| 1 | /* |
| 2 | * linux/kernel/time/tick-common.c |
| 3 | * |
| 4 | * This file contains the base functions to manage periodic tick |
| 5 | * related events. |
| 6 | * |
| 7 | * Copyright(C) 2005-2006, Thomas Gleixner <tglx@linutronix.de> |
| 8 | * Copyright(C) 2005-2007, Red Hat, Inc., Ingo Molnar |
| 9 | * Copyright(C) 2006-2007, Timesys Corp., Thomas Gleixner |
| 10 | * |
| 11 | * This code is licenced under the GPL version 2. For details see |
| 12 | * kernel-base/COPYING. |
| 13 | */ |
| 14 | #include <linux/cpu.h> |
| 15 | #include <linux/err.h> |
| 16 | #include <linux/hrtimer.h> |
| 17 | #include <linux/interrupt.h> |
| 18 | #include <linux/percpu.h> |
| 19 | #include <linux/profile.h> |
| 20 | #include <linux/sched.h> |
| 21 | |
| 22 | #include <asm/irq_regs.h> |
| 23 | |
| 24 | #include "tick-internal.h" |
| 25 | |
| 26 | /* |
| 27 | * Tick devices |
| 28 | */ |
| 29 | DEFINE_PER_CPU(struct tick_device, tick_cpu_device); |
| 30 | /* |
| 31 | * Tick next event: keeps track of the tick time |
| 32 | */ |
| 33 | ktime_t tick_next_period; |
| 34 | ktime_t tick_period; |
| 35 | int tick_do_timer_cpu __read_mostly = TICK_DO_TIMER_BOOT; |
| 36 | |
| 37 | /* |
| 38 | * Debugging: see timer_list.c |
| 39 | */ |
| 40 | struct tick_device *tick_get_device(int cpu) |
| 41 | { |
| 42 | return &per_cpu(tick_cpu_device, cpu); |
| 43 | } |
| 44 | |
| 45 | /** |
| 46 | * tick_is_oneshot_available - check for a oneshot capable event device |
| 47 | */ |
| 48 | int tick_is_oneshot_available(void) |
| 49 | { |
| 50 | struct clock_event_device *dev = __this_cpu_read(tick_cpu_device.evtdev); |
| 51 | |
| 52 | if (!dev || !(dev->features & CLOCK_EVT_FEAT_ONESHOT)) |
| 53 | return 0; |
| 54 | if (!(dev->features & CLOCK_EVT_FEAT_C3STOP)) |
| 55 | return 1; |
| 56 | return tick_broadcast_oneshot_available(); |
| 57 | } |
| 58 | |
| 59 | /* |
| 60 | * Periodic tick |
| 61 | */ |
| 62 | static void tick_periodic(int cpu) |
| 63 | { |
| 64 | if (tick_do_timer_cpu == cpu) { |
| 65 | write_seqlock(&jiffies_lock); |
| 66 | |
| 67 | /* Keep track of the next tick event */ |
| 68 | tick_next_period = ktime_add(tick_next_period, tick_period); |
| 69 | |
| 70 | do_timer(1); |
| 71 | write_sequnlock(&jiffies_lock); |
| 72 | } |
| 73 | |
| 74 | update_process_times(user_mode(get_irq_regs())); |
| 75 | profile_tick(CPU_PROFILING); |
| 76 | } |
| 77 | |
| 78 | /* |
| 79 | * Event handler for periodic ticks |
| 80 | */ |
| 81 | void tick_handle_periodic(struct clock_event_device *dev) |
| 82 | { |
| 83 | int cpu = smp_processor_id(); |
| 84 | ktime_t next; |
| 85 | |
| 86 | tick_periodic(cpu); |
| 87 | |
| 88 | if (dev->mode != CLOCK_EVT_MODE_ONESHOT) |
| 89 | return; |
| 90 | /* |
| 91 | * Setup the next period for devices, which do not have |
| 92 | * periodic mode: |
| 93 | */ |
| 94 | next = ktime_add(dev->next_event, tick_period); |
| 95 | for (;;) { |
| 96 | if (!clockevents_program_event(dev, next, false)) |
| 97 | return; |
| 98 | /* |
| 99 | * Have to be careful here. If we're in oneshot mode, |
| 100 | * before we call tick_periodic() in a loop, we need |
| 101 | * to be sure we're using a real hardware clocksource. |
| 102 | * Otherwise we could get trapped in an infinite |
| 103 | * loop, as the tick_periodic() increments jiffies, |
| 104 | * when then will increment time, posibly causing |
| 105 | * the loop to trigger again and again. |
| 106 | */ |
| 107 | if (timekeeping_valid_for_hres()) |
| 108 | tick_periodic(cpu); |
| 109 | next = ktime_add(next, tick_period); |
| 110 | } |
| 111 | } |
| 112 | |
| 113 | /* |
| 114 | * Setup the device for a periodic tick |
| 115 | */ |
| 116 | void tick_setup_periodic(struct clock_event_device *dev, int broadcast) |
| 117 | { |
| 118 | tick_set_periodic_handler(dev, broadcast); |
| 119 | |
| 120 | /* Broadcast setup ? */ |
| 121 | if (!tick_device_is_functional(dev)) |
| 122 | return; |
| 123 | |
| 124 | if ((dev->features & CLOCK_EVT_FEAT_PERIODIC) && |
| 125 | !tick_broadcast_oneshot_active()) { |
| 126 | clockevents_set_mode(dev, CLOCK_EVT_MODE_PERIODIC); |
| 127 | } else { |
| 128 | unsigned long seq; |
| 129 | ktime_t next; |
| 130 | |
| 131 | do { |
| 132 | seq = read_seqbegin(&jiffies_lock); |
| 133 | next = tick_next_period; |
| 134 | } while (read_seqretry(&jiffies_lock, seq)); |
| 135 | |
| 136 | clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT); |
| 137 | |
| 138 | for (;;) { |
| 139 | if (!clockevents_program_event(dev, next, false)) |
| 140 | return; |
| 141 | next = ktime_add(next, tick_period); |
| 142 | } |
| 143 | } |
| 144 | } |
| 145 | |
| 146 | /* |
| 147 | * Setup the tick device |
| 148 | */ |
| 149 | static void tick_setup_device(struct tick_device *td, |
| 150 | struct clock_event_device *newdev, int cpu, |
| 151 | const struct cpumask *cpumask) |
| 152 | { |
| 153 | ktime_t next_event; |
| 154 | void (*handler)(struct clock_event_device *) = NULL; |
| 155 | |
| 156 | /* |
| 157 | * First device setup ? |
| 158 | */ |
| 159 | if (!td->evtdev) { |
| 160 | /* |
| 161 | * If no cpu took the do_timer update, assign it to |
| 162 | * this cpu: |
| 163 | */ |
| 164 | if (tick_do_timer_cpu == TICK_DO_TIMER_BOOT) { |
| 165 | if (!tick_nohz_full_cpu(cpu)) |
| 166 | tick_do_timer_cpu = cpu; |
| 167 | else |
| 168 | tick_do_timer_cpu = TICK_DO_TIMER_NONE; |
| 169 | tick_next_period = ktime_get(); |
| 170 | tick_period = ktime_set(0, NSEC_PER_SEC / HZ); |
| 171 | } |
| 172 | |
| 173 | /* |
| 174 | * Startup in periodic mode first. |
| 175 | */ |
| 176 | td->mode = TICKDEV_MODE_PERIODIC; |
| 177 | } else { |
| 178 | handler = td->evtdev->event_handler; |
| 179 | next_event = td->evtdev->next_event; |
| 180 | td->evtdev->event_handler = clockevents_handle_noop; |
| 181 | } |
| 182 | |
| 183 | td->evtdev = newdev; |
| 184 | |
| 185 | /* |
| 186 | * When the device is not per cpu, pin the interrupt to the |
| 187 | * current cpu: |
| 188 | */ |
| 189 | if (!cpumask_equal(newdev->cpumask, cpumask)) |
| 190 | irq_set_affinity(newdev->irq, cpumask); |
| 191 | |
| 192 | /* |
| 193 | * When global broadcasting is active, check if the current |
| 194 | * device is registered as a placeholder for broadcast mode. |
| 195 | * This allows us to handle this x86 misfeature in a generic |
| 196 | * way. |
| 197 | */ |
| 198 | if (tick_device_uses_broadcast(newdev, cpu)) |
| 199 | return; |
| 200 | |
| 201 | if (td->mode == TICKDEV_MODE_PERIODIC) |
| 202 | tick_setup_periodic(newdev, 0); |
| 203 | else |
| 204 | tick_setup_oneshot(newdev, handler, next_event); |
| 205 | } |
| 206 | |
| 207 | /* |
| 208 | * Check, if the new registered device should be used. Called with |
| 209 | * clockevents_lock held and interrupts disabled. |
| 210 | */ |
| 211 | void tick_check_new_device(struct clock_event_device *newdev) |
| 212 | { |
| 213 | struct clock_event_device *curdev; |
| 214 | struct tick_device *td; |
| 215 | int cpu; |
| 216 | |
| 217 | cpu = smp_processor_id(); |
| 218 | if (!cpumask_test_cpu(cpu, newdev->cpumask)) |
| 219 | goto out_bc; |
| 220 | |
| 221 | td = &per_cpu(tick_cpu_device, cpu); |
| 222 | curdev = td->evtdev; |
| 223 | |
| 224 | /* cpu local device ? */ |
| 225 | if (!cpumask_equal(newdev->cpumask, cpumask_of(cpu))) { |
| 226 | |
| 227 | /* |
| 228 | * If the cpu affinity of the device interrupt can not |
| 229 | * be set, ignore it. |
| 230 | */ |
| 231 | if (!irq_can_set_affinity(newdev->irq)) |
| 232 | goto out_bc; |
| 233 | |
| 234 | /* |
| 235 | * If we have a cpu local device already, do not replace it |
| 236 | * by a non cpu local device |
| 237 | */ |
| 238 | if (curdev && cpumask_equal(curdev->cpumask, cpumask_of(cpu))) |
| 239 | goto out_bc; |
| 240 | } |
| 241 | |
| 242 | /* |
| 243 | * If we have an active device, then check the rating and the oneshot |
| 244 | * feature. |
| 245 | */ |
| 246 | if (curdev) { |
| 247 | /* |
| 248 | * Prefer one shot capable devices ! |
| 249 | */ |
| 250 | if ((curdev->features & CLOCK_EVT_FEAT_ONESHOT) && |
| 251 | !(newdev->features & CLOCK_EVT_FEAT_ONESHOT)) |
| 252 | goto out_bc; |
| 253 | /* |
| 254 | * Check the rating |
| 255 | */ |
| 256 | if (curdev->rating >= newdev->rating) |
| 257 | goto out_bc; |
| 258 | } |
| 259 | |
| 260 | /* |
| 261 | * Replace the eventually existing device by the new |
| 262 | * device. If the current device is the broadcast device, do |
| 263 | * not give it back to the clockevents layer ! |
| 264 | */ |
| 265 | if (tick_is_broadcast_device(curdev)) { |
| 266 | clockevents_shutdown(curdev); |
| 267 | curdev = NULL; |
| 268 | } |
| 269 | clockevents_exchange_device(curdev, newdev); |
| 270 | tick_setup_device(td, newdev, cpu, cpumask_of(cpu)); |
| 271 | if (newdev->features & CLOCK_EVT_FEAT_ONESHOT) |
| 272 | tick_oneshot_notify(); |
| 273 | return; |
| 274 | |
| 275 | out_bc: |
| 276 | /* |
| 277 | * Can the new device be used as a broadcast device ? |
| 278 | */ |
| 279 | tick_install_broadcast_device(newdev); |
| 280 | } |
| 281 | |
| 282 | /* |
| 283 | * Transfer the do_timer job away from a dying cpu. |
| 284 | * |
| 285 | * Called with interrupts disabled. |
| 286 | */ |
| 287 | void tick_handover_do_timer(int *cpup) |
| 288 | { |
| 289 | if (*cpup == tick_do_timer_cpu) { |
| 290 | int cpu = cpumask_first(cpu_online_mask); |
| 291 | |
| 292 | tick_do_timer_cpu = (cpu < nr_cpu_ids) ? cpu : |
| 293 | TICK_DO_TIMER_NONE; |
| 294 | } |
| 295 | } |
| 296 | |
| 297 | /* |
| 298 | * Shutdown an event device on a given cpu: |
| 299 | * |
| 300 | * This is called on a life CPU, when a CPU is dead. So we cannot |
| 301 | * access the hardware device itself. |
| 302 | * We just set the mode and remove it from the lists. |
| 303 | */ |
| 304 | void tick_shutdown(unsigned int *cpup) |
| 305 | { |
| 306 | struct tick_device *td = &per_cpu(tick_cpu_device, *cpup); |
| 307 | struct clock_event_device *dev = td->evtdev; |
| 308 | |
| 309 | td->mode = TICKDEV_MODE_PERIODIC; |
| 310 | if (dev) { |
| 311 | /* |
| 312 | * Prevent that the clock events layer tries to call |
| 313 | * the set mode function! |
| 314 | */ |
| 315 | dev->mode = CLOCK_EVT_MODE_UNUSED; |
| 316 | clockevents_exchange_device(dev, NULL); |
| 317 | dev->event_handler = clockevents_handle_noop; |
| 318 | td->evtdev = NULL; |
| 319 | } |
| 320 | } |
| 321 | |
| 322 | void tick_suspend(void) |
| 323 | { |
| 324 | struct tick_device *td = &__get_cpu_var(tick_cpu_device); |
| 325 | |
| 326 | clockevents_shutdown(td->evtdev); |
| 327 | } |
| 328 | |
| 329 | void tick_resume(void) |
| 330 | { |
| 331 | struct tick_device *td = &__get_cpu_var(tick_cpu_device); |
| 332 | int broadcast = tick_resume_broadcast(); |
| 333 | |
| 334 | clockevents_set_mode(td->evtdev, CLOCK_EVT_MODE_RESUME); |
| 335 | |
| 336 | if (!broadcast) { |
| 337 | if (td->mode == TICKDEV_MODE_PERIODIC) |
| 338 | tick_setup_periodic(td->evtdev, 0); |
| 339 | else |
| 340 | tick_resume_oneshot(); |
| 341 | } |
| 342 | } |
| 343 | |
| 344 | /** |
| 345 | * tick_init - initialize the tick control |
| 346 | */ |
| 347 | void __init tick_init(void) |
| 348 | { |
| 349 | tick_broadcast_init(); |
| 350 | } |