irqchip: gic: Add an entry point to set up irqchip flags

A common use of gic_arch_extn is to set up additional flags
to the GIC irqchip. It looks like a benign enough hack that
doesn't really require the users of that feature to be converted
to stacked domains.

Add a gic_set_irqchip_flags() function that platform code can
call instead of using the dreaded gic_arch_extn.

Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Link: https://lkml.kernel.org/r/1426088737-15817-2-git-send-email-marc.zyngier@arm.com
Signed-off-by: Jason Cooper <jason@lakedaemon.net>

drivers/irqchip/irq-gic.c

@@ -922,6 +922,11 @@ static const struct irq_domain_ops gic_default_routable_irq_domain_ops = {
 const struct irq_domain_ops *gic_routable_irq_domain_ops =
 					&gic_default_routable_irq_domain_ops;
 
+void gic_set_irqchip_flags(unsigned long flags)
+{
+	gic_chip.flags |= flags;
+}
+
 void __init gic_init_bases(unsigned int gic_nr, int irq_start,
 			   void __iomem *dist_base, void __iomem *cpu_base,
 			   u32 percpu_offset, struct device_node *node)

include/linux/irqchip/arm-gic.h

@@ -97,6 +97,7 @@ struct device_node;
 
 extern struct irq_chip gic_arch_extn;
 
+void gic_set_irqchip_flags(unsigned long flags);
 void gic_init_bases(unsigned int, int, void __iomem *, void __iomem *,
 		    u32 offset, struct device_node *);
 void gic_cascade_irq(unsigned int gic_nr, unsigned int irq);