1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * A power allocator to manage temperature
4  *
5  * Copyright (C) 2014 ARM Ltd.
6  *
7  */
8 
9 #define pr_fmt(fmt) "Power allocator: " fmt
10 
11 #include <linux/rculist.h>
12 #include <linux/slab.h>
13 #include <linux/thermal.h>
14 
15 #define CREATE_TRACE_POINTS
16 #include <trace/events/thermal_power_allocator.h>
17 
18 #include "thermal_core.h"
19 
20 #define INVALID_TRIP -1
21 
22 #define FRAC_BITS 10
23 #define int_to_frac(x) ((x) << FRAC_BITS)
24 #define frac_to_int(x) ((x) >> FRAC_BITS)
25 
26 /**
27  * mul_frac() - multiply two fixed-point numbers
28  * @x:	first multiplicand
29  * @y:	second multiplicand
30  *
31  * Return: the result of multiplying two fixed-point numbers.  The
32  * result is also a fixed-point number.
33  */
34 static inline s64 mul_frac(s64 x, s64 y)
35 {
36 	return (x * y) >> FRAC_BITS;
37 }
38 
39 /**
40  * div_frac() - divide two fixed-point numbers
41  * @x:	the dividend
42  * @y:	the divisor
43  *
44  * Return: the result of dividing two fixed-point numbers.  The
45  * result is also a fixed-point number.
46  */
47 static inline s64 div_frac(s64 x, s64 y)
48 {
49 	return div_s64(x << FRAC_BITS, y);
50 }
51 
52 /**
53  * struct power_allocator_params - parameters for the power allocator governor
54  * @allocated_tzp:	whether we have allocated tzp for this thermal zone and
55  *			it needs to be freed on unbind
56  * @err_integral:	accumulated error in the PID controller.
57  * @prev_err:	error in the previous iteration of the PID controller.
58  *		Used to calculate the derivative term.
59  * @trip_switch_on:	first passive trip point of the thermal zone.  The
60  *			governor switches on when this trip point is crossed.
61  *			If the thermal zone only has one passive trip point,
62  *			@trip_switch_on should be INVALID_TRIP.
63  * @trip_max_desired_temperature:	last passive trip point of the thermal
64  *					zone.  The temperature we are
65  *					controlling for.
66  */
67 struct power_allocator_params {
68 	bool allocated_tzp;
69 	s64 err_integral;
70 	s32 prev_err;
71 	int trip_switch_on;
72 	int trip_max_desired_temperature;
73 };
74 
75 /**
76  * estimate_sustainable_power() - Estimate the sustainable power of a thermal zone
77  * @tz: thermal zone we are operating in
78  *
79  * For thermal zones that don't provide a sustainable_power in their
80  * thermal_zone_params, estimate one.  Calculate it using the minimum
81  * power of all the cooling devices as that gives a valid value that
82  * can give some degree of functionality.  For optimal performance of
83  * this governor, provide a sustainable_power in the thermal zone's
84  * thermal_zone_params.
85  */
86 static u32 estimate_sustainable_power(struct thermal_zone_device *tz)
87 {
88 	u32 sustainable_power = 0;
89 	struct thermal_instance *instance;
90 	struct power_allocator_params *params = tz->governor_data;
91 
92 	list_for_each_entry(instance, &tz->thermal_instances, tz_node) {
93 		struct thermal_cooling_device *cdev = instance->cdev;
94 		u32 min_power;
95 
96 		if (instance->trip != params->trip_max_desired_temperature)
97 			continue;
98 
99 		if (power_actor_get_min_power(cdev, tz, &min_power))
100 			continue;
101 
102 		sustainable_power += min_power;
103 	}
104 
105 	return sustainable_power;
106 }
107 
108 /**
109  * estimate_pid_constants() - Estimate the constants for the PID controller
110  * @tz:		thermal zone for which to estimate the constants
111  * @sustainable_power:	sustainable power for the thermal zone
112  * @trip_switch_on:	trip point number for the switch on temperature
113  * @control_temp:	target temperature for the power allocator governor
114  * @force:	whether to force the update of the constants
115  *
116  * This function is used to update the estimation of the PID
117  * controller constants in struct thermal_zone_parameters.
118  * Sustainable power is provided in case it was estimated.  The
119  * estimated sustainable_power should not be stored in the
120  * thermal_zone_parameters so it has to be passed explicitly to this
121  * function.
122  *
123  * If @force is not set, the values in the thermal zone's parameters
124  * are preserved if they are not zero.  If @force is set, the values
125  * in thermal zone's parameters are overwritten.
126  */
127 static void estimate_pid_constants(struct thermal_zone_device *tz,
128 				   u32 sustainable_power, int trip_switch_on,
129 				   int control_temp, bool force)
130 {
131 	int ret;
132 	int switch_on_temp;
133 	u32 temperature_threshold;
134 
135 	ret = tz->ops->get_trip_temp(tz, trip_switch_on, &switch_on_temp);
136 	if (ret)
137 		switch_on_temp = 0;
138 
139 	temperature_threshold = control_temp - switch_on_temp;
140 	/*
141 	 * estimate_pid_constants() tries to find appropriate default
142 	 * values for thermal zones that don't provide them. If a
143 	 * system integrator has configured a thermal zone with two
144 	 * passive trip points at the same temperature, that person
145 	 * hasn't put any effort to set up the thermal zone properly
146 	 * so just give up.
147 	 */
148 	if (!temperature_threshold)
149 		return;
150 
151 	if (!tz->tzp->k_po || force)
152 		tz->tzp->k_po = int_to_frac(sustainable_power) /
153 			temperature_threshold;
154 
155 	if (!tz->tzp->k_pu || force)
156 		tz->tzp->k_pu = int_to_frac(2 * sustainable_power) /
157 			temperature_threshold;
158 
159 	if (!tz->tzp->k_i || force)
160 		tz->tzp->k_i = int_to_frac(10) / 1000;
161 	/*
162 	 * The default for k_d and integral_cutoff is 0, so we can
163 	 * leave them as they are.
164 	 */
165 }
166 
167 /**
168  * pid_controller() - PID controller
169  * @tz:	thermal zone we are operating in
170  * @control_temp:	the target temperature in millicelsius
171  * @max_allocatable_power:	maximum allocatable power for this thermal zone
172  *
173  * This PID controller increases the available power budget so that the
174  * temperature of the thermal zone gets as close as possible to
175  * @control_temp and limits the power if it exceeds it.  k_po is the
176  * proportional term when we are overshooting, k_pu is the
177  * proportional term when we are undershooting.  integral_cutoff is a
178  * threshold below which we stop accumulating the error.  The
179  * accumulated error is only valid if the requested power will make
180  * the system warmer.  If the system is mostly idle, there's no point
181  * in accumulating positive error.
182  *
183  * Return: The power budget for the next period.
184  */
185 static u32 pid_controller(struct thermal_zone_device *tz,
186 			  int control_temp,
187 			  u32 max_allocatable_power)
188 {
189 	s64 p, i, d, power_range;
190 	s32 err, max_power_frac;
191 	u32 sustainable_power;
192 	struct power_allocator_params *params = tz->governor_data;
193 
194 	max_power_frac = int_to_frac(max_allocatable_power);
195 
196 	if (tz->tzp->sustainable_power) {
197 		sustainable_power = tz->tzp->sustainable_power;
198 	} else {
199 		sustainable_power = estimate_sustainable_power(tz);
200 		estimate_pid_constants(tz, sustainable_power,
201 				       params->trip_switch_on, control_temp,
202 				       true);
203 	}
204 
205 	err = control_temp - tz->temperature;
206 	err = int_to_frac(err);
207 
208 	/* Calculate the proportional term */
209 	p = mul_frac(err < 0 ? tz->tzp->k_po : tz->tzp->k_pu, err);
210 
211 	/*
212 	 * Calculate the integral term
213 	 *
214 	 * if the error is less than cut off allow integration (but
215 	 * the integral is limited to max power)
216 	 */
217 	i = mul_frac(tz->tzp->k_i, params->err_integral);
218 
219 	if (err < int_to_frac(tz->tzp->integral_cutoff)) {
220 		s64 i_next = i + mul_frac(tz->tzp->k_i, err);
221 
222 		if (abs(i_next) < max_power_frac) {
223 			i = i_next;
224 			params->err_integral += err;
225 		}
226 	}
227 
228 	/*
229 	 * Calculate the derivative term
230 	 *
231 	 * We do err - prev_err, so with a positive k_d, a decreasing
232 	 * error (i.e. driving closer to the line) results in less
233 	 * power being applied, slowing down the controller)
234 	 */
235 	d = mul_frac(tz->tzp->k_d, err - params->prev_err);
236 	d = div_frac(d, tz->passive_delay);
237 	params->prev_err = err;
238 
239 	power_range = p + i + d;
240 
241 	/* feed-forward the known sustainable dissipatable power */
242 	power_range = sustainable_power + frac_to_int(power_range);
243 
244 	power_range = clamp(power_range, (s64)0, (s64)max_allocatable_power);
245 
246 	trace_thermal_power_allocator_pid(tz, frac_to_int(err),
247 					  frac_to_int(params->err_integral),
248 					  frac_to_int(p), frac_to_int(i),
249 					  frac_to_int(d), power_range);
250 
251 	return power_range;
252 }
253 
254 /**
255  * divvy_up_power() - divvy the allocated power between the actors
256  * @req_power:	each actor's requested power
257  * @max_power:	each actor's maximum available power
258  * @num_actors:	size of the @req_power, @max_power and @granted_power's array
259  * @total_req_power: sum of @req_power
260  * @power_range:	total allocated power
261  * @granted_power:	output array: each actor's granted power
262  * @extra_actor_power:	an appropriately sized array to be used in the
263  *			function as temporary storage of the extra power given
264  *			to the actors
265  *
266  * This function divides the total allocated power (@power_range)
267  * fairly between the actors.  It first tries to give each actor a
268  * share of the @power_range according to how much power it requested
269  * compared to the rest of the actors.  For example, if only one actor
270  * requests power, then it receives all the @power_range.  If
271  * three actors each requests 1mW, each receives a third of the
272  * @power_range.
273  *
274  * If any actor received more than their maximum power, then that
275  * surplus is re-divvied among the actors based on how far they are
276  * from their respective maximums.
277  *
278  * Granted power for each actor is written to @granted_power, which
279  * should've been allocated by the calling function.
280  */
281 static void divvy_up_power(u32 *req_power, u32 *max_power, int num_actors,
282 			   u32 total_req_power, u32 power_range,
283 			   u32 *granted_power, u32 *extra_actor_power)
284 {
285 	u32 extra_power, capped_extra_power;
286 	int i;
287 
288 	/*
289 	 * Prevent division by 0 if none of the actors request power.
290 	 */
291 	if (!total_req_power)
292 		total_req_power = 1;
293 
294 	capped_extra_power = 0;
295 	extra_power = 0;
296 	for (i = 0; i < num_actors; i++) {
297 		u64 req_range = (u64)req_power[i] * power_range;
298 
299 		granted_power[i] = DIV_ROUND_CLOSEST_ULL(req_range,
300 							 total_req_power);
301 
302 		if (granted_power[i] > max_power[i]) {
303 			extra_power += granted_power[i] - max_power[i];
304 			granted_power[i] = max_power[i];
305 		}
306 
307 		extra_actor_power[i] = max_power[i] - granted_power[i];
308 		capped_extra_power += extra_actor_power[i];
309 	}
310 
311 	if (!extra_power)
312 		return;
313 
314 	/*
315 	 * Re-divvy the reclaimed extra among actors based on
316 	 * how far they are from the max
317 	 */
318 	extra_power = min(extra_power, capped_extra_power);
319 	if (capped_extra_power > 0)
320 		for (i = 0; i < num_actors; i++)
321 			granted_power[i] += (extra_actor_power[i] *
322 					extra_power) / capped_extra_power;
323 }
324 
325 static int allocate_power(struct thermal_zone_device *tz,
326 			  int control_temp)
327 {
328 	struct thermal_instance *instance;
329 	struct power_allocator_params *params = tz->governor_data;
330 	u32 *req_power, *max_power, *granted_power, *extra_actor_power;
331 	u32 *weighted_req_power;
332 	u32 total_req_power, max_allocatable_power, total_weighted_req_power;
333 	u32 total_granted_power, power_range;
334 	int i, num_actors, total_weight, ret = 0;
335 	int trip_max_desired_temperature = params->trip_max_desired_temperature;
336 
337 	mutex_lock(&tz->lock);
338 
339 	num_actors = 0;
340 	total_weight = 0;
341 	list_for_each_entry(instance, &tz->thermal_instances, tz_node) {
342 		if ((instance->trip == trip_max_desired_temperature) &&
343 		    cdev_is_power_actor(instance->cdev)) {
344 			num_actors++;
345 			total_weight += instance->weight;
346 		}
347 	}
348 
349 	if (!num_actors) {
350 		ret = -ENODEV;
351 		goto unlock;
352 	}
353 
354 	/*
355 	 * We need to allocate five arrays of the same size:
356 	 * req_power, max_power, granted_power, extra_actor_power and
357 	 * weighted_req_power.  They are going to be needed until this
358 	 * function returns.  Allocate them all in one go to simplify
359 	 * the allocation and deallocation logic.
360 	 */
361 	BUILD_BUG_ON(sizeof(*req_power) != sizeof(*max_power));
362 	BUILD_BUG_ON(sizeof(*req_power) != sizeof(*granted_power));
363 	BUILD_BUG_ON(sizeof(*req_power) != sizeof(*extra_actor_power));
364 	BUILD_BUG_ON(sizeof(*req_power) != sizeof(*weighted_req_power));
365 	req_power = kcalloc(num_actors * 5, sizeof(*req_power), GFP_KERNEL);
366 	if (!req_power) {
367 		ret = -ENOMEM;
368 		goto unlock;
369 	}
370 
371 	max_power = &req_power[num_actors];
372 	granted_power = &req_power[2 * num_actors];
373 	extra_actor_power = &req_power[3 * num_actors];
374 	weighted_req_power = &req_power[4 * num_actors];
375 
376 	i = 0;
377 	total_weighted_req_power = 0;
378 	total_req_power = 0;
379 	max_allocatable_power = 0;
380 
381 	list_for_each_entry(instance, &tz->thermal_instances, tz_node) {
382 		int weight;
383 		struct thermal_cooling_device *cdev = instance->cdev;
384 
385 		if (instance->trip != trip_max_desired_temperature)
386 			continue;
387 
388 		if (!cdev_is_power_actor(cdev))
389 			continue;
390 
391 		if (cdev->ops->get_requested_power(cdev, tz, &req_power[i]))
392 			continue;
393 
394 		if (!total_weight)
395 			weight = 1 << FRAC_BITS;
396 		else
397 			weight = instance->weight;
398 
399 		weighted_req_power[i] = frac_to_int(weight * req_power[i]);
400 
401 		if (power_actor_get_max_power(cdev, tz, &max_power[i]))
402 			continue;
403 
404 		total_req_power += req_power[i];
405 		max_allocatable_power += max_power[i];
406 		total_weighted_req_power += weighted_req_power[i];
407 
408 		i++;
409 	}
410 
411 	power_range = pid_controller(tz, control_temp, max_allocatable_power);
412 
413 	divvy_up_power(weighted_req_power, max_power, num_actors,
414 		       total_weighted_req_power, power_range, granted_power,
415 		       extra_actor_power);
416 
417 	total_granted_power = 0;
418 	i = 0;
419 	list_for_each_entry(instance, &tz->thermal_instances, tz_node) {
420 		if (instance->trip != trip_max_desired_temperature)
421 			continue;
422 
423 		if (!cdev_is_power_actor(instance->cdev))
424 			continue;
425 
426 		power_actor_set_power(instance->cdev, instance,
427 				      granted_power[i]);
428 		total_granted_power += granted_power[i];
429 
430 		i++;
431 	}
432 
433 	trace_thermal_power_allocator(tz, req_power, total_req_power,
434 				      granted_power, total_granted_power,
435 				      num_actors, power_range,
436 				      max_allocatable_power, tz->temperature,
437 				      control_temp - tz->temperature);
438 
439 	kfree(req_power);
440 unlock:
441 	mutex_unlock(&tz->lock);
442 
443 	return ret;
444 }
445 
446 /**
447  * get_governor_trips() - get the number of the two trip points that are key for this governor
448  * @tz:	thermal zone to operate on
449  * @params:	pointer to private data for this governor
450  *
451  * The power allocator governor works optimally with two trips points:
452  * a "switch on" trip point and a "maximum desired temperature".  These
453  * are defined as the first and last passive trip points.
454  *
455  * If there is only one trip point, then that's considered to be the
456  * "maximum desired temperature" trip point and the governor is always
457  * on.  If there are no passive or active trip points, then the
458  * governor won't do anything.  In fact, its throttle function
459  * won't be called at all.
460  */
461 static void get_governor_trips(struct thermal_zone_device *tz,
462 			       struct power_allocator_params *params)
463 {
464 	int i, last_active, last_passive;
465 	bool found_first_passive;
466 
467 	found_first_passive = false;
468 	last_active = INVALID_TRIP;
469 	last_passive = INVALID_TRIP;
470 
471 	for (i = 0; i < tz->trips; i++) {
472 		enum thermal_trip_type type;
473 		int ret;
474 
475 		ret = tz->ops->get_trip_type(tz, i, &type);
476 		if (ret) {
477 			dev_warn(&tz->device,
478 				 "Failed to get trip point %d type: %d\n", i,
479 				 ret);
480 			continue;
481 		}
482 
483 		if (type == THERMAL_TRIP_PASSIVE) {
484 			if (!found_first_passive) {
485 				params->trip_switch_on = i;
486 				found_first_passive = true;
487 			} else  {
488 				last_passive = i;
489 			}
490 		} else if (type == THERMAL_TRIP_ACTIVE) {
491 			last_active = i;
492 		} else {
493 			break;
494 		}
495 	}
496 
497 	if (last_passive != INVALID_TRIP) {
498 		params->trip_max_desired_temperature = last_passive;
499 	} else if (found_first_passive) {
500 		params->trip_max_desired_temperature = params->trip_switch_on;
501 		params->trip_switch_on = INVALID_TRIP;
502 	} else {
503 		params->trip_switch_on = INVALID_TRIP;
504 		params->trip_max_desired_temperature = last_active;
505 	}
506 }
507 
508 static void reset_pid_controller(struct power_allocator_params *params)
509 {
510 	params->err_integral = 0;
511 	params->prev_err = 0;
512 }
513 
514 static void allow_maximum_power(struct thermal_zone_device *tz)
515 {
516 	struct thermal_instance *instance;
517 	struct power_allocator_params *params = tz->governor_data;
518 
519 	mutex_lock(&tz->lock);
520 	list_for_each_entry(instance, &tz->thermal_instances, tz_node) {
521 		if ((instance->trip != params->trip_max_desired_temperature) ||
522 		    (!cdev_is_power_actor(instance->cdev)))
523 			continue;
524 
525 		instance->target = 0;
526 		mutex_lock(&instance->cdev->lock);
527 		instance->cdev->updated = false;
528 		mutex_unlock(&instance->cdev->lock);
529 		thermal_cdev_update(instance->cdev);
530 	}
531 	mutex_unlock(&tz->lock);
532 }
533 
534 /**
535  * power_allocator_bind() - bind the power_allocator governor to a thermal zone
536  * @tz:	thermal zone to bind it to
537  *
538  * Initialize the PID controller parameters and bind it to the thermal
539  * zone.
540  *
541  * Return: 0 on success, or -ENOMEM if we ran out of memory.
542  */
543 static int power_allocator_bind(struct thermal_zone_device *tz)
544 {
545 	int ret;
546 	struct power_allocator_params *params;
547 	int control_temp;
548 
549 	params = kzalloc(sizeof(*params), GFP_KERNEL);
550 	if (!params)
551 		return -ENOMEM;
552 
553 	if (!tz->tzp) {
554 		tz->tzp = kzalloc(sizeof(*tz->tzp), GFP_KERNEL);
555 		if (!tz->tzp) {
556 			ret = -ENOMEM;
557 			goto free_params;
558 		}
559 
560 		params->allocated_tzp = true;
561 	}
562 
563 	if (!tz->tzp->sustainable_power)
564 		dev_warn(&tz->device, "power_allocator: sustainable_power will be estimated\n");
565 
566 	get_governor_trips(tz, params);
567 
568 	if (tz->trips > 0) {
569 		ret = tz->ops->get_trip_temp(tz,
570 					params->trip_max_desired_temperature,
571 					&control_temp);
572 		if (!ret)
573 			estimate_pid_constants(tz, tz->tzp->sustainable_power,
574 					       params->trip_switch_on,
575 					       control_temp, false);
576 	}
577 
578 	reset_pid_controller(params);
579 
580 	tz->governor_data = params;
581 
582 	return 0;
583 
584 free_params:
585 	kfree(params);
586 
587 	return ret;
588 }
589 
590 static void power_allocator_unbind(struct thermal_zone_device *tz)
591 {
592 	struct power_allocator_params *params = tz->governor_data;
593 
594 	dev_dbg(&tz->device, "Unbinding from thermal zone %d\n", tz->id);
595 
596 	if (params->allocated_tzp) {
597 		kfree(tz->tzp);
598 		tz->tzp = NULL;
599 	}
600 
601 	kfree(tz->governor_data);
602 	tz->governor_data = NULL;
603 }
604 
605 static int power_allocator_throttle(struct thermal_zone_device *tz, int trip)
606 {
607 	int ret;
608 	int switch_on_temp, control_temp;
609 	struct power_allocator_params *params = tz->governor_data;
610 
611 	/*
612 	 * We get called for every trip point but we only need to do
613 	 * our calculations once
614 	 */
615 	if (trip != params->trip_max_desired_temperature)
616 		return 0;
617 
618 	ret = tz->ops->get_trip_temp(tz, params->trip_switch_on,
619 				     &switch_on_temp);
620 	if (!ret && (tz->temperature < switch_on_temp)) {
621 		tz->passive = 0;
622 		reset_pid_controller(params);
623 		allow_maximum_power(tz);
624 		return 0;
625 	}
626 
627 	tz->passive = 1;
628 
629 	ret = tz->ops->get_trip_temp(tz, params->trip_max_desired_temperature,
630 				&control_temp);
631 	if (ret) {
632 		dev_warn(&tz->device,
633 			 "Failed to get the maximum desired temperature: %d\n",
634 			 ret);
635 		return ret;
636 	}
637 
638 	return allocate_power(tz, control_temp);
639 }
640 
641 static struct thermal_governor thermal_gov_power_allocator = {
642 	.name		= "power_allocator",
643 	.bind_to_tz	= power_allocator_bind,
644 	.unbind_from_tz	= power_allocator_unbind,
645 	.throttle	= power_allocator_throttle,
646 };
647 THERMAL_GOVERNOR_DECLARE(thermal_gov_power_allocator);
648