PM: Introduce functions for suspending and resuming device interrupts

Introduce helper functions allowing us to prevent device drivers from
getting any interrupts (without disabling interrupts on the CPU)
during suspend (or hibernation) and to make them start to receive
interrupts again during the subsequent resume.  These functions make it
possible to keep timer interrupts enabled while the "late" suspend and
"early" resume callbacks provided by device drivers are being
executed.  In turn, this allows device drivers' "late" suspend and
"early" resume callbacks to sleep, execute ACPI callbacks etc.

The functions introduced here will be used to rework the handling of
interrupts during suspend (hibernation) and resume.  Namely,
interrupts will only be disabled on the CPU right before suspending
sysdevs, while device drivers will be prevented from receiving
interrupts, with the help of the new helper function, before their
"late" suspend callbacks run (and analogously during resume).

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Acked-by: Ingo Molnar <mingo@elte.hu>

include/linux/interrupt.h

@@ -117,6 +117,15 @@ extern void disable_irq_nosync(unsigned int irq);
 extern void disable_irq(unsigned int irq);
 extern void enable_irq(unsigned int irq);
 
+/* The following three functions are for the core kernel use only. */
+extern void suspend_device_irqs(void);
+extern void resume_device_irqs(void);
+#ifdef CONFIG_PM_SLEEP
+extern int check_wakeup_irqs(void);
+#else
+static inline int check_wakeup_irqs(void) { return 0; }
+#endif
+
 #if defined(CONFIG_SMP) && defined(CONFIG_GENERIC_HARDIRQS)
 
 extern cpumask_var_t irq_default_affinity;

include/linux/irq.h

@@ -67,6 +67,7 @@ typedef	void (*irq_flow_handler_t)(unsigned int irq,
 #define IRQ_SPURIOUS_DISABLED	0x00800000	/* IRQ was disabled by the spurious trap */
 #define IRQ_MOVE_PCNTXT		0x01000000	/* IRQ migration from process context */
 #define IRQ_AFFINITY_SET	0x02000000	/* IRQ affinity was set from userspace*/
+#define IRQ_SUSPENDED		0x04000000	/* IRQ has gone through suspend sequence */
 
 #ifdef CONFIG_IRQ_PER_CPU
 # define CHECK_IRQ_PER_CPU(var) ((var) & IRQ_PER_CPU)

kernel/irq/Makefile

@@ -4,3 +4,4 @@ obj-$(CONFIG_GENERIC_IRQ_PROBE) += autoprobe.o
 obj-$(CONFIG_PROC_FS) += proc.o
 obj-$(CONFIG_GENERIC_PENDING_IRQ) += migration.o
 obj-$(CONFIG_NUMA_MIGRATE_IRQ_DESC) += numa_migrate.o
+obj-$(CONFIG_PM_SLEEP) += pm.o

kernel/irq/internals.h

@@ -12,6 +12,8 @@ extern void compat_irq_chip_set_default_handler(struct irq_desc *desc);
 
 extern int __irq_set_trigger(struct irq_desc *desc, unsigned int irq,
 		unsigned long flags);
+extern void __disable_irq(struct irq_desc *desc, unsigned int irq, bool susp);
+extern void __enable_irq(struct irq_desc *desc, unsigned int irq, bool resume);
 
 extern struct lock_class_key irq_desc_lock_class;
 extern void init_kstat_irqs(struct irq_desc *desc, int cpu, int nr);

kernel/irq/manage.c

@@ -162,6 +162,20 @@ static inline int setup_affinity(unsigned int irq, struct irq_desc *desc)
 }
 #endif
 
+void __disable_irq(struct irq_desc *desc, unsigned int irq, bool suspend)
+{
+	if (suspend) {
+		if (!desc->action || (desc->action->flags & IRQF_TIMER))
+			return;
+		desc->status |= IRQ_SUSPENDED;
+	}
+
+	if (!desc->depth++) {
+		desc->status |= IRQ_DISABLED;
+		desc->chip->disable(irq);
+	}
+}
+
 /**
  *	disable_irq_nosync - disable an irq without waiting
  *	@irq: Interrupt to disable
@@ -182,10 +196,7 @@ void disable_irq_nosync(unsigned int irq)
 		return;
 
 	spin_lock_irqsave(&desc->lock, flags);
-	if (!desc->depth++) {
-		desc->status |= IRQ_DISABLED;
-		desc->chip->disable(irq);
-	}
+	__disable_irq(desc, irq, false);
 	spin_unlock_irqrestore(&desc->lock, flags);
 }
 EXPORT_SYMBOL(disable_irq_nosync);
@@ -215,15 +226,21 @@ void disable_irq(unsigned int irq)
 }
 EXPORT_SYMBOL(disable_irq);
 
-static void __enable_irq(struct irq_desc *desc, unsigned int irq)
+void __enable_irq(struct irq_desc *desc, unsigned int irq, bool resume)
 {
+	if (resume)
+		desc->status &= ~IRQ_SUSPENDED;
+
 	switch (desc->depth) {
 	case 0:
+ err_out:
 		WARN(1, KERN_WARNING "Unbalanced enable for IRQ %d\n", irq);
 		break;
 	case 1: {
 		unsigned int status = desc->status & ~IRQ_DISABLED;
 
+		if (desc->status & IRQ_SUSPENDED)
+			goto err_out;
 		/* Prevent probing on this irq: */
 		desc->status = status | IRQ_NOPROBE;
 		check_irq_resend(desc, irq);
@@ -253,7 +270,7 @@ void enable_irq(unsigned int irq)
 		return;
 
 	spin_lock_irqsave(&desc->lock, flags);
-	__enable_irq(desc, irq);
+	__enable_irq(desc, irq, false);
 	spin_unlock_irqrestore(&desc->lock, flags);
 }
 EXPORT_SYMBOL(enable_irq);
@@ -511,7 +528,7 @@ __setup_irq(unsigned int irq, struct irq_desc *desc, struct irqaction *new)
 	 */
 	if (shared && (desc->status & IRQ_SPURIOUS_DISABLED)) {
 		desc->status &= ~IRQ_SPURIOUS_DISABLED;
-		__enable_irq(desc, irq);
+		__enable_irq(desc, irq, false);
 	}
 
 	spin_unlock_irqrestore(&desc->lock, flags);

kernel/irq/pm.c

@@ -0,0 +1,79 @@
+/*
+ * linux/kernel/irq/pm.c
+ *
+ * Copyright (C) 2009 Rafael J. Wysocki <rjw@sisk.pl>, Novell Inc.
+ *
+ * This file contains power management functions related to interrupts.
+ */
+
+#include <linux/irq.h>
+#include <linux/module.h>
+#include <linux/interrupt.h>
+
+#include "internals.h"
+
+/**
+ * suspend_device_irqs - disable all currently enabled interrupt lines
+ *
+ * During system-wide suspend or hibernation device interrupts need to be
+ * disabled at the chip level and this function is provided for this purpose.
+ * It disables all interrupt lines that are enabled at the moment and sets the
+ * IRQ_SUSPENDED flag for them.
+ */
+void suspend_device_irqs(void)
+{
+	struct irq_desc *desc;
+	int irq;
+
+	for_each_irq_desc(irq, desc) {
+		unsigned long flags;
+
+		spin_lock_irqsave(&desc->lock, flags);
+		__disable_irq(desc, irq, true);
+		spin_unlock_irqrestore(&desc->lock, flags);
+	}
+
+	for_each_irq_desc(irq, desc)
+		if (desc->status & IRQ_SUSPENDED)
+			synchronize_irq(irq);
+}
+EXPORT_SYMBOL_GPL(suspend_device_irqs);
+
+/**
+ * resume_device_irqs - enable interrupt lines disabled by suspend_device_irqs()
+ *
+ * Enable all interrupt lines previously disabled by suspend_device_irqs() that
+ * have the IRQ_SUSPENDED flag set.
+ */
+void resume_device_irqs(void)
+{
+	struct irq_desc *desc;
+	int irq;
+
+	for_each_irq_desc(irq, desc) {
+		unsigned long flags;
+
+		if (!(desc->status & IRQ_SUSPENDED))
+			continue;
+
+		spin_lock_irqsave(&desc->lock, flags);
+		__enable_irq(desc, irq, true);
+		spin_unlock_irqrestore(&desc->lock, flags);
+	}
+}
+EXPORT_SYMBOL_GPL(resume_device_irqs);
+
+/**
+ * check_wakeup_irqs - check if any wake-up interrupts are pending
+ */
+int check_wakeup_irqs(void)
+{
+	struct irq_desc *desc;
+	int irq;
+
+	for_each_irq_desc(irq, desc)
+		if ((desc->status & IRQ_WAKEUP) && (desc->status & IRQ_PENDING))
+			return -EBUSY;
+
+	return 0;
+}