[v4 PATCH 1/5]: cpuidle: Cleanup drivers/cpuidle/cpuidle.c

[Arun R Bharadwaj]

* Arun R Bharadwaj <arun at linux.vnet.ibm.com> [2009-09-01 17:07:04]:

Cleanup drivers/cpuidle/cpuidle.c

Cpuidle maintains a pm_idle_old void pointer because, currently in x86
there is no clean way of registering and unregistering a idle function.

So remove pm_idle_old and leave the responsibility of maintaining the
list of registered idle loops to the architecture specific code. If the
architecture registers cpuidle_idle_call as its idle loop, only then
this loop is called.

Also remove unwanted functions cpuidle_[un]install_idle_handler,
cpuidle_kick_cpus()

Signed-off-by: Arun R Bharadwaj <arun at linux.vnet.ibm.com>
---
 drivers/cpuidle/cpuidle.c  |   51 +++++++++++++++------------------------------
 drivers/cpuidle/governor.c |    3 --
 2 files changed, 17 insertions(+), 37 deletions(-)

Index: linux.trees.git/drivers/cpuidle/cpuidle.c
===================================================================
--- linux.trees.git.orig/drivers/cpuidle/cpuidle.c
+++ linux.trees.git/drivers/cpuidle/cpuidle.c
@@ -24,9 +24,14 @@ DEFINE_PER_CPU(struct cpuidle_device *, 
 
 DEFINE_MUTEX(cpuidle_lock);
 LIST_HEAD(cpuidle_detected_devices);
-static void (*pm_idle_old)(void);
 
 static int enabled_devices;
+static int idle_function_registered;
+
+struct idle_function_desc cpuidle_idle_desc = {
+	.name           =       "cpuidle_loop",
+	.idle_func      =       cpuidle_idle_call,
+};
 
 #if defined(CONFIG_ARCH_HAS_CPU_IDLE_WAIT)
 static void cpuidle_kick_cpus(void)
@@ -54,13 +59,10 @@ static void cpuidle_idle_call(void)
 
 	/* check if the device is ready */
 	if (!dev || !dev->enabled) {
-		if (pm_idle_old)
-			pm_idle_old();
-		else
 #if defined(CONFIG_ARCH_HAS_DEFAULT_IDLE)
-			default_idle();
+		default_idle();
 #else
-			local_irq_enable();
+		local_irq_enable();
 #endif
 		return;
 	}
@@ -94,35 +96,11 @@ static void cpuidle_idle_call(void)
 }
 
 /**
- * cpuidle_install_idle_handler - installs the cpuidle idle loop handler
- */
-void cpuidle_install_idle_handler(void)
-{
-	if (enabled_devices && (pm_idle != cpuidle_idle_call)) {
-		/* Make sure all changes finished before we switch to new idle */
-		smp_wmb();
-		pm_idle = cpuidle_idle_call;
-	}
-}
-
-/**
- * cpuidle_uninstall_idle_handler - uninstalls the cpuidle idle loop handler
- */
-void cpuidle_uninstall_idle_handler(void)
-{
-	if (enabled_devices && pm_idle_old && (pm_idle != pm_idle_old)) {
-		pm_idle = pm_idle_old;
-		cpuidle_kick_cpus();
-	}
-}
-
-/**
  * cpuidle_pause_and_lock - temporarily disables CPUIDLE
  */
 void cpuidle_pause_and_lock(void)
 {
 	mutex_lock(&cpuidle_lock);
-	cpuidle_uninstall_idle_handler();
 }
 
 EXPORT_SYMBOL_GPL(cpuidle_pause_and_lock);
@@ -132,7 +110,6 @@ EXPORT_SYMBOL_GPL(cpuidle_pause_and_lock
  */
 void cpuidle_resume_and_unlock(void)
 {
-	cpuidle_install_idle_handler();
 	mutex_unlock(&cpuidle_lock);
 }
 
@@ -287,6 +264,12 @@ static int __cpuidle_register_device(str
 	return 0;
 }
 
+static void register_cpuidle_idle_function(void)
+{
+	register_idle_function(&cpuidle_idle_desc);
+
+	idle_function_registered = 1;
+}
 /**
  * cpuidle_register_device - registers a CPU's idle PM feature
  * @dev: the cpu
@@ -303,7 +286,9 @@ int cpuidle_register_device(struct cpuid
 	}
 
 	cpuidle_enable_device(dev);
-	cpuidle_install_idle_handler();
+
+	if (!idle_function_registered)
+		register_cpuidle_idle_function();
 
 	mutex_unlock(&cpuidle_lock);
 
@@ -382,8 +367,6 @@ static int __init cpuidle_init(void)
 {
 	int ret;
 
-	pm_idle_old = pm_idle;
-
 	ret = cpuidle_add_class_sysfs(&cpu_sysdev_class);
 	if (ret)
 		return ret;
Index: linux.trees.git/drivers/cpuidle/governor.c
===================================================================
--- linux.trees.git.orig/drivers/cpuidle/governor.c
+++ linux.trees.git/drivers/cpuidle/governor.c
@@ -48,8 +48,6 @@ int cpuidle_switch_governor(struct cpuid
 	if (gov == cpuidle_curr_governor)
 		return 0;
 
-	cpuidle_uninstall_idle_handler();
-
 	if (cpuidle_curr_governor) {
 		list_for_each_entry(dev, &cpuidle_detected_devices, device_list)
 			cpuidle_disable_device(dev);
@@ -63,7 +61,6 @@ int cpuidle_switch_governor(struct cpuid
 			return -EINVAL;
 		list_for_each_entry(dev, &cpuidle_detected_devices, device_list)
 			cpuidle_enable_device(dev);
-		cpuidle_install_idle_handler();
 		printk(KERN_INFO "cpuidle: using governor %s\n", gov->name);
 	}