159 lines
3.7 KiB
C
159 lines
3.7 KiB
C
/*
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* linux/kernel/time/tick-oneshot.c
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*
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* This file contains functions which manage high resolution tick
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* related events.
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*
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* Copyright(C) 2005-2006, Thomas Gleixner <tglx@linutronix.de>
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* Copyright(C) 2005-2007, Red Hat, Inc., Ingo Molnar
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* Copyright(C) 2006-2007, Timesys Corp., Thomas Gleixner
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*
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* This code is licenced under the GPL version 2. For details see
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* kernel-base/COPYING.
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*/
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#include <linux/cpu.h>
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#include <linux/err.h>
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#include <linux/hrtimer.h>
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#include <linux/interrupt.h>
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#include <linux/percpu.h>
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#include <linux/profile.h>
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#include <linux/sched.h>
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#include <linux/tick.h>
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#include "tick-internal.h"
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/**
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* tick_program_event internal worker function
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*/
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int tick_dev_program_event(struct clock_event_device *dev, ktime_t expires,
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int force)
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{
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ktime_t now = ktime_get();
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int i;
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for (i = 0;;) {
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int ret = clockevents_program_event(dev, expires, now);
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if (!ret || !force)
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return ret;
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/*
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* We tried 2 times to program the device with the given
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* min_delta_ns. If that's not working then we double it
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* and emit a warning.
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*/
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if (++i > 2) {
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/* Increase the min. delta and try again */
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if (!dev->min_delta_ns)
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dev->min_delta_ns = 5000;
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else
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dev->min_delta_ns += dev->min_delta_ns >> 1;
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printk(KERN_WARNING
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"CE: %s increasing min_delta_ns to %lu nsec\n",
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dev->name ? dev->name : "?",
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dev->min_delta_ns << 1);
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i = 0;
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}
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now = ktime_get();
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expires = ktime_add_ns(now, dev->min_delta_ns);
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}
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}
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/**
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* tick_program_event
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*/
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int tick_program_event(ktime_t expires, int force)
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{
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struct clock_event_device *dev = __get_cpu_var(tick_cpu_device).evtdev;
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return tick_dev_program_event(dev, expires, force);
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}
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/**
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* tick_resume_onshot - resume oneshot mode
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*/
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void tick_resume_oneshot(void)
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{
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struct tick_device *td = &__get_cpu_var(tick_cpu_device);
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struct clock_event_device *dev = td->evtdev;
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clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT);
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tick_program_event(ktime_get(), 1);
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}
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/**
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* tick_setup_oneshot - setup the event device for oneshot mode (hres or nohz)
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*/
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void tick_setup_oneshot(struct clock_event_device *newdev,
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void (*handler)(struct clock_event_device *),
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ktime_t next_event)
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{
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newdev->event_handler = handler;
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clockevents_set_mode(newdev, CLOCK_EVT_MODE_ONESHOT);
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tick_dev_program_event(newdev, next_event, 1);
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}
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/**
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* tick_switch_to_oneshot - switch to oneshot mode
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*/
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int tick_switch_to_oneshot(void (*handler)(struct clock_event_device *))
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{
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struct tick_device *td = &__get_cpu_var(tick_cpu_device);
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struct clock_event_device *dev = td->evtdev;
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if (!dev || !(dev->features & CLOCK_EVT_FEAT_ONESHOT) ||
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!tick_device_is_functional(dev)) {
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printk(KERN_INFO "Clockevents: "
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"could not switch to one-shot mode:");
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if (!dev) {
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printk(" no tick device\n");
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} else {
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if (!tick_device_is_functional(dev))
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printk(" %s is not functional.\n", dev->name);
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else
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printk(" %s does not support one-shot mode.\n",
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dev->name);
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}
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return -EINVAL;
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}
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td->mode = TICKDEV_MODE_ONESHOT;
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dev->event_handler = handler;
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clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT);
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tick_broadcast_switch_to_oneshot();
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return 0;
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}
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/**
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* tick_check_oneshot_mode - check whether the system is in oneshot mode
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*
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* returns 1 when either nohz or highres are enabled. otherwise 0.
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*/
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int tick_oneshot_mode_active(void)
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{
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unsigned long flags;
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int ret;
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local_irq_save(flags);
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ret = __get_cpu_var(tick_cpu_device).mode == TICKDEV_MODE_ONESHOT;
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local_irq_restore(flags);
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return ret;
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}
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#ifdef CONFIG_HIGH_RES_TIMERS
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/**
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* tick_init_highres - switch to high resolution mode
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*
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* Called with interrupts disabled.
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*/
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int tick_init_highres(void)
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{
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return tick_switch_to_oneshot(hrtimer_interrupt);
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}
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#endif
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