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drivers: thermal: step_wise: add support for hysteresis

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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.org>

Fix hysteresis support in gov_step_wise.c

Directly get hyst value instead of going through an
optional and, now, unimplemented function.

Signed-off-by: Jürgen Kreileder <jk@blackdown.de>
This commit is contained in:
Ram Chandrasekar
2018-05-07 11:54:08 -06:00
committed by Dom Cobley
parent 9615c59d94
commit ecac91286b
1 changed files with 23 additions and 10 deletions
Download Patch File Download Diff File Expand all files Collapse all files

33
drivers/thermal/gov_step_wise.c
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@@ -17,16 +17,16 @@
#include "thermal_core.h" #include "thermal_core.h"
/* /*
* If the temperature is higher than a trip point, * If the temperature is higher than a hysteresis temperature,
* a. if the trend is THERMAL_TREND_RAISING, use higher cooling * a. if the trend is THERMAL_TREND_RAISING, use higher cooling
* state for this trip point * state for this trip point
* b. if the trend is THERMAL_TREND_DROPPING, use a lower cooling state * b. if the trend is THERMAL_TREND_DROPPING, use a lower cooling state
* for this trip point, but keep the cooling state above the applicable * for this trip point, but keep the cooling state above the applicable
* minimum * minimum
* 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 * a. if the trend is THERMAL_TREND_RAISING, do nothing
* b. if the trend is THERMAL_TREND_DROPPING, use lower cooling * b. if the trend is THERMAL_TREND_DROPPING, use the minimum applicable
* state for this trip point, if the cooling state already * cooling state for this trip point, or if the cooling state already
* equals lower limit, deactivate the thermal instance * equals lower limit, deactivate the thermal instance
*/ */
static unsigned long get_target_state(struct thermal_instance *instance, static unsigned long get_target_state(struct thermal_instance *instance,
@@ -83,23 +83,36 @@ static void thermal_zone_trip_update(struct thermal_zone_device *tz,
int trip_threshold) int trip_threshold)
{ {
const struct thermal_trip *trip = &td->trip; const struct thermal_trip *trip = &td->trip;
int hyst_temp = trip->temperature - trip->hysteresis;
bool throttle = tz->temperature >= hyst_temp;
enum thermal_trend trend = get_tz_trend(tz, trip); enum thermal_trend trend = get_tz_trend(tz, trip);
int trip_id = thermal_zone_trip_id(tz, trip); int trip_id = thermal_zone_trip_id(tz, trip);
struct thermal_instance *instance; struct thermal_instance *instance;
bool throttle = false;
if (tz->temperature >= trip_threshold) { if (throttle)
throttle = true;
trace_thermal_zone_trip(tz, trip_id, trip->type); trace_thermal_zone_trip(tz, trip_id, trip->type);
}
dev_dbg(&tz->device, "Trip%d[type=%d,temp=%d]:trend=%d,throttle=%d\n", dev_dbg(&tz->device,
trip_id, trip->type, trip_threshold, trend, throttle); "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, &td->thermal_instances, trip_node) { list_for_each_entry(instance, &td->thermal_instances, trip_node) {
int old_target; int old_target;
old_target = instance->target; 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); instance->target = get_target_state(instance, trend, throttle);
dev_dbg(&instance->cdev->device, "old_target=%d, target=%ld\n", dev_dbg(&instance->cdev->device, "old_target=%d, target=%ld\n",