gov_step_wise.c

  1// SPDX-License-Identifier: GPL-2.0-only
  2/*
  3 *  step_wise.c - A step-by-step Thermal throttling governor
  4 *
  5 *  Copyright (C) 2012 Intel Corp
  6 *  Copyright (C) 2012 Durgadoss R <durgadoss.r@intel.com>
  7 *
  8 *  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  9 *
 10 * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 11 */
 12
 13#include <linux/thermal.h>
 14#include <linux/minmax.h>
 15#include "thermal_trace.h"
 16
 17#include "thermal_core.h"
 18
 19/*
 20 * If the temperature is higher than a trip point,
 21 *    a. if the trend is THERMAL_TREND_RAISING, use higher cooling
 22 *       state for this trip point
 23 *    b. if the trend is THERMAL_TREND_DROPPING, use a lower cooling state
 24 *       for this trip point, but keep the cooling state above the applicable
 25 *       minimum
 26 * If the temperature is lower than a trip point,
 27 *    a. if the trend is THERMAL_TREND_RAISING, do nothing
 28 *    b. if the trend is THERMAL_TREND_DROPPING, use the minimum applicable
 29 *       cooling state for this trip point, or if the cooling state already
 30 *       equals lower limit, deactivate the thermal instance
 31 */
 32static unsigned long get_target_state(struct thermal_instance *instance,
 33				enum thermal_trend trend, bool throttle)
 34{
 35	struct thermal_cooling_device *cdev = instance->cdev;
 36	unsigned long cur_state;
 37
 38	/*
 39	 * We keep this instance the way it is by default.
 40	 * Otherwise, we use the current state of the
 41	 * cdev in use to determine the next_target.
 42	 */
 43	cdev->ops->get_cur_state(cdev, &cur_state);
 44	dev_dbg(&cdev->device, "cur_state=%ld\n", cur_state);
 45
 46	if (!instance->initialized) {
 47		if (throttle)
 48			return clamp(cur_state + 1, instance->lower, instance->upper);
 49
 50		return THERMAL_NO_TARGET;
 51	}
 52
 53	if (throttle) {
 54		if (trend == THERMAL_TREND_RAISING)
 55			return clamp(cur_state + 1, instance->lower, instance->upper);
 56
 57		/*
 58		 * If the zone temperature is falling, the cooling level can
 59		 * be reduced, but it should still be above the lower state of
 60		 * the given thermal instance to pull the temperature further
 61		 * down.
 62		 */
 63		if (trend == THERMAL_TREND_DROPPING)
 64			return clamp(cur_state - 1,
 65				     min(instance->lower + 1, instance->upper),
 66				     instance->upper);
 67	} else if (trend == THERMAL_TREND_DROPPING) {
 68		if (cur_state <= instance->lower)
 69			return THERMAL_NO_TARGET;
 70
 71		/*
 72		 * If 'throttle' is false, no mitigation is necessary, so
 73		 * request the lower state for this instance.
 74		 */
 75		return instance->lower;
 76	}
 77
 78	return instance->target;
 79}
 80
 81static void thermal_zone_trip_update(struct thermal_zone_device *tz,
 82				     const struct thermal_trip_desc *td,
 83				     int trip_threshold)
 84{
 85	bool throttle = tz->temperature >= trip_threshold;
 86	const struct thermal_trip *trip = &td->trip;
 87	enum thermal_trend trend = get_tz_trend(tz, trip);
 88	int trip_id = thermal_zone_trip_id(tz, trip);
 89	struct thermal_instance *instance;
 90
 91	if (throttle)
 92		trace_thermal_zone_trip(tz, trip_id, trip->type);
 93
 94	dev_dbg(&tz->device, "Trip%d[type=%d,temp=%d]:trend=%d,throttle=%d\n",
 95		trip_id, trip->type, trip_threshold, trend, throttle);
 96
 97	list_for_each_entry(instance, &td->thermal_instances, trip_node) {
 98		int old_target;
 99
100		old_target = instance->target;
101		instance->target = get_target_state(instance, trend, throttle);
102
103		dev_dbg(&instance->cdev->device, "old_target=%d, target=%ld\n",
104			old_target, instance->target);
105
106		if (instance->initialized && old_target == instance->target)
107			continue;
108
109		instance->initialized = true;
110
111		scoped_guard(cooling_dev, instance->cdev) {
112			instance->cdev->updated = false; /* cdev needs update */
113		}
114	}
115}
116
117static void step_wise_manage(struct thermal_zone_device *tz)
118{
119	const struct thermal_trip_desc *td;
120	struct thermal_instance *instance;
121
122	lockdep_assert_held(&tz->lock);
123
124	/*
125	 * Throttling Logic: Use the trend of the thermal zone to throttle.
126	 * If the thermal zone is 'heating up', throttle all of the cooling
127	 * devices associated with each trip point by one step. If the zone
128	 * is 'cooling down', it brings back the performance of the devices
129	 * by one step.
130	 */
131	for_each_trip_desc(tz, td) {
132		const struct thermal_trip *trip = &td->trip;
133
134		if (trip->temperature == THERMAL_TEMP_INVALID ||
135		    trip->type == THERMAL_TRIP_CRITICAL ||
136		    trip->type == THERMAL_TRIP_HOT)
137			continue;
138
139		thermal_zone_trip_update(tz, td, td->threshold);
140	}
141
142	for_each_trip_desc(tz, td) {
143		list_for_each_entry(instance, &td->thermal_instances, trip_node)
144			thermal_cdev_update(instance->cdev);
145	}
146}
147
148static struct thermal_governor thermal_gov_step_wise = {
149	.name	= "step_wise",
150	.manage	= step_wise_manage,
151};
152THERMAL_GOVERNOR_DECLARE(thermal_gov_step_wise);