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 if (unlikely(!evt->mult)) { 45 evt->mult = 1; 46 WARN_ON(1); 47 } 48 49 do_div(clc, evt->mult); 50 if (clc < 1000) 51 clc = 1000; 52 if (clc > LONG_MAX) 53 clc = LONG_MAX; 54 55 return (unsigned long) clc; 56 } 57 58 /** 59 * clockevents_set_mode - set the operating mode of a clock event device 60 * @dev: device to modify 61 * @mode: new mode 62 * 63 * Must be called with interrupts disabled ! 64 */ 65 void clockevents_set_mode(struct clock_event_device *dev, 66 enum clock_event_mode mode) 67 { 68 if (dev->mode != mode) { 69 dev->set_mode(mode, dev); 70 dev->mode = mode; 71 72 /* 73 * A nsec2cyc multiplicator of 0 is invalid and we'd crash 74 * on it, so fix it up and emit a warning: 75 */ 76 if (mode == CLOCK_EVT_MODE_ONESHOT) { 77 if (unlikely(!dev->mult)) { 78 dev->mult = 1; 79 WARN_ON(1); 80 } 81 } 82 } 83 } 84 85 /** 86 * clockevents_shutdown - shutdown the device and clear next_event 87 * @dev: device to shutdown 88 */ 89 void clockevents_shutdown(struct clock_event_device *dev) 90 { 91 clockevents_set_mode(dev, CLOCK_EVT_MODE_SHUTDOWN); 92 dev->next_event.tv64 = KTIME_MAX; 93 } 94 95 /** 96 * clockevents_program_event - Reprogram the clock event device. 97 * @expires: absolute expiry time (monotonic clock) 98 * 99 * Returns 0 on success, -ETIME when the event is in the past. 100 */ 101 int clockevents_program_event(struct clock_event_device *dev, ktime_t expires, 102 ktime_t now) 103 { 104 unsigned long long clc; 105 int64_t delta; 106 107 if (unlikely(expires.tv64 < 0)) { 108 WARN_ON_ONCE(1); 109 return -ETIME; 110 } 111 112 delta = ktime_to_ns(ktime_sub(expires, now)); 113 114 if (delta <= 0) 115 return -ETIME; 116 117 dev->next_event = expires; 118 119 if (dev->mode == CLOCK_EVT_MODE_SHUTDOWN) 120 return 0; 121 122 if (delta > dev->max_delta_ns) 123 delta = dev->max_delta_ns; 124 if (delta < dev->min_delta_ns) 125 delta = dev->min_delta_ns; 126 127 clc = delta * dev->mult; 128 clc >>= dev->shift; 129 130 return dev->set_next_event((unsigned long) clc, dev); 131 } 132 133 /** 134 * clockevents_register_notifier - register a clock events change listener 135 */ 136 int clockevents_register_notifier(struct notifier_block *nb) 137 { 138 int ret; 139 140 spin_lock(&clockevents_lock); 141 ret = raw_notifier_chain_register(&clockevents_chain, nb); 142 spin_unlock(&clockevents_lock); 143 144 return ret; 145 } 146 147 /* 148 * Notify about a clock event change. Called with clockevents_lock 149 * held. 150 */ 151 static void clockevents_do_notify(unsigned long reason, void *dev) 152 { 153 raw_notifier_call_chain(&clockevents_chain, reason, dev); 154 } 155 156 /* 157 * Called after a notify add to make devices available which were 158 * released from the notifier call. 159 */ 160 static void clockevents_notify_released(void) 161 { 162 struct clock_event_device *dev; 163 164 while (!list_empty(&clockevents_released)) { 165 dev = list_entry(clockevents_released.next, 166 struct clock_event_device, list); 167 list_del(&dev->list); 168 list_add(&dev->list, &clockevent_devices); 169 clockevents_do_notify(CLOCK_EVT_NOTIFY_ADD, dev); 170 } 171 } 172 173 /** 174 * clockevents_register_device - register a clock event device 175 * @dev: device to register 176 */ 177 void clockevents_register_device(struct clock_event_device *dev) 178 { 179 BUG_ON(dev->mode != CLOCK_EVT_MODE_UNUSED); 180 BUG_ON(!dev->cpumask); 181 182 spin_lock(&clockevents_lock); 183 184 list_add(&dev->list, &clockevent_devices); 185 clockevents_do_notify(CLOCK_EVT_NOTIFY_ADD, dev); 186 clockevents_notify_released(); 187 188 spin_unlock(&clockevents_lock); 189 } 190 191 /* 192 * Noop handler when we shut down an event device 193 */ 194 void clockevents_handle_noop(struct clock_event_device *dev) 195 { 196 } 197 198 /** 199 * clockevents_exchange_device - release and request clock devices 200 * @old: device to release (can be NULL) 201 * @new: device to request (can be NULL) 202 * 203 * Called from the notifier chain. clockevents_lock is held already 204 */ 205 void clockevents_exchange_device(struct clock_event_device *old, 206 struct clock_event_device *new) 207 { 208 unsigned long flags; 209 210 local_irq_save(flags); 211 /* 212 * Caller releases a clock event device. We queue it into the 213 * released list and do a notify add later. 214 */ 215 if (old) { 216 clockevents_set_mode(old, CLOCK_EVT_MODE_UNUSED); 217 list_del(&old->list); 218 list_add(&old->list, &clockevents_released); 219 } 220 221 if (new) { 222 BUG_ON(new->mode != CLOCK_EVT_MODE_UNUSED); 223 clockevents_shutdown(new); 224 } 225 local_irq_restore(flags); 226 } 227 228 #ifdef CONFIG_GENERIC_CLOCKEVENTS 229 /** 230 * clockevents_notify - notification about relevant events 231 */ 232 void clockevents_notify(unsigned long reason, void *arg) 233 { 234 struct list_head *node, *tmp; 235 236 spin_lock(&clockevents_lock); 237 clockevents_do_notify(reason, arg); 238 239 switch (reason) { 240 case CLOCK_EVT_NOTIFY_CPU_DEAD: 241 /* 242 * Unregister the clock event devices which were 243 * released from the users in the notify chain. 244 */ 245 list_for_each_safe(node, tmp, &clockevents_released) 246 list_del(node); 247 break; 248 default: 249 break; 250 } 251 spin_unlock(&clockevents_lock); 252 } 253 EXPORT_SYMBOL_GPL(clockevents_notify); 254 #endif 255