[U-Boot-Users] MMU and Linux kernel booting

llandre r&d2 at dave-tech.it
Tue Dec 7 17:13:28 CET 2004

> > I'm working with a custom hardware based on Cirrus Logic EP9315 processor.
> > As the on-chip SDRAM controller is unable to map the memory in
> > contiguous regions, I have to use the MMU to do that.
>... if you need it. Maybe one bank of memory is  sufficient  for  the
>operation of U-Boot?

It is definitively sufficient for U-Boot/Linux but I think
it is not for (please don't blame me) WindowsCE (brrrrr!).

> > 2) The second questions refers to memory tags. They should describe 
> _physical_
> > mapping, right? If this is correct, the bd->bi_dram fields should be 
> extended
> > in order to describe both physical and virtual regions. Does it make sense?
>Why would you need virtual addresses? U-Boot does not need these  for
>operation, and Linux will not use these anyway.

For example U-Boot should let the user to use one virtual and contiguous
memory region (for this purpose I suggest to introduce something
like bd->bi_dram_v). For "regular" operations, it could use the
existing bd->bi_dram fields (for example to set up the memory
tags for the kernel).



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