/* * linux/kernel/time/clockevents.c * * This file contains functions which manage clock event devices. * * Copyright(C) 2005-2006, Thomas Gleixner <tglx@linutronix.de> * Copyright(C) 2005-2007, Red Hat, Inc., Ingo Molnar * Copyright(C) 2006-2007, Timesys Corp., Thomas Gleixner * * This code is licenced under the GPL version 2. For details see * kernel-base/COPYING. */ #include <linux/clockchips.h> #include <linux/hrtimer.h> #include <linux/init.h> #include <linux/module.h> #include <linux/smp.h> #include <linux/device.h> #include "tick-internal.h" /* The registered clock event devices */ static LIST_HEAD(clockevent_devices); static LIST_HEAD(clockevents_released); /* Protection for the above */ static DEFINE_RAW_SPINLOCK(clockevents_lock); /* Protection for unbind operations */ static DEFINE_MUTEX(clockevents_mutex); struct ce_unbind { struct clock_event_device *ce; int res; }; static u64 cev_delta2ns(unsigned long latch, struct clock_event_device *evt, bool ismax) { u64 clc = (u64) latch << evt->shift; u64 rnd; if (unlikely(!evt->mult)) { evt->mult = 1; WARN_ON(1); } rnd = (u64) evt->mult - 1; /* * Upper bound sanity check. If the backwards conversion is * not equal latch, we know that the above shift overflowed. */ if ((clc >> evt->shift) != (u64)latch) clc = ~0ULL; /* * Scaled math oddities: * * For mult <= (1 << shift) we can safely add mult - 1 to * prevent integer rounding loss. So the backwards conversion * from nsec to device ticks will be correct. * * For mult > (1 << shift), i.e. device frequency is > 1GHz we * need to be careful. Adding mult - 1 will result in a value * which when converted back to device ticks can be larger * than latch by up to (mult - 1) >> shift. For the min_delta * calculation we still want to apply this in order to stay * above the minimum device ticks limit. For the upper limit * we would end up with a latch value larger than the upper * limit of the device, so we omit the add to stay below the * device upper boundary. * * Also omit the add if it would overflow the u64 boundary. */ if ((~0ULL - clc > rnd) && (!ismax || evt->mult <= (1ULL << evt->shift))) clc += rnd; do_div(clc, evt->mult); /* Deltas less than 1usec are pointless noise */ return clc > 1000 ? clc : 1000; } /** * clockevents_delta2ns - Convert a latch value (device ticks) to nanoseconds * @latch: value to convert * @evt: pointer to clock event device descriptor * * Math helper, returns latch value converted to nanoseconds (bound checked) */ u64 clockevent_delta2ns(unsigned long latch, struct clock_event_device *evt) { return cev_delta2ns(latch, evt, false); } EXPORT_SYMBOL_GPL(clockevent_delta2ns); static int __clockevents_switch_state(struct clock_event_device *dev, enum clock_event_state state) { if (dev->features & CLOCK_EVT_FEAT_DUMMY) return 0; /* Transition with new state-specific callbacks */ switch (state) { case CLOCK_EVT_STATE_DETACHED: /* The clockevent device is getting replaced. Shut it down. */ case CLOCK_EVT_STATE_SHUTDOWN: if (dev->set_state_shutdown) return dev->set_state_shutdown(dev); return 0; case CLOCK_EVT_STATE_PERIODIC: /* Core internal bug */ if (!(dev->features & CLOCK_EVT_FEAT_PERIODIC)) return -ENOSYS; if (dev->set_state_periodic) return dev->set_state_periodic(dev); return 0; case CLOCK_EVT_STATE_ONESHOT: /* Core internal bug */ if (!(dev->features & CLOCK_EVT_FEAT_ONESHOT)) return -ENOSYS; if (dev->set_state_oneshot) return dev->set_state_oneshot(dev); return 0; case CLOCK_EVT_STATE_ONESHOT_STOPPED: /* Core internal bug */ if (WARN_ONCE(!clockevent_state_oneshot(dev), "Current state: %d\n", clockevent_get_state(dev))) return -EINVAL; if (dev->set_state_oneshot_stopped) return dev->set_state_oneshot_stopped(dev); else return -ENOSYS; default: return -ENOSYS; } } /** * clockevents_switch_state - set the operating state of a clock event device * @dev: device to modify * @state: new state * * Must be called with interrupts disabled ! */ void clockevents_switch_state(struct clock_event_device *dev, enum clock_event_state state) { if (clockevent_get_state(dev) != state) { if (__clockevents_switch_state(dev, state)) return; clockevent_set_state(dev, state); /* * A nsec2cyc multiplicator of 0 is invalid and we'd crash * on it, so fix it up and emit a warning: */ if (clockevent_state_oneshot(dev)) { if (unlikely(!dev->mult)) { dev->mult = 1; WARN_ON(1); } } } } /** * clockevents_shutdown - shutdown the device and clear next_event * @dev: device to shutdown */ void clockevents_shutdown(struct clock_event_device *dev) { clockevents_switch_state(dev, CLOCK_EVT_STATE_SHUTDOWN); dev->next_event = KTIME_MAX; } /** * clockevents_tick_resume - Resume the tick device before using it again * @dev: device to resume */ int clockevents_tick_resume(struct clock_event_device *dev) { int ret = 0; if (dev->tick_resume) ret = dev->tick_resume(dev); return ret; } #ifdef CONFIG_GENERIC_CLOCKEVENTS_MIN_ADJUST /* Limit min_delta to a jiffie */ #define MIN_DELTA_LIMIT (NSEC_PER_SEC / HZ) /** * clockevents_increase_min_delta - raise minimum delta of a clock event device * @dev: device to increase the minimum delta * * Returns 0 on success, -ETIME when the minimum delta reached the limit. */ static int clockevents_increase_min_delta(struct clock_event_device *dev) { /* Nothing to do if we already reached the limit */ if (dev->min_delta_ns >= MIN_DELTA_LIMIT) { printk_deferred(KERN_WARNING "CE: Reprogramming failure. Giving up\n"); dev->next_event = KTIME_MAX; return -ETIME; } if (dev->min_delta_ns < 5000) dev->min_delta_ns = 5000; else dev->min_delta_ns += dev->min_delta_ns >> 1; if (dev->min_delta_ns > MIN_DELTA_LIMIT) dev->min_delta_ns = MIN_DELTA_LIMIT; printk_deferred(KERN_WARNING "CE: %s increased min_delta_ns to %llu nsec\n", dev->name ? dev->name : "?", (unsigned long long) dev->min_delta_ns); return 0; } /** * clockevents_program_min_delta - Set clock event device to the minimum delay. * @dev: device to program * * Returns 0 on success, -ETIME when the retry loop failed. */ static int clockevents_program_min_delta(struct clock_event_device *dev) { unsigned long long clc; int64_t delta; int i; for (i = 0;;) { delta = dev->min_delta_ns; dev->next_event = ktime_add_ns(ktime_get(), delta); if (clockevent_state_shutdown(dev)) return 0; dev->retries++; clc = ((unsigned long long) delta * dev->mult) >> dev->shift; if (dev->set_next_event((unsigned long) clc, dev) == 0) return 0; if (++i > 2) { /* * We tried 3 times to program the device with the * given min_delta_ns. Try to increase the minimum * delta, if that fails as well get out of here. */ if (clockevents_increase_min_delta(dev)) return -ETIME; i = 0; } } } #else /* CONFIG_GENERIC_CLOCKEVENTS_MIN_ADJUST */ /** * clockevents_program_min_delta - Set clock event device to the minimum delay. * @dev: device to program * * Returns 0 on success, -ETIME when the retry loop failed. */ static int clockevents_program_min_delta(struct clock_event_device *dev) { unsigned long long clc; int64_t delta; delta = dev->min_delta_ns; dev->next_event = ktime_add_ns(ktime_get(), delta); if (clockevent_state_shutdown(dev)) return 0; dev->retries++; clc = ((unsigned long long) delta * dev->mult) >> dev->shift; return dev->set_next_event((unsigned long) clc, dev); } #endif /* CONFIG_GENERIC_CLOCKEVENTS_MIN_ADJUST */ /** * clockevents_program_event - Reprogram the clock event device. * @dev: device to program * @expires: absolute expiry time (monotonic clock) * @force: program minimum delay if expires can not be set * * Returns 0 on success, -ETIME when the event is in the past. */ int clockevents_program_event(struct clock_event_device *dev, ktime_t expires, bool force) { unsigned long long clc; int64_t delta; int rc; if (unlikely(expires < 0)) { WARN_ON_ONCE(1); return -ETIME; } dev->next_event = expires; if (clockevent_state_shutdown(dev)) return 0; /* We must be in ONESHOT state here */ WARN_ONCE(!clockevent_state_oneshot(dev), "Current state: %d\n", clockevent_get_state(dev)); /* Shortcut for clockevent devices that can deal with ktime. */ if (dev->features & CLOCK_EVT_FEAT_KTIME) return dev->set_next_ktime(expires, dev); delta = ktime_to_ns(ktime_sub(expires, ktime_get())); if (delta <= 0) return force ? clockevents_program_min_delta(dev) : -ETIME; delta = min(delta, (int64_t) dev->max_delta_ns); delta = max(delta, (int64_t) dev->min_delta_ns); clc = ((unsigned long long) delta * dev->mult) >> dev->shift; rc = dev->set_next_event((unsigned long) clc, dev); return (rc && force) ? clockevents_program_min_delta(dev) : rc; } /* * Called after a notify add to make devices available which were * released from the notifier call. */ static void clockevents_notify_released(void) { struct clock_event_device *dev; while (!list_empty(&clockevents_released)) { dev = list_entry(clockevents_released.next, struct clock_event_device, list); list_del(&dev->list); list_add(&dev->list, &clockevent_devices); tick_check_new_device(dev); } } /* * Try to install a replacement clock event device */ static int clockevents_replace(struct clock_event_device *ced) { struct clock_event_device *dev, *newdev = NULL; list_for_each_entry(dev, &clockevent_devices, list) { if (dev == ced || !clockevent_state_detached(dev)) continue; if (!tick_check_replacement(newdev, dev)) continue; if (!try_module_get(dev->owner)) continue; if (newdev) module_put(newdev->owner); newdev = dev; } if (newdev) { tick_install_replacement(newdev); list_del_init(&ced->list); } return newdev ? 0 : -EBUSY; } /* * Called with clockevents_mutex and clockevents_lock held */ static int __clockevents_try_unbind(struct clock_event_device *ced, int cpu) { /* Fast track. Device is unused */ if (clockevent_state_detached(ced)) { list_del_init(&ced->list); return 0; } return ced == per_cpu(tick_cpu_device, cpu).evtdev ? -EAGAIN : -EBUSY; } /* * SMP function call to unbind a device */ static void __clockevents_unbind(void *arg) { struct ce_unbind *cu = arg; int res; raw_spin_lock(&clockevents_lock); res = __clockevents_try_unbind(cu->ce, smp_processor_id()); if (res == -EAGAIN) res = clockevents_replace(cu->ce); cu->res = res; raw_spin_unlock(&clockevents_lock); } /* * Issues smp function call to unbind a per cpu device. Called with * clockevents_mutex held. */ static int clockevents_unbind(struct clock_event_device *ced, int cpu) { struct ce_unbind cu = { .ce = ced, .res = -ENODEV }; smp_call_function_single(cpu, __clockevents_unbind, &cu, 1); return cu.res; } /* * Unbind a clockevents device. */ int clockevents_unbind_device(struct clock_event_device *ced, int cpu) { int ret; mutex_lock(&clockevents_mutex); ret = clockevents_unbind(ced, cpu); mutex_unlock(&clockevents_mutex); return ret; } EXPORT_SYMBOL_GPL(clockevents_unbind_device); /** * clockevents_register_device - register a clock event device * @dev: device to register */ void clockevents_register_device(struct clock_event_device *dev) { unsigned long flags; /* Initialize state to DETACHED */ clockevent_set_state(dev, CLOCK_EVT_STATE_DETACHED); if (!dev->cpumask) { WARN_ON(num_possible_cpus() > 1); dev->cpumask = cpumask_of(smp_processor_id()); } raw_spin_lock_irqsave(&clockevents_lock, flags); list_add(&dev->list, &clockevent_devices); tick_check_new_device(dev); clockevents_notify_released(); raw_spin_unlock_irqrestore(&clockevents_lock, flags); } EXPORT_SYMBOL_GPL(clockevents_register_device); void clockevents_config(struct clock_event_device *dev, u32 freq) { u64 sec; if (!(dev->features & CLOCK_EVT_FEAT_ONESHOT)) return; /* * Calculate the maximum number of seconds we can sleep. Limit * to 10 minutes for hardware which can program more than * 32bit ticks so we still get reasonable conversion values. */ sec = dev->max_delta_ticks; do_div(sec, freq); if (!sec) sec = 1; else if (sec > 600 && dev->max_delta_ticks > UINT_MAX) sec = 600; clockevents_calc_mult_shift(dev, freq, sec); dev->min_delta_ns = cev_delta2ns(dev->min_delta_ticks, dev, false); dev->max_delta_ns = cev_delta2ns(dev->max_delta_ticks, dev, true); } /** * clockevents_config_and_register - Configure and register a clock event device * @dev: device to register * @freq: The clock frequency * @min_delta: The minimum clock ticks to program in oneshot mode * @max_delta: The maximum clock ticks to program in oneshot mode * * min/max_delta can be 0 for devices which do not support oneshot mode. */ void clockevents_config_and_register(struct clock_event_device *dev, u32 freq, unsigned long min_delta, unsigned long max_delta) { dev->min_delta_ticks = min_delta; dev->max_delta_ticks = max_delta; clockevents_config(dev, freq); clockevents_register_device(dev); } EXPORT_SYMBOL_GPL(clockevents_config_and_register); int __clockevents_update_freq(struct clock_event_device *dev, u32 freq) { clockevents_config(dev, freq); if (clockevent_state_oneshot(dev)) return clockevents_program_event(dev, dev->next_event, false); if (clockevent_state_periodic(dev)) return __clockevents_switch_state(dev, CLOCK_EVT_STATE_PERIODIC); return 0; } /** * clockevents_update_freq - Update frequency and reprogram a clock event device. * @dev: device to modify * @freq: new device frequency * * Reconfigure and reprogram a clock event device in oneshot * mode. Must be called on the cpu for which the device delivers per * cpu timer events. If called for the broadcast device the core takes * care of serialization. * * Returns 0 on success, -ETIME when the event is in the past. */ int clockevents_update_freq(struct clock_event_device *dev, u32 freq) { unsigned long flags; int ret; local_irq_save(flags); ret = tick_broadcast_update_freq(dev, freq); if (ret == -ENODEV) ret = __clockevents_update_freq(dev, freq); local_irq_restore(flags); return ret; } /* * Noop handler when we shut down an event device */ void clockevents_handle_noop(struct clock_event_device *dev) { } /** * clockevents_exchange_device - release and request clock devices * @old: device to release (can be NULL) * @new: device to request (can be NULL) * * Called from various tick functions with clockevents_lock held and * interrupts disabled. */ void clockevents_exchange_device(struct clock_event_device *old, struct clock_event_device *new) { /* * Caller releases a clock event device. We queue it into the * released list and do a notify add later. */ if (old) { module_put(old->owner); clockevents_switch_state(old, CLOCK_EVT_STATE_DETACHED); list_del(&old->list); list_add(&old->list, &clockevents_released); } if (new) { BUG_ON(!clockevent_state_detached(new)); clockevents_shutdown(new); } } /** * clockevents_suspend - suspend clock devices */ void clockevents_suspend(void) { struct clock_event_device *dev; list_for_each_entry_reverse(dev, &clockevent_devices, list) if (dev->suspend && !clockevent_state_detached(dev)) dev->suspend(dev); } /** * clockevents_resume - resume clock devices */ void clockevents_resume(void) { struct clock_event_device *dev; list_for_each_entry(dev, &clockevent_devices, list) if (dev->resume && !clockevent_state_detached(dev)) dev->resume(dev); } #ifdef CONFIG_HOTPLUG_CPU /** * tick_cleanup_dead_cpu - Cleanup the tick and clockevents of a dead cpu */ void tick_cleanup_dead_cpu(int cpu) { struct clock_event_device *dev, *tmp; unsigned long flags; raw_spin_lock_irqsave(&clockevents_lock, flags); tick_shutdown_broadcast_oneshot(cpu); tick_shutdown_broadcast(cpu); tick_shutdown(cpu); /* * Unregister the clock event devices which were * released from the users in the notify chain. */ list_for_each_entry_safe(dev, tmp, &clockevents_released, list) list_del(&dev->list); /* * Now check whether the CPU has left unused per cpu devices */ list_for_each_entry_safe(dev, tmp, &clockevent_devices, list) { if (cpumask_test_cpu(cpu, dev->cpumask) && cpumask_weight(dev->cpumask) == 1 && !tick_is_broadcast_device(dev)) { BUG_ON(!clockevent_state_detached(dev)); list_del(&dev->list); } } raw_spin_unlock_irqrestore(&clockevents_lock, flags); } #endif #ifdef CONFIG_SYSFS static struct bus_type clockevents_subsys = { .name = "clockevents", .dev_name = "clockevent", }; static DEFINE_PER_CPU(struct device, tick_percpu_dev); static struct tick_device *tick_get_tick_dev(struct device *dev); static ssize_t sysfs_show_current_tick_dev(struct device *dev, struct device_attribute *attr, char *buf) { struct tick_device *td; ssize_t count = 0; raw_spin_lock_irq(&clockevents_lock); td = tick_get_tick_dev(dev); if (td && td->evtdev) count = snprintf(buf, PAGE_SIZE, "%s\n", td->evtdev->name); raw_spin_unlock_irq(&clockevents_lock); return count; } static DEVICE_ATTR(current_device, 0444, sysfs_show_current_tick_dev, NULL); /* We don't support the abomination of removable broadcast devices */ static ssize_t sysfs_unbind_tick_dev(struct device *dev, struct device_attribute *attr, const char *buf, size_t count) { char name[CS_NAME_LEN]; ssize_t ret = sysfs_get_uname(buf, name, count); struct clock_event_device *ce; if (ret < 0) return ret; ret = -ENODEV; mutex_lock(&clockevents_mutex); raw_spin_lock_irq(&clockevents_lock); list_for_each_entry(ce, &clockevent_devices, list) { if (!strcmp(ce->name, name)) { ret = __clockevents_try_unbind(ce, dev->id); break; } } raw_spin_unlock_irq(&clockevents_lock); /* * We hold clockevents_mutex, so ce can't go away */ if (ret == -EAGAIN) ret = clockevents_unbind(ce, dev->id); mutex_unlock(&clockevents_mutex); return ret ? ret : count; } static DEVICE_ATTR(unbind_device, 0200, NULL, sysfs_unbind_tick_dev); #ifdef CONFIG_GENERIC_CLOCKEVENTS_BROADCAST static struct device tick_bc_dev = { .init_name = "broadcast", .id = 0, .bus = &clockevents_subsys, }; static struct tick_device *tick_get_tick_dev(struct device *dev) { return dev == &tick_bc_dev ? tick_get_broadcast_device() : &per_cpu(tick_cpu_device, dev->id); } static __init int tick_broadcast_init_sysfs(void) { int err = device_register(&tick_bc_dev); if (!err) err = device_create_file(&tick_bc_dev, &dev_attr_current_device); return err; } #else static struct tick_device *tick_get_tick_dev(struct device *dev) { return &per_cpu(tick_cpu_device, dev->id); } static inline int tick_broadcast_init_sysfs(void) { return 0; } #endif static int __init tick_init_sysfs(void) { int cpu; for_each_possible_cpu(cpu) { struct device *dev = &per_cpu(tick_percpu_dev, cpu); int err; dev->id = cpu; dev->bus = &clockevents_subsys; err = device_register(dev); if (!err) err = device_create_file(dev, &dev_attr_current_device); if (!err) err = device_create_file(dev, &dev_attr_unbind_device); if (err) return err; } return tick_broadcast_init_sysfs(); } static int __init clockevents_init_sysfs(void) { int err = subsys_system_register(&clockevents_subsys, NULL); if (!err) err = tick_init_sysfs(); return err; } device_initcall(clockevents_init_sysfs); #endif /* SYSFS */