/*
* 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
