On Wednesday 13 February 2002 12:19 am, Richard Earnshaw wrote:
> > On Monday 11 February 2002 10:15 pm, Richard Earnshaw wrote:
> > > I'll have a poke around, the shark has always had ISA interrupts, so
> > > maybe that will provide a clue...
> >
> > One thought I had is that it's something to do with auto acknowledging
> > the isa interrupt (I've vague memories of looking at it, but didn't
> > really understand it.)
>
> How's that supposed to work?

I'm not 100% sure, I just know that in cats/isa/isa_machdep.c it talks about 
auto_eoi.  Looking in the shark isa_shark_machdep it talks about it being 
expensive to talk to the 8259 ICU's (15 instructions) so that could be why 
cats also has them set in eoi mode.  

That said looking at the isa handling it appears that the ISA IRQs are 
actually mapped into the 21285 at PCI_IACK_VBASE.

Either way it currently all looks a tad messy.

> Another idea is that we sometime poke some invalid address in PCI space.
> According to my 21285 data sheet that might not abort, but could well
> stall for a long time.  If that is the case, then it's going to be a pig
> to track down.

We might be, but I'd have hoped that we'd eventually come back from there. 

Chris