cpuidle.c
/*
* cpuidle.c - core cpuidle infrastructure
*
* (C) 2006-2007 Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
* Shaohua Li <shaohua.li@intel.com>
* Adam Belay <abelay@novell.com>
*
* This code is licenced under the GPL.
*/
#include <linux/clockchips.h>
#include <linux/kernel.h>
#include <linux/mutex.h>
#include <linux/sched.h>
#include <linux/notifier.h>
#include <linux/pm_qos.h>
#include <linux/cpu.h>
#include <linux/cpuidle.h>
#include <linux/ktime.h>
#include <linux/hrtimer.h>
#include <linux/module.h>
#include <trace/events/power.h>
#include "cpuidle.h"
DEFINE_PER_CPU(struct cpuidle_device *, cpuidle_devices);
DEFINE_PER_CPU(struct cpuidle_device, cpuidle_dev);
DEFINE_MUTEX(cpuidle_lock);
LIST_HEAD(cpuidle_detected_devices);
static int enabled_devices;
static int off __read_mostly;
static int initialized __read_mostly;
int cpuidle_disabled(void)
{
return off;
}
void disable_cpuidle(void)
{
off = 1;
}
/**
* cpuidle_play_dead - cpu off-lining
*
* Returns in case of an error or no driver
*/
int cpuidle_play_dead(void)
{
struct cpuidle_device *dev = __this_cpu_read(cpuidle_devices);
struct cpuidle_driver *drv = cpuidle_get_cpu_driver(dev);
int i;
if (!drv)
return -ENODEV;
/* Find lowest-power state that supports long-term idle */
for (i = drv->state_count - 1; i >= CPUIDLE_DRIVER_STATE_START; i--)
if (drv->states[i].enter_dead)
return drv->states[i].enter_dead(dev, i);
return -ENODEV;
}
/**
* cpuidle_enter_state - enter the state and update stats
* @dev: cpuidle device for this cpu
* @drv: cpuidle driver for this cpu
* @next_state: index into drv->states of the state to enter
*/
int cpuidle_enter_state(struct cpuidle_device *dev, struct cpuidle_driver *drv,
int index)
{
int entered_state;
struct cpuidle_state *target_state = &drv->states[index];
ktime_t time_start, time_end;
s64 diff;
time_start = ktime_get();
entered_state = target_state->enter(dev, drv, index);
time_end = ktime_get();
local_irq_enable();
diff = ktime_to_us(ktime_sub(time_end, time_start));
if (diff > INT_MAX)
diff = INT_MAX;
dev->last_residency = (int) diff;
if (entered_state >= 0) {
/* Update cpuidle counters */
/* This can be moved to within driver enter routine
* but that results in multiple copies of same code.
*/
dev->states_usage[entered_state].time += dev->last_residency;
dev->states_usage[entered_state].usage++;
} else {
dev->last_residency = 0;
}
return entered_state;
}
/**
* cpuidle_idle_call - the main idle loop
*
* NOTE: no locks or semaphores should be used here
* return non-zero on failure
*/
int cpuidle_idle_call(void)
{
struct cpuidle_device *dev = __this_cpu_read(cpuidle_devices);
struct cpuidle_driver *drv;
int next_state, entered_state;
bool broadcast;
if (off || !initialized)
return -ENODEV;
/* check if the device is ready */
if (!dev || !dev->enabled)
return -EBUSY;
drv = cpuidle_get_cpu_driver(dev);
/* ask the governor for the next state */
next_state = cpuidle_curr_governor->select(drv, dev);
if (need_resched()) {
dev->last_residency = 0;
/* give the governor an opportunity to reflect on the outcome */
if (cpuidle_curr_governor->reflect)
cpuidle_curr_governor->reflect(dev, next_state);
local_irq_enable();
return 0;
}
trace_cpu_idle_rcuidle(next_state, dev->cpu);
broadcast = !!(drv->states[next_state].flags & CPUIDLE_FLAG_TIMER_STOP);
if (broadcast)
clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_ENTER, &dev->cpu);
if (cpuidle_state_is_coupled(dev, drv, next_state))
entered_state = cpuidle_enter_state_coupled(dev, drv,
next_state);
else
entered_state = cpuidle_enter_state(dev, drv, next_state);
if (broadcast)
clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_EXIT, &dev->cpu);
trace_cpu_idle_rcuidle(PWR_EVENT_EXIT, dev->cpu);
/* give the governor an opportunity to reflect on the outcome */
if (cpuidle_curr_governor->reflect)
cpuidle_curr_governor->reflect(dev, entered_state);
return 0;
}
/**
* cpuidle_install_idle_handler - installs the cpuidle idle loop handler
*/
void cpuidle_install_idle_handler(void)
{
if (enabled_devices) {
/* Make sure all changes finished before we switch to new idle */
smp_wmb();
initialized = 1;
}
}
/**
* cpuidle_uninstall_idle_handler - uninstalls the cpuidle idle loop handler
*/
void cpuidle_uninstall_idle_handler(void)
{
if (enabled_devices) {
initialized = 0;
kick_all_cpus_sync();
}
}
/**
* cpuidle_pause_and_lock - temporarily disables CPUIDLE
*/
void cpuidle_pause_and_lock(void)
{
mutex_lock(&cpuidle_lock);
cpuidle_uninstall_idle_handler();
}
EXPORT_SYMBOL_GPL(cpuidle_pause_and_lock);
/**
* cpuidle_resume_and_unlock - resumes CPUIDLE operation
*/
void cpuidle_resume_and_unlock(void)
{
cpuidle_install_idle_handler();
mutex_unlock(&cpuidle_lock);
}
EXPORT_SYMBOL_GPL(cpuidle_resume_and_unlock);
/* Currently used in suspend/resume path to suspend cpuidle */
void cpuidle_pause(void)
{
mutex_lock(&cpuidle_lock);
cpuidle_uninstall_idle_handler();
mutex_unlock(&cpuidle_lock);
}
/* Currently used in suspend/resume path to resume cpuidle */
void cpuidle_resume(void)
{
mutex_lock(&cpuidle_lock);
cpuidle_install_idle_handler();
mutex_unlock(&cpuidle_lock);
}
/**
* cpuidle_enable_device - enables idle PM for a CPU
* @dev: the CPU
*
* This function must be called between cpuidle_pause_and_lock and
* cpuidle_resume_and_unlock when used externally.
*/
int cpuidle_enable_device(struct cpuidle_device *dev)
{
int ret;
struct cpuidle_driver *drv;
if (!dev)
return -EINVAL;
if (dev->enabled)
return 0;
drv = cpuidle_get_cpu_driver(dev);
if (!drv || !cpuidle_curr_governor)
return -EIO;
if (!dev->registered)
return -EINVAL;
if (!dev->state_count)
dev->state_count = drv->state_count;
ret = cpuidle_add_device_sysfs(dev);
if (ret)
return ret;
if (cpuidle_curr_governor->enable &&
(ret = cpuidle_curr_governor->enable(drv, dev)))
goto fail_sysfs;
smp_wmb();
dev->enabled = 1;
enabled_devices++;
return 0;
fail_sysfs:
cpuidle_remove_device_sysfs(dev);
return ret;
}
EXPORT_SYMBOL_GPL(cpuidle_enable_device);
/**
* cpuidle_disable_device - disables idle PM for a CPU
* @dev: the CPU
*
* This function must be called between cpuidle_pause_and_lock and
* cpuidle_resume_and_unlock when used externally.
*/
void cpuidle_disable_device(struct cpuidle_device *dev)
{
struct cpuidle_driver *drv = cpuidle_get_cpu_driver(dev);
if (!dev || !dev->enabled)
return;
if (!drv || !cpuidle_curr_governor)
return;
dev->enabled = 0;
if (cpuidle_curr_governor->disable)
cpuidle_curr_governor->disable(drv, dev);
cpuidle_remove_device_sysfs(dev);
enabled_devices--;
}
EXPORT_SYMBOL_GPL(cpuidle_disable_device);
static void __cpuidle_unregister_device(struct cpuidle_device *dev)
{
struct cpuidle_driver *drv = cpuidle_get_cpu_driver(dev);
list_del(&dev->device_list);
per_cpu(cpuidle_devices, dev->cpu) = NULL;
module_put(drv->owner);
}
static void __cpuidle_device_init(struct cpuidle_device *dev)
{
memset(dev->states_usage, 0, sizeof(dev->states_usage));
dev->last_residency = 0;
}
/**
* __cpuidle_register_device - internal register function called before register
* and enable routines
* @dev: the cpu
*
* cpuidle_lock mutex must be held before this is called
*/
static int __cpuidle_register_device(struct cpuidle_device *dev)
{
int ret;
struct cpuidle_driver *drv = cpuidle_get_cpu_driver(dev);
if (!try_module_get(drv->owner))
return -EINVAL;
per_cpu(cpuidle_devices, dev->cpu) = dev;
list_add(&dev->device_list, &cpuidle_detected_devices);
ret = cpuidle_coupled_register_device(dev);
if (ret)
__cpuidle_unregister_device(dev);
else
dev->registered = 1;
return ret;
}
/**
* cpuidle_register_device - registers a CPU's idle PM feature
* @dev: the cpu
*/
int cpuidle_register_device(struct cpuidle_device *dev)
{
int ret = -EBUSY;
if (!dev)
return -EINVAL;
mutex_lock(&cpuidle_lock);
if (dev->registered)
goto out_unlock;
__cpuidle_device_init(dev);
ret = __cpuidle_register_device(dev);
if (ret)
goto out_unlock;
ret = cpuidle_add_sysfs(dev);
if (ret)
goto out_unregister;
ret = cpuidle_enable_device(dev);
if (ret)
goto out_sysfs;
cpuidle_install_idle_handler();
out_unlock:
mutex_unlock(&cpuidle_lock);
return ret;
out_sysfs:
cpuidle_remove_sysfs(dev);
out_unregister:
__cpuidle_unregister_device(dev);
goto out_unlock;
}
EXPORT_SYMBOL_GPL(cpuidle_register_device);
/**
* cpuidle_unregister_device - unregisters a CPU's idle PM feature
* @dev: the cpu
*/
void cpuidle_unregister_device(struct cpuidle_device *dev)
{
if (!dev || dev->registered == 0)
return;
cpuidle_pause_and_lock();
cpuidle_disable_device(dev);
cpuidle_remove_sysfs(dev);
__cpuidle_unregister_device(dev);
cpuidle_coupled_unregister_device(dev);
cpuidle_resume_and_unlock();
}
EXPORT_SYMBOL_GPL(cpuidle_unregister_device);
/**
* cpuidle_unregister: unregister a driver and the devices. This function
* can be used only if the driver has been previously registered through
* the cpuidle_register function.
*
* @drv: a valid pointer to a struct cpuidle_driver
*/
void cpuidle_unregister(struct cpuidle_driver *drv)
{
int cpu;
struct cpuidle_device *device;
for_each_cpu(cpu, drv->cpumask) {
device = &per_cpu(cpuidle_dev, cpu);
cpuidle_unregister_device(device);
}
cpuidle_unregister_driver(drv);
}
EXPORT_SYMBOL_GPL(cpuidle_unregister);
/**
* cpuidle_register: registers the driver and the cpu devices with the
* coupled_cpus passed as parameter. This function is used for all common
* initialization pattern there are in the arch specific drivers. The
* devices is globally defined in this file.
*
* @drv : a valid pointer to a struct cpuidle_driver
* @coupled_cpus: a cpumask for the coupled states
*
* Returns 0 on success, < 0 otherwise
*/
int cpuidle_register(struct cpuidle_driver *drv,
const struct cpumask *const coupled_cpus)
{
int ret, cpu;
struct cpuidle_device *device;
ret = cpuidle_register_driver(drv);
if (ret) {
pr_err("failed to register cpuidle driver\n");
return ret;
}
for_each_cpu(cpu, drv->cpumask) {
device = &per_cpu(cpuidle_dev, cpu);
device->cpu = cpu;
#ifdef CONFIG_ARCH_NEEDS_CPU_IDLE_COUPLED
/*
* On multiplatform for ARM, the coupled idle states could be
* enabled in the kernel even if the cpuidle driver does not
* use it. Note, coupled_cpus is a struct copy.
*/
if (coupled_cpus)
device->coupled_cpus = *coupled_cpus;
#endif
ret = cpuidle_register_device(device);
if (!ret)
continue;
pr_err("Failed to register cpuidle device for cpu%d\n", cpu);
cpuidle_unregister(drv);
break;
}
return ret;
}
EXPORT_SYMBOL_GPL(cpuidle_register);
#ifdef CONFIG_SMP
static void smp_callback(void *v)
{
/* we already woke the CPU up, nothing more to do */
}
/*
* This function gets called when a part of the kernel has a new latency
* requirement. This means we need to get all processors out of their C-state,
* and then recalculate a new suitable C-state. Just do a cross-cpu IPI; that
* wakes them all right up.
*/
static int cpuidle_latency_notify(struct notifier_block *b,
unsigned long l, void *v)
{
smp_call_function(smp_callback, NULL, 1);
return NOTIFY_OK;
}
static struct notifier_block cpuidle_latency_notifier = {
.notifier_call = cpuidle_latency_notify,
};
static inline void latency_notifier_init(struct notifier_block *n)
{
pm_qos_add_notifier(PM_QOS_CPU_DMA_LATENCY, n);
}
#else /* CONFIG_SMP */
#define latency_notifier_init(x) do { } while (0)
#endif /* CONFIG_SMP */
/**
* cpuidle_init - core initializer
*/
static int __init cpuidle_init(void)
{
int ret;
if (cpuidle_disabled())
return -ENODEV;
ret = cpuidle_add_interface(cpu_subsys.dev_root);
if (ret)
return ret;
latency_notifier_init(&cpuidle_latency_notifier);
return 0;
}
module_param(off, int, 0444);
core_initcall(cpuidle_init);