1 /* 2 * linux/kernel/time/clockevents.c 3 * 4 * This file contains functions which manage clock event devices. 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 * This code is licenced under the GPL version 2. For details see 11 * kernel-base/COPYING. 12 */ 13 14 #include <linux/clockchips.h> 15 #include <linux/hrtimer.h> 16 #include <linux/init.h> 17 #include <linux/module.h> 18 #include <linux/notifier.h> 19 #include <linux/smp.h> 20 #include <linux/sysdev.h> 21 22 /* The registered clock event devices */ 23 static LIST_HEAD(clockevent_devices); 24 static LIST_HEAD(clockevents_released); 25 26 /* Notification for clock events */ 27 static RAW_NOTIFIER_HEAD(clockevents_chain); 28 29 /* Protection for the above */ 30 static DEFINE_SPINLOCK(clockevents_lock); 31 32 /** 33 * clockevents_delta2ns - Convert a latch value (device ticks) to nanoseconds 34 * @latch: value to convert 35 * @evt: pointer to clock event device descriptor 36 * 37 * Math helper, returns latch value converted to nanoseconds (bound checked) 38 */ 39 unsigned long clockevent_delta2ns(unsigned long latch, 40 struct clock_event_device *evt) 41 { 42 u64 clc = ((u64) latch << evt->shift); 43 44 do_div(clc, evt->mult); 45 if (clc < 1000) 46 clc = 1000; 47 if (clc > LONG_MAX) 48 clc = LONG_MAX; 49 50 return (unsigned long) clc; 51 } 52 53 /** 54 * clockevents_set_mode - set the operating mode of a clock event device 55 * @dev: device to modify 56 * @mode: new mode 57 * 58 * Must be called with interrupts disabled ! 59 */ 60 void clockevents_set_mode(struct clock_event_device *dev, 61 enum clock_event_mode mode) 62 { 63 if (dev->mode != mode) { 64 dev->set_mode(mode, dev); 65 dev->mode = mode; 66 } 67 } 68 69 /** 70 * clockevents_program_event - Reprogram the clock event device. 71 * @expires: absolute expiry time (monotonic clock) 72 * 73 * Returns 0 on success, -ETIME when the event is in the past. 74 */ 75 int clockevents_program_event(struct clock_event_device *dev, ktime_t expires, 76 ktime_t now) 77 { 78 unsigned long long clc; 79 int64_t delta; 80 81 delta = ktime_to_ns(ktime_sub(expires, now)); 82 83 if (delta <= 0) 84 return -ETIME; 85 86 dev->next_event = expires; 87 88 if (dev->mode == CLOCK_EVT_MODE_SHUTDOWN) 89 return 0; 90 91 if (delta > dev->max_delta_ns) 92 delta = dev->max_delta_ns; 93 if (delta < dev->min_delta_ns) 94 delta = dev->min_delta_ns; 95 96 clc = delta * dev->mult; 97 clc >>= dev->shift; 98 99 return dev->set_next_event((unsigned long) clc, dev); 100 } 101 102 /** 103 * clockevents_register_notifier - register a clock events change listener 104 */ 105 int clockevents_register_notifier(struct notifier_block *nb) 106 { 107 int ret; 108 109 spin_lock(&clockevents_lock); 110 ret = raw_notifier_chain_register(&clockevents_chain, nb); 111 spin_unlock(&clockevents_lock); 112 113 return ret; 114 } 115 116 /** 117 * clockevents_unregister_notifier - unregister a clock events change listener 118 */ 119 void clockevents_unregister_notifier(struct notifier_block *nb) 120 { 121 spin_lock(&clockevents_lock); 122 raw_notifier_chain_unregister(&clockevents_chain, nb); 123 spin_unlock(&clockevents_lock); 124 } 125 126 /* 127 * Notify about a clock event change. Called with clockevents_lock 128 * held. 129 */ 130 static void clockevents_do_notify(unsigned long reason, void *dev) 131 { 132 raw_notifier_call_chain(&clockevents_chain, reason, dev); 133 } 134 135 /* 136 * Called after a notify add to make devices availble which were 137 * released from the notifier call. 138 */ 139 static void clockevents_notify_released(void) 140 { 141 struct clock_event_device *dev; 142 143 while (!list_empty(&clockevents_released)) { 144 dev = list_entry(clockevents_released.next, 145 struct clock_event_device, list); 146 list_del(&dev->list); 147 list_add(&dev->list, &clockevent_devices); 148 clockevents_do_notify(CLOCK_EVT_NOTIFY_ADD, dev); 149 } 150 } 151 152 /** 153 * clockevents_register_device - register a clock event device 154 * @dev: device to register 155 */ 156 void clockevents_register_device(struct clock_event_device *dev) 157 { 158 BUG_ON(dev->mode != CLOCK_EVT_MODE_UNUSED); 159 160 spin_lock(&clockevents_lock); 161 162 list_add(&dev->list, &clockevent_devices); 163 clockevents_do_notify(CLOCK_EVT_NOTIFY_ADD, dev); 164 clockevents_notify_released(); 165 166 spin_unlock(&clockevents_lock); 167 } 168 169 /* 170 * Noop handler when we shut down an event device 171 */ 172 static void clockevents_handle_noop(struct clock_event_device *dev) 173 { 174 } 175 176 /** 177 * clockevents_exchange_device - release and request clock devices 178 * @old: device to release (can be NULL) 179 * @new: device to request (can be NULL) 180 * 181 * Called from the notifier chain. clockevents_lock is held already 182 */ 183 void clockevents_exchange_device(struct clock_event_device *old, 184 struct clock_event_device *new) 185 { 186 unsigned long flags; 187 188 local_irq_save(flags); 189 /* 190 * Caller releases a clock event device. We queue it into the 191 * released list and do a notify add later. 192 */ 193 if (old) { 194 old->event_handler = clockevents_handle_noop; 195 clockevents_set_mode(old, CLOCK_EVT_MODE_UNUSED); 196 list_del(&old->list); 197 list_add(&old->list, &clockevents_released); 198 } 199 200 if (new) { 201 BUG_ON(new->mode != CLOCK_EVT_MODE_UNUSED); 202 clockevents_set_mode(new, CLOCK_EVT_MODE_SHUTDOWN); 203 } 204 local_irq_restore(flags); 205 } 206 207 /** 208 * clockevents_notify - notification about relevant events 209 */ 210 void clockevents_notify(unsigned long reason, void *arg) 211 { 212 spin_lock(&clockevents_lock); 213 clockevents_do_notify(reason, arg); 214 215 switch (reason) { 216 case CLOCK_EVT_NOTIFY_CPU_DEAD: 217 /* 218 * Unregister the clock event devices which were 219 * released from the users in the notify chain. 220 */ 221 while (!list_empty(&clockevents_released)) { 222 struct clock_event_device *dev; 223 224 dev = list_entry(clockevents_released.next, 225 struct clock_event_device, list); 226 list_del(&dev->list); 227 } 228 break; 229 default: 230 break; 231 } 232 spin_unlock(&clockevents_lock); 233 } 234 EXPORT_SYMBOL_GPL(clockevents_notify); 235 236