Re: [ECOS] Re: On ARM7 can one of FIQ/IRQ be used for non-eCos stuff?

[Andrew Lunn <andrew@lunn.ch>]

On Wed, Apr 02, 2008 at 09:25:19PM +0200, Alexander Neundorf wrote:
> On Wednesday 02 April 2008, Grant Edwards wrote:
> ...
> > The main point of the CDL would be to avoid having to fork the
> > arm/arch code.  I don't really like maintaining my own separate
> > versions of files unless I absolutely have to.  Besides,
> > somebody else might actually want to use the new "feature".
> 
> Yes. I think providing an official way how to use the FIQ with lowest possible 
> overhead under eCos would be good. Some kind of communication with eCos is 
> required I think, e.g. a recommended way how to generate a regular interrupt 
> so that if some condition is detected in the FIQ handler a regular ISR can 
> overtake.

I've done this before, but it used hardware support.

The Intel StrongARM interrupt controller had a bit you could set to
cause an IRQ interrupt to happen. So in the FIQ you hit this bit and
exit the FIQ. Once interrupts are re-enabled the IRQ goes off and you
are in normal eCos interrupt context.

I don't know of a generic way to do this. There is no standardised
interrupt controller for ARMs.

          Andrew

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