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Thread: SMP in ppcoea-renovation




SMP in ppcoea-renovation
country flaguser name
United States
2007-10-02 17:13:55
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Hello,

now that I have a dual G4 box I gave ppcoea-renovation a
shot. Here's  
what I found:
- - uniprocessor kernels seem to work just fine, as
expected
- - SMP kernels don't compile but that's trivial to fix, the
secondary  
CPU startup code tries to write to some OpenPIC register to
make sure  
only the 1st CPU gets interrupts.
- - with those things fixed the kernel stops in cpu_spinup()
when  
trying to reset the 2nd CPU via out8(gpio, 4)

The code looks ok to me, gpio is the same as in a 4.0 kernel
which  
works. So I suspected missing or wrong BAT mappings for the
gpio's  
address but changing oeaofw_ppcinit() back to use the same
code as  
macppc in 4.0 didn't help.

So, what needs to be done is:
- - find out why out8(gpio, 4) hangs the machine
- - add an abstract interface for IPIs , hide information
which vector  
to use etc. inside the PIC drivers, find a sane way to
register IPI  
handlers.
- - deal with special cases where only CPU0 can handle
interrupts like  
with legacy Apple PICs. Find out if that's a hardware
limitation or  
just laziness. Unfortunately I don't have an Old World SMP
box.
- - do we need to add locking to interrupt handling code? At
least with  
Old World PICs we probably have to if we want both CPUs to
take  
interrupt. OpenPIC seems to do something like that in
hardware?

have fun
Michael
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