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From 05a13bbd7fbb76b4f690042173749a55d85de831 Mon Sep 17 00:00:00 2001
From: Ram Chandrasekar <rkumbako@codeaurora.org>
Date: Mon, 7 May 2018 11:54:08 -0600
Subject: [PATCH] drivers: thermal: step_wise: add support for
hysteresis
From: Ram Chandrasekar <rkumbako@codeaurora.org>
Step wise governor increases the mitigation level when the temperature
goes above a threshold and will decrease the mitigation when the
temperature falls below the threshold. If it were a case, where the
temperature hovers around a threshold, the mitigation will be applied
and removed at every iteration. This reaction to the temperature is
inefficient for performance.
The use of hysteresis temperature could avoid this ping-pong of
mitigation by relaxing the mitigation to happen only when the
temperature goes below this lower hysteresis value.
Signed-off-by: Ram Chandrasekar <rkumbako@codeaurora.org>
Signed-off-by: Lina Iyer <ilina@codeaurora.org>
---
drivers/thermal/step_wise.c | 33 +++++++++++++++++++++++----------
1 file changed, 23 insertions(+), 10 deletions(-)
--- a/drivers/thermal/step_wise.c
+++ b/drivers/thermal/step_wise.c
@@ -36,7 +36,7 @@
* for this trip point
* d. if the trend is THERMAL_TREND_DROP_FULL, use lower limit
* for this trip point
- * If the temperature is lower than a trip point,
+ * If the temperature is lower than a hysteresis temperature,
* a. if the trend is THERMAL_TREND_RAISING, do nothing
* b. if the trend is THERMAL_TREND_DROPPING, use lower cooling
* state for this trip point, if the cooling state already
@@ -127,7 +127,7 @@ static void update_passive_instance(stru
static void thermal_zone_trip_update(struct thermal_zone_device *tz, int trip)
{
- int trip_temp;
+ int trip_temp, hyst_temp;
enum thermal_trip_type trip_type;
enum thermal_trend trend;
struct thermal_instance *instance;
@@ -135,22 +135,23 @@ static void thermal_zone_trip_update(str
int old_target;
if (trip == THERMAL_TRIPS_NONE) {
- trip_temp = tz->forced_passive;
+ hyst_temp = trip_temp = tz->forced_passive;
trip_type = THERMAL_TRIPS_NONE;
} else {
tz->ops->get_trip_temp(tz, trip, &trip_temp);
+ hyst_temp = trip_temp;
+ if (tz->ops->get_trip_hyst) {
+ tz->ops->get_trip_hyst(tz, trip, &hyst_temp);
+ hyst_temp = trip_temp - hyst_temp;
+ }
tz->ops->get_trip_type(tz, trip, &trip_type);
}
trend = get_tz_trend(tz, trip);
- if (tz->temperature >= trip_temp) {
- throttle = true;
- trace_thermal_zone_trip(tz, trip, trip_type);
- }
-
- dev_dbg(&tz->device, "Trip%d[type=%d,temp=%d]:trend=%d,throttle=%d\n",
- trip, trip_type, trip_temp, trend, throttle);
+ dev_dbg(&tz->device,
+ "Trip%d[type=%d,temp=%d,hyst=%d]:trend=%d,throttle=%d\n",
+ trip, trip_type, trip_temp, hyst_temp, trend, throttle);
mutex_lock(&tz->lock);
@@ -159,6 +160,18 @@ static void thermal_zone_trip_update(str
continue;
old_target = instance->target;
+ throttle = false;
+ /*
+ * Lower the mitigation only if the temperature
+ * goes below the hysteresis temperature.
+ */
+ if (tz->temperature >= trip_temp ||
+ (tz->temperature >= hyst_temp &&
+ old_target != THERMAL_NO_TARGET)) {
+ throttle = true;
+ trace_thermal_zone_trip(tz, trip, trip_type);
+ }
+
instance->target = get_target_state(instance, trend, throttle);
dev_dbg(&instance->cdev->device, "old_target=%d, target=%d\n",
old_target, (int)instance->target);
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