Commit-ID: a6220fc19afc07fe77cfd16f5b8e568615517091
Gitweb: http://git.kernel.org/tip/a6220fc19afc07fe77cfd16f5b8e568615517091
Author: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
AuthorDate: Mon, 5 May 2014 00:51:54 +0200
Committer: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
CommitDate: Wed, 7 May 2014 01:49:28 +0200
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@xxxxxxxxx>
Tested-by: Aubrey Li <aubrey.li@xxxxxxxxxxxxxxx>
---
drivers/cpuidle/cpuidle.c | 45 ++++++++++++++++++++++++++++++++++++++++++++-
include/linux/cpuidle.h | 2 ++
kernel/power/suspend.c | 2 ++
3 files changed, 48 insertions(+), 1 deletion(-)
diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c
index f38359f..cb70199 100644
--- a/drivers/cpuidle/cpuidle.c
+++ b/drivers/cpuidle/cpuidle.c
@@ -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)
{
@@ -65,6 +66,45 @@ int cpuidle_play_dead(void)
}
/**
+ * 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
* @drv: cpuidle driver 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);
}
diff --git a/include/linux/cpuidle.h b/include/linux/cpuidle.h
index a8d5bd3..c51a436 100644
--- a/include/linux/cpuidle.h
+++ b/include/linux/cpuidle.h
@@ -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
diff --git a/kernel/power/suspend.c b/kernel/power/suspend.c
index 8233cd4..155721f 100644
--- a/kernel/power/suspend.c
+++ b/kernel/power/suspend.c
@@ -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)
--
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