genirq: Allow the affinity of a percpu interrupt to be set/retrieved

In order to prepare the genirq layer for the concept of partitionned
percpu interrupts, let's allow an affinity to be associated with
such an interrupt. We introduce:

- irq_set_percpu_devid_partition: flag an interrupt as a percpu-devid
  interrupt, and associate it with an affinity
- irq_get_percpu_devid_partition: allow the affinity of that interrupt
  to be retrieved.

This will allow a driver to discover which CPUs the per-cpu interrupt
can actually fire on.

Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: devicetree@vger.kernel.org
Cc: Jason Cooper <jason@lakedaemon.net>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Rob Herring <robh+dt@kernel.org>
Link: http://lkml.kernel.org/r/1460365075-7316-3-git-send-email-marc.zyngier@arm.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

include/linux/irq.h

@@ -530,6 +530,10 @@ static inline void irq_set_chip_and_handler(unsigned int irq, struct irq_chip *c
 }
 
 extern int irq_set_percpu_devid(unsigned int irq);
+extern int irq_set_percpu_devid_partition(unsigned int irq,
+					  const struct cpumask *affinity);
+extern int irq_get_percpu_devid_partition(unsigned int irq,
+					  struct cpumask *affinity);
 
 extern void
 __irq_set_handler(unsigned int irq, irq_flow_handler_t handle, int is_chained,

include/linux/irqdesc.h

@@ -66,6 +66,7 @@ struct irq_desc {
 	int			threads_handled_last;
 	raw_spinlock_t		lock;
 	struct cpumask		*percpu_enabled;
+	const struct cpumask	*percpu_affinity;
 #ifdef CONFIG_SMP
 	const struct cpumask	*affinity_hint;
 	struct irq_affinity_notify *affinity_notify;

kernel/irq/irqdesc.c

@@ -595,7 +595,8 @@ void __irq_put_desc_unlock(struct irq_desc *desc, unsigned long flags, bool bus)
 		chip_bus_sync_unlock(desc);
 }
 
-int irq_set_percpu_devid(unsigned int irq)
+int irq_set_percpu_devid_partition(unsigned int irq,
+				   const struct cpumask *affinity)
 {
 	struct irq_desc *desc = irq_to_desc(irq);
 
@@ -610,10 +611,33 @@ int irq_set_percpu_devid(unsigned int irq)
 	if (!desc->percpu_enabled)
 		return -ENOMEM;
 
+	if (affinity)
+		desc->percpu_affinity = affinity;
+	else
+		desc->percpu_affinity = cpu_possible_mask;
+
 	irq_set_percpu_devid_flags(irq);
 	return 0;
 }
 
+int irq_set_percpu_devid(unsigned int irq)
+{
+	return irq_set_percpu_devid_partition(irq, NULL);
+}
+
+int irq_get_percpu_devid_partition(unsigned int irq, struct cpumask *affinity)
+{
+	struct irq_desc *desc = irq_to_desc(irq);
+
+	if (!desc || !desc->percpu_enabled)
+		return -EINVAL;
+
+	if (affinity)
+		cpumask_copy(affinity, desc->percpu_affinity);
+
+	return 0;
+}
+
 void kstat_incr_irq_this_cpu(unsigned int irq)
 {
 	kstat_incr_irqs_this_cpu(irq_to_desc(irq));