powerpc/cpuidle: Handle power_save=off

This patch makes pseries_idle_driver not to be registered when
power_save=off kernel boot option is specified. The
cpuidle_disable variable used here is similar to
its usage on x86. If cpuidle_disable is set then
sysfs entries for cpuidle framework are not created
and the required drivers are not loaded.

Signed-off-by: Deepthi Dharwar <deepthi@linux.vnet.ibm.com>
Signed-off-by: Trinabh Gupta <g.trinabh@gmail.com>
Signed-off-by: Arun R Bharadwaj <arun.r.bharadwaj@gmail.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/include/asm/processor.h

@@ -382,6 +382,7 @@ static inline unsigned long get_clean_sp(struct pt_regs *regs, int is_32)
 }
 #endif
 
+extern unsigned long cpuidle_disable;
 enum idle_boot_override {IDLE_NO_OVERRIDE = 0, IDLE_POWERSAVE_OFF};
 
 #endif /* __KERNEL__ */

arch/powerpc/platforms/pseries/processor_idle.c

@@ -269,6 +269,9 @@ static int pseries_idle_probe(void)
 	if (!firmware_has_feature(FW_FEATURE_SPLPAR))
 		return -ENODEV;
 
+	if (cpuidle_disable != IDLE_NO_OVERRIDE)
+		return -ENODEV;
+
 	if (max_idle_state == 0) {
 		printk(KERN_DEBUG "pseries processor idle disabled.\n");
 		return -EPERM;