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/irq.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 27 */ 28 int tick_program_event(ktime_t expires, int force) 29 { 30 struct clock_event_device *dev = __get_cpu_var(tick_cpu_device).evtdev; 31 ktime_t now = ktime_get(); 32 33 while (1) { 34 int ret = clockevents_program_event(dev, expires, now); 35 36 if (!ret || !force) 37 return ret; 38 now = ktime_get(); 39 expires = ktime_add(now, ktime_set(0, dev->min_delta_ns)); 40 } 41 } 42 43 /** 44 * tick_setup_oneshot - setup the event device for oneshot mode (hres or nohz) 45 */ 46 void tick_setup_oneshot(struct clock_event_device *newdev, 47 void (*handler)(struct clock_event_device *), 48 ktime_t next_event) 49 { 50 newdev->event_handler = handler; 51 clockevents_set_mode(newdev, CLOCK_EVT_MODE_ONESHOT); 52 clockevents_program_event(newdev, next_event, ktime_get()); 53 } 54 55 /** 56 * tick_switch_to_oneshot - switch to oneshot mode 57 */ 58 int tick_switch_to_oneshot(void (*handler)(struct clock_event_device *)) 59 { 60 struct tick_device *td = &__get_cpu_var(tick_cpu_device); 61 struct clock_event_device *dev = td->evtdev; 62 63 if (!dev || !(dev->features & CLOCK_EVT_FEAT_ONESHOT) || 64 !tick_device_is_functional(dev)) 65 return -EINVAL; 66 67 td->mode = TICKDEV_MODE_ONESHOT; 68 dev->event_handler = handler; 69 clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT); 70 tick_broadcast_switch_to_oneshot(); 71 return 0; 72 } 73 74 #ifdef CONFIG_HIGH_RES_TIMERS 75 /** 76 * tick_init_highres - switch to high resolution mode 77 * 78 * Called with interrupts disabled. 79 */ 80 int tick_init_highres(void) 81 { 82 return tick_switch_to_oneshot(hrtimer_interrupt); 83 } 84 #endif 85