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+/*
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+ * linux/kernel/time/tick-broadcast.c
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+ *
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+ * This file contains functions which emulate a local clock-event
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+ * device via a broadcast event source.
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+ *
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+ * Copyright(C) 2005-2006, Thomas Gleixner <tglx@linutronix.de>
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+ * Copyright(C) 2005-2007, Red Hat, Inc., Ingo Molnar
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+ * Copyright(C) 2006-2007, Timesys Corp., Thomas Gleixner
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+ *
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+ * This code is licenced under the GPL version 2. For details see
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+ * kernel-base/COPYING.
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+ */
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+#include <linux/cpu.h>
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+#include <linux/err.h>
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+#include <linux/hrtimer.h>
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+#include <linux/irq.h>
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+#include <linux/percpu.h>
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+#include <linux/profile.h>
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+#include <linux/sched.h>
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+#include <linux/tick.h>
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+
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+#include "tick-internal.h"
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+
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+/*
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+ * Broadcast support for broken x86 hardware, where the local apic
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+ * timer stops in C3 state.
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+ */
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+
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+struct tick_device tick_broadcast_device;
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+static cpumask_t tick_broadcast_mask;
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+DEFINE_SPINLOCK(tick_broadcast_lock);
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+
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+/*
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+ * Start the device in periodic mode
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+ */
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+static void tick_broadcast_start_periodic(struct clock_event_device *bc)
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+{
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+ if (bc && bc->mode == CLOCK_EVT_MODE_SHUTDOWN)
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+ tick_setup_periodic(bc, 1);
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+}
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+
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+/*
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+ * Check, if the device can be utilized as broadcast device:
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+ */
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+int tick_check_broadcast_device(struct clock_event_device *dev)
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+{
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+ if (tick_broadcast_device.evtdev ||
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+ (dev->features & CLOCK_EVT_FEAT_C3STOP))
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+ return 0;
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+
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+ clockevents_exchange_device(NULL, dev);
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+ tick_broadcast_device.evtdev = dev;
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+ if (!cpus_empty(tick_broadcast_mask))
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+ tick_broadcast_start_periodic(dev);
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+ return 1;
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+}
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+
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+/*
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+ * Check, if the device is the broadcast device
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+ */
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+int tick_is_broadcast_device(struct clock_event_device *dev)
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+{
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+ return (dev && tick_broadcast_device.evtdev == dev);
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+}
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+
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+/*
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+ * Check, if the device is disfunctional and a place holder, which
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+ * needs to be handled by the broadcast device.
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+ */
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+int tick_device_uses_broadcast(struct clock_event_device *dev, int cpu)
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+{
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+ unsigned long flags;
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+ int ret = 0;
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+
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+ spin_lock_irqsave(&tick_broadcast_lock, flags);
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+
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+ /*
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+ * Devices might be registered with both periodic and oneshot
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+ * mode disabled. This signals, that the device needs to be
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+ * operated from the broadcast device and is a placeholder for
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+ * the cpu local device.
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+ */
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+ if (!tick_device_is_functional(dev)) {
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+ dev->event_handler = tick_handle_periodic;
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+ cpu_set(cpu, tick_broadcast_mask);
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+ tick_broadcast_start_periodic(tick_broadcast_device.evtdev);
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+ ret = 1;
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+ }
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+
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+ spin_unlock_irqrestore(&tick_broadcast_lock, flags);
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+ return ret;
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+}
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+
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+/*
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+ * Broadcast the event to the cpus, which are set in the mask
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+ */
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+int tick_do_broadcast(cpumask_t mask)
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+{
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+ int ret = 0, cpu = smp_processor_id();
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+ struct tick_device *td;
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+
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+ /*
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+ * Check, if the current cpu is in the mask
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+ */
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+ if (cpu_isset(cpu, mask)) {
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+ cpu_clear(cpu, mask);
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+ td = &per_cpu(tick_cpu_device, cpu);
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+ td->evtdev->event_handler(td->evtdev);
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+ ret = 1;
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+ }
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+
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+ if (!cpus_empty(mask)) {
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+ /*
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+ * It might be necessary to actually check whether the devices
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+ * have different broadcast functions. For now, just use the
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+ * one of the first device. This works as long as we have this
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+ * misfeature only on x86 (lapic)
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+ */
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+ cpu = first_cpu(mask);
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+ td = &per_cpu(tick_cpu_device, cpu);
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+ td->evtdev->broadcast(mask);
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+ ret = 1;
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+ }
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+ return ret;
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+}
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+
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+/*
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+ * Periodic broadcast:
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+ * - invoke the broadcast handlers
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+ */
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+static void tick_do_periodic_broadcast(void)
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+{
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+ cpumask_t mask;
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+
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+ spin_lock(&tick_broadcast_lock);
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+
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+ cpus_and(mask, cpu_online_map, tick_broadcast_mask);
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+ tick_do_broadcast(mask);
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+
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+ spin_unlock(&tick_broadcast_lock);
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+}
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+
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+/*
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+ * Event handler for periodic broadcast ticks
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+ */
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+static void tick_handle_periodic_broadcast(struct clock_event_device *dev)
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+{
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+ dev->next_event.tv64 = KTIME_MAX;
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+
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+ tick_do_periodic_broadcast();
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+
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+ /*
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+ * The device is in periodic mode. No reprogramming necessary:
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+ */
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+ if (dev->mode == CLOCK_EVT_MODE_PERIODIC)
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+ return;
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+
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+ /*
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+ * Setup the next period for devices, which do not have
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+ * periodic mode:
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+ */
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+ for (;;) {
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+ ktime_t next = ktime_add(dev->next_event, tick_period);
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+
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+ if (!clockevents_program_event(dev, next, ktime_get()))
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+ return;
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+ tick_do_periodic_broadcast();
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+ }
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+}
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+
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+/*
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+ * Powerstate information: The system enters/leaves a state, where
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+ * affected devices might stop
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+ */
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+static void tick_do_broadcast_on_off(void *why)
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+{
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+ struct clock_event_device *bc, *dev;
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+ struct tick_device *td;
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+ unsigned long flags, *reason = why;
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+ int cpu;
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+
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+ spin_lock_irqsave(&tick_broadcast_lock, flags);
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+
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+ cpu = smp_processor_id();
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+ td = &per_cpu(tick_cpu_device, cpu);
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+ dev = td->evtdev;
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+ bc = tick_broadcast_device.evtdev;
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+
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+ /*
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+ * Is the device in broadcast mode forever or is it not
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+ * affected by the powerstate ?
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+ */
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+ if (!dev || !tick_device_is_functional(dev) ||
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+ !(dev->features & CLOCK_EVT_FEAT_C3STOP))
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+ goto out;
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+
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+ if (*reason == CLOCK_EVT_NOTIFY_BROADCAST_ON) {
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+ if (!cpu_isset(cpu, tick_broadcast_mask)) {
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+ cpu_set(cpu, tick_broadcast_mask);
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+ if (td->mode == TICKDEV_MODE_PERIODIC)
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+ clockevents_set_mode(dev,
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+ CLOCK_EVT_MODE_SHUTDOWN);
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+ }
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+ } else {
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+ if (cpu_isset(cpu, tick_broadcast_mask)) {
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+ cpu_clear(cpu, tick_broadcast_mask);
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+ if (td->mode == TICKDEV_MODE_PERIODIC)
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+ tick_setup_periodic(dev, 0);
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+ }
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+ }
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+
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+ if (cpus_empty(tick_broadcast_mask))
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+ clockevents_set_mode(bc, CLOCK_EVT_MODE_SHUTDOWN);
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+ else {
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+ if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)
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+ tick_broadcast_start_periodic(bc);
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+ }
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+out:
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+ spin_unlock_irqrestore(&tick_broadcast_lock, flags);
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+}
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+
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+/*
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+ * Powerstate information: The system enters/leaves a state, where
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+ * affected devices might stop.
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+ */
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+void tick_broadcast_on_off(unsigned long reason, int *oncpu)
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+{
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+ int cpu = get_cpu();
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+
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+ if (cpu == *oncpu)
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+ tick_do_broadcast_on_off(&reason);
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+ else
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+ smp_call_function_single(*oncpu, tick_do_broadcast_on_off,
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+ &reason, 1, 1);
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+ put_cpu();
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+}
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+
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+/*
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+ * Set the periodic handler depending on broadcast on/off
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+ */
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+void tick_set_periodic_handler(struct clock_event_device *dev, int broadcast)
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+{
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+ if (!broadcast)
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+ dev->event_handler = tick_handle_periodic;
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+ else
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+ dev->event_handler = tick_handle_periodic_broadcast;
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+}
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+
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+/*
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+ * Remove a CPU from broadcasting
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+ */
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+void tick_shutdown_broadcast(unsigned int *cpup)
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+{
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+ struct clock_event_device *bc;
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+ unsigned long flags;
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+ unsigned int cpu = *cpup;
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+
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+ spin_lock_irqsave(&tick_broadcast_lock, flags);
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+
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+ bc = tick_broadcast_device.evtdev;
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+ cpu_clear(cpu, tick_broadcast_mask);
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+
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+ if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC) {
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+ if (bc && cpus_empty(tick_broadcast_mask))
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+ clockevents_set_mode(bc, CLOCK_EVT_MODE_SHUTDOWN);
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+ }
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+
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+ spin_unlock_irqrestore(&tick_broadcast_lock, flags);
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+}
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Thomas Gleixner