/* * linux/kernel/time/tick-broadcast.c * * This file contains functions which emulate a local clock-event * device via a broadcast event source. * * 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/cpu.h> #include <linux/err.h> #include <linux/hrtimer.h> #include <linux/interrupt.h> #include <linux/percpu.h> #include <linux/profile.h> #include <linux/sched.h> #include <linux/tick.h> #include "tick-internal.h" /* * Broadcast support for broken x86 hardware, where the local apic * timer stops in C3 state. */ struct tick_device tick_broadcast_device; static cpumask_t tick_broadcast_mask; static DEFINE_SPINLOCK(tick_broadcast_lock); #ifdef CONFIG_TICK_ONESHOT static void tick_broadcast_clear_oneshot(int cpu); #else static inline void tick_broadcast_clear_oneshot(int cpu) { } #endif /* * Debugging: see timer_list.c */ struct tick_device *tick_get_broadcast_device(void) { return &tick_broadcast_device; } cpumask_t *tick_get_broadcast_mask(void) { return &tick_broadcast_mask; } /* * Start the device in periodic mode */ static void tick_broadcast_start_periodic(struct clock_event_device *bc) { if (bc) tick_setup_periodic(bc, 1); } /* * Check, if the device can be utilized as broadcast device: */ int tick_check_broadcast_device(struct clock_event_device *dev) { if ((tick_broadcast_device.evtdev && tick_broadcast_device.evtdev->rating >= dev->rating) || (dev->features & CLOCK_EVT_FEAT_C3STOP)) return 0; clockevents_exchange_device(NULL, dev); tick_broadcast_device.evtdev = dev; if (!cpus_empty(tick_broadcast_mask)) tick_broadcast_start_periodic(dev); return 1; } /* * Check, if the device is the broadcast device */ int tick_is_broadcast_device(struct clock_event_device *dev) { return (dev && tick_broadcast_device.evtdev == dev); } /* * Check, if the device is disfunctional and a place holder, which * needs to be handled by the broadcast device. */ int tick_device_uses_broadcast(struct clock_event_device *dev, int cpu) { unsigned long flags; int ret = 0; spin_lock_irqsave(&tick_broadcast_lock, flags); /* * Devices might be registered with both periodic and oneshot * mode disabled. This signals, that the device needs to be * operated from the broadcast device and is a placeholder for * the cpu local device. */ if (!tick_device_is_functional(dev)) { dev->event_handler = tick_handle_periodic; cpu_set(cpu, tick_broadcast_mask); tick_broadcast_start_periodic(tick_broadcast_device.evtdev); ret = 1; } else { /* * When the new device is not affected by the stop * feature and the cpu is marked in the broadcast mask * then clear the broadcast bit. */ if (!(dev->features & CLOCK_EVT_FEAT_C3STOP)) { int cpu = smp_processor_id(); cpu_clear(cpu, tick_broadcast_mask); tick_broadcast_clear_oneshot(cpu); } } spin_unlock_irqrestore(&tick_broadcast_lock, flags); return ret; } /* * Broadcast the event to the cpus, which are set in the mask */ static void tick_do_broadcast(cpumask_t mask) { int cpu = smp_processor_id(); struct tick_device *td; /* * Check, if the current cpu is in the mask */ if (cpu_isset(cpu, mask)) { cpu_clear(cpu, mask); td = &per_cpu(tick_cpu_device, cpu); td->evtdev->event_handler(td->evtdev); } if (!cpus_empty(mask)) { /* * It might be necessary to actually check whether the devices * have different broadcast functions. For now, just use the * one of the first device. This works as long as we have this * misfeature only on x86 (lapic) */ cpu = first_cpu(mask); td = &per_cpu(tick_cpu_device, cpu); td->evtdev->broadcast(mask); } } /* * Periodic broadcast: * - invoke the broadcast handlers */ static void tick_do_periodic_broadcast(void) { cpumask_t mask; spin_lock(&tick_broadcast_lock); cpus_and(mask, cpu_online_map, tick_broadcast_mask); tick_do_broadcast(mask); spin_unlock(&tick_broadcast_lock); } /* * Event handler for periodic broadcast ticks */ static void tick_handle_periodic_broadcast(struct clock_event_device *dev) { tick_do_periodic_broadcast(); /* * The device is in periodic mode. No reprogramming necessary: */ if (dev->mode == CLOCK_EVT_MODE_PERIODIC) return; /* * Setup the next period for devices, which do not have * periodic mode: */ for (;;) { ktime_t next = ktime_add(dev->next_event, tick_period); if (!clockevents_program_event(dev, next, ktime_get())) return; tick_do_periodic_broadcast(); } } /* * Powerstate information: The system enters/leaves a state, where * affected devices might stop */ static void tick_do_broadcast_on_off(void *why) { struct clock_event_device *bc, *dev; struct tick_device *td; unsigned long flags, *reason = why; int cpu; spin_lock_irqsave(&tick_broadcast_lock, flags); cpu = smp_processor_id(); td = &per_cpu(tick_cpu_device, cpu); dev = td->evtdev; bc = tick_broadcast_device.evtdev; /* * Is the device not affected by the powerstate ? */ if (!dev || !(dev->features & CLOCK_EVT_FEAT_C3STOP)) goto out; if (!tick_device_is_functional(dev)) goto out; switch (*reason) { case CLOCK_EVT_NOTIFY_BROADCAST_ON: case CLOCK_EVT_NOTIFY_BROADCAST_FORCE: if (!cpu_isset(cpu, tick_broadcast_mask)) { cpu_set(cpu, tick_broadcast_mask); if (td->mode == TICKDEV_MODE_PERIODIC) clockevents_set_mode(dev, CLOCK_EVT_MODE_SHUTDOWN); } if (*reason == CLOCK_EVT_NOTIFY_BROADCAST_FORCE) dev->features |= CLOCK_EVT_FEAT_DUMMY; break; case CLOCK_EVT_NOTIFY_BROADCAST_OFF: if (cpu_isset(cpu, tick_broadcast_mask)) { cpu_clear(cpu, tick_broadcast_mask); if (td->mode == TICKDEV_MODE_PERIODIC) tick_setup_periodic(dev, 0); } break; } if (cpus_empty(tick_broadcast_mask)) clockevents_set_mode(bc, CLOCK_EVT_MODE_SHUTDOWN); else { if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC) tick_broadcast_start_periodic(bc); else tick_broadcast_setup_oneshot(bc); } out: spin_unlock_irqrestore(&tick_broadcast_lock, flags); } /* * Powerstate information: The system enters/leaves a state, where * affected devices might stop. */ void tick_broadcast_on_off(unsigned long reason, int *oncpu) { if (!cpu_isset(*oncpu, cpu_online_map)) printk(KERN_ERR "tick-broadcast: ignoring broadcast for " "offline CPU #%d\n", *oncpu); else smp_call_function_single(*oncpu, tick_do_broadcast_on_off, &reason, 1, 1); } /* * Set the periodic handler depending on broadcast on/off */ void tick_set_periodic_handler(struct clock_event_device *dev, int broadcast) { if (!broadcast) dev->event_handler = tick_handle_periodic; else dev->event_handler = tick_handle_periodic_broadcast; } /* * Remove a CPU from broadcasting */ void tick_shutdown_broadcast(unsigned int *cpup) { struct clock_event_device *bc; unsigned long flags; unsigned int cpu = *cpup; spin_lock_irqsave(&tick_broadcast_lock, flags); bc = tick_broadcast_device.evtdev; cpu_clear(cpu, tick_broadcast_mask); if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC) { if (bc && cpus_empty(tick_broadcast_mask)) clockevents_set_mode(bc, CLOCK_EVT_MODE_SHUTDOWN); } spin_unlock_irqrestore(&tick_broadcast_lock, flags); } void tick_suspend_broadcast(void) { struct clock_event_device *bc; unsigned long flags; spin_lock_irqsave(&tick_broadcast_lock, flags); bc = tick_broadcast_device.evtdev; if (bc) clockevents_set_mode(bc, CLOCK_EVT_MODE_SHUTDOWN); spin_unlock_irqrestore(&tick_broadcast_lock, flags); } int tick_resume_broadcast(void) { struct clock_event_device *bc; unsigned long flags; int broadcast = 0; spin_lock_irqsave(&tick_broadcast_lock, flags); bc = tick_broadcast_device.evtdev; if (bc) { clockevents_set_mode(bc, CLOCK_EVT_MODE_RESUME); switch (tick_broadcast_device.mode) { case TICKDEV_MODE_PERIODIC: if(!cpus_empty(tick_broadcast_mask)) tick_broadcast_start_periodic(bc); broadcast = cpu_isset(smp_processor_id(), tick_broadcast_mask); break; case TICKDEV_MODE_ONESHOT: broadcast = tick_resume_broadcast_oneshot(bc); break; } } spin_unlock_irqrestore(&tick_broadcast_lock, flags); return broadcast; } #ifdef CONFIG_TICK_ONESHOT static cpumask_t tick_broadcast_oneshot_mask; /* * Debugging: see timer_list.c */ cpumask_t *tick_get_broadcast_oneshot_mask(void) { return &tick_broadcast_oneshot_mask; } static int tick_broadcast_set_event(ktime_t expires, int force) { struct clock_event_device *bc = tick_broadcast_device.evtdev; ktime_t now = ktime_get(); int res; for(;;) { res = clockevents_program_event(bc, expires, now); if (!res || !force) return res; now = ktime_get(); expires = ktime_add(now, ktime_set(0, bc->min_delta_ns)); } } int tick_resume_broadcast_oneshot(struct clock_event_device *bc) { clockevents_set_mode(bc, CLOCK_EVT_MODE_ONESHOT); return 0; } /* * Handle oneshot mode broadcasting */ static void tick_handle_oneshot_broadcast(struct clock_event_device *dev) { struct tick_device *td; cpumask_t mask; ktime_t now, next_event; int cpu; spin_lock(&tick_broadcast_lock); again: dev->next_event.tv64 = KTIME_MAX; next_event.tv64 = KTIME_MAX; mask = CPU_MASK_NONE; now = ktime_get(); /* Find all expired events */ for (cpu = first_cpu(tick_broadcast_oneshot_mask); cpu != NR_CPUS; cpu = next_cpu(cpu, tick_broadcast_oneshot_mask)) { td = &per_cpu(tick_cpu_device, cpu); if (td->evtdev->next_event.tv64 <= now.tv64) cpu_set(cpu, mask); else if (td->evtdev->next_event.tv64 < next_event.tv64) next_event.tv64 = td->evtdev->next_event.tv64; } /* * Wakeup the cpus which have an expired event. */ tick_do_broadcast(mask); /* * Two reasons for reprogram: * * - The global event did not expire any CPU local * events. This happens in dyntick mode, as the maximum PIT * delta is quite small. * * - There are pending events on sleeping CPUs which were not * in the event mask */ if (next_event.tv64 != KTIME_MAX) { /* * Rearm the broadcast device. If event expired, * repeat the above */ if (tick_broadcast_set_event(next_event, 0)) goto again; } spin_unlock(&tick_broadcast_lock); } /* * Powerstate information: The system enters/leaves a state, where * affected devices might stop */ void tick_broadcast_oneshot_control(unsigned long reason) { struct clock_event_device *bc, *dev; struct tick_device *td; unsigned long flags; int cpu; spin_lock_irqsave(&tick_broadcast_lock, flags); /* * Periodic mode does not care about the enter/exit of power * states */ if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC) goto out; bc = tick_broadcast_device.evtdev; cpu = smp_processor_id(); td = &per_cpu(tick_cpu_device, cpu); dev = td->evtdev; if (!(dev->features & CLOCK_EVT_FEAT_C3STOP)) goto out; if (reason == CLOCK_EVT_NOTIFY_BROADCAST_ENTER) { if (!cpu_isset(cpu, tick_broadcast_oneshot_mask)) { cpu_set(cpu, tick_broadcast_oneshot_mask); clockevents_set_mode(dev, CLOCK_EVT_MODE_SHUTDOWN); if (dev->next_event.tv64 < bc->next_event.tv64) tick_broadcast_set_event(dev->next_event, 1); } } else { if (cpu_isset(cpu, tick_broadcast_oneshot_mask)) { cpu_clear(cpu, tick_broadcast_oneshot_mask); clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT); if (dev->next_event.tv64 != KTIME_MAX) tick_program_event(dev->next_event, 1); } } out: spin_unlock_irqrestore(&tick_broadcast_lock, flags); } /* * Reset the one shot broadcast for a cpu * * Called with tick_broadcast_lock held */ static void tick_broadcast_clear_oneshot(int cpu) { cpu_clear(cpu, tick_broadcast_oneshot_mask); } /** * tick_broadcast_setup_oneshot - setup the broadcast device */ void tick_broadcast_setup_oneshot(struct clock_event_device *bc) { bc->event_handler = tick_handle_oneshot_broadcast; clockevents_set_mode(bc, CLOCK_EVT_MODE_ONESHOT); bc->next_event.tv64 = KTIME_MAX; } /* * Select oneshot operating mode for the broadcast device */ void tick_broadcast_switch_to_oneshot(void) { struct clock_event_device *bc; unsigned long flags; spin_lock_irqsave(&tick_broadcast_lock, flags); tick_broadcast_device.mode = TICKDEV_MODE_ONESHOT; bc = tick_broadcast_device.evtdev; if (bc) tick_broadcast_setup_oneshot(bc); spin_unlock_irqrestore(&tick_broadcast_lock, flags); } /* * Remove a dead CPU from broadcasting */ void tick_shutdown_broadcast_oneshot(unsigned int *cpup) { unsigned long flags; unsigned int cpu = *cpup; spin_lock_irqsave(&tick_broadcast_lock, flags); /* * Clear the broadcast mask flag for the dead cpu, but do not * stop the broadcast device! */ cpu_clear(cpu, tick_broadcast_oneshot_mask); spin_unlock_irqrestore(&tick_broadcast_lock, flags); } #endif