cpuidle: create bootparam "cpuidle.off=1"

useful for disabling cpuidle to fall back
to architecture-default idle loop

cpuidle drivers and governors will fail to register.
on x86 they'll say so:

intel_idle: intel_idle yielding to (null)
ACPI: acpi_idle yielding to (null)

Signed-off-by: Len Brown <len.brown@intel.com>

5 files changed, 20 insertions, 0 deletions

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index aa47be71df4..9b8e62d75a0 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -546,6 +546,9 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
                         /proc/<pid>/coredump_filter.
                         See also Documentation/filesystems/proc.txt.
 
+        cpuidle.off=1   [CPU_IDLE]
+                        disable the cpuidle sub-system
+
         cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
                         Format:
                         <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c
index bf5092455a8..faae2c357ba 100644
--- a/drivers/cpuidle/cpuidle.c
+++ b/drivers/cpuidle/cpuidle.c
@@ -28,6 +28,12 @@ LIST_HEAD(cpuidle_detected_devices);
 static void (*pm_idle_old)(void);
 
 static int enabled_devices;
+static int off __read_mostly;
+
+int cpuidle_disabled(void)
+{
+        return off;
+}
 
 #if defined(CONFIG_ARCH_HAS_CPU_IDLE_WAIT)
 static void cpuidle_kick_cpus(void)
@@ -427,6 +433,9 @@ static int __init cpuidle_init(void)
 {
         int ret;
 
+        if (cpuidle_disabled())
+                return -ENODEV;
+
         pm_idle_old = pm_idle;
 
         ret = cpuidle_add_class_sysfs(&cpu_sysdev_class);
@@ -438,4 +447,5 @@ static int __init cpuidle_init(void)
         return 0;
 }
 
+module_param(off, int, 0444);
 core_initcall(cpuidle_init);
diff --git a/drivers/cpuidle/cpuidle.h b/drivers/cpuidle/cpuidle.h
index 33e50d556f1..38c3fd8b9d7 100644
--- a/drivers/cpuidle/cpuidle.h
+++ b/drivers/cpuidle/cpuidle.h
@@ -13,6 +13,7 @@ extern struct list_head cpuidle_governors;
 extern struct list_head cpuidle_detected_devices;
 extern struct mutex cpuidle_lock;
 extern spinlock_t cpuidle_driver_lock;
+extern int cpuidle_disabled(void);
 
 /* idle loop */
 extern void cpuidle_install_idle_handler(void);
diff --git a/drivers/cpuidle/driver.c b/drivers/cpuidle/driver.c
index fd1601e3d12..3f7e3cedd13 100644
--- a/drivers/cpuidle/driver.c
+++ b/drivers/cpuidle/driver.c
@@ -26,6 +26,9 @@ int cpuidle_register_driver(struct cpuidle_driver *drv)
         if (!drv)
                 return -EINVAL;
 
+        if (cpuidle_disabled())
+                return -ENODEV;
+
         spin_lock(&cpuidle_driver_lock);
         if (cpuidle_curr_driver) {
                 spin_unlock(&cpuidle_driver_lock);
diff --git a/drivers/cpuidle/governor.c b/drivers/cpuidle/governor.c
index 724c164d31c..ea2f8e7aa24 100644
--- a/drivers/cpuidle/governor.c
+++ b/drivers/cpuidle/governor.c
@@ -81,6 +81,9 @@ int cpuidle_register_governor(struct cpuidle_governor *gov)
         if (!gov || !gov->select)
                 return -EINVAL;
 
+        if (cpuidle_disabled())
+                return -ENODEV;
+
         mutex_lock(&cpuidle_lock);
         if (__cpuidle_find_governor(gov->name) == NULL) {
                 ret = 0;