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linux-stable/include/linux/cpuidle.h
Colin Cross 4126c0197b cpuidle: add support for states that affect multiple cpus 
On some ARM SMP SoCs (OMAP4460, Tegra 2, and probably more), the
cpus cannot be independently powered down, either due to
sequencing restrictions (on Tegra 2, cpu 0 must be the last to
power down), or due to HW bugs (on OMAP4460, a cpu powering up
will corrupt the gic state unless the other cpu runs a work
around).  Each cpu has a power state that it can enter without
coordinating with the other cpu (usually Wait For Interrupt, or
WFI), and one or more "coupled" power states that affect blocks
shared between the cpus (L2 cache, interrupt controller, and
sometimes the whole SoC).  Entering a coupled power state must
be tightly controlled on both cpus.

The easiest solution to implementing coupled cpu power states is
to hotplug all but one cpu whenever possible, usually using a
cpufreq governor that looks at cpu load to determine when to
enable the secondary cpus.  This causes problems, as hotplug is an
expensive operation, so the number of hotplug transitions must be
minimized, leading to very slow response to loads, often on the
order of seconds.

This file implements an alternative solution, where each cpu will
wait in the WFI state until all cpus are ready to enter a coupled
state, at which point the coupled state function will be called
on all cpus at approximately the same time.

Once all cpus are ready to enter idle, they are woken by an smp
cross call.  At this point, there is a chance that one of the
cpus will find work to do, and choose not to enter idle.  A
final pass is needed to guarantee that all cpus will call the
power state enter function at the same time.  During this pass,
each cpu will increment the ready counter, and continue once the
ready counter matches the number of online coupled cpus.  If any
cpu exits idle, the other cpus will decrement their counter and
retry.

To use coupled cpuidle states, a cpuidle driver must:

   Set struct cpuidle_device.coupled_cpus to the mask of all
   coupled cpus, usually the same as cpu_possible_mask if all cpus
   are part of the same cluster.  The coupled_cpus mask must be
   set in the struct cpuidle_device for each cpu.

   Set struct cpuidle_device.safe_state to a state that is not a
   coupled state.  This is usually WFI.

   Set CPUIDLE_FLAG_COUPLED in struct cpuidle_state.flags for each
   state that affects multiple cpus.

   Provide a struct cpuidle_state.enter function for each state
   that affects multiple cpus.  This function is guaranteed to be
   called on all cpus at approximately the same time.  The driver
   should ensure that the cpus all abort together if any cpu tries
   to abort once the function is called.

update1:

cpuidle: coupled: fix count of online cpus

online_count was never incremented on boot, and was also counting
cpus that were not part of the coupled set.  Fix both issues by
introducting a new function that counts online coupled cpus, and
call it from register as well as the hotplug notifier.

update2:

cpuidle: coupled: fix decrementing ready count

cpuidle_coupled_set_not_ready sometimes refuses to decrement the
ready count in order to prevent a race condition.  This makes it
unsuitable for use when finished with idle.  Add a new function
cpuidle_coupled_set_done that decrements both the ready count and
waiting count, and call it after idle is complete.

Cc: Amit Kucheria <amit.kucheria@linaro.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Trinabh Gupta <g.trinabh@gmail.com>
Cc: Deepthi Dharwar <deepthi@linux.vnet.ibm.com>
Reviewed-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Tested-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Reviewed-by: Kevin Hilman <khilman@ti.com>
Tested-by: Kevin Hilman <khilman@ti.com>
Signed-off-by: Colin Cross <ccross@android.com>
Acked-by: Rafael J. Wysocki <rjw@sisk.pl>
Signed-off-by: Len Brown <len.brown@intel.com>
2012-06-02 00:49:09 -04:00

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/*
* cpuidle.h - a generic framework for CPU idle power management
*
* (C) 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.
*/
#ifndef _LINUX_CPUIDLE_H
#define _LINUX_CPUIDLE_H
#include <linux/percpu.h>
#include <linux/list.h>
#include <linux/kobject.h>
#include <linux/completion.h>
#include <linux/hrtimer.h>
#define CPUIDLE_STATE_MAX 8
#define CPUIDLE_NAME_LEN 16
#define CPUIDLE_DESC_LEN 32
struct module;
struct cpuidle_device;
struct cpuidle_driver;
/****************************
* CPUIDLE DEVICE INTERFACE *
****************************/
struct cpuidle_state_usage {
void *driver_data;
unsigned long long usage;
unsigned long long time; /* in US */
};
struct cpuidle_state {
char name[CPUIDLE_NAME_LEN];
char desc[CPUIDLE_DESC_LEN];
unsigned int flags;
unsigned int exit_latency; /* in US */
int power_usage; /* in mW */
unsigned int target_residency; /* in US */
unsigned int disable;
int (*enter) (struct cpuidle_device *dev,
struct cpuidle_driver *drv,
int index);
int (*enter_dead) (struct cpuidle_device *dev, int index);
};
/* Idle State Flags */
#define CPUIDLE_FLAG_TIME_VALID (0x01) /* is residency time measurable? */
#define CPUIDLE_FLAG_COUPLED (0x02) /* state applies to multiple cpus */
#define CPUIDLE_DRIVER_FLAGS_MASK (0xFFFF0000)
/**
* cpuidle_get_statedata - retrieves private driver state data
* @st_usage: the state usage statistics
*/
static inline void *cpuidle_get_statedata(struct cpuidle_state_usage *st_usage)
{
return st_usage->driver_data;
}
/**
* cpuidle_set_statedata - stores private driver state data
* @st_usage: the state usage statistics
* @data: the private data
*/
static inline void
cpuidle_set_statedata(struct cpuidle_state_usage *st_usage, void *data)
{
st_usage->driver_data = data;
}
struct cpuidle_state_kobj {
struct cpuidle_state *state;
struct cpuidle_state_usage *state_usage;
struct completion kobj_unregister;
struct kobject kobj;
};
struct cpuidle_device {
unsigned int registered:1;
unsigned int enabled:1;
unsigned int cpu;
int last_residency;
int state_count;
struct cpuidle_state_usage states_usage[CPUIDLE_STATE_MAX];
struct cpuidle_state_kobj *kobjs[CPUIDLE_STATE_MAX];
struct list_head device_list;
struct kobject kobj;
struct completion kobj_unregister;
#ifdef CONFIG_ARCH_NEEDS_CPU_IDLE_COUPLED
int safe_state_index;
cpumask_t coupled_cpus;
struct cpuidle_coupled *coupled;
#endif
};
DECLARE_PER_CPU(struct cpuidle_device *, cpuidle_devices);
/**
* cpuidle_get_last_residency - retrieves the last state's residency time
* @dev: the target CPU
*
* NOTE: this value is invalid if CPUIDLE_FLAG_TIME_VALID isn't set
*/
static inline int cpuidle_get_last_residency(struct cpuidle_device *dev)
{
return dev->last_residency;
}
/****************************
* CPUIDLE DRIVER INTERFACE *
****************************/
struct cpuidle_driver {
const char *name;
struct module *owner;
unsigned int power_specified:1;
/* set to 1 to use the core cpuidle time keeping (for all states). */
unsigned int en_core_tk_irqen:1;
struct cpuidle_state states[CPUIDLE_STATE_MAX];
int state_count;
int safe_state_index;
};
#ifdef CONFIG_CPU_IDLE
extern void disable_cpuidle(void);
extern int cpuidle_idle_call(void);
extern int cpuidle_register_driver(struct cpuidle_driver *drv);
struct cpuidle_driver *cpuidle_get_driver(void);
extern void cpuidle_unregister_driver(struct cpuidle_driver *drv);
extern int cpuidle_register_device(struct cpuidle_device *dev);
extern void cpuidle_unregister_device(struct cpuidle_device *dev);
extern void cpuidle_pause_and_lock(void);
extern void cpuidle_resume_and_unlock(void);
extern int cpuidle_enable_device(struct cpuidle_device *dev);
extern void cpuidle_disable_device(struct cpuidle_device *dev);
extern int cpuidle_wrap_enter(struct cpuidle_device *dev,
struct cpuidle_driver *drv, int index,
int (*enter)(struct cpuidle_device *dev,
struct cpuidle_driver *drv, int index));
extern int cpuidle_play_dead(void);
#else
static inline void disable_cpuidle(void) { }
static inline int cpuidle_idle_call(void) { return -ENODEV; }
static inline int cpuidle_register_driver(struct cpuidle_driver *drv)
{return -ENODEV; }
static inline struct cpuidle_driver *cpuidle_get_driver(void) {return NULL; }
static inline void cpuidle_unregister_driver(struct cpuidle_driver *drv) { }
static inline int cpuidle_register_device(struct cpuidle_device *dev)
{return -ENODEV; }
static inline void cpuidle_unregister_device(struct cpuidle_device *dev) { }
static inline void cpuidle_pause_and_lock(void) { }
static inline void cpuidle_resume_and_unlock(void) { }
static inline int cpuidle_enable_device(struct cpuidle_device *dev)
{return -ENODEV; }
static inline void cpuidle_disable_device(struct cpuidle_device *dev) { }
static inline int cpuidle_wrap_enter(struct cpuidle_device *dev,
struct cpuidle_driver *drv, int index,
int (*enter)(struct cpuidle_device *dev,
struct cpuidle_driver *drv, int index))
{ return -ENODEV; }
static inline int cpuidle_play_dead(void) {return -ENODEV; }
#endif
/******************************
* CPUIDLE GOVERNOR INTERFACE *
******************************/
struct cpuidle_governor {
char name[CPUIDLE_NAME_LEN];
struct list_head governor_list;
unsigned int rating;
int (*enable) (struct cpuidle_driver *drv,
struct cpuidle_device *dev);
void (*disable) (struct cpuidle_driver *drv,
struct cpuidle_device *dev);
int (*select) (struct cpuidle_driver *drv,
struct cpuidle_device *dev);
void (*reflect) (struct cpuidle_device *dev, int index);
struct module *owner;
};
#ifdef CONFIG_CPU_IDLE
extern int cpuidle_register_governor(struct cpuidle_governor *gov);
extern void cpuidle_unregister_governor(struct cpuidle_governor *gov);
#ifdef CONFIG_INTEL_IDLE
extern int intel_idle_cpu_init(int cpu);
#else
static inline int intel_idle_cpu_init(int cpu) { return -1; }
#endif
#else
static inline int intel_idle_cpu_init(int cpu) { return -1; }
static inline int cpuidle_register_governor(struct cpuidle_governor *gov)
{return 0;}
static inline void cpuidle_unregister_governor(struct cpuidle_governor *gov) { }
#endif
#ifdef CONFIG_ARCH_HAS_CPU_RELAX
#define CPUIDLE_DRIVER_STATE_START 1
#else
#define CPUIDLE_DRIVER_STATE_START 0
#endif
#endif /* _LINUX_CPUIDLE_H */
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