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 dev->next_event = KTIME_MAX; 37 return 0; 38 } 39 40 if (unlikely(clockevent_state_oneshot_stopped(dev))) { 41 /* 42 * We need the clock event again, configure it in ONESHOT mode 43 * before using it. 44 */ 45 clockevents_switch_state(dev, CLOCK_EVT_STATE_ONESHOT); 46 } 47 48 return clockevents_program_event(dev, expires, force); 49 } 50 51 /** 52 * tick_resume_onshot - resume oneshot mode 53 */ 54 void tick_resume_oneshot(void) 55 { 56 struct clock_event_device *dev = __this_cpu_read(tick_cpu_device.evtdev); 57 58 clockevents_switch_state(dev, CLOCK_EVT_STATE_ONESHOT); 59 clockevents_program_event(dev, ktime_get(), true); 60 } 61 62 /** 63 * tick_setup_oneshot - setup the event device for oneshot mode (hres or nohz) 64 */ 65 void tick_setup_oneshot(struct clock_event_device *newdev, 66 void (*handler)(struct clock_event_device *), 67 ktime_t next_event) 68 { 69 newdev->event_handler = handler; 70 clockevents_switch_state(newdev, CLOCK_EVT_STATE_ONESHOT); 71 clockevents_program_event(newdev, next_event, true); 72 } 73 74 /** 75 * tick_switch_to_oneshot - switch to oneshot mode 76 */ 77 int tick_switch_to_oneshot(void (*handler)(struct clock_event_device *)) 78 { 79 struct tick_device *td = this_cpu_ptr(&tick_cpu_device); 80 struct clock_event_device *dev = td->evtdev; 81 82 if (!dev || !(dev->features & CLOCK_EVT_FEAT_ONESHOT) || 83 !tick_device_is_functional(dev)) { 84 85 printk(KERN_INFO "Clockevents: " 86 "could not switch to one-shot mode:"); 87 if (!dev) { 88 printk(" no tick device\n"); 89 } else { 90 if (!tick_device_is_functional(dev)) 91 printk(" %s is not functional.\n", dev->name); 92 else 93 printk(" %s does not support one-shot mode.\n", 94 dev->name); 95 } 96 return -EINVAL; 97 } 98 99 td->mode = TICKDEV_MODE_ONESHOT; 100 dev->event_handler = handler; 101 clockevents_switch_state(dev, CLOCK_EVT_STATE_ONESHOT); 102 tick_broadcast_switch_to_oneshot(); 103 return 0; 104 } 105 106 /** 107 * tick_check_oneshot_mode - check whether the system is in oneshot mode 108 * 109 * returns 1 when either nohz or highres are enabled. otherwise 0. 110 */ 111 int tick_oneshot_mode_active(void) 112 { 113 unsigned long flags; 114 int ret; 115 116 local_irq_save(flags); 117 ret = __this_cpu_read(tick_cpu_device.mode) == TICKDEV_MODE_ONESHOT; 118 local_irq_restore(flags); 119 120 return ret; 121 } 122 123 #ifdef CONFIG_HIGH_RES_TIMERS 124 /** 125 * tick_init_highres - switch to high resolution mode 126 * 127 * Called with interrupts disabled. 128 */ 129 int tick_init_highres(void) 130 { 131 return tick_switch_to_oneshot(hrtimer_interrupt); 132 } 133 #endif 134