1/*
  2 * A power allocator to manage temperature
  3 *
  4 * Copyright (C) 2014 ARM Ltd.
  5 *
  6 * This program is free software; you can redistribute it and/or modify
  7 * it under the terms of the GNU General Public License version 2 as
  8 * published by the Free Software Foundation.
  9 *
 10 * This program is distributed "as is" WITHOUT ANY WARRANTY of any
 11 * kind, whether express or implied; without even the implied warranty
 12 * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 13 * GNU General Public License for more details.
 14 */
 15
 16#define pr_fmt(fmt) "Power allocator: " fmt
 17
 18#include <linux/rculist.h>
 19#include <linux/slab.h>
 20#include <linux/thermal.h>
 21
 22#define CREATE_TRACE_POINTS
 23#include <trace/events/thermal_power_allocator.h>
 24
 25#include "thermal_core.h"
 26
 27#define INVALID_TRIP -1
 28
 29#define FRAC_BITS 10
 30#define int_to_frac(x) ((x) << FRAC_BITS)
 31#define frac_to_int(x) ((x) >> FRAC_BITS)
 32
 33/**
 34 * mul_frac() - multiply two fixed-point numbers
 35 * @x:	first multiplicand
 36 * @y:	second multiplicand
 37 *
 38 * Return: the result of multiplying two fixed-point numbers.  The
 39 * result is also a fixed-point number.
 40 */
 41static inline s64 mul_frac(s64 x, s64 y)
 42{
 43	return (x * y) >> FRAC_BITS;
 44}
 45
 46/**
 47 * div_frac() - divide two fixed-point numbers
 48 * @x:	the dividend
 49 * @y:	the divisor
 50 *
 51 * Return: the result of dividing two fixed-point numbers.  The
 52 * result is also a fixed-point number.
 53 */
 54static inline s64 div_frac(s64 x, s64 y)
 55{
 56	return div_s64(x << FRAC_BITS, y);
 57}
 58
 59/**
 60 * struct power_allocator_params - parameters for the power allocator governor
 61 * @allocated_tzp:	whether we have allocated tzp for this thermal zone and
 62 *			it needs to be freed on unbind
 63 * @err_integral:	accumulated error in the PID controller.
 64 * @prev_err:	error in the previous iteration of the PID controller.
 65 *		Used to calculate the derivative term.
 66 * @trip_switch_on:	first passive trip point of the thermal zone.  The
 67 *			governor switches on when this trip point is crossed.
 68 *			If the thermal zone only has one passive trip point,
 69 *			@trip_switch_on should be INVALID_TRIP.
 70 * @trip_max_desired_temperature:	last passive trip point of the thermal
 71 *					zone.  The temperature we are
 72 *					controlling for.
 73 */
 74struct power_allocator_params {
 75	bool allocated_tzp;
 76	s64 err_integral;
 77	s32 prev_err;
 78	int trip_switch_on;
 79	int trip_max_desired_temperature;
 80};
 81
 82/**
 83 * estimate_sustainable_power() - Estimate the sustainable power of a thermal zone
 84 * @tz: thermal zone we are operating in
 85 *
 86 * For thermal zones that don't provide a sustainable_power in their
 87 * thermal_zone_params, estimate one.  Calculate it using the minimum
 88 * power of all the cooling devices as that gives a valid value that
 89 * can give some degree of functionality.  For optimal performance of
 90 * this governor, provide a sustainable_power in the thermal zone's
 91 * thermal_zone_params.
 92 */
 93static u32 estimate_sustainable_power(struct thermal_zone_device *tz)
 94{
 95	u32 sustainable_power = 0;
 96	struct thermal_instance *instance;
 97	struct power_allocator_params *params = tz->governor_data;
 98
 99	list_for_each_entry(instance, &tz->thermal_instances, tz_node) {
100		struct thermal_cooling_device *cdev = instance->cdev;
101		u32 min_power;
102
103		if (instance->trip != params->trip_max_desired_temperature)
104			continue;
105
106		if (power_actor_get_min_power(cdev, tz, &min_power))
107			continue;
108
109		sustainable_power += min_power;
110	}
111
112	return sustainable_power;
113}
114
115/**
116 * estimate_pid_constants() - Estimate the constants for the PID controller
117 * @tz:		thermal zone for which to estimate the constants
118 * @sustainable_power:	sustainable power for the thermal zone
119 * @trip_switch_on:	trip point number for the switch on temperature
120 * @control_temp:	target temperature for the power allocator governor
121 * @force:	whether to force the update of the constants
122 *
123 * This function is used to update the estimation of the PID
124 * controller constants in struct thermal_zone_parameters.
125 * Sustainable power is provided in case it was estimated.  The
126 * estimated sustainable_power should not be stored in the
127 * thermal_zone_parameters so it has to be passed explicitly to this
128 * function.
129 *
130 * If @force is not set, the values in the thermal zone's parameters
131 * are preserved if they are not zero.  If @force is set, the values
132 * in thermal zone's parameters are overwritten.
133 */
134static void estimate_pid_constants(struct thermal_zone_device *tz,
135				   u32 sustainable_power, int trip_switch_on,
136				   int control_temp, bool force)
137{
138	int ret;
139	int switch_on_temp;
140	u32 temperature_threshold;
141
142	ret = tz->ops->get_trip_temp(tz, trip_switch_on, &switch_on_temp);
143	if (ret)
144		switch_on_temp = 0;
145
146	temperature_threshold = control_temp - switch_on_temp;
147	/*
148	 * estimate_pid_constants() tries to find appropriate default
149	 * values for thermal zones that don't provide them. If a
150	 * system integrator has configured a thermal zone with two
151	 * passive trip points at the same temperature, that person
152	 * hasn't put any effort to set up the thermal zone properly
153	 * so just give up.
154	 */
155	if (!temperature_threshold)
156		return;
157
158	if (!tz->tzp->k_po || force)
159		tz->tzp->k_po = int_to_frac(sustainable_power) /
160			temperature_threshold;
161
162	if (!tz->tzp->k_pu || force)
163		tz->tzp->k_pu = int_to_frac(2 * sustainable_power) /
164			temperature_threshold;
165
166	if (!tz->tzp->k_i || force)
167		tz->tzp->k_i = int_to_frac(10) / 1000;
168	/*
169	 * The default for k_d and integral_cutoff is 0, so we can
170	 * leave them as they are.
171	 */
172}
173
174/**
175 * pid_controller() - PID controller
176 * @tz:	thermal zone we are operating in
177 * @control_temp:	the target temperature in millicelsius
178 * @max_allocatable_power:	maximum allocatable power for this thermal zone
179 *
180 * This PID controller increases the available power budget so that the
181 * temperature of the thermal zone gets as close as possible to
182 * @control_temp and limits the power if it exceeds it.  k_po is the
183 * proportional term when we are overshooting, k_pu is the
184 * proportional term when we are undershooting.  integral_cutoff is a
185 * threshold below which we stop accumulating the error.  The
186 * accumulated error is only valid if the requested power will make
187 * the system warmer.  If the system is mostly idle, there's no point
188 * in accumulating positive error.
189 *
190 * Return: The power budget for the next period.
191 */
192static u32 pid_controller(struct thermal_zone_device *tz,
193			  int control_temp,
194			  u32 max_allocatable_power)
195{
196	s64 p, i, d, power_range;
197	s32 err, max_power_frac;
198	u32 sustainable_power;
199	struct power_allocator_params *params = tz->governor_data;
200
201	max_power_frac = int_to_frac(max_allocatable_power);
202
203	if (tz->tzp->sustainable_power) {
204		sustainable_power = tz->tzp->sustainable_power;
205	} else {
206		sustainable_power = estimate_sustainable_power(tz);
207		estimate_pid_constants(tz, sustainable_power,
208				       params->trip_switch_on, control_temp,
209				       true);
210	}
211
212	err = control_temp - tz->temperature;
213	err = int_to_frac(err);
214
215	/* Calculate the proportional term */
216	p = mul_frac(err < 0 ? tz->tzp->k_po : tz->tzp->k_pu, err);
217
218	/*
219	 * Calculate the integral term
220	 *
221	 * if the error is less than cut off allow integration (but
222	 * the integral is limited to max power)
223	 */
224	i = mul_frac(tz->tzp->k_i, params->err_integral);
225
226	if (err < int_to_frac(tz->tzp->integral_cutoff)) {
227		s64 i_next = i + mul_frac(tz->tzp->k_i, err);
228
229		if (abs(i_next) < max_power_frac) {
230			i = i_next;
231			params->err_integral += err;
232		}
233	}
234
235	/*
236	 * Calculate the derivative term
237	 *
238	 * We do err - prev_err, so with a positive k_d, a decreasing
239	 * error (i.e. driving closer to the line) results in less
240	 * power being applied, slowing down the controller)
241	 */
242	d = mul_frac(tz->tzp->k_d, err - params->prev_err);
243	d = div_frac(d, tz->passive_delay);
244	params->prev_err = err;
245
246	power_range = p + i + d;
247
248	/* feed-forward the known sustainable dissipatable power */
249	power_range = sustainable_power + frac_to_int(power_range);
250
251	power_range = clamp(power_range, (s64)0, (s64)max_allocatable_power);
252
253	trace_thermal_power_allocator_pid(tz, frac_to_int(err),
254					  frac_to_int(params->err_integral),
255					  frac_to_int(p), frac_to_int(i),
256					  frac_to_int(d), power_range);
257
258	return power_range;
259}
260
261/**
262 * divvy_up_power() - divvy the allocated power between the actors
263 * @req_power:	each actor's requested power
264 * @max_power:	each actor's maximum available power
265 * @num_actors:	size of the @req_power, @max_power and @granted_power's array
266 * @total_req_power: sum of @req_power
267 * @power_range:	total allocated power
268 * @granted_power:	output array: each actor's granted power
269 * @extra_actor_power:	an appropriately sized array to be used in the
270 *			function as temporary storage of the extra power given
271 *			to the actors
272 *
273 * This function divides the total allocated power (@power_range)
274 * fairly between the actors.  It first tries to give each actor a
275 * share of the @power_range according to how much power it requested
276 * compared to the rest of the actors.  For example, if only one actor
277 * requests power, then it receives all the @power_range.  If
278 * three actors each requests 1mW, each receives a third of the
279 * @power_range.
280 *
281 * If any actor received more than their maximum power, then that
282 * surplus is re-divvied among the actors based on how far they are
283 * from their respective maximums.
284 *
285 * Granted power for each actor is written to @granted_power, which
286 * should've been allocated by the calling function.
287 */
288static void divvy_up_power(u32 *req_power, u32 *max_power, int num_actors,
289			   u32 total_req_power, u32 power_range,
290			   u32 *granted_power, u32 *extra_actor_power)
291{
292	u32 extra_power, capped_extra_power;
293	int i;
294
295	/*
296	 * Prevent division by 0 if none of the actors request power.
297	 */
298	if (!total_req_power)
299		total_req_power = 1;
300
301	capped_extra_power = 0;
302	extra_power = 0;
303	for (i = 0; i < num_actors; i++) {
304		u64 req_range = (u64)req_power[i] * power_range;
305
306		granted_power[i] = DIV_ROUND_CLOSEST_ULL(req_range,
307							 total_req_power);
308
309		if (granted_power[i] > max_power[i]) {
310			extra_power += granted_power[i] - max_power[i];
311			granted_power[i] = max_power[i];
312		}
313
314		extra_actor_power[i] = max_power[i] - granted_power[i];
315		capped_extra_power += extra_actor_power[i];
316	}
317
318	if (!extra_power)
319		return;
320
321	/*
322	 * Re-divvy the reclaimed extra among actors based on
323	 * how far they are from the max
324	 */
325	extra_power = min(extra_power, capped_extra_power);
326	if (capped_extra_power > 0)
327		for (i = 0; i < num_actors; i++)
328			granted_power[i] += (extra_actor_power[i] *
329					extra_power) / capped_extra_power;
330}
331
332static int allocate_power(struct thermal_zone_device *tz,
333			  int control_temp)
334{
335	struct thermal_instance *instance;
336	struct power_allocator_params *params = tz->governor_data;
337	u32 *req_power, *max_power, *granted_power, *extra_actor_power;
338	u32 *weighted_req_power;
339	u32 total_req_power, max_allocatable_power, total_weighted_req_power;
340	u32 total_granted_power, power_range;
341	int i, num_actors, total_weight, ret = 0;
342	int trip_max_desired_temperature = params->trip_max_desired_temperature;
343
344	mutex_lock(&tz->lock);
345
346	num_actors = 0;
347	total_weight = 0;
348	list_for_each_entry(instance, &tz->thermal_instances, tz_node) {
349		if ((instance->trip == trip_max_desired_temperature) &&
350		    cdev_is_power_actor(instance->cdev)) {
351			num_actors++;
352			total_weight += instance->weight;
353		}
354	}
355
356	if (!num_actors) {
357		ret = -ENODEV;
358		goto unlock;
359	}
360
361	/*
362	 * We need to allocate five arrays of the same size:
363	 * req_power, max_power, granted_power, extra_actor_power and
364	 * weighted_req_power.  They are going to be needed until this
365	 * function returns.  Allocate them all in one go to simplify
366	 * the allocation and deallocation logic.
367	 */
368	BUILD_BUG_ON(sizeof(*req_power) != sizeof(*max_power));
369	BUILD_BUG_ON(sizeof(*req_power) != sizeof(*granted_power));
370	BUILD_BUG_ON(sizeof(*req_power) != sizeof(*extra_actor_power));
371	BUILD_BUG_ON(sizeof(*req_power) != sizeof(*weighted_req_power));
372	req_power = kcalloc(num_actors * 5, sizeof(*req_power), GFP_KERNEL);
373	if (!req_power) {
374		ret = -ENOMEM;
375		goto unlock;
376	}
377
378	max_power = &req_power[num_actors];
379	granted_power = &req_power[2 * num_actors];
380	extra_actor_power = &req_power[3 * num_actors];
381	weighted_req_power = &req_power[4 * num_actors];
382
383	i = 0;
384	total_weighted_req_power = 0;
385	total_req_power = 0;
386	max_allocatable_power = 0;
387
388	list_for_each_entry(instance, &tz->thermal_instances, tz_node) {
389		int weight;
390		struct thermal_cooling_device *cdev = instance->cdev;
391
392		if (instance->trip != trip_max_desired_temperature)
393			continue;
394
395		if (!cdev_is_power_actor(cdev))
396			continue;
397
398		if (cdev->ops->get_requested_power(cdev, tz, &req_power[i]))
399			continue;
400
401		if (!total_weight)
402			weight = 1 << FRAC_BITS;
403		else
404			weight = instance->weight;
405
406		weighted_req_power[i] = frac_to_int(weight * req_power[i]);
407
408		if (power_actor_get_max_power(cdev, tz, &max_power[i]))
409			continue;
410
411		total_req_power += req_power[i];
412		max_allocatable_power += max_power[i];
413		total_weighted_req_power += weighted_req_power[i];
414
415		i++;
416	}
417
418	power_range = pid_controller(tz, control_temp, max_allocatable_power);
419
420	divvy_up_power(weighted_req_power, max_power, num_actors,
421		       total_weighted_req_power, power_range, granted_power,
422		       extra_actor_power);
423
424	total_granted_power = 0;
425	i = 0;
426	list_for_each_entry(instance, &tz->thermal_instances, tz_node) {
427		if (instance->trip != trip_max_desired_temperature)
428			continue;
429
430		if (!cdev_is_power_actor(instance->cdev))
431			continue;
432
433		power_actor_set_power(instance->cdev, instance,
434				      granted_power[i]);
435		total_granted_power += granted_power[i];
436
437		i++;
438	}
439
440	trace_thermal_power_allocator(tz, req_power, total_req_power,
441				      granted_power, total_granted_power,
442				      num_actors, power_range,
443				      max_allocatable_power, tz->temperature,
444				      control_temp - tz->temperature);
445
446	kfree(req_power);
447unlock:
448	mutex_unlock(&tz->lock);
449
450	return ret;
451}
452
453/**
454 * get_governor_trips() - get the number of the two trip points that are key for this governor
455 * @tz:	thermal zone to operate on
456 * @params:	pointer to private data for this governor
457 *
458 * The power allocator governor works optimally with two trips points:
459 * a "switch on" trip point and a "maximum desired temperature".  These
460 * are defined as the first and last passive trip points.
461 *
462 * If there is only one trip point, then that's considered to be the
463 * "maximum desired temperature" trip point and the governor is always
464 * on.  If there are no passive or active trip points, then the
465 * governor won't do anything.  In fact, its throttle function
466 * won't be called at all.
467 */
468static void get_governor_trips(struct thermal_zone_device *tz,
469			       struct power_allocator_params *params)
470{
471	int i, last_active, last_passive;
472	bool found_first_passive;
473
474	found_first_passive = false;
475	last_active = INVALID_TRIP;
476	last_passive = INVALID_TRIP;
477
478	for (i = 0; i < tz->trips; i++) {
479		enum thermal_trip_type type;
480		int ret;
481
482		ret = tz->ops->get_trip_type(tz, i, &type);
483		if (ret) {
484			dev_warn(&tz->device,
485				 "Failed to get trip point %d type: %d\n", i,
486				 ret);
487			continue;
488		}
489
490		if (type == THERMAL_TRIP_PASSIVE) {
491			if (!found_first_passive) {
492				params->trip_switch_on = i;
493				found_first_passive = true;
494			} else  {
495				last_passive = i;
496			}
497		} else if (type == THERMAL_TRIP_ACTIVE) {
498			last_active = i;
499		} else {
500			break;
501		}
502	}
503
504	if (last_passive != INVALID_TRIP) {
505		params->trip_max_desired_temperature = last_passive;
506	} else if (found_first_passive) {
507		params->trip_max_desired_temperature = params->trip_switch_on;
508		params->trip_switch_on = INVALID_TRIP;
509	} else {
510		params->trip_switch_on = INVALID_TRIP;
511		params->trip_max_desired_temperature = last_active;
512	}
513}
514
515static void reset_pid_controller(struct power_allocator_params *params)
516{
517	params->err_integral = 0;
518	params->prev_err = 0;
519}
520
521static void allow_maximum_power(struct thermal_zone_device *tz)
522{
523	struct thermal_instance *instance;
524	struct power_allocator_params *params = tz->governor_data;
525
526	mutex_lock(&tz->lock);
527	list_for_each_entry(instance, &tz->thermal_instances, tz_node) {
528		if ((instance->trip != params->trip_max_desired_temperature) ||
529		    (!cdev_is_power_actor(instance->cdev)))
530			continue;
531
532		instance->target = 0;
533		mutex_lock(&instance->cdev->lock);
534		instance->cdev->updated = false;
535		mutex_unlock(&instance->cdev->lock);
536		thermal_cdev_update(instance->cdev);
537	}
538	mutex_unlock(&tz->lock);
539}
540
541/**
542 * power_allocator_bind() - bind the power_allocator governor to a thermal zone
543 * @tz:	thermal zone to bind it to
544 *
545 * Initialize the PID controller parameters and bind it to the thermal
546 * zone.
547 *
548 * Return: 0 on success, or -ENOMEM if we ran out of memory.
549 */
550static int power_allocator_bind(struct thermal_zone_device *tz)
551{
552	int ret;
553	struct power_allocator_params *params;
554	int control_temp;
555
556	params = kzalloc(sizeof(*params), GFP_KERNEL);
557	if (!params)
558		return -ENOMEM;
559
560	if (!tz->tzp) {
561		tz->tzp = kzalloc(sizeof(*tz->tzp), GFP_KERNEL);
562		if (!tz->tzp) {
563			ret = -ENOMEM;
564			goto free_params;
565		}
566
567		params->allocated_tzp = true;
568	}
569
570	if (!tz->tzp->sustainable_power)
571		dev_warn(&tz->device, "power_allocator: sustainable_power will be estimated\n");
572
573	get_governor_trips(tz, params);
574
575	if (tz->trips > 0) {
576		ret = tz->ops->get_trip_temp(tz,
577					params->trip_max_desired_temperature,
578					&control_temp);
579		if (!ret)
580			estimate_pid_constants(tz, tz->tzp->sustainable_power,
581					       params->trip_switch_on,
582					       control_temp, false);
583	}
584
585	reset_pid_controller(params);
586
587	tz->governor_data = params;
588
589	return 0;
590
591free_params:
592	kfree(params);
593
594	return ret;
595}
596
597static void power_allocator_unbind(struct thermal_zone_device *tz)
598{
599	struct power_allocator_params *params = tz->governor_data;
600
601	dev_dbg(&tz->device, "Unbinding from thermal zone %d\n", tz->id);
602
603	if (params->allocated_tzp) {
604		kfree(tz->tzp);
605		tz->tzp = NULL;
606	}
607
608	kfree(tz->governor_data);
609	tz->governor_data = NULL;
610}
611
612static int power_allocator_throttle(struct thermal_zone_device *tz, int trip)
613{
614	int ret;
615	int switch_on_temp, control_temp;
616	struct power_allocator_params *params = tz->governor_data;
617
618	/*
619	 * We get called for every trip point but we only need to do
620	 * our calculations once
621	 */
622	if (trip != params->trip_max_desired_temperature)
623		return 0;
624
625	ret = tz->ops->get_trip_temp(tz, params->trip_switch_on,
626				     &switch_on_temp);
627	if (!ret && (tz->temperature < switch_on_temp)) {
628		tz->passive = 0;
629		reset_pid_controller(params);
630		allow_maximum_power(tz);
631		return 0;
632	}
633
634	tz->passive = 1;
635
636	ret = tz->ops->get_trip_temp(tz, params->trip_max_desired_temperature,
637				&control_temp);
638	if (ret) {
639		dev_warn(&tz->device,
640			 "Failed to get the maximum desired temperature: %d\n",
641			 ret);
642		return ret;
643	}
644
645	return allocate_power(tz, control_temp);
646}
647
648static struct thermal_governor thermal_gov_power_allocator = {
649	.name		= "power_allocator",
650	.bind_to_tz	= power_allocator_bind,
651	.unbind_from_tz	= power_allocator_unbind,
652	.throttle	= power_allocator_throttle,
653};
654THERMAL_GOVERNOR_DECLARE(thermal_gov_power_allocator);