Thomas Gleixner | 79bf2bb | 2007-02-16 01:28:03 -0800 | [diff] [blame] | 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> |
Russell King | d7b9068 | 2008-04-17 07:46:24 +0200 | [diff] [blame] | 17 | #include <linux/interrupt.h> |
Thomas Gleixner | 79bf2bb | 2007-02-16 01:28:03 -0800 | [diff] [blame] | 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 | |
Thomas Gleixner | 80a05b9 | 2010-03-12 17:34:14 +0100 | [diff] [blame] | 25 | /* Limit min_delta to a jiffie */ |
| 26 | #define MIN_DELTA_LIMIT (NSEC_PER_SEC / HZ) |
| 27 | |
| 28 | static int tick_increase_min_delta(struct clock_event_device *dev) |
| 29 | { |
| 30 | /* Nothing to do if we already reached the limit */ |
| 31 | if (dev->min_delta_ns >= MIN_DELTA_LIMIT) |
| 32 | return -ETIME; |
| 33 | |
| 34 | if (dev->min_delta_ns < 5000) |
| 35 | dev->min_delta_ns = 5000; |
| 36 | else |
| 37 | dev->min_delta_ns += dev->min_delta_ns >> 1; |
| 38 | |
| 39 | if (dev->min_delta_ns > MIN_DELTA_LIMIT) |
| 40 | dev->min_delta_ns = MIN_DELTA_LIMIT; |
| 41 | |
| 42 | printk(KERN_WARNING "CE: %s increased min_delta_ns to %llu nsec\n", |
| 43 | dev->name ? dev->name : "?", |
| 44 | (unsigned long long) dev->min_delta_ns); |
| 45 | return 0; |
| 46 | } |
| 47 | |
Thomas Gleixner | 79bf2bb | 2007-02-16 01:28:03 -0800 | [diff] [blame] | 48 | /** |
Thomas Gleixner | 7205656 | 2008-09-03 21:37:03 +0000 | [diff] [blame] | 49 | * tick_program_event internal worker function |
Thomas Gleixner | 79bf2bb | 2007-02-16 01:28:03 -0800 | [diff] [blame] | 50 | */ |
Thomas Gleixner | 1fb9b7d | 2008-09-03 21:37:14 +0000 | [diff] [blame] | 51 | int tick_dev_program_event(struct clock_event_device *dev, ktime_t expires, |
| 52 | int force) |
Thomas Gleixner | 79bf2bb | 2007-02-16 01:28:03 -0800 | [diff] [blame] | 53 | { |
Thomas Gleixner | 79bf2bb | 2007-02-16 01:28:03 -0800 | [diff] [blame] | 54 | ktime_t now = ktime_get(); |
Thomas Gleixner | 1fb9b7d | 2008-09-03 21:37:14 +0000 | [diff] [blame] | 55 | int i; |
Thomas Gleixner | 79bf2bb | 2007-02-16 01:28:03 -0800 | [diff] [blame] | 56 | |
Thomas Gleixner | 1fb9b7d | 2008-09-03 21:37:14 +0000 | [diff] [blame] | 57 | for (i = 0;;) { |
Thomas Gleixner | 79bf2bb | 2007-02-16 01:28:03 -0800 | [diff] [blame] | 58 | int ret = clockevents_program_event(dev, expires, now); |
| 59 | |
| 60 | if (!ret || !force) |
| 61 | return ret; |
Thomas Gleixner | 1fb9b7d | 2008-09-03 21:37:14 +0000 | [diff] [blame] | 62 | |
Thomas Gleixner | 80a05b9 | 2010-03-12 17:34:14 +0100 | [diff] [blame] | 63 | dev->retries++; |
Thomas Gleixner | 1fb9b7d | 2008-09-03 21:37:14 +0000 | [diff] [blame] | 64 | /* |
Thomas Gleixner | 80a05b9 | 2010-03-12 17:34:14 +0100 | [diff] [blame] | 65 | * We tried 3 times to program the device with the given |
| 66 | * min_delta_ns. If that's not working then we increase it |
Thomas Gleixner | 1fb9b7d | 2008-09-03 21:37:14 +0000 | [diff] [blame] | 67 | * and emit a warning. |
| 68 | */ |
| 69 | if (++i > 2) { |
Thomas Gleixner | 61c22c3 | 2008-09-09 21:38:57 +0200 | [diff] [blame] | 70 | /* Increase the min. delta and try again */ |
Thomas Gleixner | 80a05b9 | 2010-03-12 17:34:14 +0100 | [diff] [blame] | 71 | if (tick_increase_min_delta(dev)) { |
| 72 | /* |
| 73 | * Get out of the loop if min_delta_ns |
| 74 | * hit the limit already. That's |
| 75 | * better than staying here forever. |
| 76 | * |
| 77 | * We clear next_event so we have a |
| 78 | * chance that the box survives. |
| 79 | */ |
| 80 | printk(KERN_WARNING |
| 81 | "CE: Reprogramming failure. Giving up\n"); |
| 82 | dev->next_event.tv64 = KTIME_MAX; |
| 83 | return -ETIME; |
| 84 | } |
Thomas Gleixner | 1fb9b7d | 2008-09-03 21:37:14 +0000 | [diff] [blame] | 85 | i = 0; |
| 86 | } |
| 87 | |
Thomas Gleixner | 79bf2bb | 2007-02-16 01:28:03 -0800 | [diff] [blame] | 88 | now = ktime_get(); |
Thomas Gleixner | 1fb9b7d | 2008-09-03 21:37:14 +0000 | [diff] [blame] | 89 | expires = ktime_add_ns(now, dev->min_delta_ns); |
Thomas Gleixner | 79bf2bb | 2007-02-16 01:28:03 -0800 | [diff] [blame] | 90 | } |
| 91 | } |
| 92 | |
| 93 | /** |
Thomas Gleixner | 7205656 | 2008-09-03 21:37:03 +0000 | [diff] [blame] | 94 | * tick_program_event |
| 95 | */ |
| 96 | int tick_program_event(ktime_t expires, int force) |
| 97 | { |
| 98 | struct clock_event_device *dev = __get_cpu_var(tick_cpu_device).evtdev; |
| 99 | |
Thomas Gleixner | 1fb9b7d | 2008-09-03 21:37:14 +0000 | [diff] [blame] | 100 | return tick_dev_program_event(dev, expires, force); |
Thomas Gleixner | 7205656 | 2008-09-03 21:37:03 +0000 | [diff] [blame] | 101 | } |
| 102 | |
| 103 | /** |
Thomas Gleixner | cd05a1f | 2007-03-17 00:25:52 +0100 | [diff] [blame] | 104 | * tick_resume_onshot - resume oneshot mode |
| 105 | */ |
| 106 | void tick_resume_oneshot(void) |
| 107 | { |
| 108 | struct tick_device *td = &__get_cpu_var(tick_cpu_device); |
| 109 | struct clock_event_device *dev = td->evtdev; |
| 110 | |
| 111 | clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT); |
| 112 | tick_program_event(ktime_get(), 1); |
| 113 | } |
| 114 | |
| 115 | /** |
Thomas Gleixner | 79bf2bb | 2007-02-16 01:28:03 -0800 | [diff] [blame] | 116 | * tick_setup_oneshot - setup the event device for oneshot mode (hres or nohz) |
| 117 | */ |
| 118 | void tick_setup_oneshot(struct clock_event_device *newdev, |
| 119 | void (*handler)(struct clock_event_device *), |
| 120 | ktime_t next_event) |
| 121 | { |
| 122 | newdev->event_handler = handler; |
| 123 | clockevents_set_mode(newdev, CLOCK_EVT_MODE_ONESHOT); |
Thomas Gleixner | 1fb9b7d | 2008-09-03 21:37:14 +0000 | [diff] [blame] | 124 | tick_dev_program_event(newdev, next_event, 1); |
Thomas Gleixner | 79bf2bb | 2007-02-16 01:28:03 -0800 | [diff] [blame] | 125 | } |
| 126 | |
| 127 | /** |
| 128 | * tick_switch_to_oneshot - switch to oneshot mode |
| 129 | */ |
| 130 | int tick_switch_to_oneshot(void (*handler)(struct clock_event_device *)) |
| 131 | { |
| 132 | struct tick_device *td = &__get_cpu_var(tick_cpu_device); |
| 133 | struct clock_event_device *dev = td->evtdev; |
| 134 | |
| 135 | if (!dev || !(dev->features & CLOCK_EVT_FEAT_ONESHOT) || |
Ingo Molnar | 820de5c | 2007-07-21 04:37:36 -0700 | [diff] [blame] | 136 | !tick_device_is_functional(dev)) { |
| 137 | |
| 138 | printk(KERN_INFO "Clockevents: " |
| 139 | "could not switch to one-shot mode:"); |
| 140 | if (!dev) { |
| 141 | printk(" no tick device\n"); |
| 142 | } else { |
| 143 | if (!tick_device_is_functional(dev)) |
| 144 | printk(" %s is not functional.\n", dev->name); |
| 145 | else |
| 146 | printk(" %s does not support one-shot mode.\n", |
| 147 | dev->name); |
| 148 | } |
Thomas Gleixner | 79bf2bb | 2007-02-16 01:28:03 -0800 | [diff] [blame] | 149 | return -EINVAL; |
Ingo Molnar | 820de5c | 2007-07-21 04:37:36 -0700 | [diff] [blame] | 150 | } |
Thomas Gleixner | 79bf2bb | 2007-02-16 01:28:03 -0800 | [diff] [blame] | 151 | |
| 152 | td->mode = TICKDEV_MODE_ONESHOT; |
| 153 | dev->event_handler = handler; |
| 154 | clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT); |
| 155 | tick_broadcast_switch_to_oneshot(); |
| 156 | return 0; |
| 157 | } |
| 158 | |
Thomas Gleixner | cd6d95d | 2009-06-12 11:29:27 +0200 | [diff] [blame] | 159 | /** |
| 160 | * tick_check_oneshot_mode - check whether the system is in oneshot mode |
| 161 | * |
| 162 | * returns 1 when either nohz or highres are enabled. otherwise 0. |
| 163 | */ |
| 164 | int tick_oneshot_mode_active(void) |
| 165 | { |
| 166 | unsigned long flags; |
| 167 | int ret; |
| 168 | |
| 169 | local_irq_save(flags); |
| 170 | ret = __get_cpu_var(tick_cpu_device).mode == TICKDEV_MODE_ONESHOT; |
| 171 | local_irq_restore(flags); |
| 172 | |
| 173 | return ret; |
| 174 | } |
| 175 | |
Thomas Gleixner | 79bf2bb | 2007-02-16 01:28:03 -0800 | [diff] [blame] | 176 | #ifdef CONFIG_HIGH_RES_TIMERS |
| 177 | /** |
| 178 | * tick_init_highres - switch to high resolution mode |
| 179 | * |
| 180 | * Called with interrupts disabled. |
| 181 | */ |
| 182 | int tick_init_highres(void) |
| 183 | { |
| 184 | return tick_switch_to_oneshot(hrtimer_interrupt); |
| 185 | } |
| 186 | #endif |