thermal: gov_fair_share: Use .manage() callback instead of .throttle()

The Fair Share governor tries very hard to be stateless and so it
calls get_trip_level() from fair_share_throttle() every time, even
though the number produced by this function for all of the trips
during a given thermal zone update is actually the same.  Since
get_trip_level() walks all of the trips in the thermal zone every
time it is called, doing this may generate quite a bit of completely
useless overhead.

For this reason, make the governor use the new .manage() callback
instead of .throttle() which allows it to call get_trip_level() just
once and use the value computed by it to handle all of the trips.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Lukasz Luba <lukasz.luba@arm.com>

diff --git a/drivers/thermal/gov_fair_share.c b/drivers/thermal/gov_fair_share.c
index 6ef8cfde7749a9019ce63df561cf342463c96c66..ff81aeb5ac040e7c3be359a470d7c3813f157991 100644 (file)
--- a/drivers/thermal/gov_fair_share.c
+++ b/drivers/thermal/gov_fair_share.c
@@ -53,6 +53,7 @@ static long get_target_state(struct thermal_zone_device *tz,
  * fair_share_throttle - throttles devices associated with the given zone
  * @tz: thermal_zone_device
  * @trip: trip point
+ * @trip_level: number of trips crossed by the zone temperature
  *
  * Throttling Logic: This uses three parameters to calculate the new
  * throttle state of the cooling devices associated with the given zone.
@@ -61,22 +62,19 @@ static long get_target_state(struct thermal_zone_device *tz,
  * P1. max_state: Maximum throttle state exposed by the cooling device.
  * P2. percentage[i]/100:
  *     How 'effective' the 'i'th device is, in cooling the given zone.
- * P3. cur_trip_level/max_no_of_trips:
+ * P3. trip_level/max_no_of_trips:
  *     This describes the extent to which the devices should be throttled.
  *     We do not want to throttle too much when we trip a lower temperature,
  *     whereas the throttling is at full swing if we trip critical levels.
- *     (Heavily assumes the trip points are in ascending order)
  * new_state of cooling device = P3 * P2 * P1
  */
-static int fair_share_throttle(struct thermal_zone_device *tz,
-                              const struct thermal_trip *trip)
+static void fair_share_throttle(struct thermal_zone_device *tz,
+                               const struct thermal_trip *trip,
+                               int trip_level)
 {
        struct thermal_instance *instance;
        int total_weight = 0;
        int total_instance = 0;
-       int cur_trip_level = get_trip_level(tz);
-
-       lockdep_assert_held(&tz->lock);
 
        list_for_each_entry(instance, &tz->thermal_instances, tz_node) {
                if (instance->trip != trip)
@@ -99,18 +97,35 @@ static int fair_share_throttle(struct thermal_zone_device *tz,
                        percentage = (instance->weight * 100) / total_weight;
 
                instance->target = get_target_state(tz, cdev, percentage,
-                                                   cur_trip_level);
+                                                   trip_level);
 
                mutex_lock(&cdev->lock);
                __thermal_cdev_update(cdev);
                mutex_unlock(&cdev->lock);
        }
+}
+
+static void fair_share_manage(struct thermal_zone_device *tz)
+{
+       int trip_level = get_trip_level(tz);
+       const struct thermal_trip_desc *td;
+
+       lockdep_assert_held(&tz->lock);
+
+       for_each_trip_desc(tz, td) {
+               const struct thermal_trip *trip = &td->trip;
 
-       return 0;
+               if (trip->temperature == THERMAL_TEMP_INVALID ||
+                   trip->type == THERMAL_TRIP_CRITICAL ||
+                   trip->type == THERMAL_TRIP_HOT)
+                       continue;
+
+               fair_share_throttle(tz, trip, trip_level);
+       }
 }
 
 static struct thermal_governor thermal_gov_fair_share = {
-       .name           = "fair_share",
-       .throttle       = fair_share_throttle,
+       .name   = "fair_share",
+       .manage = fair_share_manage,
 };
 THERMAL_GOVERNOR_DECLARE(thermal_gov_fair_share);