genirq: Add support for per-cpu dev_id interrupts

The ARM GIC interrupt controller offers per CPU interrupts (PPIs),
which are usually used to connect local timers to each core. Each CPU
has its own private interface to the GIC, and only sees the PPIs that
are directly connect to it.

While these timers are separate devices and have a separate interrupt
line to a core, they all use the same IRQ number.

For these devices, request_irq() is not the right API as it assumes
that an IRQ number is visible by a number of CPUs (through the
affinity setting), but makes it very awkward to express that an IRQ
number can be handled by all CPUs, and yet be a different interrupt
line on each CPU, requiring a different dev_id cookie to be passed
back to the handler.

The *_percpu_irq() functions is designed to overcome these
limitations, by providing a per-cpu dev_id vector:

int request_percpu_irq(unsigned int irq, irq_handler_t handler,
		   const char *devname, void __percpu *percpu_dev_id);
void free_percpu_irq(unsigned int, void __percpu *);
int setup_percpu_irq(unsigned int irq, struct irqaction *new);
void remove_percpu_irq(unsigned int irq, struct irqaction *act);
void enable_percpu_irq(unsigned int irq);
void disable_percpu_irq(unsigned int irq);

The API has a number of limitations:
- no interrupt sharing
- no threading
- common handler across all the CPUs

Once the interrupt is requested using setup_percpu_irq() or
request_percpu_irq(), it must be enabled by each core that wishes its
local interrupt to be delivered.

Based on an initial patch by Thomas Gleixner.

Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Cc: linux-arm-kernel@lists.infradead.org
Link: http://lkml.kernel.org/r/1316793788-14500-2-git-send-email-marc.zyngier@arm.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 31 insertions, 1 deletions

diff --git a/kernel/irq/irqdesc.c b/kernel/irq/irqdesc.c
index 039b889..1550e84 100644
--- a/kernel/irq/irqdesc.c
+++ b/kernel/irq/irqdesc.c
@@ -424,11 +424,22 @@ unsigned int irq_get_next_irq(unsigned int offset)
 }
 
 struct irq_desc *
-__irq_get_desc_lock(unsigned int irq, unsigned long *flags, bool bus)
+__irq_get_desc_lock(unsigned int irq, unsigned long *flags, bool bus,
+		    unsigned int check)
 {
 	struct irq_desc *desc = irq_to_desc(irq);
 
 	if (desc) {
+		if (check & _IRQ_DESC_CHECK) {
+			if ((check & _IRQ_DESC_PERCPU) &&
+			    !irq_settings_is_per_cpu_devid(desc))
+				return NULL;
+
+			if (!(check & _IRQ_DESC_PERCPU) &&
+			    irq_settings_is_per_cpu_devid(desc))
+				return NULL;
+		}
+
 		if (bus)
 			chip_bus_lock(desc);
 		raw_spin_lock_irqsave(&desc->lock, *flags);
@@ -443,6 +454,25 @@ 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)
+{
+	struct irq_desc *desc = irq_to_desc(irq);
+
+	if (!desc)
+		return -EINVAL;
+
+	if (desc->percpu_enabled)
+		return -EINVAL;
+
+	desc->percpu_enabled = kzalloc(sizeof(*desc->percpu_enabled), GFP_KERNEL);
+
+	if (!desc->percpu_enabled)
+		return -ENOMEM;
+
+	irq_set_percpu_devid_flags(irq);
+	return 0;
+}
+
 /**
  * dynamic_irq_cleanup - cleanup a dynamically allocated irq
  * @irq:	irq number to initialize