On Mon, Jun 13, 2011 at 05:51:11PM -0400, Guenter Roeck wrote:
[ ... ]
> > >
> > > The actual interrupt causing trouble and spurious interrupts in my case
> > > is,
> > > oddly enough, STATUSF_IP0. So far I have been unable to track down how
> > > that
> > > is triggered; I don't see the bit being set set in C0_CAUSE anywhere.
> > >
> > > Are there any means to trigger an IP0 interrupt other than by writing
> > > STATUSF_IP0
> > > into the C0_CAUSE register ?
> > >
> > No. Nothing that I know of ever uses IP0 and IP1, so they should always
> > be cleared.
> Exactly what I figured, yet I still get those spurious interrupts if IP0 is
> Something odd is definitely going on in my system.
> Besides the above, my hopefully final problem is that timer interrupts are
> received by CPU 0. Any idea what to look for to fix this problem ?
Found the problem. Apparently the BIOS resets CvmCtl[IPTI] to 0. This causes
the spurious interrupt on IP0 without setting C0_CAUSE, and the (perceived)
lack of timer interrupts. In other words, it _is_ possible to trigger IP0
without setting STATUSF_IP0 in C0_CAUSE ... the interrupt will happen, but
will not be set.
Interesting learning experience...