[RFC PATCH 1/3] genirq: add support for per-cpu dev_id interrupts

[Russell King - ARM Linux]

On Mon, Sep 19, 2011 at 04:00:34PM +0100, Marc Zyngier wrote:
> Replying to myself after a quick investigation... Looks like the Qualcomm
> implementation does exactly what is mentioned above:
> 
> arch/arm/mach-msm/platsmp.c:
> void __cpuinit platform_secondary_init(unsigned int cpu)
> {
> 	/* Configure edge-triggered PPIs */
> 	writel(GIC_PPI_EDGE_MASK, MSM_QGIC_DIST_BASE + GIC_DIST_CONFIG + 4);
> 	[...]
> 
> The way I understand it, this "MSM_QGIC_DIST_BASE + GIC_DIST_CONFIG + 4"
> is a banked register (otherwise we would not do it in platform_secondary_init(),
> right?) So doing a set_type() from __setup_irq() would be just wrong. It really
> needs to be done on a per-CPU basis.

All the registers to do with the first 32 interrupts in the distributer
are banked - the enable, configuration, and priority registers are all
only accessible to the specific CPU which owns the PPIs and SGIs.