From: Lukasz Luba <l.luba@partner.samsung.com>
Date: Thu, 8 Nov 2018 18:02:26 +0000 (+0100)
Subject: sched/power: implement simple PI with integral decaying
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=7176b729c9f7e5e33273be5dcc99b2ec313a8818;p=platform%2Fkernel%2Flinux-exynos.git

sched/power: implement simple PI with integral decaying

The patch adds simple implementation of control algorithm
based on PI with additional decaying for integral.

Signed-off-by: Lukasz Luba <l.luba@partner.samsung.com>
---

diff --git a/kernel/sched/power.c b/kernel/sched/power.c
index f74c59e83d4f..20f5618d8f2b 100644
--- a/kernel/sched/power.c
+++ b/kernel/sched/power.c
@@ -475,6 +475,9 @@ struct trip_ctrl_alg {
 	int switch_on_temp;
 	int desired_id;
 	int desired_temp;
+	int k_p;
+	int k_i;
+	s64 integral;
 };
 
 struct _thermal_zone {
@@ -532,16 +535,33 @@ static u32 calc_power_budget(struct _thermal_zone *zone)
 {
 	s64 temp_diff;
 	int desired_temp = zone->trip_ctrl_alg.desired_temp;
-	s64 power_budget;
+	s64 power_budget, p, i;
+	s64 decay;
+	int k_i = zone->trip_ctrl_alg.k_i;
 	struct thermal_zone_device *tz = zone->tz;
 
 	/* temperature is represented in milidegress */
 	temp_diff = desired_temp - tz->temperature;
 
-	power_budget = temp_diff;
+	p = temp_diff * zone->trip_ctrl_alg.k_p;
+
+	i = zone->trip_ctrl_alg.integral * k_i;
+
+	if (temp_diff < 0) {
+		s64 i_0 = i + k_i * temp_diff;
+
+		zone->trip_ctrl_alg.integral += temp_diff;
+	}
+
+	power_budget = p + i;
+	power_budget >>= 10;
 
 	power_budget = max(0LL, power_budget);
 
+	/* decay of 1/8 (~12.5%), after a while will reach 0 */
+	decay = zone->trip_ctrl_alg.integral >> 3;
+	zone->trip_ctrl_alg.integral -= decay;
+
 	return power_budget;
 }
 
@@ -764,6 +784,8 @@ static int sched_power_setup_trips(struct _thermal_zone *zone)
 
 	zone->trip_ctrl_alg.switch_on_id = -EINVAL;
 	zone->trip_ctrl_alg.desired_id = -EINVAL;
+	zone->trip_ctrl_alg.k_p = DEFAULT_K_P;
+	zone->trip_ctrl_alg.k_i = DEFAULT_K_I;
 
 	for (i = 0; i < tz->trips; i++) {
 		ret = tz->ops->get_trip_ctrl_alg_flag(tz, i,
diff --git a/kernel/sched/power.h b/kernel/sched/power.h
index 77516a6f5809..340b3924ecd7 100644
--- a/kernel/sched/power.h
+++ b/kernel/sched/power.h
@@ -19,6 +19,8 @@
 
 #define MAX_WEIGHT 1024
 #define DEFAULT_WEIGHT MAX_WEIGHT
+#define DEFAULT_K_P 500
+#define DEFAULT_K_I 50
 
 struct power_budget {
 	s64 temp;