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  * @sustainable_power:	Sustainable power (heat) that this thermal zone can
67  *			dissipate
68  */
69 struct power_allocator_params {
70 	bool allocated_tzp;
71 	s64 err_integral;
72 	s32 prev_err;
73 	int trip_switch_on;
74 	int trip_max_desired_temperature;
75 	u32 sustainable_power;
76 };
77 
78 /**
79  * estimate_sustainable_power() - Estimate the sustainable power of a thermal zone
80  * @tz: thermal zone we are operating in
81  *
82  * For thermal zones that don't provide a sustainable_power in their
83  * thermal_zone_params, estimate one.  Calculate it using the minimum
84  * power of all the cooling devices as that gives a valid value that
85  * can give some degree of functionality.  For optimal performance of
86  * this governor, provide a sustainable_power in the thermal zone's
87  * thermal_zone_params.
88  */
89 static u32 estimate_sustainable_power(struct thermal_zone_device *tz)
90 {
91 	u32 sustainable_power = 0;
92 	struct thermal_instance *instance;
93 	struct power_allocator_params *params = tz->governor_data;
94 
95 	list_for_each_entry(instance, &tz->thermal_instances, tz_node) {
96 		struct thermal_cooling_device *cdev = instance->cdev;
97 		u32 min_power;
98 
99 		if (instance->trip != params->trip_max_desired_temperature)
100 			continue;
101 
102 		if (!cdev_is_power_actor(cdev))
103 			continue;
104 
105 		if (cdev->ops->state2power(cdev, instance->upper, &min_power))
106 			continue;
107 
108 		sustainable_power += min_power;
109 	}
110 
111 	return sustainable_power;
112 }
113 
114 /**
115  * estimate_pid_constants() - Estimate the constants for the PID controller
116  * @tz:		thermal zone for which to estimate the constants
117  * @sustainable_power:	sustainable power for the thermal zone
118  * @trip_switch_on:	trip point number for the switch on temperature
119  * @control_temp:	target temperature for the power allocator governor
120  *
121  * This function is used to update the estimation of the PID
122  * controller constants in struct thermal_zone_parameters.
123  */
124 static void estimate_pid_constants(struct thermal_zone_device *tz,
125 				   u32 sustainable_power, int trip_switch_on,
126 				   int control_temp)
127 {
128 	int ret;
129 	int switch_on_temp;
130 	u32 temperature_threshold;
131 	s32 k_i;
132 
133 	ret = tz->ops->get_trip_temp(tz, trip_switch_on, &switch_on_temp);
134 	if (ret)
135 		switch_on_temp = 0;
136 
137 	temperature_threshold = control_temp - switch_on_temp;
138 	/*
139 	 * estimate_pid_constants() tries to find appropriate default
140 	 * values for thermal zones that don't provide them. If a
141 	 * system integrator has configured a thermal zone with two
142 	 * passive trip points at the same temperature, that person
143 	 * hasn't put any effort to set up the thermal zone properly
144 	 * so just give up.
145 	 */
146 	if (!temperature_threshold)
147 		return;
148 
149 	tz->tzp->k_po = int_to_frac(sustainable_power) /
150 		temperature_threshold;
151 
152 	tz->tzp->k_pu = int_to_frac(2 * sustainable_power) /
153 		temperature_threshold;
154 
155 	k_i = tz->tzp->k_pu / 10;
156 	tz->tzp->k_i = k_i > 0 ? k_i : 1;
157 
158 	/*
159 	 * The default for k_d and integral_cutoff is 0, so we can
160 	 * leave them as they are.
161 	 */
162 }
163 
164 /**
165  * get_sustainable_power() - Get the right sustainable power
166  * @tz:		thermal zone for which to estimate the constants
167  * @params:	parameters for the power allocator governor
168  * @control_temp:	target temperature for the power allocator governor
169  *
170  * This function is used for getting the proper sustainable power value based
171  * on variables which might be updated by the user sysfs interface. If that
172  * happen the new value is going to be estimated and updated. It is also used
173  * after thermal zone binding, where the initial values where set to 0.
174  */
175 static u32 get_sustainable_power(struct thermal_zone_device *tz,
176 				 struct power_allocator_params *params,
177 				 int control_temp)
178 {
179 	u32 sustainable_power;
180 
181 	if (!tz->tzp->sustainable_power)
182 		sustainable_power = estimate_sustainable_power(tz);
183 	else
184 		sustainable_power = tz->tzp->sustainable_power;
185 
186 	/* Check if it's init value 0 or there was update via sysfs */
187 	if (sustainable_power != params->sustainable_power) {
188 		estimate_pid_constants(tz, sustainable_power,
189 				       params->trip_switch_on, control_temp);
190 
191 		/* Do the estimation only once and make available in sysfs */
192 		tz->tzp->sustainable_power = sustainable_power;
193 		params->sustainable_power = sustainable_power;
194 	}
195 
196 	return sustainable_power;
197 }
198 
199 /**
200  * pid_controller() - PID controller
201  * @tz:	thermal zone we are operating in
202  * @control_temp:	the target temperature in millicelsius
203  * @max_allocatable_power:	maximum allocatable power for this thermal zone
204  *
205  * This PID controller increases the available power budget so that the
206  * temperature of the thermal zone gets as close as possible to
207  * @control_temp and limits the power if it exceeds it.  k_po is the
208  * proportional term when we are overshooting, k_pu is the
209  * proportional term when we are undershooting.  integral_cutoff is a
210  * threshold below which we stop accumulating the error.  The
211  * accumulated error is only valid if the requested power will make
212  * the system warmer.  If the system is mostly idle, there's no point
213  * in accumulating positive error.
214  *
215  * Return: The power budget for the next period.
216  */
217 static u32 pid_controller(struct thermal_zone_device *tz,
218 			  int control_temp,
219 			  u32 max_allocatable_power)
220 {
221 	s64 p, i, d, power_range;
222 	s32 err, max_power_frac;
223 	u32 sustainable_power;
224 	struct power_allocator_params *params = tz->governor_data;
225 
226 	max_power_frac = int_to_frac(max_allocatable_power);
227 
228 	sustainable_power = get_sustainable_power(tz, params, control_temp);
229 
230 	err = control_temp - tz->temperature;
231 	err = int_to_frac(err);
232 
233 	/* Calculate the proportional term */
234 	p = mul_frac(err < 0 ? tz->tzp->k_po : tz->tzp->k_pu, err);
235 
236 	/*
237 	 * Calculate the integral term
238 	 *
239 	 * if the error is less than cut off allow integration (but
240 	 * the integral is limited to max power)
241 	 */
242 	i = mul_frac(tz->tzp->k_i, params->err_integral);
243 
244 	if (err < int_to_frac(tz->tzp->integral_cutoff)) {
245 		s64 i_next = i + mul_frac(tz->tzp->k_i, err);
246 
247 		if (abs(i_next) < max_power_frac) {
248 			i = i_next;
249 			params->err_integral += err;
250 		}
251 	}
252 
253 	/*
254 	 * Calculate the derivative term
255 	 *
256 	 * We do err - prev_err, so with a positive k_d, a decreasing
257 	 * error (i.e. driving closer to the line) results in less
258 	 * power being applied, slowing down the controller)
259 	 */
260 	d = mul_frac(tz->tzp->k_d, err - params->prev_err);
261 	d = div_frac(d, tz->passive_delay);
262 	params->prev_err = err;
263 
264 	power_range = p + i + d;
265 
266 	/* feed-forward the known sustainable dissipatable power */
267 	power_range = sustainable_power + frac_to_int(power_range);
268 
269 	power_range = clamp(power_range, (s64)0, (s64)max_allocatable_power);
270 
271 	trace_thermal_power_allocator_pid(tz, frac_to_int(err),
272 					  frac_to_int(params->err_integral),
273 					  frac_to_int(p), frac_to_int(i),
274 					  frac_to_int(d), power_range);
275 
276 	return power_range;
277 }
278 
279 /**
280  * power_actor_set_power() - limit the maximum power a cooling device consumes
281  * @cdev:	pointer to &thermal_cooling_device
282  * @instance:	thermal instance to update
283  * @power:	the power in milliwatts
284  *
285  * Set the cooling device to consume at most @power milliwatts. The limit is
286  * expected to be a cap at the maximum power consumption.
287  *
288  * Return: 0 on success, -EINVAL if the cooling device does not
289  * implement the power actor API or -E* for other failures.
290  */
291 static int
292 power_actor_set_power(struct thermal_cooling_device *cdev,
293 		      struct thermal_instance *instance, u32 power)
294 {
295 	unsigned long state;
296 	int ret;
297 
298 	ret = cdev->ops->power2state(cdev, power, &state);
299 	if (ret)
300 		return ret;
301 
302 	instance->target = clamp_val(state, instance->lower, instance->upper);
303 	mutex_lock(&cdev->lock);
304 	cdev->updated = false;
305 	mutex_unlock(&cdev->lock);
306 	thermal_cdev_update(cdev);
307 
308 	return 0;
309 }
310 
311 /**
312  * divvy_up_power() - divvy the allocated power between the actors
313  * @req_power:	each actor's requested power
314  * @max_power:	each actor's maximum available power
315  * @num_actors:	size of the @req_power, @max_power and @granted_power's array
316  * @total_req_power: sum of @req_power
317  * @power_range:	total allocated power
318  * @granted_power:	output array: each actor's granted power
319  * @extra_actor_power:	an appropriately sized array to be used in the
320  *			function as temporary storage of the extra power given
321  *			to the actors
322  *
323  * This function divides the total allocated power (@power_range)
324  * fairly between the actors.  It first tries to give each actor a
325  * share of the @power_range according to how much power it requested
326  * compared to the rest of the actors.  For example, if only one actor
327  * requests power, then it receives all the @power_range.  If
328  * three actors each requests 1mW, each receives a third of the
329  * @power_range.
330  *
331  * If any actor received more than their maximum power, then that
332  * surplus is re-divvied among the actors based on how far they are
333  * from their respective maximums.
334  *
335  * Granted power for each actor is written to @granted_power, which
336  * should've been allocated by the calling function.
337  */
338 static void divvy_up_power(u32 *req_power, u32 *max_power, int num_actors,
339 			   u32 total_req_power, u32 power_range,
340 			   u32 *granted_power, u32 *extra_actor_power)
341 {
342 	u32 extra_power, capped_extra_power;
343 	int i;
344 
345 	/*
346 	 * Prevent division by 0 if none of the actors request power.
347 	 */
348 	if (!total_req_power)
349 		total_req_power = 1;
350 
351 	capped_extra_power = 0;
352 	extra_power = 0;
353 	for (i = 0; i < num_actors; i++) {
354 		u64 req_range = (u64)req_power[i] * power_range;
355 
356 		granted_power[i] = DIV_ROUND_CLOSEST_ULL(req_range,
357 							 total_req_power);
358 
359 		if (granted_power[i] > max_power[i]) {
360 			extra_power += granted_power[i] - max_power[i];
361 			granted_power[i] = max_power[i];
362 		}
363 
364 		extra_actor_power[i] = max_power[i] - granted_power[i];
365 		capped_extra_power += extra_actor_power[i];
366 	}
367 
368 	if (!extra_power)
369 		return;
370 
371 	/*
372 	 * Re-divvy the reclaimed extra among actors based on
373 	 * how far they are from the max
374 	 */
375 	extra_power = min(extra_power, capped_extra_power);
376 	if (capped_extra_power > 0)
377 		for (i = 0; i < num_actors; i++)
378 			granted_power[i] += (extra_actor_power[i] *
379 					extra_power) / capped_extra_power;
380 }
381 
382 static int allocate_power(struct thermal_zone_device *tz,
383 			  int control_temp)
384 {
385 	struct thermal_instance *instance;
386 	struct power_allocator_params *params = tz->governor_data;
387 	u32 *req_power, *max_power, *granted_power, *extra_actor_power;
388 	u32 *weighted_req_power;
389 	u32 total_req_power, max_allocatable_power, total_weighted_req_power;
390 	u32 total_granted_power, power_range;
391 	int i, num_actors, total_weight, ret = 0;
392 	int trip_max_desired_temperature = params->trip_max_desired_temperature;
393 
394 	mutex_lock(&tz->lock);
395 
396 	num_actors = 0;
397 	total_weight = 0;
398 	list_for_each_entry(instance, &tz->thermal_instances, tz_node) {
399 		if ((instance->trip == trip_max_desired_temperature) &&
400 		    cdev_is_power_actor(instance->cdev)) {
401 			num_actors++;
402 			total_weight += instance->weight;
403 		}
404 	}
405 
406 	if (!num_actors) {
407 		ret = -ENODEV;
408 		goto unlock;
409 	}
410 
411 	/*
412 	 * We need to allocate five arrays of the same size:
413 	 * req_power, max_power, granted_power, extra_actor_power and
414 	 * weighted_req_power.  They are going to be needed until this
415 	 * function returns.  Allocate them all in one go to simplify
416 	 * the allocation and deallocation logic.
417 	 */
418 	BUILD_BUG_ON(sizeof(*req_power) != sizeof(*max_power));
419 	BUILD_BUG_ON(sizeof(*req_power) != sizeof(*granted_power));
420 	BUILD_BUG_ON(sizeof(*req_power) != sizeof(*extra_actor_power));
421 	BUILD_BUG_ON(sizeof(*req_power) != sizeof(*weighted_req_power));
422 	req_power = kcalloc(num_actors * 5, sizeof(*req_power), GFP_KERNEL);
423 	if (!req_power) {
424 		ret = -ENOMEM;
425 		goto unlock;
426 	}
427 
428 	max_power = &req_power[num_actors];
429 	granted_power = &req_power[2 * num_actors];
430 	extra_actor_power = &req_power[3 * num_actors];
431 	weighted_req_power = &req_power[4 * num_actors];
432 
433 	i = 0;
434 	total_weighted_req_power = 0;
435 	total_req_power = 0;
436 	max_allocatable_power = 0;
437 
438 	list_for_each_entry(instance, &tz->thermal_instances, tz_node) {
439 		int weight;
440 		struct thermal_cooling_device *cdev = instance->cdev;
441 
442 		if (instance->trip != trip_max_desired_temperature)
443 			continue;
444 
445 		if (!cdev_is_power_actor(cdev))
446 			continue;
447 
448 		if (cdev->ops->get_requested_power(cdev, &req_power[i]))
449 			continue;
450 
451 		if (!total_weight)
452 			weight = 1 << FRAC_BITS;
453 		else
454 			weight = instance->weight;
455 
456 		weighted_req_power[i] = frac_to_int(weight * req_power[i]);
457 
458 		if (cdev->ops->state2power(cdev, instance->lower,
459 					   &max_power[i]))
460 			continue;
461 
462 		total_req_power += req_power[i];
463 		max_allocatable_power += max_power[i];
464 		total_weighted_req_power += weighted_req_power[i];
465 
466 		i++;
467 	}
468 
469 	power_range = pid_controller(tz, control_temp, max_allocatable_power);
470 
471 	divvy_up_power(weighted_req_power, max_power, num_actors,
472 		       total_weighted_req_power, power_range, granted_power,
473 		       extra_actor_power);
474 
475 	total_granted_power = 0;
476 	i = 0;
477 	list_for_each_entry(instance, &tz->thermal_instances, tz_node) {
478 		if (instance->trip != trip_max_desired_temperature)
479 			continue;
480 
481 		if (!cdev_is_power_actor(instance->cdev))
482 			continue;
483 
484 		power_actor_set_power(instance->cdev, instance,
485 				      granted_power[i]);
486 		total_granted_power += granted_power[i];
487 
488 		i++;
489 	}
490 
491 	trace_thermal_power_allocator(tz, req_power, total_req_power,
492 				      granted_power, total_granted_power,
493 				      num_actors, power_range,
494 				      max_allocatable_power, tz->temperature,
495 				      control_temp - tz->temperature);
496 
497 	kfree(req_power);
498 unlock:
499 	mutex_unlock(&tz->lock);
500 
501 	return ret;
502 }
503 
504 /**
505  * get_governor_trips() - get the number of the two trip points that are key for this governor
506  * @tz:	thermal zone to operate on
507  * @params:	pointer to private data for this governor
508  *
509  * The power allocator governor works optimally with two trips points:
510  * a "switch on" trip point and a "maximum desired temperature".  These
511  * are defined as the first and last passive trip points.
512  *
513  * If there is only one trip point, then that's considered to be the
514  * "maximum desired temperature" trip point and the governor is always
515  * on.  If there are no passive or active trip points, then the
516  * governor won't do anything.  In fact, its throttle function
517  * won't be called at all.
518  */
519 static void get_governor_trips(struct thermal_zone_device *tz,
520 			       struct power_allocator_params *params)
521 {
522 	int i, last_active, last_passive;
523 	bool found_first_passive;
524 
525 	found_first_passive = false;
526 	last_active = INVALID_TRIP;
527 	last_passive = INVALID_TRIP;
528 
529 	for (i = 0; i < tz->trips; i++) {
530 		enum thermal_trip_type type;
531 		int ret;
532 
533 		ret = tz->ops->get_trip_type(tz, i, &type);
534 		if (ret) {
535 			dev_warn(&tz->device,
536 				 "Failed to get trip point %d type: %d\n", i,
537 				 ret);
538 			continue;
539 		}
540 
541 		if (type == THERMAL_TRIP_PASSIVE) {
542 			if (!found_first_passive) {
543 				params->trip_switch_on = i;
544 				found_first_passive = true;
545 			} else  {
546 				last_passive = i;
547 			}
548 		} else if (type == THERMAL_TRIP_ACTIVE) {
549 			last_active = i;
550 		} else {
551 			break;
552 		}
553 	}
554 
555 	if (last_passive != INVALID_TRIP) {
556 		params->trip_max_desired_temperature = last_passive;
557 	} else if (found_first_passive) {
558 		params->trip_max_desired_temperature = params->trip_switch_on;
559 		params->trip_switch_on = INVALID_TRIP;
560 	} else {
561 		params->trip_switch_on = INVALID_TRIP;
562 		params->trip_max_desired_temperature = last_active;
563 	}
564 }
565 
566 static void reset_pid_controller(struct power_allocator_params *params)
567 {
568 	params->err_integral = 0;
569 	params->prev_err = 0;
570 }
571 
572 static void allow_maximum_power(struct thermal_zone_device *tz)
573 {
574 	struct thermal_instance *instance;
575 	struct power_allocator_params *params = tz->governor_data;
576 
577 	mutex_lock(&tz->lock);
578 	list_for_each_entry(instance, &tz->thermal_instances, tz_node) {
579 		if ((instance->trip != params->trip_max_desired_temperature) ||
580 		    (!cdev_is_power_actor(instance->cdev)))
581 			continue;
582 
583 		instance->target = 0;
584 		mutex_lock(&instance->cdev->lock);
585 		instance->cdev->updated = false;
586 		mutex_unlock(&instance->cdev->lock);
587 		thermal_cdev_update(instance->cdev);
588 	}
589 	mutex_unlock(&tz->lock);
590 }
591 
592 /**
593  * power_allocator_bind() - bind the power_allocator governor to a thermal zone
594  * @tz:	thermal zone to bind it to
595  *
596  * Initialize the PID controller parameters and bind it to the thermal
597  * zone.
598  *
599  * Return: 0 on success, or -ENOMEM if we ran out of memory.
600  */
601 static int power_allocator_bind(struct thermal_zone_device *tz)
602 {
603 	int ret;
604 	struct power_allocator_params *params;
605 	int control_temp;
606 
607 	params = kzalloc(sizeof(*params), GFP_KERNEL);
608 	if (!params)
609 		return -ENOMEM;
610 
611 	if (!tz->tzp) {
612 		tz->tzp = kzalloc(sizeof(*tz->tzp), GFP_KERNEL);
613 		if (!tz->tzp) {
614 			ret = -ENOMEM;
615 			goto free_params;
616 		}
617 
618 		params->allocated_tzp = true;
619 	}
620 
621 	if (!tz->tzp->sustainable_power)
622 		dev_warn(&tz->device, "power_allocator: sustainable_power will be estimated\n");
623 
624 	get_governor_trips(tz, params);
625 
626 	if (tz->trips > 0) {
627 		ret = tz->ops->get_trip_temp(tz,
628 					params->trip_max_desired_temperature,
629 					&control_temp);
630 		if (!ret)
631 			estimate_pid_constants(tz, tz->tzp->sustainable_power,
632 					       params->trip_switch_on,
633 					       control_temp);
634 	}
635 
636 	reset_pid_controller(params);
637 
638 	tz->governor_data = params;
639 
640 	return 0;
641 
642 free_params:
643 	kfree(params);
644 
645 	return ret;
646 }
647 
648 static void power_allocator_unbind(struct thermal_zone_device *tz)
649 {
650 	struct power_allocator_params *params = tz->governor_data;
651 
652 	dev_dbg(&tz->device, "Unbinding from thermal zone %d\n", tz->id);
653 
654 	if (params->allocated_tzp) {
655 		kfree(tz->tzp);
656 		tz->tzp = NULL;
657 	}
658 
659 	kfree(tz->governor_data);
660 	tz->governor_data = NULL;
661 }
662 
663 static int power_allocator_throttle(struct thermal_zone_device *tz, int trip)
664 {
665 	int ret;
666 	int switch_on_temp, control_temp;
667 	struct power_allocator_params *params = tz->governor_data;
668 
669 	/*
670 	 * We get called for every trip point but we only need to do
671 	 * our calculations once
672 	 */
673 	if (trip != params->trip_max_desired_temperature)
674 		return 0;
675 
676 	ret = tz->ops->get_trip_temp(tz, params->trip_switch_on,
677 				     &switch_on_temp);
678 	if (!ret && (tz->temperature < switch_on_temp)) {
679 		tz->passive = 0;
680 		reset_pid_controller(params);
681 		allow_maximum_power(tz);
682 		return 0;
683 	}
684 
685 	tz->passive = 1;
686 
687 	ret = tz->ops->get_trip_temp(tz, params->trip_max_desired_temperature,
688 				&control_temp);
689 	if (ret) {
690 		dev_warn(&tz->device,
691 			 "Failed to get the maximum desired temperature: %d\n",
692 			 ret);
693 		return ret;
694 	}
695 
696 	return allocate_power(tz, control_temp);
697 }
698 
699 static struct thermal_governor thermal_gov_power_allocator = {
700 	.name		= "power_allocator",
701 	.bind_to_tz	= power_allocator_bind,
702 	.unbind_from_tz	= power_allocator_unbind,
703 	.throttle	= power_allocator_throttle,
704 };
705 THERMAL_GOVERNOR_DECLARE(thermal_gov_power_allocator);
706