Subject: Re: Motorola PowerStack II / Estrella 300 and options FIRMWORKSBUGS
To: Jochen Kunz <>
From: Wolfgang Solfrank <>
List: port-powerpc
Date: 11/06/2002 00:52:03

>>>[some printfs later]
>>>        /*
>>>         * Initialize kernel pmap and hardware.
>>>         */
>>>        for (i = 0; i < 16; i++) {
>>>                pmap_kernel()->pm_sr[i] = EMPTY_SEGMENT;
>>>                __asm __volatile ("mtsrin %0,%1"
>>>                     :: "r"(EMPTY_SEGMENT), "r"(i << ADDR_SR_SHFT));
>>>        }
>>>It hangs at the first execution of the inline ASM instruction. 
>>That's to be expexcted: the kernel is modifying the mmu configuration,
>>but OpenFirmware isn't aware of that.
> But why is the machine crashing when the MMU is reinitialized? I would
> expect a crash at the next call to the OFW. Or is it because the kernel
> expects to run still in "real" mode, i.e. MMU turned off, but the MMU is
> active and so it crashes as it reloads the segment registers? (PSL_IR
> and PSL_DR are 1 at that time.)

Well, I assumed that you tried to step over the mtsrin instruction via
the OFW debugger.  If you discovered the hang via some other means
(which I'd wonder how actually), I'd need more data.

But if my assumption is correct, you _are_ entering OFW immediately
after this instruction (as the OFW debugger is of course part of OFW).
So OFW doesn't find the environment it expects (which probably includes
even the trap vector of the debugging trap in this case, i.e. OFW doesn't
execute even one of its instructions in this case :-)).

ws@TooLs.DE     Wolfgang Solfrank, TooLs GmbH 	+49-228-985800