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>

include/linux/interrupt.h

@@ -95,6 +95,7 @@ typedef irqreturn_t (*irq_handler_t)(int, void *);
  * @flags:	flags (see IRQF_* above)
  * @name:	name of the device
  * @dev_id:	cookie to identify the device
+ * @percpu_dev_id:	cookie to identify the device
  * @next:	pointer to the next irqaction for shared interrupts
  * @irq:	interrupt number
  * @dir:	pointer to the proc/irq/NN/name entry
@@ -104,17 +105,18 @@ typedef irqreturn_t (*irq_handler_t)(int, void *);
  * @thread_mask:	bitmask for keeping track of @thread activity
  */
 struct irqaction {
-	irq_handler_t handler;
-	unsigned long flags;
-	void *dev_id;
-	struct irqaction *next;
-	int irq;
-	irq_handler_t thread_fn;
-	struct task_struct *thread;
-	unsigned long thread_flags;
-	unsigned long thread_mask;
-	const char *name;
-	struct proc_dir_entry *dir;
+	irq_handler_t		handler;
+	unsigned long		flags;
+	void			*dev_id;
+	void __percpu		*percpu_dev_id;
+	struct irqaction	*next;
+	int			irq;
+	irq_handler_t		thread_fn;
+	struct task_struct	*thread;
+	unsigned long		thread_flags;
+	unsigned long		thread_mask;
+	const char		*name;
+	struct proc_dir_entry	*dir;
 } ____cacheline_internodealigned_in_smp;
 
 extern irqreturn_t no_action(int cpl, void *dev_id);
@@ -136,6 +138,10 @@ extern int __must_check
 request_any_context_irq(unsigned int irq, irq_handler_t handler,
 			unsigned long flags, const char *name, void *dev_id);
 
+extern int __must_check
+request_percpu_irq(unsigned int irq, irq_handler_t handler,
+		   const char *devname, void __percpu *percpu_dev_id);
+
 extern void exit_irq_thread(void);
 #else
 
@@ -164,10 +170,18 @@ request_any_context_irq(unsigned int irq, irq_handler_t handler,
 	return request_irq(irq, handler, flags, name, dev_id);
 }
 
+static inline int __must_check
+request_percpu_irq(unsigned int irq, irq_handler_t handler,
+		   const char *devname, void __percpu *percpu_dev_id)
+{
+	return request_irq(irq, handler, 0, devname, percpu_dev_id);
+}
+
 static inline void exit_irq_thread(void) { }
 #endif
 
 extern void free_irq(unsigned int, void *);
+extern void free_percpu_irq(unsigned int, void __percpu *);
 
 struct device;
 
@@ -207,7 +221,9 @@ extern void devm_free_irq(struct device *dev, unsigned int irq, void *dev_id);
 
 extern void disable_irq_nosync(unsigned int irq);
 extern void disable_irq(unsigned int irq);
+extern void disable_percpu_irq(unsigned int irq);
 extern void enable_irq(unsigned int irq);
+extern void enable_percpu_irq(unsigned int irq);
 
 /* The following three functions are for the core kernel use only. */
 #ifdef CONFIG_GENERIC_HARDIRQS

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);

include/linux/irqdesc.h

@@ -53,6 +53,7 @@ struct irq_desc {
 	unsigned long		last_unhandled;	/* Aging timer for unhandled count */
 	unsigned int		irqs_unhandled;
 	raw_spinlock_t		lock;
+	struct cpumask		*percpu_enabled;
 #ifdef CONFIG_SMP
 	const struct cpumask	*affinity_hint;
 	struct irq_affinity_notify *affinity_notify;

kernel/irq/chip.c

@@ -26,7 +26,7 @@
 int irq_set_chip(unsigned int irq, struct irq_chip *chip)
 {
 	unsigned long flags;
-	struct irq_desc *desc = irq_get_desc_lock(irq, &flags);
+	struct irq_desc *desc = irq_get_desc_lock(irq, &flags, 0);
 
 	if (!desc)
 		return -EINVAL;
@@ -54,7 +54,7 @@ EXPORT_SYMBOL(irq_set_chip);
 int irq_set_irq_type(unsigned int irq, unsigned int type)
 {
 	unsigned long flags;
-	struct irq_desc *desc = irq_get_desc_buslock(irq, &flags);
+	struct irq_desc *desc = irq_get_desc_buslock(irq, &flags, IRQ_GET_DESC_CHECK_GLOBAL);
 	int ret = 0;
 
 	if (!desc)
@@ -78,7 +78,7 @@ EXPORT_SYMBOL(irq_set_irq_type);
 int irq_set_handler_data(unsigned int irq, void *data)
 {
 	unsigned long flags;
-	struct irq_desc *desc = irq_get_desc_lock(irq, &flags);
+	struct irq_desc *desc = irq_get_desc_lock(irq, &flags, 0);
 
 	if (!desc)
 		return -EINVAL;
@@ -98,7 +98,7 @@ EXPORT_SYMBOL(irq_set_handler_data);
 int irq_set_msi_desc(unsigned int irq, struct msi_desc *entry)
 {
 	unsigned long flags;
-	struct irq_desc *desc = irq_get_desc_lock(irq, &flags);
+	struct irq_desc *desc = irq_get_desc_lock(irq, &flags, IRQ_GET_DESC_CHECK_GLOBAL);
 
 	if (!desc)
 		return -EINVAL;
@@ -119,7 +119,7 @@ int irq_set_msi_desc(unsigned int irq, struct msi_desc *entry)
 int irq_set_chip_data(unsigned int irq, void *data)
 {
 	unsigned long flags;
-	struct irq_desc *desc = irq_get_desc_lock(irq, &flags);
+	struct irq_desc *desc = irq_get_desc_lock(irq, &flags, 0);
 
 	if (!desc)
 		return -EINVAL;
@@ -204,6 +204,24 @@ void irq_disable(struct irq_desc *desc)
 	}
 }
 
+void irq_percpu_enable(struct irq_desc *desc, unsigned int cpu)
+{
+	if (desc->irq_data.chip->irq_enable)
+		desc->irq_data.chip->irq_enable(&desc->irq_data);
+	else
+		desc->irq_data.chip->irq_unmask(&desc->irq_data);
+	cpumask_set_cpu(cpu, desc->percpu_enabled);
+}
+
+void irq_percpu_disable(struct irq_desc *desc, unsigned int cpu)
+{
+	if (desc->irq_data.chip->irq_disable)
+		desc->irq_data.chip->irq_disable(&desc->irq_data);
+	else
+		desc->irq_data.chip->irq_mask(&desc->irq_data);
+	cpumask_clear_cpu(cpu, desc->percpu_enabled);
+}
+
 static inline void mask_ack_irq(struct irq_desc *desc)
 {
 	if (desc->irq_data.chip->irq_mask_ack)
@@ -544,12 +562,44 @@ handle_percpu_irq(unsigned int irq, struct irq_desc *desc)
 		chip->irq_eoi(&desc->irq_data);
 }
 
+/**
+ * handle_percpu_devid_irq - Per CPU local irq handler with per cpu dev ids
+ * @irq:	the interrupt number
+ * @desc:	the interrupt description structure for this irq
+ *
+ * Per CPU interrupts on SMP machines without locking requirements. Same as
+ * handle_percpu_irq() above but with the following extras:
+ *
+ * action->percpu_dev_id is a pointer to percpu variables which
+ * contain the real device id for the cpu on which this handler is
+ * called
+ */
+void handle_percpu_devid_irq(unsigned int irq, struct irq_desc *desc)
+{
+	struct irq_chip *chip = irq_desc_get_chip(desc);
+	struct irqaction *action = desc->action;
+	void *dev_id = __this_cpu_ptr(action->percpu_dev_id);
+	irqreturn_t res;
+
+	kstat_incr_irqs_this_cpu(irq, desc);
+
+	if (chip->irq_ack)
+		chip->irq_ack(&desc->irq_data);
+
+	trace_irq_handler_entry(irq, action);
+	res = action->handler(irq, dev_id);
+	trace_irq_handler_exit(irq, action, res);
+
+	if (chip->irq_eoi)
+		chip->irq_eoi(&desc->irq_data);
+}
+
 void
 __irq_set_handler(unsigned int irq, irq_flow_handler_t handle, int is_chained,
 		  const char *name)
 {
 	unsigned long flags;
-	struct irq_desc *desc = irq_get_desc_buslock(irq, &flags);
+	struct irq_desc *desc = irq_get_desc_buslock(irq, &flags, 0);
 
 	if (!desc)
 		return;
@@ -593,7 +643,7 @@ irq_set_chip_and_handler_name(unsigned int irq, struct irq_chip *chip,
 void irq_modify_status(unsigned int irq, unsigned long clr, unsigned long set)
 {
 	unsigned long flags;
-	struct irq_desc *desc = irq_get_desc_lock(irq, &flags);
+	struct irq_desc *desc = irq_get_desc_lock(irq, &flags, 0);
 
 	if (!desc)
 		return;

kernel/irq/internals.h

@@ -71,6 +71,8 @@ extern int irq_startup(struct irq_desc *desc);
 extern void irq_shutdown(struct irq_desc *desc);
 extern void irq_enable(struct irq_desc *desc);
 extern void irq_disable(struct irq_desc *desc);
+extern void irq_percpu_enable(struct irq_desc *desc, unsigned int cpu);
+extern void irq_percpu_disable(struct irq_desc *desc, unsigned int cpu);
 extern void mask_irq(struct irq_desc *desc);
 extern void unmask_irq(struct irq_desc *desc);
 
@@ -114,14 +116,21 @@ static inline void chip_bus_sync_unlock(struct irq_desc *desc)
 		desc->irq_data.chip->irq_bus_sync_unlock(&desc->irq_data);
 }
 
+#define _IRQ_DESC_CHECK		(1 << 0)
+#define _IRQ_DESC_PERCPU	(1 << 1)
+
+#define IRQ_GET_DESC_CHECK_GLOBAL	(_IRQ_DESC_CHECK)
+#define IRQ_GET_DESC_CHECK_PERCPU	(_IRQ_DESC_CHECK | _IRQ_DESC_PERCPU)
+
 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);
 void __irq_put_desc_unlock(struct irq_desc *desc, unsigned long flags, bool bus);
 
 static inline struct irq_desc *
-irq_get_desc_buslock(unsigned int irq, unsigned long *flags)
+irq_get_desc_buslock(unsigned int irq, unsigned long *flags, unsigned int check)
 {
-	return __irq_get_desc_lock(irq, flags, true);
+	return __irq_get_desc_lock(irq, flags, true, check);
 }
 
 static inline void
@@ -131,9 +140,9 @@ irq_put_desc_busunlock(struct irq_desc *desc, unsigned long flags)
 }
 
 static inline struct irq_desc *
-irq_get_desc_lock(unsigned int irq, unsigned long *flags)
+irq_get_desc_lock(unsigned int irq, unsigned long *flags, unsigned int check)
 {
-	return __irq_get_desc_lock(irq, flags, false);
+	return __irq_get_desc_lock(irq, flags, false, check);
 }
 
 static inline void

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