linux/drivers/cpuidle/cpuidle.c
Ai Li 71abbbf856 cpuidle: extend cpuidle and menu governor to handle dynamic states
On some SoC chips, HW resources may be in use during any particular idle
period.  As a consequence, the cpuidle states that the SoC is safe to
enter can change from idle period to idle period.  In addition, the
latency and threshold of each cpuidle state can vary, depending on the
operating condition when the CPU becomes idle, e.g.  the current cpu
frequency, the current state of the HW blocks, etc.

cpuidle core and the menu governor, in the current form, are geared
towards cpuidle states that are static, i.e.  the availabiltiy of the
states, their latencies, their thresholds are non-changing during run
time.  cpuidle does not provide any hook that cpuidle drivers can use to
adjust those values on the fly for the current idle period before the menu
governor selects the target cpuidle state.

This patch extends cpuidle core and the menu governor to handle states
that are dynamic.  There are three additions in the patch and the patch
maintains backwards-compatibility with existing cpuidle drivers.

1) add prepare() to struct cpuidle_device.  A cpuidle driver can hook
   into the callback and cpuidle will call prepare() before calling the
   governor's select function.  The callback gives the cpuidle driver a
   chance to update the dynamic information of the cpuidle states for the
   current idle period, e.g.  state availability, latencies, thresholds,
   power values, etc.

2) add CPUIDLE_FLAG_IGNORE as one of the state flags.  In the prepare()
   function, a cpuidle driver can set/clear the flag to indicate to the
   menu governor whether a cpuidle state should be ignored, i.e.  not
   available, during the current idle period.

3) add power_specified bit to struct cpuidle_device.  The menu governor
   currently assumes that the cpuidle states are arranged in the order of
   increasing latency, threshold, and power savings.  This is true or can
   be made true for static states.  Once the state parameters are dynamic,
   the latencies, thresholds, and power savings for the cpuidle states can
   increase or decrease by different amounts from idle period to idle
   period.  So the assumption of increasing latency, threshold, and power
   savings from Cn to C(n+1) can no longer be guaranteed.

It can be straightforward to calculate the power consumption of each
available state and to specify it in power_usage for the idle period.
Using the power_usage fields, the menu governor then selects the state
that has the lowest power consumption and that still satisfies all other
critieria.  The power_specified bit defaults to 0.  For existing cpuidle
drivers, cpuidle detects that power_specified is 0 and fills in a dummy
set of power_usage values.

Signed-off-by: Ai Li <aili@codeaurora.org>
Cc: Len Brown <len.brown@intel.com>
Acked-by: Arjan van de Ven <arjan@linux.intel.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Venkatesh Pallipadi <venki@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2010-08-09 20:45:04 -07:00

435 lines
9.6 KiB
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/kernel.h>
#include <linux/mutex.h>
#include <linux/sched.h>
#include <linux/notifier.h>
#include <linux/pm_qos_params.h>
#include <linux/cpu.h>
#include <linux/cpuidle.h>
#include <linux/ktime.h>
#include <linux/hrtimer.h>
#include <trace/events/power.h>
#include "cpuidle.h"
DEFINE_PER_CPU(struct cpuidle_device *, cpuidle_devices);
DEFINE_MUTEX(cpuidle_lock);
LIST_HEAD(cpuidle_detected_devices);
static void (*pm_idle_old)(void);
static int enabled_devices;
#if defined(CONFIG_ARCH_HAS_CPU_IDLE_WAIT)
static void cpuidle_kick_cpus(void)
{
cpu_idle_wait();
}
#elif defined(CONFIG_SMP)
# error "Arch needs cpu_idle_wait() equivalent here"
#else /* !CONFIG_ARCH_HAS_CPU_IDLE_WAIT && !CONFIG_SMP */
static void cpuidle_kick_cpus(void) {}
#endif
static int __cpuidle_register_device(struct cpuidle_device *dev);
/**
* cpuidle_idle_call - the main idle loop
*
* NOTE: no locks or semaphores should be used here
*/
static void cpuidle_idle_call(void)
{
struct cpuidle_device *dev = __get_cpu_var(cpuidle_devices);
struct cpuidle_state *target_state;
int next_state;
/* check if the device is ready */
if (!dev || !dev->enabled) {
if (pm_idle_old)
pm_idle_old();
else
#if defined(CONFIG_ARCH_HAS_DEFAULT_IDLE)
default_idle();
#else
local_irq_enable();
#endif
return;
}
#if 0
/* shows regressions, re-enable for 2.6.29 */
/*
* run any timers that can be run now, at this point
* before calculating the idle duration etc.
*/
hrtimer_peek_ahead_timers();
#endif
/*
* Call the device's prepare function before calling the
* governor's select function. ->prepare gives the device's
* cpuidle driver a chance to update any dynamic information
* of its cpuidle states for the current idle period, e.g.
* state availability, latencies, residencies, etc.
*/
if (dev->prepare)
dev->prepare(dev);
/* ask the governor for the next state */
next_state = cpuidle_curr_governor->select(dev);
if (need_resched()) {
local_irq_enable();
return;
}
target_state = &dev->states[next_state];
/* enter the state and update stats */
dev->last_state = target_state;
dev->last_residency = target_state->enter(dev, target_state);
if (dev->last_state)
target_state = dev->last_state;
target_state->time += (unsigned long long)dev->last_residency;
target_state->usage++;
/* give the governor an opportunity to reflect on the outcome */
if (cpuidle_curr_governor->reflect)
cpuidle_curr_governor->reflect(dev);
trace_power_end(smp_processor_id());
}
/**
* cpuidle_install_idle_handler - installs the cpuidle idle loop handler
*/
void cpuidle_install_idle_handler(void)
{
if (enabled_devices && (pm_idle != cpuidle_idle_call)) {
/* Make sure all changes finished before we switch to new idle */
smp_wmb();
pm_idle = cpuidle_idle_call;
}
}
/**
* cpuidle_uninstall_idle_handler - uninstalls the cpuidle idle loop handler
*/
void cpuidle_uninstall_idle_handler(void)
{
if (enabled_devices && pm_idle_old && (pm_idle != pm_idle_old)) {
pm_idle = pm_idle_old;
cpuidle_kick_cpus();
}
}
/**
* 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);
/**
* 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, i;
if (dev->enabled)
return 0;
if (!cpuidle_get_driver() || !cpuidle_curr_governor)
return -EIO;
if (!dev->state_count)
return -EINVAL;
if (dev->registered == 0) {
ret = __cpuidle_register_device(dev);
if (ret)
return ret;
}
if ((ret = cpuidle_add_state_sysfs(dev)))
return ret;
if (cpuidle_curr_governor->enable &&
(ret = cpuidle_curr_governor->enable(dev)))
goto fail_sysfs;
for (i = 0; i < dev->state_count; i++) {
dev->states[i].usage = 0;
dev->states[i].time = 0;
}
dev->last_residency = 0;
dev->last_state = NULL;
smp_wmb();
dev->enabled = 1;
enabled_devices++;
return 0;
fail_sysfs:
cpuidle_remove_state_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)
{
if (!dev->enabled)
return;
if (!cpuidle_get_driver() || !cpuidle_curr_governor)
return;
dev->enabled = 0;
if (cpuidle_curr_governor->disable)
cpuidle_curr_governor->disable(dev);
cpuidle_remove_state_sysfs(dev);
enabled_devices--;
}
EXPORT_SYMBOL_GPL(cpuidle_disable_device);
#ifdef CONFIG_ARCH_HAS_CPU_RELAX
static int poll_idle(struct cpuidle_device *dev, struct cpuidle_state *st)
{
ktime_t t1, t2;
s64 diff;
int ret;
t1 = ktime_get();
local_irq_enable();
while (!need_resched())
cpu_relax();
t2 = ktime_get();
diff = ktime_to_us(ktime_sub(t2, t1));
if (diff > INT_MAX)
diff = INT_MAX;
ret = (int) diff;
return ret;
}
static void poll_idle_init(struct cpuidle_device *dev)
{
struct cpuidle_state *state = &dev->states[0];
cpuidle_set_statedata(state, NULL);
snprintf(state->name, CPUIDLE_NAME_LEN, "C0");
snprintf(state->desc, CPUIDLE_DESC_LEN, "CPUIDLE CORE POLL IDLE");
state->exit_latency = 0;
state->target_residency = 0;
state->power_usage = -1;
state->flags = CPUIDLE_FLAG_POLL;
state->enter = poll_idle;
}
#else
static void poll_idle_init(struct cpuidle_device *dev) {}
#endif /* CONFIG_ARCH_HAS_CPU_RELAX */
/**
* __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 sys_device *sys_dev = get_cpu_sysdev((unsigned long)dev->cpu);
struct cpuidle_driver *cpuidle_driver = cpuidle_get_driver();
if (!sys_dev)
return -EINVAL;
if (!try_module_get(cpuidle_driver->owner))
return -EINVAL;
init_completion(&dev->kobj_unregister);
poll_idle_init(dev);
/*
* cpuidle driver should set the dev->power_specified bit
* before registering the device if the driver provides
* power_usage numbers.
*
* For those devices whose ->power_specified is not set,
* we fill in power_usage with decreasing values as the
* cpuidle code has an implicit assumption that state Cn
* uses less power than C(n-1).
*
* With CONFIG_ARCH_HAS_CPU_RELAX, C0 is already assigned
* an power value of -1. So we use -2, -3, etc, for other
* c-states.
*/
if (!dev->power_specified) {
int i;
for (i = CPUIDLE_DRIVER_STATE_START; i < dev->state_count; i++)
dev->states[i].power_usage = -1 - i;
}
per_cpu(cpuidle_devices, dev->cpu) = dev;
list_add(&dev->device_list, &cpuidle_detected_devices);
if ((ret = cpuidle_add_sysfs(sys_dev))) {
module_put(cpuidle_driver->owner);
return ret;
}
dev->registered = 1;
return 0;
}
/**
* cpuidle_register_device - registers a CPU's idle PM feature
* @dev: the cpu
*/
int cpuidle_register_device(struct cpuidle_device *dev)
{
int ret;
mutex_lock(&cpuidle_lock);
if ((ret = __cpuidle_register_device(dev))) {
mutex_unlock(&cpuidle_lock);
return ret;
}
cpuidle_enable_device(dev);
cpuidle_install_idle_handler();
mutex_unlock(&cpuidle_lock);
return 0;
}
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)
{
struct sys_device *sys_dev = get_cpu_sysdev((unsigned long)dev->cpu);
struct cpuidle_driver *cpuidle_driver = cpuidle_get_driver();
if (dev->registered == 0)
return;
cpuidle_pause_and_lock();
cpuidle_disable_device(dev);
cpuidle_remove_sysfs(sys_dev);
list_del(&dev->device_list);
wait_for_completion(&dev->kobj_unregister);
per_cpu(cpuidle_devices, dev->cpu) = NULL;
cpuidle_resume_and_unlock();
module_put(cpuidle_driver->owner);
}
EXPORT_SYMBOL_GPL(cpuidle_unregister_device);
#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;
pm_idle_old = pm_idle;
ret = cpuidle_add_class_sysfs(&cpu_sysdev_class);
if (ret)
return ret;
latency_notifier_init(&cpuidle_latency_notifier);
return 0;
}
core_initcall(cpuidle_init);