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 return clockevents_program_event(dev, expires, force); 32 } 33 34 /** 35 * tick_resume_onshot - resume oneshot mode 36 */ 37 void tick_resume_oneshot(void) 38 { 39 struct clock_event_device *dev = __this_cpu_read(tick_cpu_device.evtdev); 40 41 clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT); 42 clockevents_program_event(dev, ktime_get(), true); 43 } 44 45 /** 46 * tick_setup_oneshot - setup the event device for oneshot mode (hres or nohz) 47 */ 48 void tick_setup_oneshot(struct clock_event_device *newdev, 49 void (*handler)(struct clock_event_device *), 50 ktime_t next_event) 51 { 52 newdev->event_handler = handler; 53 clockevents_set_mode(newdev, CLOCK_EVT_MODE_ONESHOT); 54 clockevents_program_event(newdev, next_event, true); 55 } 56 57 /** 58 * tick_switch_to_oneshot - switch to oneshot mode 59 */ 60 int tick_switch_to_oneshot(void (*handler)(struct clock_event_device *)) 61 { 62 struct tick_device *td = &__get_cpu_var(tick_cpu_device); 63 struct clock_event_device *dev = td->evtdev; 64 65 if (!dev || !(dev->features & CLOCK_EVT_FEAT_ONESHOT) || 66 !tick_device_is_functional(dev)) { 67 68 printk(KERN_INFO "Clockevents: " 69 "could not switch to one-shot mode:"); 70 if (!dev) { 71 printk(" no tick device\n"); 72 } else { 73 if (!tick_device_is_functional(dev)) 74 printk(" %s is not functional.\n", dev->name); 75 else 76 printk(" %s does not support one-shot mode.\n", 77 dev->name); 78 } 79 return -EINVAL; 80 } 81 82 td->mode = TICKDEV_MODE_ONESHOT; 83 dev->event_handler = handler; 84 clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT); 85 tick_broadcast_switch_to_oneshot(); 86 return 0; 87 } 88 89 /** 90 * tick_check_oneshot_mode - check whether the system is in oneshot mode 91 * 92 * returns 1 when either nohz or highres are enabled. otherwise 0. 93 */ 94 int tick_oneshot_mode_active(void) 95 { 96 unsigned long flags; 97 int ret; 98 99 local_irq_save(flags); 100 ret = __this_cpu_read(tick_cpu_device.mode) == TICKDEV_MODE_ONESHOT; 101 local_irq_restore(flags); 102 103 return ret; 104 } 105 106 #ifdef CONFIG_HIGH_RES_TIMERS 107 /** 108 * tick_init_highres - switch to high resolution mode 109 * 110 * Called with interrupts disabled. 111 */ 112 int tick_init_highres(void) 113 { 114 return tick_switch_to_oneshot(hrtimer_interrupt); 115 } 116 #endif 117