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