Re: [ECOS] sa11x0 spurious interrupts

[Gary Thomas <gthomas at cambridge dot redhat dot com>]

On 13-Feb-2001 Jonathan Larmour wrote:
> Robin Farine wrote:
>> 
>> Hello,
>> 
>> While looking at the way the sa11x0 hal's routine 'hal_IRQ_handler()' decodes
>> interrupt sources, I noticed that when it does not find an interrupt source,
>> the routine returns CYGNUM_HAL_INTERRUPT_NONE, which equals to -1 for this
>> platform. However, the common ARM code in "vectors.S" assumes that a spurious
>> interrupt always have the vector #0. And worse, 'handle_IRQ_or_FIQ' will call
>> 'hal_interrupt_handlers[-1]' which contains 0 and thus reboot!
>> 
>> Did I miss something?
> 
> I don't think so. 0 can be a valid ISR. What's worse is that the default
> ISR in hal/common also returns 0 to indicate a spurious interrupt.

The default ISR handler returning 0 is a whole separate matter.

> 
> Anyone got any opinions why this isn't simply all wrong?

Actually, it does seem to be rather messed up.  It comes from having a large
number of ports and this particular behaviour is platform specific, thus 
we've somehow ended up with no less than 3 different answers here.

These should all be changed to return CYGNUM_HAL_INTERRUPT_NONE and have
the code in 'vectors.S' handle this as a special case.  However, what one
actually does when there is a spurious interrupt is tinder for a large
flame war :-)