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PM / suspend: Always use deepest C-state in the "freeze" sleep state 

If freeze_enter() is called, we want to bypass the current cpuidle
governor and always use the deepest available (that is, not disabled)
C-state, because we want to save as much energy as reasonably possible
then and runtime latency constraints don't matter at that point, since
the system is in a sleep state anyway.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Tested-by: Aubrey Li <aubrey.li@linux.intel.com>
hifive-unleashed-5.1
Rafael J. Wysocki 2014-05-05 00:51:54 +02:00
parent bed4d597a0
commit a6220fc19a
3 changed files with 48 additions and 1 deletions
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45
drivers/cpuidle/cpuidle.c
View File

@ -32,6 +32,7 @@ LIST_HEAD(cpuidle_detected_devices);
static int enabled_devices;
static int off __read_mostly;
static int initialized __read_mostly;
static bool use_deepest_state __read_mostly;
int cpuidle_disabled(void)
{
@ -64,6 +65,45 @@ int cpuidle_play_dead(void)
return -ENODEV;
}
/**
* cpuidle_use_deepest_state - Enable/disable the "deepest idle" mode.
* @enable: Whether enable or disable the feature.
*
* If the "deepest idle" mode is enabled, cpuidle will ignore the governor and
* always use the state with the greatest exit latency (out of the states that
* are not disabled).
*
* This function can only be called after cpuidle_pause() to avoid races.
*/
void cpuidle_use_deepest_state(bool enable)
{
use_deepest_state = enable;
}
/**
* cpuidle_find_deepest_state - Find the state of the greatest exit latency.
* @drv: cpuidle driver for a given CPU.
* @dev: cpuidle device for a given CPU.
*/
static int cpuidle_find_deepest_state(struct cpuidle_driver *drv,
struct cpuidle_device *dev)
{
unsigned int latency_req = 0;
int i, ret = CPUIDLE_DRIVER_STATE_START - 1;
for (i = CPUIDLE_DRIVER_STATE_START; i < drv->state_count; i++) {
struct cpuidle_state *s = &drv->states[i];
struct cpuidle_state_usage *su = &dev->states_usage[i];
if (s->disabled || su->disable || s->exit_latency <= latency_req)
continue;
latency_req = s->exit_latency;
ret = i;
}
return ret;
}
/**
* cpuidle_enter_state - enter the state and update stats
* @dev: cpuidle device for this cpu
@ -124,6 +164,9 @@ int cpuidle_select(struct cpuidle_driver *drv, struct cpuidle_device *dev)
if (!drv || !dev || !dev->enabled)
return -EBUSY;
if (unlikely(use_deepest_state))
return cpuidle_find_deepest_state(drv, dev);
return cpuidle_curr_governor->select(drv, dev);
}
@ -155,7 +198,7 @@ int cpuidle_enter(struct cpuidle_driver *drv, struct cpuidle_device *dev,
*/
void cpuidle_reflect(struct cpuidle_device *dev, int index)
{
if (cpuidle_curr_governor->reflect)
if (cpuidle_curr_governor->reflect && !unlikely(use_deepest_state))
cpuidle_curr_governor->reflect(dev, index);
}

2
include/linux/cpuidle.h
View File

@ -143,6 +143,7 @@ extern void cpuidle_resume(void);
extern int cpuidle_enable_device(struct cpuidle_device *dev);
extern void cpuidle_disable_device(struct cpuidle_device *dev);
extern int cpuidle_play_dead(void);
extern void cpuidle_use_deepest_state(bool enable);
extern struct cpuidle_driver *cpuidle_get_cpu_driver(struct cpuidle_device *dev);
#else
@ -175,6 +176,7 @@ 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_play_dead(void) {return -ENODEV; }
static inline void cpuidle_use_deepest_state(bool enable) {}
static inline struct cpuidle_driver *cpuidle_get_cpu_driver(
struct cpuidle_device *dev) {return NULL; }
#endif

2
kernel/power/suspend.c
View File

@ -54,9 +54,11 @@ static void freeze_begin(void)
static void freeze_enter(void)
{
cpuidle_use_deepest_state(true);
cpuidle_resume();
wait_event(suspend_freeze_wait_head, suspend_freeze_wake);
cpuidle_pause();
cpuidle_use_deepest_state(false);
}
void freeze_wake(void)