Can not access memory after turning MMU on

Can not access memory after turning MMU on

[Freddy Lugo]

Hi,

After turning the MMU (turn_on_mmu) the next memory
access instruction (stwu) can not be translated, the
memory can not be accessed and the system halt.  I
check the list archives and there are references to
set the Debug Enable Register (DER) to an
"appropriate" value.  I am working with the MPC750 and
in the Users Manual I can't find any reference to such
register.  Also I checked my bdi2000 (in case it was a
register on the bdi) and I didn't found anything.

This register exists or has its counterpart on the
MPC750?  Besides the DER value, there are other
methods to work and find the problem?

Thanks,

Freddy Lugo

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Re: Can not access memory after turning MMU on

[Paul White]

Hi Freddy,

What address is it trying to address next?  It needs to be sure its in the
range of the BATS setup by initial_bats, which maps the first 16Meg of
memory to KERNELBASE.
After turning MMU on, it should finish relocating the kernel.  Is this the
part thats failing?

I'm referencing arch/ppc/kernel/head.S above.

Paul W.

At 01:41 PM 5/7/2001 -0700, Freddy Lugo wrote:
>
>Hi,
>
>After turning the MMU (turn_on_mmu) the next memory
>access instruction (stwu) can not be translated, the
>memory can not be accessed and the system halt.  I
>check the list archives and there are references to
>set the Debug Enable Register (DER) to an
>"appropriate" value.  I am working with the MPC750 and
>in the Users Manual I can't find any reference to such
>register.  Also I checked my bdi2000 (in case it was a
>register on the bdi) and I didn't found anything.
>
>This register exists or has its counterpart on the
>MPC750?  Besides the DER value, there are other
>methods to work and find the problem?
>
>Thanks,
>
>Freddy Lugo
>
>
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Re: Can not access memory after turning MMU on

[Dan Malek]

Freddy Lugo wrote:

> This register exists or has its counterpart on the
> MPC750?  Besides the DER value, there are other
> methods to work and find the problem?

You are way, way, way lost...........You can't be building MPC8xx
code and expecting it to run on the 750.  You need to select a
kernel configuration that enables 6xx/7xx/74xx processors and
a CHRP reference design.


	-- Dan

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