[PATCH 5/7] ARM: EXYNOS4: Add support external GIC

[Will Deacon]

On Thu, Oct 13, 2011 at 12:09:28PM +0100, Russell King - ARM Linux wrote:
> On Mon, Oct 10, 2011 at 02:02:09PM +0100, Marc Zyngier wrote:
> > On 07/10/11 16:16, Will Deacon wrote:
> > > On Fri, Oct 07, 2011 at 10:44:59AM +0100, Marc Zyngier wrote:
> > >> +static void __cpuinit exynos4_secondary_init(unsigned int cpu)
> > >>  {
> > >>  	void __iomem *dist_base = S5P_VA_GIC_DIST +
> > >> -				(gic_bank_offset * smp_processor_id());
> > >> +				(gic_bank_offset * cpu_logical_map(cpu));
> > > 
> > > Again, I'm deeply suspicious of this code :) Is there not a common memory
> > > alias for the distributor across all of the CPUs?
> > 
> > Kukjin, could you please comment on the presence of a common memory
> > region for the distributor? This seem quite odd...
> 
> It's not odd when you consider that there's per-CPU registers within the
> GIC distributor as well (for the first 32 GIC IRQs) as the per-CPU GIC
> CPU interfaces.

Agreed, but it is odd for those registers not to be banked in hardware. Marc
and I spoke to some of the hardware chaps at ARM and they don't see this as
a common setup in the future, so rather than litter the GIC driver with
__percpu variables, we might be better off adding some extra platform callbacks
to the set that we already have.

Will