[U-Boot-Users] PPC440GX reset command doesn't work

Andrew Wozniak awozniak at mc.com
Tue Jun 7 18:38:01 CEST 2005

Andrew Wozniak wrote:
> We have a custom PPC440GX board running a ported version of U-Boot based
> on the OCOTEA codebase. Most U-Boot commands are working - life is good.
> Except for the 'reset' command. The do_reset() source code at
> cpu/ppc4xx/cpu.c appears to be the function for doing the reset via the
> PPC "debug control register". The PPC manual shows that a cpu reset is
> possible thru this register, but I'm a PPC assembly newbee and need to
> figure it out the macros in the cpu.c source code.
> Just wondering if anyone else with a PPC440 target had any special
> modifications to make 'reset' work.

Ok, understand the assembly macro (except for the ::: "r3"). Must have
something to do with do_reset args?

Anyway, it appears that a PPC "system reset" does not work as
implemented via DBCR0 value 0x30000000.

If I change the value to 0x20000000 to do a "chip reset", the U-Boot
'reset' command works!

Is this an appropriate solution or might our hardware design have a flaw?

Thanks for all suggestions.

> Thank you.

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