cpuidle: Make ladder governor honor latency requirements fully

ladder governor only honored latency requirement when promoting C-states.
Instead. it should check for latency requirement on each idle call,
and demote to appropriate C-state when there is a latency requirement change.

Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Signed-off-by: Andi Kleen <ak@linux.intel.com>

1 files changed, 12 insertions, 0 deletions

diff --git a/drivers/cpuidle/governors/ladder.c b/drivers/cpuidle/governors/ladder.c
index 27ab3bfe375b..a4bec3f919aa 100644
--- a/drivers/cpuidle/governors/ladder.c
+++ b/drivers/cpuidle/governors/ladder.c
@@ -99,6 +99,18 @@ static int ladder_select_state(struct cpuidle_device *dev)
 
         /* consider demotion */
         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;