openwrt/target/linux/bcm27xx/patches-6.6/950-0887-drivers-thermal-step_wise-add-support-for-hysteresis.patch

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From c2e058716ec515ea8a36376de9791cfb18b3249b Mon Sep 17 00:00:00 2001
From: Ram Chandrasekar <rkumbako@codeaurora.org>
Date: Mon, 7 May 2018 11:54:08 -0600
Subject: [PATCH 0887/1085] drivers: thermal: step_wise: add support for
hysteresis
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: avoid throttling at hysteresis temperature after dropping below it
Signed-off-by: Serge Schneider <serge@raspberrypi.com>
---
drivers/thermal/gov_step_wise.c | 23 +++++++++++++++++------
1 file changed, 17 insertions(+), 6 deletions(-)
--- a/drivers/thermal/gov_step_wise.c
+++ b/drivers/thermal/gov_step_wise.c
@@ -86,22 +86,33 @@ static void thermal_zone_trip_update(str
struct thermal_instance *instance;
bool throttle = false;
int old_target;
+ int hyst_temp;
trend = get_tz_trend(tz, trip_id);
- if (tz->temperature >= trip->temperature) {
- throttle = true;
- trace_thermal_zone_trip(tz, trip_id, trip->type);
- }
+ hyst_temp = trip->temperature - trip->hysteresis;
- dev_dbg(&tz->device, "Trip%d[type=%d,temp=%d]:trend=%d,throttle=%d\n",
- trip_id, trip->type, trip->temperature, trend, throttle);
+ dev_dbg(&tz->device,
+ "Trip%d[type=%d,temp=%d,hyst=%d]:trend=%d,throttle=%d\n",
+ trip_id, trip->type, trip->temperature, hyst_temp, trend, throttle);
list_for_each_entry(instance, &tz->thermal_instances, tz_node) {
if (instance->trip != trip)
continue;
old_target = instance->target;
+ throttle = false;
+ /*
+ * Lower the mitigation only if the temperature
+ * goes below the hysteresis temperature.
+ */
+ if (tz->temperature >= trip->temperature ||
+ (tz->temperature >= hyst_temp &&
+ old_target == instance->upper)) {
+ throttle = true;
+ trace_thermal_zone_trip(tz, trip_id, 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);