1 /* 2 * linux/kernel/time/tick-oneshot.c 3 * 4 * This file contains functions which manage high resolution tick 5 * related events. 6 * 7 * Copyright(C) 2005-2006, Thomas Gleixner <tglx@linutronix.de> 8 * Copyright(C) 2005-2007, Red Hat, Inc., Ingo Molnar 9 * Copyright(C) 2006-2007, Timesys Corp., Thomas Gleixner 10 * 11 * This code is licenced under the GPL version 2. For details see 12 * kernel-base/COPYING. 13 */ 14 #include <linux/cpu.h> 15 #include <linux/err.h> 16 #include <linux/hrtimer.h> 17 #include <linux/interrupt.h> 18 #include <linux/percpu.h> 19 #include <linux/profile.h> 20 #include <linux/sched.h> 21 22 #include "tick-internal.h" 23 24 /** 25 * tick_program_event 26 */ 27 int tick_program_event(ktime_t expires, int force) 28 { 29 struct clock_event_device *dev = __this_cpu_read(tick_cpu_device.evtdev); 30 31 if (unlikely(expires == KTIME_MAX)) { 32 /* 33 * We don't need the clock event device any more, stop it. 34 */ 35 clockevents_switch_state(dev, CLOCK_EVT_STATE_ONESHOT_STOPPED); 36 return 0; 37 } 38 39 if (unlikely(clockevent_state_oneshot_stopped(dev))) { 40 /* 41 * We need the clock event again, configure it in ONESHOT mode 42 * before using it. 43 */ 44 clockevents_switch_state(dev, CLOCK_EVT_STATE_ONESHOT); 45 } 46 47 return clockevents_program_event(dev, expires, force); 48 } 49 50 /** 51 * tick_resume_onshot - resume oneshot mode 52 */ 53 void tick_resume_oneshot(void) 54 { 55 struct clock_event_device *dev = __this_cpu_read(tick_cpu_device.evtdev); 56 57 clockevents_switch_state(dev, CLOCK_EVT_STATE_ONESHOT); 58 clockevents_program_event(dev, ktime_get(), true); 59 } 60 61 /** 62 * tick_setup_oneshot - setup the event device for oneshot mode (hres or nohz) 63 */ 64 void tick_setup_oneshot(struct clock_event_device *newdev, 65 void (*handler)(struct clock_event_device *), 66 ktime_t next_event) 67 { 68 newdev->event_handler = handler; 69 clockevents_switch_state(newdev, CLOCK_EVT_STATE_ONESHOT); 70 clockevents_program_event(newdev, next_event, true); 71 } 72 73 /** 74 * tick_switch_to_oneshot - switch to oneshot mode 75 */ 76 int tick_switch_to_oneshot(void (*handler)(struct clock_event_device *)) 77 { 78 struct tick_device *td = this_cpu_ptr(&tick_cpu_device); 79 struct clock_event_device *dev = td->evtdev; 80 81 if (!dev || !(dev->features & CLOCK_EVT_FEAT_ONESHOT) || 82 !tick_device_is_functional(dev)) { 83 84 printk(KERN_INFO "Clockevents: " 85 "could not switch to one-shot mode:"); 86 if (!dev) { 87 printk(" no tick device\n"); 88 } else { 89 if (!tick_device_is_functional(dev)) 90 printk(" %s is not functional.\n", dev->name); 91 else 92 printk(" %s does not support one-shot mode.\n", 93 dev->name); 94 } 95 return -EINVAL; 96 } 97 98 td->mode = TICKDEV_MODE_ONESHOT; 99 dev->event_handler = handler; 100 clockevents_switch_state(dev, CLOCK_EVT_STATE_ONESHOT); 101 tick_broadcast_switch_to_oneshot(); 102 return 0; 103 } 104 105 /** 106 * tick_check_oneshot_mode - check whether the system is in oneshot mode 107 * 108 * returns 1 when either nohz or highres are enabled. otherwise 0. 109 */ 110 int tick_oneshot_mode_active(void) 111 { 112 unsigned long flags; 113 int ret; 114 115 local_irq_save(flags); 116 ret = __this_cpu_read(tick_cpu_device.mode) == TICKDEV_MODE_ONESHOT; 117 local_irq_restore(flags); 118 119 return ret; 120 } 121 122 #ifdef CONFIG_HIGH_RES_TIMERS 123 /** 124 * tick_init_highres - switch to high resolution mode 125 * 126 * Called with interrupts disabled. 127 */ 128 int tick_init_highres(void) 129 { 130 return tick_switch_to_oneshot(hrtimer_interrupt); 131 } 132 #endif 133