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 #include <linux/tick.h> 22 23 /* The registered clock event devices */ 24 static LIST_HEAD(clockevent_devices); 25 static LIST_HEAD(clockevents_released); 26 27 /* Notification for clock events */ 28 static RAW_NOTIFIER_HEAD(clockevents_chain); 29 30 /* Protection for the above */ 31 static DEFINE_SPINLOCK(clockevents_lock); 32 33 /** 34 * clockevents_delta2ns - Convert a latch value (device ticks) to nanoseconds 35 * @latch: value to convert 36 * @evt: pointer to clock event device descriptor 37 * 38 * Math helper, returns latch value converted to nanoseconds (bound checked) 39 */ 40 unsigned long clockevent_delta2ns(unsigned long latch, 41 struct clock_event_device *evt) 42 { 43 u64 clc = ((u64) latch << evt->shift); 44 45 if (unlikely(!evt->mult)) { 46 evt->mult = 1; 47 WARN_ON(1); 48 } 49 50 do_div(clc, evt->mult); 51 if (clc < 1000) 52 clc = 1000; 53 if (clc > LONG_MAX) 54 clc = LONG_MAX; 55 56 return (unsigned long) clc; 57 } 58 EXPORT_SYMBOL_GPL(clockevent_delta2ns); 59 60 /** 61 * clockevents_set_mode - set the operating mode of a clock event device 62 * @dev: device to modify 63 * @mode: new mode 64 * 65 * Must be called with interrupts disabled ! 66 */ 67 void clockevents_set_mode(struct clock_event_device *dev, 68 enum clock_event_mode mode) 69 { 70 if (dev->mode != mode) { 71 dev->set_mode(mode, dev); 72 dev->mode = mode; 73 74 /* 75 * A nsec2cyc multiplicator of 0 is invalid and we'd crash 76 * on it, so fix it up and emit a warning: 77 */ 78 if (mode == CLOCK_EVT_MODE_ONESHOT) { 79 if (unlikely(!dev->mult)) { 80 dev->mult = 1; 81 WARN_ON(1); 82 } 83 } 84 } 85 } 86 87 /** 88 * clockevents_shutdown - shutdown the device and clear next_event 89 * @dev: device to shutdown 90 */ 91 void clockevents_shutdown(struct clock_event_device *dev) 92 { 93 clockevents_set_mode(dev, CLOCK_EVT_MODE_SHUTDOWN); 94 dev->next_event.tv64 = KTIME_MAX; 95 } 96 97 /** 98 * clockevents_program_event - Reprogram the clock event device. 99 * @expires: absolute expiry time (monotonic clock) 100 * 101 * Returns 0 on success, -ETIME when the event is in the past. 102 */ 103 int clockevents_program_event(struct clock_event_device *dev, ktime_t expires, 104 ktime_t now) 105 { 106 unsigned long long clc; 107 int64_t delta; 108 109 if (unlikely(expires.tv64 < 0)) { 110 WARN_ON_ONCE(1); 111 return -ETIME; 112 } 113 114 delta = ktime_to_ns(ktime_sub(expires, now)); 115 116 if (delta <= 0) 117 return -ETIME; 118 119 dev->next_event = expires; 120 121 if (dev->mode == CLOCK_EVT_MODE_SHUTDOWN) 122 return 0; 123 124 if (delta > dev->max_delta_ns) 125 delta = dev->max_delta_ns; 126 if (delta < dev->min_delta_ns) 127 delta = dev->min_delta_ns; 128 129 clc = delta * dev->mult; 130 clc >>= dev->shift; 131 132 return dev->set_next_event((unsigned long) clc, dev); 133 } 134 135 /** 136 * clockevents_register_notifier - register a clock events change listener 137 */ 138 int clockevents_register_notifier(struct notifier_block *nb) 139 { 140 int ret; 141 142 spin_lock(&clockevents_lock); 143 ret = raw_notifier_chain_register(&clockevents_chain, nb); 144 spin_unlock(&clockevents_lock); 145 146 return ret; 147 } 148 149 /* 150 * Notify about a clock event change. Called with clockevents_lock 151 * held. 152 */ 153 static void clockevents_do_notify(unsigned long reason, void *dev) 154 { 155 raw_notifier_call_chain(&clockevents_chain, reason, dev); 156 } 157 158 /* 159 * Called after a notify add to make devices available which were 160 * released from the notifier call. 161 */ 162 static void clockevents_notify_released(void) 163 { 164 struct clock_event_device *dev; 165 166 while (!list_empty(&clockevents_released)) { 167 dev = list_entry(clockevents_released.next, 168 struct clock_event_device, list); 169 list_del(&dev->list); 170 list_add(&dev->list, &clockevent_devices); 171 clockevents_do_notify(CLOCK_EVT_NOTIFY_ADD, dev); 172 } 173 } 174 175 /** 176 * clockevents_register_device - register a clock event device 177 * @dev: device to register 178 */ 179 void clockevents_register_device(struct clock_event_device *dev) 180 { 181 BUG_ON(dev->mode != CLOCK_EVT_MODE_UNUSED); 182 BUG_ON(!dev->cpumask); 183 184 spin_lock(&clockevents_lock); 185 186 list_add(&dev->list, &clockevent_devices); 187 clockevents_do_notify(CLOCK_EVT_NOTIFY_ADD, dev); 188 clockevents_notify_released(); 189 190 spin_unlock(&clockevents_lock); 191 } 192 EXPORT_SYMBOL_GPL(clockevents_register_device); 193 194 /* 195 * Noop handler when we shut down an event device 196 */ 197 void clockevents_handle_noop(struct clock_event_device *dev) 198 { 199 } 200 201 /** 202 * clockevents_exchange_device - release and request clock devices 203 * @old: device to release (can be NULL) 204 * @new: device to request (can be NULL) 205 * 206 * Called from the notifier chain. clockevents_lock is held already 207 */ 208 void clockevents_exchange_device(struct clock_event_device *old, 209 struct clock_event_device *new) 210 { 211 unsigned long flags; 212 213 local_irq_save(flags); 214 /* 215 * Caller releases a clock event device. We queue it into the 216 * released list and do a notify add later. 217 */ 218 if (old) { 219 clockevents_set_mode(old, CLOCK_EVT_MODE_UNUSED); 220 list_del(&old->list); 221 list_add(&old->list, &clockevents_released); 222 } 223 224 if (new) { 225 BUG_ON(new->mode != CLOCK_EVT_MODE_UNUSED); 226 clockevents_shutdown(new); 227 } 228 local_irq_restore(flags); 229 } 230 231 #ifdef CONFIG_GENERIC_CLOCKEVENTS 232 /** 233 * clockevents_notify - notification about relevant events 234 */ 235 void clockevents_notify(unsigned long reason, void *arg) 236 { 237 struct list_head *node, *tmp; 238 239 spin_lock(&clockevents_lock); 240 clockevents_do_notify(reason, arg); 241 242 switch (reason) { 243 case CLOCK_EVT_NOTIFY_CPU_DEAD: 244 /* 245 * Unregister the clock event devices which were 246 * released from the users in the notify chain. 247 */ 248 list_for_each_safe(node, tmp, &clockevents_released) 249 list_del(node); 250 break; 251 default: 252 break; 253 } 254 spin_unlock(&clockevents_lock); 255 } 256 EXPORT_SYMBOL_GPL(clockevents_notify); 257 #endif 258