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Commit a6220fc1 authored by Rafael J. Wysocki's avatar Rafael J. Wysocki
Browse files

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: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
Tested-by: default avatarAubrey Li <aubrey.li@linux.intel.com>
parent bed4d597

drivers/cpuidle/cpuidle.c

+44 −1
Original line number Diff line number Diff line
@@ -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);

}

include/linux/cpuidle.h

+2 −0
Original line number Diff line number Diff line
@@ -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

kernel/power/suspend.c

+2 −0
Original line number Diff line number Diff line
@@ -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)