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 */ 23 int tick_program_event(ktime_t expires, int force) 24 { 25 struct clock_event_device *dev = __this_cpu_read(tick_cpu_device.evtdev); 26 27 if (unlikely(expires == KTIME_MAX)) { 28 /* 29 * We don't need the clock event device any more, stop it. 30 */ 31 clockevents_switch_state(dev, CLOCK_EVT_STATE_ONESHOT_STOPPED); 32 dev->next_event = KTIME_MAX; 33 return 0; 34 } 35 36 if (unlikely(clockevent_state_oneshot_stopped(dev))) { 37 /* 38 * We need the clock event again, configure it in ONESHOT mode 39 * before using it. 40 */ 41 clockevents_switch_state(dev, CLOCK_EVT_STATE_ONESHOT); 42 } 43 44 return clockevents_program_event(dev, expires, force); 45 } 46 47 /** 48 * tick_resume_oneshot - resume oneshot mode 49 */ 50 void tick_resume_oneshot(void) 51 { 52 struct clock_event_device *dev = __this_cpu_read(tick_cpu_device.evtdev); 53 54 clockevents_switch_state(dev, CLOCK_EVT_STATE_ONESHOT); 55 clockevents_program_event(dev, ktime_get(), true); 56 } 57 58 /** 59 * tick_setup_oneshot - setup the event device for oneshot mode (hres or nohz) 60 */ 61 void tick_setup_oneshot(struct clock_event_device *newdev, 62 void (*handler)(struct clock_event_device *), 63 ktime_t next_event) 64 { 65 newdev->event_handler = handler; 66 clockevents_switch_state(newdev, CLOCK_EVT_STATE_ONESHOT); 67 clockevents_program_event(newdev, next_event, true); 68 } 69 70 /** 71 * tick_switch_to_oneshot - switch to oneshot mode 72 */ 73 int tick_switch_to_oneshot(void (*handler)(struct clock_event_device *)) 74 { 75 struct tick_device *td = this_cpu_ptr(&tick_cpu_device); 76 struct clock_event_device *dev = td->evtdev; 77 78 if (!dev || !(dev->features & CLOCK_EVT_FEAT_ONESHOT) || 79 !tick_device_is_functional(dev)) { 80 81 pr_info("Clockevents: could not switch to one-shot mode:"); 82 if (!dev) { 83 pr_cont(" no tick device\n"); 84 } else { 85 if (!tick_device_is_functional(dev)) 86 pr_cont(" %s is not functional.\n", dev->name); 87 else 88 pr_cont(" %s does not support one-shot mode.\n", 89 dev->name); 90 } 91 return -EINVAL; 92 } 93 94 td->mode = TICKDEV_MODE_ONESHOT; 95 dev->event_handler = handler; 96 clockevents_switch_state(dev, CLOCK_EVT_STATE_ONESHOT); 97 tick_broadcast_switch_to_oneshot(); 98 return 0; 99 } 100 101 /** 102 * tick_oneshot_mode_active - check whether the system is in oneshot mode 103 * 104 * returns 1 when either nohz or highres are enabled. otherwise 0. 105 */ 106 int tick_oneshot_mode_active(void) 107 { 108 unsigned long flags; 109 int ret; 110 111 local_irq_save(flags); 112 ret = __this_cpu_read(tick_cpu_device.mode) == TICKDEV_MODE_ONESHOT; 113 local_irq_restore(flags); 114 115 return ret; 116 } 117 118 #ifdef CONFIG_HIGH_RES_TIMERS 119 /** 120 * tick_init_highres - switch to high resolution mode 121 * 122 * Called with interrupts disabled. 123 */ 124 int tick_init_highres(void) 125 { 126 return tick_switch_to_oneshot(hrtimer_interrupt); 127 } 128 #endif 129