[RFC PATCH 1/3] cpuidle: split cpuidle_idle_call main function into functions

[Daniel Lezcano <daniel.lezcano@linaro.org>]

In order to allow better integration between the cpuidle framework and the
scheduler, reducing the distance between the sub-component helps.

This patch splits the cpuidle_idle_call main entry function into 3 big chunks
of API:
 1. select the idle state
 2. enter the idle state
 3. reflect the idle state

The cpuidle_idle_call now calls these three functions to implement the main
idle entry function.

Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
---
 drivers/cpuidle/cpuidle.c |  105 ++++++++++++++++++++++++++++++++-------------
 include/linux/cpuidle.h   |    7 +++
 2 files changed, 83 insertions(+), 29 deletions(-)

diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c
index a55e68f..a8fbb28 100644
--- a/drivers/cpuidle/cpuidle.c
+++ b/drivers/cpuidle/cpuidle.c
@@ -108,6 +108,74 @@ int cpuidle_enter_state(struct cpuidle_device *dev, struct cpuidle_driver *drv,
 }
 
 /**
+ * cpuidle_select - ask the cpuidle framework to choose an idle state
+ *
+ * @drv: the cpuidle driver
+ * @dev: the cpuidle device
+ *
+ * Returns the index of the idle state. On error it returns:
+ * -NODEV : the cpuidle framework is available
+ * -EBUSY : the cpuidle framework is not initialized
+ */
+int cpuidle_select(struct cpuidle_driver *drv, struct cpuidle_device *dev)
+{
+	if (off || !initialized)
+		return -ENODEV;
+
+	if (!drv || !dev || !dev->enabled)
+		return -EBUSY;
+
+	return cpuidle_curr_governor->select(drv, dev);
+}
+EXPORT_SYMBOL(cpuidle_select);
+
+/**
+ * cpuidle_enter - enter into the specified idle state
+ *
+ * @drv:   the cpuidle driver tied with the cpu
+ * @dev:   the cpuidle device
+ * @index: the index in the idle state table
+ *
+ * Returns the index in the idle state, < 0 in case of error.
+ * The error code depends on the backend driver
+ */
+int cpuidle_enter(struct cpuidle_driver *drv, struct cpuidle_device *dev,
+		  int index)
+{
+	int entered_state;
+	bool broadcast = !!(drv->states[index].flags & CPUIDLE_FLAG_TIMER_STOP);
+
+	if (broadcast)
+		clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_ENTER, &dev->cpu);
+
+	if (cpuidle_state_is_coupled(dev, drv, index))
+		entered_state = cpuidle_enter_state_coupled(dev, drv, index);
+	else
+		entered_state = cpuidle_enter_state(dev, drv, index);
+
+	if (broadcast)
+		clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_EXIT, &dev->cpu);
+
+	return entered_state;
+}
+EXPORT_SYMBOL(cpuidle_enter);
+
+/**
+ * cpuidle_reflect - tell the underlying governor what was the state
+ * we were in
+ *
+ * @dev  : the cpuidle device
+ * @index: the index in the idle state table
+ *
+ */
+void cpuidle_reflect(struct cpuidle_device *dev, int index)
+{
+	if (cpuidle_curr_governor->reflect)
+		cpuidle_curr_governor->reflect(dev, index);
+}
+EXPORT_SYMBOL(cpuidle_reflect);
+
+/**
  * cpuidle_idle_call - the main idle loop
  *
  * NOTE: no locks or semaphores should be used here
@@ -116,51 +184,30 @@ int cpuidle_enter_state(struct cpuidle_device *dev, struct cpuidle_driver *drv,
 int cpuidle_idle_call(void)
 {
 	struct cpuidle_device *dev = __this_cpu_read(cpuidle_devices);
-	struct cpuidle_driver *drv;
+	struct cpuidle_driver *drv = cpuidle_get_cpu_driver(dev);
 	int next_state, entered_state;
-	bool broadcast;
-
-	if (off || !initialized)
-		return -ENODEV;
-
-	/* check if the device is ready */
-	if (!dev || !dev->enabled)
-		return -EBUSY;
-
-	drv = cpuidle_get_cpu_driver(dev);
 
 	/* ask the governor for the next state */
-	next_state = cpuidle_curr_governor->select(drv, dev);
+	next_state = cpuidle_select(drv, dev);
+	if (next_state < 0)
+		return next_state;
+
 	if (need_resched()) {
 		dev->last_residency = 0;
 		/* give the governor an opportunity to reflect on the outcome */
-		if (cpuidle_curr_governor->reflect)
-			cpuidle_curr_governor->reflect(dev, next_state);
+		cpuidle_reflect(dev, next_state);
 		local_irq_enable();
 		return 0;
 	}
 
 	trace_cpu_idle_rcuidle(next_state, dev->cpu);
 
-	broadcast = !!(drv->states[next_state].flags & CPUIDLE_FLAG_TIMER_STOP);
-
-	if (broadcast)
-		clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_ENTER, &dev->cpu);
-
-	if (cpuidle_state_is_coupled(dev, drv, next_state))
-		entered_state = cpuidle_enter_state_coupled(dev, drv,
-							    next_state);
-	else
-		entered_state = cpuidle_enter_state(dev, drv, next_state);
-
-	if (broadcast)
-		clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_EXIT, &dev->cpu);
+	entered_state = cpuidle_enter(drv, dev, next_state);
 
 	trace_cpu_idle_rcuidle(PWR_EVENT_EXIT, dev->cpu);
 
 	/* give the governor an opportunity to reflect on the outcome */
-	if (cpuidle_curr_governor->reflect)
-		cpuidle_curr_governor->reflect(dev, entered_state);
+	cpuidle_reflect(dev, entered_state);
 
 	return 0;
 }
diff --git a/include/linux/cpuidle.h b/include/linux/cpuidle.h
index 50fcbb0..1ebe9ff 100644
--- a/include/linux/cpuidle.h
+++ b/include/linux/cpuidle.h
@@ -119,6 +119,13 @@ struct cpuidle_driver {
 
 #ifdef CONFIG_CPU_IDLE
 extern void disable_cpuidle(void);
+
+extern int cpuidle_select(struct cpuidle_driver *drv,
+			  struct cpuidle_device *dev);
+extern int cpuidle_enter(struct cpuidle_driver *drv,
+			 struct cpuidle_device *dev, int index);
+extern void cpuidle_reflect(struct cpuidle_device *dev, int index);
+
 extern int cpuidle_idle_call(void);
 extern int cpuidle_register_driver(struct cpuidle_driver *drv);
 extern struct cpuidle_driver *cpuidle_get_driver(void);
-- 
1.7.9.5