[U-Boot-Users] MPC8540 Custom Board _start_e500

Dan Malek dan at embeddededge.com
Thu Jan 13 19:00:36 CET 2005

On Jan 13, 2005, at 11:28 AM, Jeff Stevens wrote:

> I am in the process of bringing up a custom SBC with
> an MPC8540.  I am using the BDI2000 to debug.  When I
> trace through the code, the system halts in
> _start_e500 in start.S where it invalidates MMU L1/L2.

Not surprised.  Debugging the e500 core at this level
is much more challenging than classic PowerPC cores
due to the MMU and debug implementation.  I never
found a way to fully single step through the entire
initialization phase, you have to go as far as you
can with the debugger, inspect the next bunch of code
by hand, assume it works, and then trap the processor
at a later time.  Any time you stop the e500 core (and
you really never stop it, the BDI2000 kinda makes it
appear that way) you have to also stop and think
about the environment at that time, if you can continue
from that point, and then gather the necessary information.
In most cases, you can single step the e500 just like
a classic core, but anything related to MMU change
is likely to cause a more challenging debug environment.

I have debugged several e500 core boot roms with
the BDI2000, and you will get the hang of it.  You
just have to change your methods a little, and most
of all stop thinking the processor core or the debugger
isn't working correctly.  They are both probably doing
exactly what you told them to do.

Good Luck! :-)

	-- Dan

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