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 #include <linux/tick.h> 22 23 #include "tick-internal.h" 24 25 /** 26 * tick_program_event internal worker function 27 */ 28 int tick_dev_program_event(struct clock_event_device *dev, ktime_t expires, 29 int force) 30 { 31 ktime_t now = ktime_get(); 32 int i; 33 34 for (i = 0;;) { 35 int ret = clockevents_program_event(dev, expires, now); 36 37 if (!ret || !force) 38 return ret; 39 40 /* 41 * We tried 2 times to program the device with the given 42 * min_delta_ns. If that's not working then we double it 43 * and emit a warning. 44 */ 45 if (++i > 2) { 46 /* Increase the min. delta and try again */ 47 if (!dev->min_delta_ns) 48 dev->min_delta_ns = 5000; 49 else 50 dev->min_delta_ns += dev->min_delta_ns >> 1; 51 52 printk(KERN_WARNING 53 "CE: %s increasing min_delta_ns to %llu nsec\n", 54 dev->name ? dev->name : "?", 55 (unsigned long long) dev->min_delta_ns << 1); 56 57 i = 0; 58 } 59 60 now = ktime_get(); 61 expires = ktime_add_ns(now, dev->min_delta_ns); 62 } 63 } 64 65 /** 66 * tick_program_event 67 */ 68 int tick_program_event(ktime_t expires, int force) 69 { 70 struct clock_event_device *dev = __get_cpu_var(tick_cpu_device).evtdev; 71 72 return tick_dev_program_event(dev, expires, force); 73 } 74 75 /** 76 * tick_resume_onshot - resume oneshot mode 77 */ 78 void tick_resume_oneshot(void) 79 { 80 struct tick_device *td = &__get_cpu_var(tick_cpu_device); 81 struct clock_event_device *dev = td->evtdev; 82 83 clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT); 84 tick_program_event(ktime_get(), 1); 85 } 86 87 /** 88 * tick_setup_oneshot - setup the event device for oneshot mode (hres or nohz) 89 */ 90 void tick_setup_oneshot(struct clock_event_device *newdev, 91 void (*handler)(struct clock_event_device *), 92 ktime_t next_event) 93 { 94 newdev->event_handler = handler; 95 clockevents_set_mode(newdev, CLOCK_EVT_MODE_ONESHOT); 96 tick_dev_program_event(newdev, next_event, 1); 97 } 98 99 /** 100 * tick_switch_to_oneshot - switch to oneshot mode 101 */ 102 int tick_switch_to_oneshot(void (*handler)(struct clock_event_device *)) 103 { 104 struct tick_device *td = &__get_cpu_var(tick_cpu_device); 105 struct clock_event_device *dev = td->evtdev; 106 107 if (!dev || !(dev->features & CLOCK_EVT_FEAT_ONESHOT) || 108 !tick_device_is_functional(dev)) { 109 110 printk(KERN_INFO "Clockevents: " 111 "could not switch to one-shot mode:"); 112 if (!dev) { 113 printk(" no tick device\n"); 114 } else { 115 if (!tick_device_is_functional(dev)) 116 printk(" %s is not functional.\n", dev->name); 117 else 118 printk(" %s does not support one-shot mode.\n", 119 dev->name); 120 } 121 return -EINVAL; 122 } 123 124 td->mode = TICKDEV_MODE_ONESHOT; 125 dev->event_handler = handler; 126 clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT); 127 tick_broadcast_switch_to_oneshot(); 128 return 0; 129 } 130 131 /** 132 * tick_check_oneshot_mode - check whether the system is in oneshot mode 133 * 134 * returns 1 when either nohz or highres are enabled. otherwise 0. 135 */ 136 int tick_oneshot_mode_active(void) 137 { 138 unsigned long flags; 139 int ret; 140 141 local_irq_save(flags); 142 ret = __get_cpu_var(tick_cpu_device).mode == TICKDEV_MODE_ONESHOT; 143 local_irq_restore(flags); 144 145 return ret; 146 } 147 148 #ifdef CONFIG_HIGH_RES_TIMERS 149 /** 150 * tick_init_highres - switch to high resolution mode 151 * 152 * Called with interrupts disabled. 153 */ 154 int tick_init_highres(void) 155 { 156 return tick_switch_to_oneshot(hrtimer_interrupt); 157 } 158 #endif 159