thermal: fair_share: generalize the weight concept

The fair share governor has the concept of weights, which is the
influence of each cooling device in a thermal zone.  The current
implementation forces the weights of all cooling devices in a thermal
zone to add up to a 100.  This complicates setups, as you need to know
in advance how many cooling devices you are going to have.  If you bind a
new cooling device, you have to modify all the other cooling devices
weights, which is error prone.  Furthermore, you can't specify a
"default" weight for platforms since that default value depends on the
number of cooling devices in the platform.

This patch generalizes the concept of weight by allowing any number to
be a "weight".  Weights are now relative to each other.  Platforms that
don't specify weights get the same default value for all their cooling
devices, so all their cdevs are considered to be equally influential.

It's important to note that previous users of the weights don't need to
alter the code: percentages continue to work as they used to.  This
patch just removes the constraint of all the weights in a thermal zone
having to add up to a 100.  If they do, you get the same behavior as
before.  If they don't, fair share now works for that platform.

Cc: Zhang Rui <rui.zhang@intel.com>
Cc: Eduardo Valentin <edubezval@gmail.com>
Cc: Durgadoss R <durgadoss.r@intel.com>
Acked-by: Durgadoss R <durgadoss.r@intel.com>
Signed-off-by: Javi Merino <javi.merino@arm.com>
Signed-off-by: Eduardo Valentin <edubezval@gmail.com>

1 files changed, 21 insertions, 5 deletions

diff --git a/drivers/thermal/fair_share.c b/drivers/thermal/fair_share.c
index 692f4053f08b..c2c10bbe24d6 100644
--- a/drivers/thermal/fair_share.c
+++ b/drivers/thermal/fair_share.c
@@ -59,13 +59,13 @@ static int get_trip_level(struct thermal_zone_device *tz)
 }
 
 static long get_target_state(struct thermal_zone_device *tz,
-		struct thermal_cooling_device *cdev, int weight, int level)
+		struct thermal_cooling_device *cdev, int percentage, int level)
 {
 	unsigned long max_state;
 
 	cdev->ops->get_max_state(cdev, &max_state);
 
-	return (long)(weight * level * max_state) / (100 * tz->trips);
+	return (long)(percentage * level * max_state) / (100 * tz->trips);
 }
 
 /**
@@ -77,7 +77,7 @@ static long get_target_state(struct thermal_zone_device *tz,
  *
  * Parameters used for Throttling:
  * P1. max_state: Maximum throttle state exposed by the cooling device.
- * P2. weight[i]/100:
+ * P2. percentage[i]/100:
  *	How 'effective' the 'i'th device is, in cooling the given zone.
  * P3. cur_trip_level/max_no_of_trips:
  *	This describes the extent to which the devices should be throttled.
@@ -89,16 +89,32 @@ static long get_target_state(struct thermal_zone_device *tz,
 static int fair_share_throttle(struct thermal_zone_device *tz, int trip)
 {
 	struct thermal_instance *instance;
+	int total_weight = 0;
+	int total_instance = 0;
 	int cur_trip_level = get_trip_level(tz);
 
 	list_for_each_entry(instance, &tz->thermal_instances, tz_node) {
+		if (instance->trip != trip)
+			continue;
+
+		total_weight += instance->weight;
+		total_instance++;
+	}
+
+	list_for_each_entry(instance, &tz->thermal_instances, tz_node) {
+		int percentage;
 		struct thermal_cooling_device *cdev = instance->cdev;
 
 		if (instance->trip != trip)
 			continue;
 
-		instance->target = get_target_state(tz, cdev,
-					instance->weight, cur_trip_level);
+		if (!total_weight)
+			percentage = 100 / total_instance;
+		else
+			percentage = (instance->weight * 100) / total_weight;
+
+		instance->target = get_target_state(tz, cdev, percentage,
+						    cur_trip_level);
 
 		instance->cdev->updated = false;
 		thermal_cdev_update(cdev);