >>           Kevin K.
> >
> > --
> > Gr{oetje,eeting}s,
> >
> >                                                Geert
> >
> > --
> > Geert Uytterhoeven -- There's lots of Linux beyond ia32 --
> > geert@linux-m68k.org
> >
> > In personal conversations with technical people, I call myself a hacker.
> > But
> > when I'm talking to journalists I just say "programmer" or something like
> > that.
> >                                                            -- Linus
> > Torvalds



-- 
Best regards, Florian Fainelli
Email : florian@openwrt.org
http://openwrt.org
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