3 files changed, 132 insertions, 0 deletions

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index bfcf4228036..c8d94dcd8ef 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -346,6 +346,21 @@ config PREEMPT
 	  Say Y here if you are building a kernel for a desktop, embedded
 	  or real-time system.  Say N if you are unsure.
 
+config NO_IDLE_HZ
+	bool "Dynamic tick timer"
+	help
+	  Select this option if you want to disable continuous timer ticks
+	  and have them programmed to occur as required. This option saves
+	  power as the system can remain in idle state for longer.
+
+	  By default dynamic tick is disabled during the boot, and can be
+	  manually enabled with:
+
+	    echo 1 > /sys/devices/system/timer/timer0/dyn_tick
+
+	  Alternatively, if you want dynamic tick automatically enabled
+	  during boot, pass "dyntick=enable" via the kernel command string.
+
 config ARCH_DISCONTIGMEM_ENABLE
 	bool
 	default (ARCH_LH7A40X && !LH7A40X_CONTIGMEM)
diff --git a/arch/arm/kernel/irq.c b/arch/arm/kernel/irq.c
index ff187f4308f..395137a8fad 100644
--- a/arch/arm/kernel/irq.c
+++ b/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
@@ -329,6 +334,15 @@ __do_irq(unsigned int irq, struct irqaction *action, struct pt_regs *regs)
 
 	spin_unlock(&irq_controller_lock);
 
+#ifdef CONFIG_NO_IDLE_HZ
+	if (!(action->flags & SA_TIMER) && system_timer->dyn_tick != NULL) {
+		write_seqlock(&xtime_lock);
+		if (system_timer->dyn_tick->state & DYN_TICK_ENABLED)
+			system_timer->dyn_tick->handler(irq, 0, regs);
+		write_sequnlock(&xtime_lock);
+	}
+#endif
+
 	if (!(action->flags & SA_INTERRUPT))
 		local_irq_enable();
 
diff --git a/arch/arm/kernel/time.c b/arch/arm/kernel/time.c
index c232f24f4a6..06054c9ba07 100644
--- a/arch/arm/kernel/time.c
+++ b/arch/arm/kernel/time.c
@@ -381,6 +381,95 @@ static struct sysdev_class timer_sysclass = {
 	.resume		= timer_resume,
 };
 
+#ifdef CONFIG_NO_IDLE_HZ
+static int timer_dyn_tick_enable(void)
+{
+	struct dyn_tick_timer *dyn_tick = system_timer->dyn_tick;
+	unsigned long flags;
+	int ret = -ENODEV;
+
+	if (dyn_tick) {
+		write_seqlock_irqsave(&xtime_lock, flags);
+		ret = 0;
+		if (!(dyn_tick->state & DYN_TICK_ENABLED)) {
+			ret = dyn_tick->enable();
+
+			if (ret == 0)
+				dyn_tick->state |= DYN_TICK_ENABLED;
+		}
+		write_sequnlock_irqrestore(&xtime_lock, flags);
+	}
+
+	return ret;
+}
+
+static int timer_dyn_tick_disable(void)
+{
+	struct dyn_tick_timer *dyn_tick = system_timer->dyn_tick;
+	unsigned long flags;
+	int ret = -ENODEV;
+
+	if (dyn_tick) {
+		write_seqlock_irqsave(&xtime_lock, flags);
+		ret = 0;
+		if (dyn_tick->state & DYN_TICK_ENABLED) {
+			ret = dyn_tick->disable();
+
+			if (ret == 0)
+				dyn_tick->state &= ~DYN_TICK_ENABLED;
+		}
+		write_sequnlock_irqrestore(&xtime_lock, flags);
+	}
+
+	return ret;
+}
+
+void timer_dyn_reprogram(void)
+{
+	struct dyn_tick_timer *dyn_tick = system_timer->dyn_tick;
+	unsigned long flags;
+
+	write_seqlock_irqsave(&xtime_lock, flags);
+	if (dyn_tick->state & DYN_TICK_ENABLED)
+		dyn_tick->reprogram(next_timer_interrupt() - jiffies);
+	write_sequnlock_irqrestore(&xtime_lock, flags);
+}
+
+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)
+{
+	unsigned int enable = simple_strtoul(buf, NULL, 2);
+
+	if (enable)
+		timer_dyn_tick_enable();
+	else
+		timer_dyn_tick_disable();
+
+	return count;
+}
+static SYSDEV_ATTR(dyn_tick, 0644, timer_show_dyn_tick, timer_set_dyn_tick);
+
+/*
+ * dyntick=enable|disable
+ */
+static char dyntick_str[4] __initdata = "";
+
+static int __init dyntick_setup(char *str)
+{
+	if (str)
+		strlcpy(dyntick_str, str, sizeof(dyntick_str));
+	return 1;
+}
+
+__setup("dyntick=", dyntick_setup);
+#endif
+
 static int __init timer_init_sysfs(void)
 {
 	int ret = sysdev_class_register(&timer_sysclass);
@@ -388,6 +477,20 @@ static int __init timer_init_sysfs(void)
 		system_timer->dev.cls = &timer_sysclass;
 		ret = sysdev_register(&system_timer->dev);
 	}
+
+#ifdef CONFIG_NO_IDLE_HZ
+	if (ret == 0 && system_timer->dyn_tick) {
+		ret = sysdev_create_file(&system_timer->dev, &attr_dyn_tick);
+
+		/*
+		 * Turn on dynamic tick after calibrate delay
+		 * for correct bogomips
+		 */
+		if (ret == 0 && dyntick_str[0] == 'e')
+			ret = timer_dyn_tick_enable();
+	}
+#endif
+
 	return ret;
 }