MMU on the power pc 860

[Joe Hamman]

Hi Cecilia,

The comment on the Vision* tools' MMU support is incorrect.  The visionICE II and visionPROBE II support up to four regions of
translation.  You need to enter the details manually:

BKM>CF MMU LINUX
BKM>CF MMUA C0000000 0 FF000000

Use the CF MMUL to list the translation table entries currently defined in the tool.  You can get the details from WRS.  This will
allow you to use visionCLICK (or SingleStep w/vision) to debug anything statically linked into the kernel, from address 0 through
init.

Unless you have specific reasons not to switch, I recommend using the U-Boot bootloader.

Regards,
Joe


-----Original Message-----
From: owner-linuxppc-embedded at lists.linuxppc.org
[mailto:owner-linuxppc-embedded at lists.linuxppc.org]On Behalf Of Wolfgang
Denk
Sent: Saturday, December 21, 2002 2:59 PM
To: Muaddi, Cecilia
Cc: 'linuxppc-embedded at lists.linuxppc.org'
Subject: Re: MMU on the power pc 860



Dear Cecilia,

in message <885489B3B89FB6449F93E525DF78777F06451E at srvnt506.ALLOPTIC.COM> you wrote:
>
> I am porting the timeSys Linux to a custom Power PC 860 board.  Our board
> currently runs
> windRiver VxWorks.  I have modified the VxWorks bootrom to allow me to
> download a motorola
> hex record, and I have modified the timeSys bootcode
> arch/ppc/boot/mbx/misc.c:decompress_kernel

This is the generic Linux bootstrap loader, it has nothing to do with
TimeSys.

> loaded at:     00400000 0040C30C
> board data at: 004001C0 004001E4
> relocated to:  0040C0E8 0040C10C
> zimage at:     0040C30C 004BC440
> avail ram:     004BD000 00800000
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

This loos strange to me. Didn't you map RAM to 0x0000?

> I was able to use the VisionICE BDM to single step, and see it does jump to
> the address 0, and
> begin execute the instruction in kernel/arch/ppc/kernel/head_8xx.S:_start

You will not get far  with  the  Vision*;  better  use  a  tool  that
understands the MMU, like the Abatron BDI2000.

> I think the MMU TLB setup I have is not exactly correct, since the vxWorks
> BOOTROM does not
> initialize any MMU registers.  Can someone tell me if I need to initialize
> the M_TWB register for the

MMU should be switched off when starting Linux.

> to be the value for this register?  My physical memory map consists of RAM
> at location 0 to 0x1ffffff

This is not what I see above.

> and my IMMR is set to 0x2b00 0000

And this is plain wrong. The IMMR _must_ be mapped above 0xF0000000.



Best regards,

Wolfgang Denk

--
Software Engineering:  Embedded and Realtime Systems,  Embedded Linux
Phone: (+49)-8142-4596-87  Fax: (+49)-8142-4596-88  Email: wd at denx.de
Use C++ to confuse your enemies; use C to produce stable code.

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