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

Wolfgang Denk wd at denx.de
Tue Dec 7 16:12:24 CET 2004

In message < at> you wrote:
> 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?

> 1) In my understanding the function cleanup_before_linux 
> (cpu/arm920t/cpu.c) is supposed to
> perform this opearation but it does not. Is this the right place to turn 
> MMU off?


> 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.

Best regards,

Wolfgang Denk

Software Engineering:  Embedded and Realtime Systems,  Embedded Linux
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de
You could end up being oddly sad and full of a strange, diffuse  com-
passion  which would lead you to believe that it might be a good idea
to wipe out the whole human race and start again with amoebas.
                                 - Terry Pratchett, _Guards! Guards!_

More information about the U-Boot mailing list