1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * This file contains functions which manage high resolution tick 4 * related events. 5 * 6 * Copyright(C) 2005-2006, Thomas Gleixner <tglx@linutronix.de> 7 * Copyright(C) 2005-2007, Red Hat, Inc., Ingo Molnar 8 * Copyright(C) 2006-2007, Timesys Corp., Thomas Gleixner 9 */ 10 #include <linux/cpu.h> 11 #include <linux/err.h> 12 #include <linux/hrtimer.h> 13 #include <linux/interrupt.h> 14 #include <linux/percpu.h> 15 #include <linux/profile.h> 16 #include <linux/sched.h> 17 18 #include "tick-internal.h" 19 20 /** 21 * tick_program_event - program the CPU local timer device for the next event 22 * @expires: the time at which the next timer event should occur 23 * @force: flag to force reprograming even if the event time hasn't changed 24 * 25 * Return: 0 on success, negative error code on failure 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_oneshot - 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 * @newdev: Pointer to the clock event device to configure 65 * @handler: Function to be called when the event device triggers an interrupt 66 * @next_event: Initial expiry time for the next event (in ktime) 67 * 68 * Configures the specified clock event device for onshot mode, 69 * assigns the given handler as its event callback, and programs 70 * the device to trigger at the specified next event time. 71 */ 72 void tick_setup_oneshot(struct clock_event_device *newdev, 73 void (*handler)(struct clock_event_device *), 74 ktime_t next_event) 75 { 76 newdev->event_handler = handler; 77 clockevents_switch_state(newdev, CLOCK_EVT_STATE_ONESHOT); 78 clockevents_program_event(newdev, next_event, true); 79 } 80 81 /** 82 * tick_switch_to_oneshot - switch to oneshot mode 83 * @handler: function to call when an event occurs on the tick device 84 * 85 * Return: 0 on success, -EINVAL if the tick device is not present, 86 * not functional, or does not support oneshot mode. 87 */ 88 int tick_switch_to_oneshot(void (*handler)(struct clock_event_device *)) 89 { 90 struct tick_device *td = this_cpu_ptr(&tick_cpu_device); 91 struct clock_event_device *dev = td->evtdev; 92 93 if (!dev || !(dev->features & CLOCK_EVT_FEAT_ONESHOT) || 94 !tick_device_is_functional(dev)) { 95 96 pr_info("Clockevents: could not switch to one-shot mode:"); 97 if (!dev) { 98 pr_cont(" no tick device\n"); 99 } else { 100 if (!tick_device_is_functional(dev)) 101 pr_cont(" %s is not functional.\n", dev->name); 102 else 103 pr_cont(" %s does not support one-shot mode.\n", 104 dev->name); 105 } 106 return -EINVAL; 107 } 108 109 td->mode = TICKDEV_MODE_ONESHOT; 110 dev->event_handler = handler; 111 clockevents_switch_state(dev, CLOCK_EVT_STATE_ONESHOT); 112 tick_broadcast_switch_to_oneshot(); 113 return 0; 114 } 115 116 /** 117 * tick_oneshot_mode_active - check whether the system is in oneshot mode 118 * 119 * Return: 1 when either nohz or highres are enabled, otherwise 0. 120 */ 121 int tick_oneshot_mode_active(void) 122 { 123 unsigned long flags; 124 int ret; 125 126 local_irq_save(flags); 127 ret = __this_cpu_read(tick_cpu_device.mode) == TICKDEV_MODE_ONESHOT; 128 local_irq_restore(flags); 129 130 return ret; 131 } 132 133 #ifdef CONFIG_HIGH_RES_TIMERS 134 /** 135 * tick_init_highres - switch to high resolution mode 136 * 137 * Called with interrupts disabled. 138 * 139 * Return: 0 on success, -EINVAL if the tick device cannot switch 140 * to oneshot/high-resolution mode. 141 */ 142 int tick_init_highres(void) 143 { 144 return tick_switch_to_oneshot(hrtimer_interrupt); 145 } 146 #endif 147