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, 15 insertions, 1 deletions

diff --git a/include/linux/irq.h b/include/linux/irq.h
index 73e31abeba1c..59e49c80cc2c 100644
--- a/include/linux/irq.h
+++ b/include/linux/irq.h
@@ -66,6 +66,7 @@ typedef	void (*irq_preflow_handler_t)(struct irq_data *data);
  * IRQ_NO_BALANCING             - Interrupt cannot be balanced (affinity set)
  * IRQ_MOVE_PCNTXT              - Interrupt can be migrated from process context
  * IRQ_NESTED_TRHEAD            - Interrupt nests into another thread
+ * IRQ_PER_CPU_DEVID            - Dev_id is a per-cpu variable
  */
 enum {
         IRQ_TYPE_NONE           = 0x00000000,
@@ -88,12 +89,13 @@ enum {
         IRQ_MOVE_PCNTXT         = (1 << 14),
         IRQ_NESTED_THREAD       = (1 << 15),
         IRQ_NOTHREAD            = (1 << 16),
+        IRQ_PER_CPU_DEVID       = (1 << 17),
 };
 
 #define IRQF_MODIFY_MASK        \
         (IRQ_TYPE_SENSE_MASK | IRQ_NOPROBE | IRQ_NOREQUEST | \
          IRQ_NOAUTOEN | IRQ_MOVE_PCNTXT | IRQ_LEVEL | IRQ_NO_BALANCING | \
-         IRQ_PER_CPU | IRQ_NESTED_THREAD)
+         IRQ_PER_CPU | IRQ_NESTED_THREAD | IRQ_NOTHREAD | IRQ_PER_CPU_DEVID)
 
 #define IRQ_NO_BALANCING_MASK   (IRQ_PER_CPU | IRQ_NO_BALANCING)
 
@@ -367,6 +369,8 @@ enum {
 struct irqaction;
 extern int setup_irq(unsigned int irq, struct irqaction *new);
 extern void remove_irq(unsigned int irq, struct irqaction *act);
+extern int setup_percpu_irq(unsigned int irq, struct irqaction *new);
+extern void remove_percpu_irq(unsigned int irq, struct irqaction *act);
 
 extern void irq_cpu_online(void);
 extern void irq_cpu_offline(void);
@@ -394,6 +398,7 @@ extern void handle_edge_irq(unsigned int irq, struct irq_desc *desc);
 extern void handle_edge_eoi_irq(unsigned int irq, struct irq_desc *desc);
 extern void handle_simple_irq(unsigned int irq, struct irq_desc *desc);
 extern void handle_percpu_irq(unsigned int irq, struct irq_desc *desc);
+extern void handle_percpu_devid_irq(unsigned int irq, struct irq_desc *desc);
 extern void handle_bad_irq(unsigned int irq, struct irq_desc *desc);
 extern void handle_nested_irq(unsigned int irq);
 
@@ -422,6 +427,8 @@ static inline void irq_set_chip_and_handler(unsigned int irq, struct irq_chip *c
         irq_set_chip_and_handler_name(irq, chip, handle, NULL);
 }
 
+extern int irq_set_percpu_devid(unsigned int irq);
+
 extern void
 __irq_set_handler(unsigned int irq, irq_flow_handler_t handle, int is_chained,
                   const char *name);
@@ -483,6 +490,13 @@ static inline void irq_set_nested_thread(unsigned int irq, bool nest)
                 irq_clear_status_flags(irq, IRQ_NESTED_THREAD);
 }
 
+static inline void irq_set_percpu_devid_flags(unsigned int irq)
+{
+        irq_set_status_flags(irq,
+                             IRQ_NOAUTOEN | IRQ_PER_CPU | IRQ_NOTHREAD |
+                             IRQ_NOPROBE | IRQ_PER_CPU_DEVID);
+}
+
 /* Handle dynamic irq creation and destruction */
 extern unsigned int create_irq_nr(unsigned int irq_want, int node);
 extern int create_irq(void);