From 8749af68216e1ebf6460992fce548f400ecf63a4 Mon Sep 17 00:00:00 2001 From: Russell King Date: Sat, 25 Jun 2005 19:39:45 +0100 Subject: [PATCH] ARM: Generic Dynamic Tick Timer support for ARM, take 4 This patch adds support for Dynamic Tick Timer for ARM. Dynamic Tick is also known as VST (Variable Scheduling Timeouts). Dynamic Tick has been in use in the OMAP tree since last October. The patch is not intrusive, and does not do anything unless CONFIG_NO_IDLE_HZ is defined. This patch has the following fixed based on comments from RMK: - Time is updated before calling interrupt handlers. - Added new interrupt flag SA_TIMER to avoid duplicate timer interrupts - Moved struct dyn_tick_timer to time.h until we at some point probably have an arch independent dyn-tick.h - Cleaned up testing for DYN_TICK_ENABLED in irq.c I've cleaned up this patch to fix some remaining issues: - Call the timer tick handler with irqs disabled, as it would be from a normal interrupt - if we have a dyn_tick, we better implement all methods. - generic timer_dyn_reprogram() call, to be called before sleeping - added command line option - "dyntick=" to allow boot-time control of this feature -- rmk Signed-off-by: Tony Lindgren Signed-off-by: Russell King --- arch/arm/kernel/time.c | 103 +++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 103 insertions(+) (limited to 'arch/arm/kernel/time.c') diff --git a/arch/arm/kernel/time.c b/arch/arm/kernel/time.c index c232f24f4a60..06054c9ba074 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; } -- cgit v1.2.3