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Re: again ROMRAM startup on SA1100



The PID can't do MMU tricks either... it is a good idea... you build up
the post MMU enabled memory map with the new image in RAM and flicking the
memory map switch puts the right code under the program counter...

Dave.



On Mon, 11 Jun 2001, Gary Thomas wrote:

> 
> On 11-Jun-2001 Andrew Lunn wrote:
> >  > The b __new_pc is important. This is where is jumps from ROM to
> >> > RAM. Do you have an equivelent somewhere? You have to be carefull
> >> > about the address you are branching to. You dont want to make a
> >> > relative jump of 1 instruction, since you still end up on ROM. You
> >> > have to make big jump down into RAM. I just copied this code from Dave
> >> > Airlie.
> >> 
> >> I believe that it happens implicitly when the MMU gets turned on - pretty slick.
> > 
> > ?
> > 
> > Could you expand on that. I don't see how this works.
> 
> It probably depends on which platform he's using.  On the EBSA, I'm not sure
> that it will work because the setup of the MMU is way too late. On the SA11x0
> though, the MMU is setup in PLATFORM_SETUP and the last step is to enable the
> MMU, including changing the address space which is just like your code.
> 
> Look at hal/arm/sa11x0/ipaq/current/include/hal_platform_setup.h for an example.
> 

-- 
      David Airlie, Software Engineer, Parthus Technologies plc.,
       Mary Rosse Centre, National Tech Park, Limerick, Ireland.
   t: +353-61-508116 / f: +353-61-508101 / David.Airlie@parthus.com


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