1 // SPDX-License-Identifier: GPL-2.0
3 * A power allocator to manage temperature
5 * Copyright (C) 2014 ARM Ltd.
9 #define pr_fmt(fmt) "Power allocator: " fmt
11 #include <linux/slab.h>
12 #include <linux/thermal.h>
14 #define CREATE_TRACE_POINTS
15 #include "thermal_trace_ipa.h"
17 #include "thermal_core.h"
20 #define int_to_frac(x) ((x) << FRAC_BITS)
21 #define frac_to_int(x) ((x) >> FRAC_BITS)
24 * mul_frac() - multiply two fixed-point numbers
25 * @x: first multiplicand
26 * @y: second multiplicand
28 * Return: the result of multiplying two fixed-point numbers. The
29 * result is also a fixed-point number.
31 static inline s64 mul_frac(s64 x, s64 y)
33 return (x * y) >> FRAC_BITS;
37 * div_frac() - divide two fixed-point numbers
41 * Return: the result of dividing two fixed-point numbers. The
42 * result is also a fixed-point number.
44 static inline s64 div_frac(s64 x, s64 y)
46 return div_s64(x << FRAC_BITS, y);
50 * struct power_actor - internal power information for power actor
51 * @req_power: requested power value (not weighted)
52 * @max_power: max allocatable power for this actor
53 * @granted_power: granted power for this actor
54 * @extra_actor_power: extra power that this actor can receive
55 * @weighted_req_power: weighted requested power as input to IPA
61 u32 extra_actor_power;
62 u32 weighted_req_power;
66 * struct power_allocator_params - parameters for the power allocator governor
67 * @allocated_tzp: whether we have allocated tzp for this thermal zone and
68 * it needs to be freed on unbind
69 * @err_integral: accumulated error in the PID controller.
70 * @prev_err: error in the previous iteration of the PID controller.
71 * Used to calculate the derivative term.
72 * @sustainable_power: Sustainable power (heat) that this thermal zone can
74 * @trip_switch_on: first passive trip point of the thermal zone. The
75 * governor switches on when this trip point is crossed.
76 * If the thermal zone only has one passive trip point,
77 * @trip_switch_on should be NULL.
78 * @trip_max: last passive trip point of the thermal zone. The
79 * temperature we are controlling for.
80 * @total_weight: Sum of all thermal instances weights
81 * @num_actors: number of cooling devices supporting IPA callbacks
82 * @buffer_size: internal buffer size, to avoid runtime re-calculation
83 * @power: buffer for all power actors internal power information
85 struct power_allocator_params {
89 u32 sustainable_power;
90 const struct thermal_trip *trip_switch_on;
91 const struct thermal_trip *trip_max;
93 unsigned int num_actors;
94 unsigned int buffer_size;
95 struct power_actor *power;
98 static bool power_actor_is_valid(struct power_allocator_params *params,
99 struct thermal_instance *instance)
101 return (instance->trip == params->trip_max &&
102 cdev_is_power_actor(instance->cdev));
106 * estimate_sustainable_power() - Estimate the sustainable power of a thermal zone
107 * @tz: thermal zone we are operating in
109 * For thermal zones that don't provide a sustainable_power in their
110 * thermal_zone_params, estimate one. Calculate it using the minimum
111 * power of all the cooling devices as that gives a valid value that
112 * can give some degree of functionality. For optimal performance of
113 * this governor, provide a sustainable_power in the thermal zone's
114 * thermal_zone_params.
116 static u32 estimate_sustainable_power(struct thermal_zone_device *tz)
118 struct power_allocator_params *params = tz->governor_data;
119 struct thermal_cooling_device *cdev;
120 struct thermal_instance *instance;
121 u32 sustainable_power = 0;
124 list_for_each_entry(instance, &tz->thermal_instances, tz_node) {
125 if (!power_actor_is_valid(params, instance))
128 cdev = instance->cdev;
129 if (cdev->ops->state2power(cdev, instance->upper, &min_power))
132 sustainable_power += min_power;
135 return sustainable_power;
139 * estimate_pid_constants() - Estimate the constants for the PID controller
140 * @tz: thermal zone for which to estimate the constants
141 * @sustainable_power: sustainable power for the thermal zone
142 * @trip_switch_on: trip point for the switch on temperature
143 * @control_temp: target temperature for the power allocator governor
145 * This function is used to update the estimation of the PID
146 * controller constants in struct thermal_zone_parameters.
148 static void estimate_pid_constants(struct thermal_zone_device *tz,
149 u32 sustainable_power,
150 const struct thermal_trip *trip_switch_on,
153 u32 temperature_threshold = control_temp;
157 temperature_threshold -= trip_switch_on->temperature;
160 * estimate_pid_constants() tries to find appropriate default
161 * values for thermal zones that don't provide them. If a
162 * system integrator has configured a thermal zone with two
163 * passive trip points at the same temperature, that person
164 * hasn't put any effort to set up the thermal zone properly
167 if (!temperature_threshold)
170 tz->tzp->k_po = int_to_frac(sustainable_power) /
171 temperature_threshold;
173 tz->tzp->k_pu = int_to_frac(2 * sustainable_power) /
174 temperature_threshold;
176 k_i = tz->tzp->k_pu / 10;
177 tz->tzp->k_i = k_i > 0 ? k_i : 1;
180 * The default for k_d and integral_cutoff is 0, so we can
181 * leave them as they are.
186 * get_sustainable_power() - Get the right sustainable power
187 * @tz: thermal zone for which to estimate the constants
188 * @params: parameters for the power allocator governor
189 * @control_temp: target temperature for the power allocator governor
191 * This function is used for getting the proper sustainable power value based
192 * on variables which might be updated by the user sysfs interface. If that
193 * happen the new value is going to be estimated and updated. It is also used
194 * after thermal zone binding, where the initial values where set to 0.
196 static u32 get_sustainable_power(struct thermal_zone_device *tz,
197 struct power_allocator_params *params,
200 u32 sustainable_power;
202 if (!tz->tzp->sustainable_power)
203 sustainable_power = estimate_sustainable_power(tz);
205 sustainable_power = tz->tzp->sustainable_power;
207 /* Check if it's init value 0 or there was update via sysfs */
208 if (sustainable_power != params->sustainable_power) {
209 estimate_pid_constants(tz, sustainable_power,
210 params->trip_switch_on, control_temp);
212 /* Do the estimation only once and make available in sysfs */
213 tz->tzp->sustainable_power = sustainable_power;
214 params->sustainable_power = sustainable_power;
217 return sustainable_power;
221 * pid_controller() - PID controller
222 * @tz: thermal zone we are operating in
223 * @control_temp: the target temperature in millicelsius
224 * @max_allocatable_power: maximum allocatable power for this thermal zone
226 * This PID controller increases the available power budget so that the
227 * temperature of the thermal zone gets as close as possible to
228 * @control_temp and limits the power if it exceeds it. k_po is the
229 * proportional term when we are overshooting, k_pu is the
230 * proportional term when we are undershooting. integral_cutoff is a
231 * threshold below which we stop accumulating the error. The
232 * accumulated error is only valid if the requested power will make
233 * the system warmer. If the system is mostly idle, there's no point
234 * in accumulating positive error.
236 * Return: The power budget for the next period.
238 static u32 pid_controller(struct thermal_zone_device *tz,
240 u32 max_allocatable_power)
242 struct power_allocator_params *params = tz->governor_data;
243 s64 p, i, d, power_range;
244 s32 err, max_power_frac;
245 u32 sustainable_power;
247 max_power_frac = int_to_frac(max_allocatable_power);
249 sustainable_power = get_sustainable_power(tz, params, control_temp);
251 err = control_temp - tz->temperature;
252 err = int_to_frac(err);
254 /* Calculate the proportional term */
255 p = mul_frac(err < 0 ? tz->tzp->k_po : tz->tzp->k_pu, err);
258 * Calculate the integral term
260 * if the error is less than cut off allow integration (but
261 * the integral is limited to max power)
263 i = mul_frac(tz->tzp->k_i, params->err_integral);
265 if (err < int_to_frac(tz->tzp->integral_cutoff)) {
266 s64 i_next = i + mul_frac(tz->tzp->k_i, err);
268 if (abs(i_next) < max_power_frac) {
270 params->err_integral += err;
275 * Calculate the derivative term
277 * We do err - prev_err, so with a positive k_d, a decreasing
278 * error (i.e. driving closer to the line) results in less
279 * power being applied, slowing down the controller)
281 d = mul_frac(tz->tzp->k_d, err - params->prev_err);
282 d = div_frac(d, jiffies_to_msecs(tz->passive_delay_jiffies));
283 params->prev_err = err;
285 power_range = p + i + d;
287 /* feed-forward the known sustainable dissipatable power */
288 power_range = sustainable_power + frac_to_int(power_range);
290 power_range = clamp(power_range, (s64)0, (s64)max_allocatable_power);
292 trace_thermal_power_allocator_pid(tz, frac_to_int(err),
293 frac_to_int(params->err_integral),
294 frac_to_int(p), frac_to_int(i),
295 frac_to_int(d), power_range);
301 * power_actor_set_power() - limit the maximum power a cooling device consumes
302 * @cdev: pointer to &thermal_cooling_device
303 * @instance: thermal instance to update
304 * @power: the power in milliwatts
306 * Set the cooling device to consume at most @power milliwatts. The limit is
307 * expected to be a cap at the maximum power consumption.
309 * Return: 0 on success, -EINVAL if the cooling device does not
310 * implement the power actor API or -E* for other failures.
313 power_actor_set_power(struct thermal_cooling_device *cdev,
314 struct thermal_instance *instance, u32 power)
319 ret = cdev->ops->power2state(cdev, power, &state);
323 instance->target = clamp_val(state, instance->lower, instance->upper);
324 mutex_lock(&cdev->lock);
325 __thermal_cdev_update(cdev);
326 mutex_unlock(&cdev->lock);
332 * divvy_up_power() - divvy the allocated power between the actors
333 * @power: buffer for all power actors internal power information
334 * @num_actors: number of power actors in this thermal zone
335 * @total_req_power: sum of all weighted requested power for all actors
336 * @power_range: total allocated power
338 * This function divides the total allocated power (@power_range)
339 * fairly between the actors. It first tries to give each actor a
340 * share of the @power_range according to how much power it requested
341 * compared to the rest of the actors. For example, if only one actor
342 * requests power, then it receives all the @power_range. If
343 * three actors each requests 1mW, each receives a third of the
346 * If any actor received more than their maximum power, then that
347 * surplus is re-divvied among the actors based on how far they are
348 * from their respective maximums.
350 static void divvy_up_power(struct power_actor *power, int num_actors,
351 u32 total_req_power, u32 power_range)
353 u32 capped_extra_power = 0;
358 * Prevent division by 0 if none of the actors request power.
360 if (!total_req_power)
363 for (i = 0; i < num_actors; i++) {
364 struct power_actor *pa = &power[i];
365 u64 req_range = (u64)pa->req_power * power_range;
367 pa->granted_power = DIV_ROUND_CLOSEST_ULL(req_range,
370 if (pa->granted_power > pa->max_power) {
371 extra_power += pa->granted_power - pa->max_power;
372 pa->granted_power = pa->max_power;
375 pa->extra_actor_power = pa->max_power - pa->granted_power;
376 capped_extra_power += pa->extra_actor_power;
379 if (!extra_power || !capped_extra_power)
383 * Re-divvy the reclaimed extra among actors based on
384 * how far they are from the max
386 extra_power = min(extra_power, capped_extra_power);
388 for (i = 0; i < num_actors; i++) {
389 struct power_actor *pa = &power[i];
390 u64 extra_range = pa->extra_actor_power;
392 extra_range *= extra_power;
393 pa->granted_power += DIV_ROUND_CLOSEST_ULL(extra_range,
398 static int allocate_power(struct thermal_zone_device *tz, int control_temp)
400 struct power_allocator_params *params = tz->governor_data;
401 unsigned int num_actors = params->num_actors;
402 struct power_actor *power = params->power;
403 struct thermal_cooling_device *cdev;
404 struct thermal_instance *instance;
405 u32 total_weighted_req_power = 0;
406 u32 max_allocatable_power = 0;
407 u32 total_granted_power = 0;
408 u32 total_req_power = 0;
409 u32 power_range, weight;
415 /* Clean all buffers for new power estimations */
416 memset(power, 0, params->buffer_size);
418 list_for_each_entry(instance, &tz->thermal_instances, tz_node) {
419 struct power_actor *pa = &power[i];
421 if (!power_actor_is_valid(params, instance))
424 cdev = instance->cdev;
426 ret = cdev->ops->get_requested_power(cdev, &pa->req_power);
430 if (!params->total_weight)
431 weight = 1 << FRAC_BITS;
433 weight = instance->weight;
435 pa->weighted_req_power = frac_to_int(weight * pa->req_power);
437 ret = cdev->ops->state2power(cdev, instance->lower,
442 total_req_power += pa->req_power;
443 max_allocatable_power += pa->max_power;
444 total_weighted_req_power += pa->weighted_req_power;
449 power_range = pid_controller(tz, control_temp, max_allocatable_power);
451 divvy_up_power(power, num_actors, total_weighted_req_power,
455 list_for_each_entry(instance, &tz->thermal_instances, tz_node) {
456 struct power_actor *pa = &power[i];
458 if (!power_actor_is_valid(params, instance))
461 power_actor_set_power(instance->cdev, instance,
463 total_granted_power += pa->granted_power;
465 trace_thermal_power_actor(tz, i, pa->req_power,
470 trace_thermal_power_allocator(tz, total_req_power, total_granted_power,
471 num_actors, power_range,
472 max_allocatable_power, tz->temperature,
473 control_temp - tz->temperature);
479 * get_governor_trips() - get the two trip points that are key for this governor
480 * @tz: thermal zone to operate on
481 * @params: pointer to private data for this governor
483 * The power allocator governor works optimally with two trips points:
484 * a "switch on" trip point and a "maximum desired temperature". These
485 * are defined as the first and last passive trip points.
487 * If there is only one trip point, then that's considered to be the
488 * "maximum desired temperature" trip point and the governor is always
489 * on. If there are no passive or active trip points, then the
490 * governor won't do anything. In fact, its throttle function
491 * won't be called at all.
493 static void get_governor_trips(struct thermal_zone_device *tz,
494 struct power_allocator_params *params)
496 const struct thermal_trip *first_passive = NULL;
497 const struct thermal_trip *last_passive = NULL;
498 const struct thermal_trip *last_active = NULL;
499 const struct thermal_trip *trip;
501 for_each_trip(tz, trip) {
502 switch (trip->type) {
503 case THERMAL_TRIP_PASSIVE:
504 if (!first_passive) {
505 first_passive = trip;
510 case THERMAL_TRIP_ACTIVE:
519 params->trip_switch_on = first_passive;
520 params->trip_max = last_passive;
521 } else if (first_passive) {
522 params->trip_switch_on = NULL;
523 params->trip_max = first_passive;
525 params->trip_switch_on = NULL;
526 params->trip_max = last_active;
530 static void reset_pid_controller(struct power_allocator_params *params)
532 params->err_integral = 0;
533 params->prev_err = 0;
536 static void allow_maximum_power(struct thermal_zone_device *tz, bool update)
538 struct power_allocator_params *params = tz->governor_data;
539 struct thermal_cooling_device *cdev;
540 struct thermal_instance *instance;
543 list_for_each_entry(instance, &tz->thermal_instances, tz_node) {
544 if (!power_actor_is_valid(params, instance))
547 cdev = instance->cdev;
549 instance->target = 0;
550 mutex_lock(&cdev->lock);
552 * Call for updating the cooling devices local stats and avoid
553 * periods of dozen of seconds when those have not been
556 cdev->ops->get_requested_power(cdev, &req_power);
559 __thermal_cdev_update(cdev);
561 mutex_unlock(&cdev->lock);
566 * check_power_actors() - Check all cooling devices and warn when they are
568 * @tz: thermal zone to operate on
569 * @params: power allocator private data
571 * Check all cooling devices in the @tz and warn every time they are missing
572 * power actor API. The warning should help to investigate the issue, which
573 * could be e.g. lack of Energy Model for a given device.
575 * If all of the cooling devices currently attached to @tz implement the power
576 * actor API, return the number of them (which may be 0, because some cooling
577 * devices may be attached later). Otherwise, return -EINVAL.
579 static int check_power_actors(struct thermal_zone_device *tz,
580 struct power_allocator_params *params)
582 struct thermal_instance *instance;
585 list_for_each_entry(instance, &tz->thermal_instances, tz_node) {
586 if (instance->trip != params->trip_max)
589 if (!cdev_is_power_actor(instance->cdev)) {
590 dev_warn(&tz->device, "power_allocator: %s is not a power actor\n",
591 instance->cdev->type);
600 static int allocate_actors_buffer(struct power_allocator_params *params,
605 kfree(params->power);
607 /* There might be no cooling devices yet. */
613 params->power = kcalloc(num_actors, sizeof(struct power_actor),
615 if (!params->power) {
620 params->num_actors = num_actors;
621 params->buffer_size = num_actors * sizeof(struct power_actor);
626 params->num_actors = 0;
627 params->buffer_size = 0;
628 params->power = NULL;
632 static void power_allocator_update_tz(struct thermal_zone_device *tz,
633 enum thermal_notify_event reason)
635 struct power_allocator_params *params = tz->governor_data;
636 struct thermal_instance *instance;
640 case THERMAL_TZ_BIND_CDEV:
641 case THERMAL_TZ_UNBIND_CDEV:
642 list_for_each_entry(instance, &tz->thermal_instances, tz_node)
643 if (power_actor_is_valid(params, instance))
646 if (num_actors == params->num_actors)
649 allocate_actors_buffer(params, num_actors);
651 case THERMAL_INSTANCE_WEIGHT_CHANGED:
652 params->total_weight = 0;
653 list_for_each_entry(instance, &tz->thermal_instances, tz_node)
654 if (power_actor_is_valid(params, instance))
655 params->total_weight += instance->weight;
663 * power_allocator_bind() - bind the power_allocator governor to a thermal zone
664 * @tz: thermal zone to bind it to
666 * Initialize the PID controller parameters and bind it to the thermal
669 * Return: 0 on success, or -ENOMEM if we ran out of memory, or -EINVAL
670 * when there are unsupported cooling devices in the @tz.
672 static int power_allocator_bind(struct thermal_zone_device *tz)
674 struct power_allocator_params *params;
677 params = kzalloc(sizeof(*params), GFP_KERNEL);
681 get_governor_trips(tz, params);
682 if (!params->trip_max) {
683 dev_warn(&tz->device, "power_allocator: missing trip_max\n");
688 ret = check_power_actors(tz, params);
690 dev_warn(&tz->device, "power_allocator: binding failed\n");
695 ret = allocate_actors_buffer(params, ret);
697 dev_warn(&tz->device, "power_allocator: allocation failed\n");
703 tz->tzp = kzalloc(sizeof(*tz->tzp), GFP_KERNEL);
709 params->allocated_tzp = true;
712 if (!tz->tzp->sustainable_power)
713 dev_warn(&tz->device, "power_allocator: sustainable_power will be estimated\n");
715 params->sustainable_power = tz->tzp->sustainable_power;
717 estimate_pid_constants(tz, tz->tzp->sustainable_power,
718 params->trip_switch_on,
719 params->trip_max->temperature);
721 reset_pid_controller(params);
723 tz->governor_data = params;
728 kfree(params->power);
734 static void power_allocator_unbind(struct thermal_zone_device *tz)
736 struct power_allocator_params *params = tz->governor_data;
738 dev_dbg(&tz->device, "Unbinding from thermal zone %d\n", tz->id);
740 if (params->allocated_tzp) {
745 kfree(params->power);
746 kfree(tz->governor_data);
747 tz->governor_data = NULL;
750 static int power_allocator_throttle(struct thermal_zone_device *tz,
751 const struct thermal_trip *trip)
753 struct power_allocator_params *params = tz->governor_data;
756 lockdep_assert_held(&tz->lock);
759 * We get called for every trip point but we only need to do
760 * our calculations once
762 if (trip != params->trip_max)
765 trip = params->trip_switch_on;
766 if (trip && tz->temperature < trip->temperature) {
767 update = tz->passive;
769 reset_pid_controller(params);
770 allow_maximum_power(tz, update);
776 return allocate_power(tz, params->trip_max->temperature);
779 static struct thermal_governor thermal_gov_power_allocator = {
780 .name = "power_allocator",
781 .bind_to_tz = power_allocator_bind,
782 .unbind_from_tz = power_allocator_unbind,
783 .throttle = power_allocator_throttle,
784 .update_tz = power_allocator_update_tz,
786 THERMAL_GOVERNOR_DECLARE(thermal_gov_power_allocator);