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>

1 files changed, 10 insertions, 0 deletions

diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c
index bf5092455a8f..faae2c357bab 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);