[PATCH] ARM: gic: use handle_fasteoi_irq for SPIs

[Will Deacon]

Hi Rabin,

> On Mon, Feb 14, 2011 at 20:56, Will Deacon <will.deacon at arm.com> wrote:
> > Currently, the gic uses handle_level_irq for handling SPIs (Shared
> > Peripheral Interrupts), requiring active interrupts to be masked at
> > the distributor level during IRQ handling.
> >
> > On a virtualised system, only the CPU interfaces are virtualised in
> > hardware. Accesses to the distributor must be trapped by the hypervisor,
> > adding latency to the critical interrupt path in Linux.
> >
> > This patch modifies the GIC code to use handle_fasteoi_irq for handling
> > interrupts, which only requires us to signal EOI to the CPU interface
> > when handling is complete. Cascaded IRQ handling is also updated so that
> > EOI is signalled after handling.
> 
> Several of the platforms using the GIC also have GPIO code which uses
> set_irq_chained_handler().  I think you will have to modify all of
> these to call irq_eoi() appropriately and not the other functions.
> Some of these will also likely be used with other interrupt handlers
> than the GIC, though.

Hmm, I had a quick look at some platforms that do this (mach-dove and 
plat-spear) and I don't see what the problem is. They use their own irq_chip
structures, with their own function pointers, so this doesn't seem to relate
to the GIC at all. What am I missing?!

Cheers,

Will