1 files changed, 22 insertions, 4 deletions

diff --git a/drivers/cpuidle/governors/ladder.c b/drivers/cpuidle/governors/ladder.c
index ba7b9a6b17a1..a4bec3f919aa 100644
--- a/drivers/cpuidle/governors/ladder.c
+++ b/drivers/cpuidle/governors/ladder.c
@@ -67,10 +67,17 @@ static int ladder_select_state(struct cpuidle_device *dev)
         struct ladder_device *ldev = &__get_cpu_var(ladder_devices);
         struct ladder_device_state *last_state;
         int last_residency, last_idx = ldev->last_state_idx;
+        int latency_req = pm_qos_requirement(PM_QOS_CPU_DMA_LATENCY);
 
         if (unlikely(!ldev))
                 return 0;
 
+        /* Special case when user has set very strict latency requirement */
+        if (unlikely(latency_req == 0)) {
+                ladder_do_selection(ldev, last_idx, 0);
+                return 0;
+        }
+
         last_state = &ldev->states[last_idx];
 
         if (dev->states[last_idx].flags & CPUIDLE_FLAG_TIME_VALID)
@@ -81,8 +88,7 @@ static int ladder_select_state(struct cpuidle_device *dev)
         /* consider promotion */
         if (last_idx < dev->state_count - 1 &&
             last_residency > last_state->threshold.promotion_time &&
-            dev->states[last_idx + 1].exit_latency <=
-                        pm_qos_requirement(PM_QOS_CPU_DMA_LATENCY)) {
+            dev->states[last_idx + 1].exit_latency <= latency_req) {
                 last_state->stats.promotion_count++;
                 last_state->stats.demotion_count = 0;
                 if (last_state->stats.promotion_count >= last_state->threshold.promotion_count) {
@@ -92,7 +98,19 @@ static int ladder_select_state(struct cpuidle_device *dev)
         }
 
         /* consider demotion */
-        if (last_idx > 0 &&
+        if (last_idx > CPUIDLE_DRIVER_STATE_START &&
+            dev->states[last_idx].exit_latency > latency_req) {
+                int i;
+
+                for (i = last_idx - 1; i > CPUIDLE_DRIVER_STATE_START; i--) {
+                        if (dev->states[i].exit_latency <= latency_req)
+                                break;
+                }
+                ladder_do_selection(ldev, last_idx, i);
+                return i;
+        }
+
+        if (last_idx > CPUIDLE_DRIVER_STATE_START &&
             last_residency < last_state->threshold.demotion_time) {
                 last_state->stats.demotion_count++;
                 last_state->stats.promotion_count = 0;
@@ -117,7 +135,7 @@ static int ladder_enable_device(struct cpuidle_device *dev)
         struct ladder_device_state *lstate;
         struct cpuidle_state *state;
 
-        ldev->last_state_idx = 0;
+        ldev->last_state_idx = CPUIDLE_DRIVER_STATE_START;
 
         for (i = 0; i < dev->state_count; i++) {
                 state = &dev->states[i];