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Javi Merino6b775e82015-03-02 17:17:19 +00001/*
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
Javi Merino6828a472015-03-02 17:17:20 +000022#define CREATE_TRACE_POINTS
23#include <trace/events/thermal_power_allocator.h>
24
Javi Merino6b775e82015-03-02 17:17:19 +000025#include "thermal_core.h"
26
27#define FRAC_BITS 10
28#define int_to_frac(x) ((x) << FRAC_BITS)
29#define frac_to_int(x) ((x) >> FRAC_BITS)
30
31/**
32 * mul_frac() - multiply two fixed-point numbers
33 * @x: first multiplicand
34 * @y: second multiplicand
35 *
36 * Return: the result of multiplying two fixed-point numbers. The
37 * result is also a fixed-point number.
38 */
39static inline s64 mul_frac(s64 x, s64 y)
40{
41 return (x * y) >> FRAC_BITS;
42}
43
44/**
45 * div_frac() - divide two fixed-point numbers
46 * @x: the dividend
47 * @y: the divisor
48 *
49 * Return: the result of dividing two fixed-point numbers. The
50 * result is also a fixed-point number.
51 */
52static inline s64 div_frac(s64 x, s64 y)
53{
54 return div_s64(x << FRAC_BITS, y);
55}
56
57/**
58 * struct power_allocator_params - parameters for the power allocator governor
59 * @err_integral: accumulated error in the PID controller.
60 * @prev_err: error in the previous iteration of the PID controller.
61 * Used to calculate the derivative term.
62 * @trip_switch_on: first passive trip point of the thermal zone. The
63 * governor switches on when this trip point is crossed.
64 * @trip_max_desired_temperature: last passive trip point of the thermal
65 * zone. The temperature we are
66 * controlling for.
67 */
68struct power_allocator_params {
69 s64 err_integral;
70 s32 prev_err;
71 int trip_switch_on;
72 int trip_max_desired_temperature;
73};
74
75/**
76 * pid_controller() - PID controller
77 * @tz: thermal zone we are operating in
78 * @current_temp: the current temperature in millicelsius
79 * @control_temp: the target temperature in millicelsius
80 * @max_allocatable_power: maximum allocatable power for this thermal zone
81 *
82 * This PID controller increases the available power budget so that the
83 * temperature of the thermal zone gets as close as possible to
84 * @control_temp and limits the power if it exceeds it. k_po is the
85 * proportional term when we are overshooting, k_pu is the
86 * proportional term when we are undershooting. integral_cutoff is a
87 * threshold below which we stop accumulating the error. The
88 * accumulated error is only valid if the requested power will make
89 * the system warmer. If the system is mostly idle, there's no point
90 * in accumulating positive error.
91 *
92 * Return: The power budget for the next period.
93 */
94static u32 pid_controller(struct thermal_zone_device *tz,
95 unsigned long current_temp,
96 unsigned long control_temp,
97 u32 max_allocatable_power)
98{
99 s64 p, i, d, power_range;
100 s32 err, max_power_frac;
101 struct power_allocator_params *params = tz->governor_data;
102
103 max_power_frac = int_to_frac(max_allocatable_power);
104
105 err = ((s32)control_temp - (s32)current_temp);
106 err = int_to_frac(err);
107
108 /* Calculate the proportional term */
109 p = mul_frac(err < 0 ? tz->tzp->k_po : tz->tzp->k_pu, err);
110
111 /*
112 * Calculate the integral term
113 *
114 * if the error is less than cut off allow integration (but
115 * the integral is limited to max power)
116 */
117 i = mul_frac(tz->tzp->k_i, params->err_integral);
118
119 if (err < int_to_frac(tz->tzp->integral_cutoff)) {
120 s64 i_next = i + mul_frac(tz->tzp->k_i, err);
121
122 if (abs64(i_next) < max_power_frac) {
123 i = i_next;
124 params->err_integral += err;
125 }
126 }
127
128 /*
129 * Calculate the derivative term
130 *
131 * We do err - prev_err, so with a positive k_d, a decreasing
132 * error (i.e. driving closer to the line) results in less
133 * power being applied, slowing down the controller)
134 */
135 d = mul_frac(tz->tzp->k_d, err - params->prev_err);
136 d = div_frac(d, tz->passive_delay);
137 params->prev_err = err;
138
139 power_range = p + i + d;
140
141 /* feed-forward the known sustainable dissipatable power */
142 power_range = tz->tzp->sustainable_power + frac_to_int(power_range);
143
Javi Merino6828a472015-03-02 17:17:20 +0000144 power_range = clamp(power_range, (s64)0, (s64)max_allocatable_power);
145
146 trace_thermal_power_allocator_pid(tz, frac_to_int(err),
147 frac_to_int(params->err_integral),
148 frac_to_int(p), frac_to_int(i),
149 frac_to_int(d), power_range);
150
151 return power_range;
Javi Merino6b775e82015-03-02 17:17:19 +0000152}
153
154/**
155 * divvy_up_power() - divvy the allocated power between the actors
156 * @req_power: each actor's requested power
157 * @max_power: each actor's maximum available power
158 * @num_actors: size of the @req_power, @max_power and @granted_power's array
159 * @total_req_power: sum of @req_power
160 * @power_range: total allocated power
161 * @granted_power: output array: each actor's granted power
162 * @extra_actor_power: an appropriately sized array to be used in the
163 * function as temporary storage of the extra power given
164 * to the actors
165 *
166 * This function divides the total allocated power (@power_range)
167 * fairly between the actors. It first tries to give each actor a
168 * share of the @power_range according to how much power it requested
169 * compared to the rest of the actors. For example, if only one actor
170 * requests power, then it receives all the @power_range. If
171 * three actors each requests 1mW, each receives a third of the
172 * @power_range.
173 *
174 * If any actor received more than their maximum power, then that
175 * surplus is re-divvied among the actors based on how far they are
176 * from their respective maximums.
177 *
178 * Granted power for each actor is written to @granted_power, which
179 * should've been allocated by the calling function.
180 */
181static void divvy_up_power(u32 *req_power, u32 *max_power, int num_actors,
182 u32 total_req_power, u32 power_range,
183 u32 *granted_power, u32 *extra_actor_power)
184{
185 u32 extra_power, capped_extra_power;
186 int i;
187
188 /*
189 * Prevent division by 0 if none of the actors request power.
190 */
191 if (!total_req_power)
192 total_req_power = 1;
193
194 capped_extra_power = 0;
195 extra_power = 0;
196 for (i = 0; i < num_actors; i++) {
197 u64 req_range = req_power[i] * power_range;
198
Javi Merinoea54cac2015-05-02 10:15:24 +0100199 granted_power[i] = DIV_ROUND_CLOSEST_ULL(req_range,
200 total_req_power);
Javi Merino6b775e82015-03-02 17:17:19 +0000201
202 if (granted_power[i] > max_power[i]) {
203 extra_power += granted_power[i] - max_power[i];
204 granted_power[i] = max_power[i];
205 }
206
207 extra_actor_power[i] = max_power[i] - granted_power[i];
208 capped_extra_power += extra_actor_power[i];
209 }
210
211 if (!extra_power)
212 return;
213
214 /*
215 * Re-divvy the reclaimed extra among actors based on
216 * how far they are from the max
217 */
218 extra_power = min(extra_power, capped_extra_power);
219 if (capped_extra_power > 0)
220 for (i = 0; i < num_actors; i++)
221 granted_power[i] += (extra_actor_power[i] *
222 extra_power) / capped_extra_power;
223}
224
225static int allocate_power(struct thermal_zone_device *tz,
226 unsigned long current_temp,
227 unsigned long control_temp)
228{
229 struct thermal_instance *instance;
230 struct power_allocator_params *params = tz->governor_data;
231 u32 *req_power, *max_power, *granted_power, *extra_actor_power;
Javi Merinod5f83102015-07-03 10:24:33 +0100232 u32 *weighted_req_power;
233 u32 total_req_power, max_allocatable_power, total_weighted_req_power;
Javi Merino6828a472015-03-02 17:17:20 +0000234 u32 total_granted_power, power_range;
Javi Merino6b775e82015-03-02 17:17:19 +0000235 int i, num_actors, total_weight, ret = 0;
236 int trip_max_desired_temperature = params->trip_max_desired_temperature;
237
238 mutex_lock(&tz->lock);
239
240 num_actors = 0;
241 total_weight = 0;
242 list_for_each_entry(instance, &tz->thermal_instances, tz_node) {
243 if ((instance->trip == trip_max_desired_temperature) &&
244 cdev_is_power_actor(instance->cdev)) {
245 num_actors++;
246 total_weight += instance->weight;
247 }
248 }
249
250 /*
Javi Merinod5f83102015-07-03 10:24:33 +0100251 * We need to allocate five arrays of the same size:
252 * req_power, max_power, granted_power, extra_actor_power and
253 * weighted_req_power. They are going to be needed until this
254 * function returns. Allocate them all in one go to simplify
255 * the allocation and deallocation logic.
Javi Merino6b775e82015-03-02 17:17:19 +0000256 */
257 BUILD_BUG_ON(sizeof(*req_power) != sizeof(*max_power));
258 BUILD_BUG_ON(sizeof(*req_power) != sizeof(*granted_power));
259 BUILD_BUG_ON(sizeof(*req_power) != sizeof(*extra_actor_power));
Javi Merinod5f83102015-07-03 10:24:33 +0100260 BUILD_BUG_ON(sizeof(*req_power) != sizeof(*weighted_req_power));
261 req_power = devm_kcalloc(&tz->device, num_actors * 5,
Javi Merino6b775e82015-03-02 17:17:19 +0000262 sizeof(*req_power), GFP_KERNEL);
263 if (!req_power) {
264 ret = -ENOMEM;
265 goto unlock;
266 }
267
268 max_power = &req_power[num_actors];
269 granted_power = &req_power[2 * num_actors];
270 extra_actor_power = &req_power[3 * num_actors];
Javi Merinod5f83102015-07-03 10:24:33 +0100271 weighted_req_power = &req_power[4 * num_actors];
Javi Merino6b775e82015-03-02 17:17:19 +0000272
273 i = 0;
Javi Merinod5f83102015-07-03 10:24:33 +0100274 total_weighted_req_power = 0;
Javi Merino6b775e82015-03-02 17:17:19 +0000275 total_req_power = 0;
276 max_allocatable_power = 0;
277
278 list_for_each_entry(instance, &tz->thermal_instances, tz_node) {
279 int weight;
280 struct thermal_cooling_device *cdev = instance->cdev;
281
282 if (instance->trip != trip_max_desired_temperature)
283 continue;
284
285 if (!cdev_is_power_actor(cdev))
286 continue;
287
288 if (cdev->ops->get_requested_power(cdev, tz, &req_power[i]))
289 continue;
290
291 if (!total_weight)
292 weight = 1 << FRAC_BITS;
293 else
294 weight = instance->weight;
295
Javi Merinod5f83102015-07-03 10:24:33 +0100296 weighted_req_power[i] = frac_to_int(weight * req_power[i]);
Javi Merino6b775e82015-03-02 17:17:19 +0000297
298 if (power_actor_get_max_power(cdev, tz, &max_power[i]))
299 continue;
300
301 total_req_power += req_power[i];
302 max_allocatable_power += max_power[i];
Javi Merinod5f83102015-07-03 10:24:33 +0100303 total_weighted_req_power += weighted_req_power[i];
Javi Merino6b775e82015-03-02 17:17:19 +0000304
305 i++;
306 }
307
308 power_range = pid_controller(tz, current_temp, control_temp,
309 max_allocatable_power);
310
Javi Merinod5f83102015-07-03 10:24:33 +0100311 divvy_up_power(weighted_req_power, max_power, num_actors,
312 total_weighted_req_power, power_range, granted_power,
313 extra_actor_power);
Javi Merino6b775e82015-03-02 17:17:19 +0000314
Javi Merino6828a472015-03-02 17:17:20 +0000315 total_granted_power = 0;
Javi Merino6b775e82015-03-02 17:17:19 +0000316 i = 0;
317 list_for_each_entry(instance, &tz->thermal_instances, tz_node) {
318 if (instance->trip != trip_max_desired_temperature)
319 continue;
320
321 if (!cdev_is_power_actor(instance->cdev))
322 continue;
323
324 power_actor_set_power(instance->cdev, instance,
325 granted_power[i]);
Javi Merino6828a472015-03-02 17:17:20 +0000326 total_granted_power += granted_power[i];
Javi Merino6b775e82015-03-02 17:17:19 +0000327
328 i++;
329 }
330
Javi Merino6828a472015-03-02 17:17:20 +0000331 trace_thermal_power_allocator(tz, req_power, total_req_power,
332 granted_power, total_granted_power,
333 num_actors, power_range,
334 max_allocatable_power, current_temp,
335 (s32)control_temp - (s32)current_temp);
336
Dmitry Torokhovcf736ea2015-08-04 09:33:40 -0700337 kfree(req_power);
Javi Merino6b775e82015-03-02 17:17:19 +0000338unlock:
339 mutex_unlock(&tz->lock);
340
341 return ret;
342}
343
344static int get_governor_trips(struct thermal_zone_device *tz,
345 struct power_allocator_params *params)
346{
347 int i, ret, last_passive;
348 bool found_first_passive;
349
350 found_first_passive = false;
351 last_passive = -1;
352 ret = -EINVAL;
353
354 for (i = 0; i < tz->trips; i++) {
355 enum thermal_trip_type type;
356
357 ret = tz->ops->get_trip_type(tz, i, &type);
358 if (ret)
359 return ret;
360
361 if (!found_first_passive) {
362 if (type == THERMAL_TRIP_PASSIVE) {
363 params->trip_switch_on = i;
364 found_first_passive = true;
365 }
366 } else if (type == THERMAL_TRIP_PASSIVE) {
367 last_passive = i;
368 } else {
369 break;
370 }
371 }
372
373 if (last_passive != -1) {
374 params->trip_max_desired_temperature = last_passive;
375 ret = 0;
376 } else {
377 ret = -EINVAL;
378 }
379
380 return ret;
381}
382
383static void reset_pid_controller(struct power_allocator_params *params)
384{
385 params->err_integral = 0;
386 params->prev_err = 0;
387}
388
389static void allow_maximum_power(struct thermal_zone_device *tz)
390{
391 struct thermal_instance *instance;
392 struct power_allocator_params *params = tz->governor_data;
393
394 list_for_each_entry(instance, &tz->thermal_instances, tz_node) {
395 if ((instance->trip != params->trip_max_desired_temperature) ||
396 (!cdev_is_power_actor(instance->cdev)))
397 continue;
398
399 instance->target = 0;
400 instance->cdev->updated = false;
401 thermal_cdev_update(instance->cdev);
402 }
403}
404
405/**
406 * power_allocator_bind() - bind the power_allocator governor to a thermal zone
407 * @tz: thermal zone to bind it to
408 *
409 * Check that the thermal zone is valid for this governor, that is, it
410 * has two thermal trips. If so, initialize the PID controller
411 * parameters and bind it to the thermal zone.
412 *
413 * Return: 0 on success, -EINVAL if the trips were invalid or -ENOMEM
414 * if we ran out of memory.
415 */
416static int power_allocator_bind(struct thermal_zone_device *tz)
417{
418 int ret;
419 struct power_allocator_params *params;
420 unsigned long switch_on_temp, control_temp;
421 u32 temperature_threshold;
422
423 if (!tz->tzp || !tz->tzp->sustainable_power) {
424 dev_err(&tz->device,
425 "power_allocator: missing sustainable_power\n");
426 return -EINVAL;
427 }
428
Dmitry Torokhovcf736ea2015-08-04 09:33:40 -0700429 params = kzalloc(sizeof(*params), GFP_KERNEL);
Javi Merino6b775e82015-03-02 17:17:19 +0000430 if (!params)
431 return -ENOMEM;
432
433 ret = get_governor_trips(tz, params);
434 if (ret) {
435 dev_err(&tz->device,
436 "thermal zone %s has wrong trip setup for power allocator\n",
437 tz->type);
438 goto free;
439 }
440
441 ret = tz->ops->get_trip_temp(tz, params->trip_switch_on,
442 &switch_on_temp);
443 if (ret)
444 goto free;
445
446 ret = tz->ops->get_trip_temp(tz, params->trip_max_desired_temperature,
447 &control_temp);
448 if (ret)
449 goto free;
450
451 temperature_threshold = control_temp - switch_on_temp;
452
453 tz->tzp->k_po = tz->tzp->k_po ?:
454 int_to_frac(tz->tzp->sustainable_power) / temperature_threshold;
455 tz->tzp->k_pu = tz->tzp->k_pu ?:
456 int_to_frac(2 * tz->tzp->sustainable_power) /
457 temperature_threshold;
458 tz->tzp->k_i = tz->tzp->k_i ?: int_to_frac(10) / 1000;
459 /*
460 * The default for k_d and integral_cutoff is 0, so we can
461 * leave them as they are.
462 */
463
464 reset_pid_controller(params);
465
466 tz->governor_data = params;
467
468 return 0;
469
470free:
Dmitry Torokhovcf736ea2015-08-04 09:33:40 -0700471 kfree(params);
Javi Merino6b775e82015-03-02 17:17:19 +0000472 return ret;
473}
474
475static void power_allocator_unbind(struct thermal_zone_device *tz)
476{
477 dev_dbg(&tz->device, "Unbinding from thermal zone %d\n", tz->id);
Dmitry Torokhovcf736ea2015-08-04 09:33:40 -0700478 kfree(tz->governor_data);
Javi Merino6b775e82015-03-02 17:17:19 +0000479 tz->governor_data = NULL;
480}
481
482static int power_allocator_throttle(struct thermal_zone_device *tz, int trip)
483{
484 int ret;
485 unsigned long switch_on_temp, control_temp, current_temp;
486 struct power_allocator_params *params = tz->governor_data;
487
488 /*
489 * We get called for every trip point but we only need to do
490 * our calculations once
491 */
492 if (trip != params->trip_max_desired_temperature)
493 return 0;
494
495 ret = thermal_zone_get_temp(tz, &current_temp);
496 if (ret) {
497 dev_warn(&tz->device, "Failed to get temperature: %d\n", ret);
498 return ret;
499 }
500
501 ret = tz->ops->get_trip_temp(tz, params->trip_switch_on,
502 &switch_on_temp);
503 if (ret) {
504 dev_warn(&tz->device,
505 "Failed to get switch on temperature: %d\n", ret);
506 return ret;
507 }
508
509 if (current_temp < switch_on_temp) {
510 tz->passive = 0;
511 reset_pid_controller(params);
512 allow_maximum_power(tz);
513 return 0;
514 }
515
516 tz->passive = 1;
517
518 ret = tz->ops->get_trip_temp(tz, params->trip_max_desired_temperature,
519 &control_temp);
520 if (ret) {
521 dev_warn(&tz->device,
522 "Failed to get the maximum desired temperature: %d\n",
523 ret);
524 return ret;
525 }
526
527 return allocate_power(tz, current_temp, control_temp);
528}
529
530static struct thermal_governor thermal_gov_power_allocator = {
531 .name = "power_allocator",
532 .bind_to_tz = power_allocator_bind,
533 .unbind_from_tz = power_allocator_unbind,
534 .throttle = power_allocator_throttle,
535};
536
537int thermal_gov_power_allocator_register(void)
538{
539 return thermal_register_governor(&thermal_gov_power_allocator);
540}
541
542void thermal_gov_power_allocator_unregister(void)
543{
544 thermal_unregister_governor(&thermal_gov_power_allocator);
545}