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