ARM: Add support for dynamic tick timer

Adds ARM generic support for dynamic tick timer.
Signed-off-by: Tony Lindgren <tony@atomide.com>

arch/arm/kernel/irq.c

@@ -4,6 +4,10 @@
  *  Copyright (C) 1992 Linus Torvalds
  *  Modifications for ARM processor Copyright (C) 1995-2000 Russell King.
  *
+ *  Support for Dynamic Tick Timer Copyright (C) 2004-2005 Nokia Corporation.
+ *  Dynamic Tick Timer written by Tony Lindgren <tony@atomide.com> and
+ *  Tuukka Tikkanen <tuukka.tikkanen@elektrobit.com>.
+ *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 2 as
  * published by the Free Software Foundation.
@@ -37,6 +41,7 @@
 #include <asm/irq.h>
 #include <asm/system.h>
 #include <asm/mach/irq.h>
+#include <asm/mach/time.h>
 
 /*
  * Maximum IRQ count.  Currently, this is arbitary.  However, it should
@@ -332,6 +337,12 @@ __do_irq(unsigned int irq, struct irqaction *action, struct pt_regs *regs)
 	if (!(action->flags & SA_INTERRUPT))
 		local_irq_enable();
 
+#ifdef CONFIG_NO_IDLE_HZ
+	if ((!(action->flags & SA_TIMER)) && system_timer->dyn_tick->handler &&
+	    (system_timer->dyn_tick->state & DYN_TICK_ENABLED))
+		system_timer->dyn_tick->handler(irq, 0, regs);
+#endif
+
 	status = 0;
 	do {
 		ret = action->handler(irq, action->dev_id, regs);

arch/arm/kernel/time.c

@@ -28,6 +28,7 @@
 #include <linux/profile.h>
 #include <linux/sysdev.h>
 #include <linux/timer.h>
+#include <linux/pm.h>
 
 #include <asm/hardware.h>
 #include <asm/io.h>
@@ -350,6 +351,49 @@ void timer_tick(struct pt_regs *regs)
 #endif
 }
 
+#ifdef CONFIG_NO_IDLE_HZ
+int timer_dyn_tick_enable(void)
+{
+	unsigned long flags;
+	int ret = -ENODEV;
+
+	write_seqlock_irqsave(&xtime_lock, flags);
+	if (!system_timer->dyn_tick || !system_timer->dyn_tick->enable)
+		goto out_err;
+
+	ret = system_timer->dyn_tick->enable();
+	if (ret != 0)
+		goto out_err;
+
+	if (system_timer->dyn_tick->handler)
+		system_timer->dyn_tick->state |= DYN_TICK_ENABLED;
+
+	write_sequnlock_irqrestore(&xtime_lock, flags);
+
+	return ret;
+
+out_err:
+	system_timer->dyn_tick->state &= ~DYN_TICK_ENABLED;
+	write_sequnlock_irqrestore(&xtime_lock, flags);
+	return ret;
+}
+
+int timer_dyn_tick_disable(void)
+{
+	unsigned long flags;
+	int ret = 0;
+
+	write_seqlock_irqsave(&xtime_lock, flags);
+	if (system_timer->dyn_tick && system_timer->dyn_tick->disable)
+		ret = system_timer->dyn_tick->disable();
+
+	system_timer->dyn_tick->state &= ~DYN_TICK_ENABLED;
+	write_sequnlock_irqrestore(&xtime_lock, flags);
+
+	return ret;
+}
+#endif
+
 #ifdef CONFIG_PM
 static int timer_suspend(struct sys_device *dev, pm_message_t state)
 {
@@ -381,6 +425,29 @@ static struct sysdev_class timer_sysclass = {
 	.resume		= timer_resume,
 };
 
+#ifdef CONFIG_NO_IDLE_HZ
+static ssize_t timer_show_dyn_tick(struct sys_device *dev, char *buf)
+{
+	return sprintf(buf, "%i\n",
+		       (system_timer->dyn_tick->state & DYN_TICK_ENABLED) >> 1);
+}
+
+static ssize_t timer_set_dyn_tick(struct sys_device *dev, const char *buf,
+				  size_t count)
+{
+	int ret = 0;
+	unsigned int enable = simple_strtoul(buf, NULL, 2);
+
+	if (enable)
+		ret = timer_dyn_tick_enable();
+	else
+		ret = timer_dyn_tick_disable();
+
+	return count;
+}
+static SYSDEV_ATTR(dyn_tick, 0644, timer_show_dyn_tick, timer_set_dyn_tick);
+#endif
+
 static int __init timer_init_sysfs(void)
 {
 	int ret = sysdev_class_register(&timer_sysclass);
@@ -388,6 +455,15 @@ static int __init timer_init_sysfs(void)
 		system_timer->dev.cls = &timer_sysclass;
 		ret = sysdev_register(&system_timer->dev);
 	}
+
+#ifdef CONFIG_NO_IDLE_HZ
+	ret = sysdev_create_file(&system_timer->dev, &attr_dyn_tick);
+#if defined(CONFIG_NO_IDLE_HZ_ENABLED)
+	/* Turn on dynamic tick after calibrate delay for correct bogomips */
+	ret = timer_dyn_tick_enable();
+#endif
+#endif
+
 	return ret;
 }
 

include/asm-arm/mach/time.h

@@ -39,7 +39,27 @@ struct sys_timer {
 	void			(*suspend)(void);
 	void			(*resume)(void);
 	unsigned long		(*offset)(void);
+
+#ifdef CONFIG_NO_IDLE_HZ
+	struct dyn_tick_timer	*dyn_tick;
+#endif
+
+};
+
+#ifdef CONFIG_NO_IDLE_HZ
+
+#define DYN_TICK_SKIPPING	(1 << 2)
+#define DYN_TICK_ENABLED	(1 << 1)
+#define DYN_TICK_SUITABLE	(1 << 0)
+
+struct dyn_tick_timer {
+	unsigned int	state;			/* Current state */
+	int		(*enable)(void);	/* Enables dynamic tick */
+	int		(*disable)(void);	/* Disables dynamic tick */
+	void		(*reprogram)(void);	/* Reprograms the timer */
+	int		(*handler)(int, void *, struct pt_regs *);
 };
+#endif
 
 extern struct sys_timer *system_timer;
 extern void timer_tick(struct pt_regs *);

include/linux/signal.h

@@ -14,8 +14,10 @@
  *
  * SA_INTERRUPT is also used by the irq handling routines.
  * SA_SHIRQ is for shared interrupt support on PCI and EISA.
+ * SA_TIMER is used by dynamic tick timer.
  */
 #define SA_PROBE		SA_ONESHOT
+#define SA_TIMER		SA_NOMASK
 #define SA_SAMPLE_RANDOM	SA_RESTART
 #define SA_SHIRQ		0x04000000