1 files changed, 31 insertions, 0 deletions

diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c
index dbefe15bd582..a50710843378 100644
--- a/drivers/cpuidle/cpuidle.c
+++ b/drivers/cpuidle/cpuidle.c
@@ -74,6 +74,17 @@ static void cpuidle_idle_call(void)
          */
         hrtimer_peek_ahead_timers();
 #endif
+
+        /*
+         * Call the device's prepare function before calling the
+         * governor's select function.  ->prepare gives the device's
+         * cpuidle driver a chance to update any dynamic information
+         * of its cpuidle states for the current idle period, e.g.
+         * state availability, latencies, residencies, etc.
+         */
+        if (dev->prepare)
+                dev->prepare(dev);
+
         /* ask the governor for the next state */
         next_state = cpuidle_curr_governor->select(dev);
         if (need_resched()) {
@@ -282,6 +293,26 @@ static int __cpuidle_register_device(struct cpuidle_device *dev)
 
         poll_idle_init(dev);
 
+        /*
+         * cpuidle driver should set the dev->power_specified bit
+         * before registering the device if the driver provides
+         * power_usage numbers.
+         *
+         * For those devices whose ->power_specified is not set,
+         * we fill in power_usage with decreasing values as the
+         * cpuidle code has an implicit assumption that state Cn
+         * uses less power than C(n-1).
+         *
+         * With CONFIG_ARCH_HAS_CPU_RELAX, C0 is already assigned
+         * an power value of -1.  So we use -2, -3, etc, for other
+         * c-states.
+         */
+        if (!dev->power_specified) {
+                int i;
+                for (i = CPUIDLE_DRIVER_STATE_START; i < dev->state_count; i++)
+                        dev->states[i].power_usage = -1 - i;
+        }
+
         per_cpu(cpuidle_devices, dev->cpu) = dev;
         list_add(&dev->device_list, &cpuidle_detected_devices);
         if ((ret = cpuidle_add_sysfs(sys_dev))) {