summaryrefslogtreecommitdiffstats
path: root/drivers/thermal/power_allocator.c
blob: 9c8a7aad0252e5de75c862213db2f001f06bf9dd (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
/*
 * A power allocator to manage temperature
 *
 * Copyright (C) 2014 ARM Ltd.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * This program is distributed "as is" WITHOUT ANY WARRANTY of any
 * kind, whether express or implied; without even the implied warranty
 * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 */

#define pr_fmt(fmt) "Power allocator: " fmt

#include <linux/rculist.h>
#include <linux/slab.h>
#include <linux/thermal.h>

#define CREATE_TRACE_POINTS
#include <trace/events/thermal_power_allocator.h>

#include "thermal_core.h"

#define FRAC_BITS 10
#define int_to_frac(x) ((x) << FRAC_BITS)
#define frac_to_int(x) ((x) >> FRAC_BITS)

/**
 * mul_frac() - multiply two fixed-point numbers
 * @x:	first multiplicand
 * @y:	second multiplicand
 *
 * Return: the result of multiplying two fixed-point numbers.  The
 * result is also a fixed-point number.
 */
static inline s64 mul_frac(s64 x, s64 y)
{
	return (x * y) >> FRAC_BITS;
}

/**
 * div_frac() - divide two fixed-point numbers
 * @x:	the dividend
 * @y:	the divisor
 *
 * Return: the result of dividing two fixed-point numbers.  The
 * result is also a fixed-point number.
 */
static inline s64 div_frac(s64 x, s64 y)
{
	return div_s64(x << FRAC_BITS, y);
}

/**
 * struct power_allocator_params - parameters for the power allocator governor
 * @err_integral:	accumulated error in the PID controller.
 * @prev_err:	error in the previous iteration of the PID controller.
 *		Used to calculate the derivative term.
 * @trip_switch_on:	first passive trip point of the thermal zone.  The
 *			governor switches on when this trip point is crossed.
 * @trip_max_desired_temperature:	last passive trip point of the thermal
 *					zone.  The temperature we are
 *					controlling for.
 */
struct power_allocator_params {
	s64 err_integral;
	s32 prev_err;
	int trip_switch_on;
	int trip_max_desired_temperature;
};

/**
 * pid_controller() - PID controller
 * @tz:	thermal zone we are operating in
 * @current_temp:	the current temperature in millicelsius
 * @control_temp:	the target temperature in millicelsius
 * @max_allocatable_power:	maximum allocatable power for this thermal zone
 *
 * This PID controller increases the available power budget so that the
 * temperature of the thermal zone gets as close as possible to
 * @control_temp and limits the power if it exceeds it.  k_po is the
 * proportional term when we are overshooting, k_pu is the
 * proportional term when we are undershooting.  integral_cutoff is a
 * threshold below which we stop accumulating the error.  The
 * accumulated error is only valid if the requested power will make
 * the system warmer.  If the system is mostly idle, there's no point
 * in accumulating positive error.
 *
 * Return: The power budget for the next period.
 */
static u32 pid_controller(struct thermal_zone_device *tz,
			  int current_temp,
			  int control_temp,
			  u32 max_allocatable_power)
{
	s64 p, i, d, power_range;
	s32 err, max_power_frac;
	struct power_allocator_params *params = tz->governor_data;

	max_power_frac = int_to_frac(max_allocatable_power);

	err = control_temp - current_temp;
	err = int_to_frac(err);

	/* Calculate the proportional term */
	p = mul_frac(err < 0 ? tz->tzp->k_po : tz->tzp->k_pu, err);

	/*
	 * Calculate the integral term
	 *
	 * if the error is less than cut off allow integration (but
	 * the integral is limited to max power)
	 */
	i = mul_frac(tz->tzp->k_i, params->err_integral);

	if (err < int_to_frac(tz->tzp->integral_cutoff)) {
		s64 i_next = i + mul_frac(tz->tzp->k_i, err);

		if (abs64(i_next) < max_power_frac) {
			i = i_next;
			params->err_integral += err;
		}
	}

	/*
	 * Calculate the derivative term
	 *
	 * We do err - prev_err, so with a positive k_d, a decreasing
	 * error (i.e. driving closer to the line) results in less
	 * power being applied, slowing down the controller)
	 */
	d = mul_frac(tz->tzp->k_d, err - params->prev_err);
	d = div_frac(d, tz->passive_delay);
	params->prev_err = err;

	power_range = p + i + d;

	/* feed-forward the known sustainable dissipatable power */
	power_range = tz->tzp->sustainable_power + frac_to_int(power_range);

	power_range = clamp(power_range, (s64)0, (s64)max_allocatable_power);

	trace_thermal_power_allocator_pid(tz, frac_to_int(err),
					  frac_to_int(params->err_integral),
					  frac_to_int(p), frac_to_int(i),
					  frac_to_int(d), power_range);

	return power_range;
}

/**
 * divvy_up_power() - divvy the allocated power between the actors
 * @req_power:	each actor's requested power
 * @max_power:	each actor's maximum available power
 * @num_actors:	size of the @req_power, @max_power and @granted_power's array
 * @total_req_power: sum of @req_power
 * @power_range:	total allocated power
 * @granted_power:	output array: each actor's granted power
 * @extra_actor_power:	an appropriately sized array to be used in the
 *			function as temporary storage of the extra power given
 *			to the actors
 *
 * This function divides the total allocated power (@power_range)
 * fairly between the actors.  It first tries to give each actor a
 * share of the @power_range according to how much power it requested
 * compared to the rest of the actors.  For example, if only one actor
 * requests power, then it receives all the @power_range.  If
 * three actors each requests 1mW, each receives a third of the
 * @power_range.
 *
 * If any actor received more than their maximum power, then that
 * surplus is re-divvied among the actors based on how far they are
 * from their respective maximums.
 *
 * Granted power for each actor is written to @granted_power, which
 * should've been allocated by the calling function.
 */
static void divvy_up_power(u32 *req_power, u32 *max_power, int num_actors,
			   u32 total_req_power, u32 power_range,
			   u32 *granted_power, u32 *extra_actor_power)
{
	u32 extra_power, capped_extra_power;
	int i;

	/*
	 * Prevent division by 0 if none of the actors request power.
	 */
	if (!total_req_power)
		total_req_power = 1;

	capped_extra_power = 0;
	extra_power = 0;
	for (i = 0; i < num_actors; i++) {
		u64 req_range = req_power[i] * power_range;

		granted_power[i] = DIV_ROUND_CLOSEST_ULL(req_range,
							 total_req_power);

		if (granted_power[i] > max_power[i]) {
			extra_power += granted_power[i] - max_power[i];
			granted_power[i] = max_power[i];
		}

		extra_actor_power[i] = max_power[i] - granted_power[i];
		capped_extra_power += extra_actor_power[i];
	}

	if (!extra_power)
		return;

	/*
	 * Re-divvy the reclaimed extra among actors based on
	 * how far they are from the max
	 */
	extra_power = min(extra_power, capped_extra_power);
	if (capped_extra_power > 0)
		for (i = 0; i < num_actors; i++)
			granted_power[i] += (extra_actor_power[i] *
					extra_power) / capped_extra_power;
}

static int allocate_power(struct thermal_zone_device *tz,
			  int current_temp,
			  int control_temp)
{
	struct thermal_instance *instance;
	struct power_allocator_params *params = tz->governor_data;
	u32 *req_power, *max_power, *granted_power, *extra_actor_power;
	u32 *weighted_req_power;
	u32 total_req_power, max_allocatable_power, total_weighted_req_power;
	u32 total_granted_power, power_range;
	int i, num_actors, total_weight, ret = 0;
	int trip_max_desired_temperature = params->trip_max_desired_temperature;

	mutex_lock(&tz->lock);

	num_actors = 0;
	total_weight = 0;
	list_for_each_entry(instance, &tz->thermal_instances, tz_node) {
		if ((instance->trip == trip_max_desired_temperature) &&
		    cdev_is_power_actor(instance->cdev)) {
			num_actors++;
			total_weight += instance->weight;
		}
	}

	/*
	 * We need to allocate five arrays of the same size:
	 * req_power, max_power, granted_power, extra_actor_power and
	 * weighted_req_power.  They are going to be needed until this
	 * function returns.  Allocate them all in one go to simplify
	 * the allocation and deallocation logic.
	 */
	BUILD_BUG_ON(sizeof(*req_power) != sizeof(*max_power));
	BUILD_BUG_ON(sizeof(*req_power) != sizeof(*granted_power));
	BUILD_BUG_ON(sizeof(*req_power) != sizeof(*extra_actor_power));
	BUILD_BUG_ON(sizeof(*req_power) != sizeof(*weighted_req_power));
	req_power = kcalloc(num_actors * 5, sizeof(*req_power), GFP_KERNEL);
	if (!req_power) {
		ret = -ENOMEM;
		goto unlock;
	}

	max_power = &req_power[num_actors];
	granted_power = &req_power[2 * num_actors];
	extra_actor_power = &req_power[3 * num_actors];
	weighted_req_power = &req_power[4 * num_actors];

	i = 0;
	total_weighted_req_power = 0;
	total_req_power = 0;
	max_allocatable_power = 0;

	list_for_each_entry(instance, &tz->thermal_instances, tz_node) {
		int weight;
		struct thermal_cooling_device *cdev = instance->cdev;

		if (instance->trip != trip_max_desired_temperature)
			continue;

		if (!cdev_is_power_actor(cdev))
			continue;

		if (cdev->ops->get_requested_power(cdev, tz, &req_power[i]))
			continue;

		if (!total_weight)
			weight = 1 << FRAC_BITS;
		else
			weight = instance->weight;

		weighted_req_power[i] = frac_to_int(weight * req_power[i]);

		if (power_actor_get_max_power(cdev, tz, &max_power[i]))
			continue;

		total_req_power += req_power[i];
		max_allocatable_power += max_power[i];
		total_weighted_req_power += weighted_req_power[i];

		i++;
	}

	power_range = pid_controller(tz, current_temp, control_temp,
				     max_allocatable_power);

	divvy_up_power(weighted_req_power, max_power, num_actors,
		       total_weighted_req_power, power_range, granted_power,
		       extra_actor_power);

	total_granted_power = 0;
	i = 0;
	list_for_each_entry(instance, &tz->thermal_instances, tz_node) {
		if (instance->trip != trip_max_desired_temperature)
			continue;

		if (!cdev_is_power_actor(instance->cdev))
			continue;

		power_actor_set_power(instance->cdev, instance,
				      granted_power[i]);
		total_granted_power += granted_power[i];

		i++;
	}

	trace_thermal_power_allocator(tz, req_power, total_req_power,
				      granted_power, total_granted_power,
				      num_actors, power_range,
				      max_allocatable_power, current_temp,
				      control_temp - current_temp);

	kfree(req_power);
unlock:
	mutex_unlock(&tz->lock);

	return ret;
}

static int get_governor_trips(struct thermal_zone_device *tz,
			      struct power_allocator_params *params)
{
	int i, ret, last_passive;
	bool found_first_passive;

	found_first_passive = false;
	last_passive = -1;
	ret = -EINVAL;

	for (i = 0; i < tz->trips; i++) {
		enum thermal_trip_type type;

		ret = tz->ops->get_trip_type(tz, i, &type);
		if (ret)
			return ret;

		if (!found_first_passive) {
			if (type == THERMAL_TRIP_PASSIVE) {
				params->trip_switch_on = i;
				found_first_passive = true;
			}
		} else if (type == THERMAL_TRIP_PASSIVE) {
			last_passive = i;
		} else {
			break;
		}
	}

	if (last_passive != -1) {
		params->trip_max_desired_temperature = last_passive;
		ret = 0;
	} else {
		ret = -EINVAL;
	}

	return ret;
}

static void reset_pid_controller(struct power_allocator_params *params)
{
	params->err_integral = 0;
	params->prev_err = 0;
}

static void allow_maximum_power(struct thermal_zone_device *tz)
{
	struct thermal_instance *instance;
	struct power_allocator_params *params = tz->governor_data;

	list_for_each_entry(instance, &tz->thermal_instances, tz_node) {
		if ((instance->trip != params->trip_max_desired_temperature) ||
		    (!cdev_is_power_actor(instance->cdev)))
			continue;

		instance->target = 0;
		instance->cdev->updated = false;
		thermal_cdev_update(instance->cdev);
	}
}

/**
 * power_allocator_bind() - bind the power_allocator governor to a thermal zone
 * @tz:	thermal zone to bind it to
 *
 * Check that the thermal zone is valid for this governor, that is, it
 * has two thermal trips.  If so, initialize the PID controller
 * parameters and bind it to the thermal zone.
 *
 * Return: 0 on success, -EINVAL if the trips were invalid or -ENOMEM
 * if we ran out of memory.
 */
static int power_allocator_bind(struct thermal_zone_device *tz)
{
	int ret;
	struct power_allocator_params *params;
	int switch_on_temp, control_temp;
	u32 temperature_threshold;

	if (!tz->tzp || !tz->tzp->sustainable_power) {
		dev_err(&tz->device,
			"power_allocator: missing sustainable_power\n");
		return -EINVAL;
	}

	params = kzalloc(sizeof(*params), GFP_KERNEL);
	if (!params)
		return -ENOMEM;

	ret = get_governor_trips(tz, params);
	if (ret) {
		dev_err(&tz->device,
			"thermal zone %s has wrong trip setup for power allocator\n",
			tz->type);
		goto free;
	}

	ret = tz->ops->get_trip_temp(tz, params->trip_switch_on,
				     &switch_on_temp);
	if (ret)
		goto free;

	ret = tz->ops->get_trip_temp(tz, params->trip_max_desired_temperature,
				     &control_temp);
	if (ret)
		goto free;

	temperature_threshold = control_temp - switch_on_temp;

	tz->tzp->k_po = tz->tzp->k_po ?:
		int_to_frac(tz->tzp->sustainable_power) / temperature_threshold;
	tz->tzp->k_pu = tz->tzp->k_pu ?:
		int_to_frac(2 * tz->tzp->sustainable_power) /
		temperature_threshold;
	tz->tzp->k_i = tz->tzp->k_i ?: int_to_frac(10) / 1000;
	/*
	 * The default for k_d and integral_cutoff is 0, so we can
	 * leave them as they are.
	 */

	reset_pid_controller(params);

	tz->governor_data = params;

	return 0;

free:
	kfree(params);
	return ret;
}

static void power_allocator_unbind(struct thermal_zone_device *tz)
{
	dev_dbg(&tz->device, "Unbinding from thermal zone %d\n", tz->id);
	kfree(tz->governor_data);
	tz->governor_data = NULL;
}

static int power_allocator_throttle(struct thermal_zone_device *tz, int trip)
{
	int ret;
	int switch_on_temp, control_temp, current_temp;
	struct power_allocator_params *params = tz->governor_data;

	/*
	 * We get called for every trip point but we only need to do
	 * our calculations once
	 */
	if (trip != params->trip_max_desired_temperature)
		return 0;

	ret = thermal_zone_get_temp(tz, &current_temp);
	if (ret) {
		dev_warn(&tz->device, "Failed to get temperature: %d\n", ret);
		return ret;
	}

	ret = tz->ops->get_trip_temp(tz, params->trip_switch_on,
				     &switch_on_temp);
	if (ret) {
		dev_warn(&tz->device,
			 "Failed to get switch on temperature: %d\n", ret);
		return ret;
	}

	if (current_temp < switch_on_temp) {
		tz->passive = 0;
		reset_pid_controller(params);
		allow_maximum_power(tz);
		return 0;
	}

	tz->passive = 1;

	ret = tz->ops->get_trip_temp(tz, params->trip_max_desired_temperature,
				&control_temp);
	if (ret) {
		dev_warn(&tz->device,
			 "Failed to get the maximum desired temperature: %d\n",
			 ret);
		return ret;
	}

	return allocate_power(tz, current_temp, control_temp);
}

static struct thermal_governor thermal_gov_power_allocator = {
	.name		= "power_allocator",
	.bind_to_tz	= power_allocator_bind,
	.unbind_from_tz	= power_allocator_unbind,
	.throttle	= power_allocator_throttle,
};

int thermal_gov_power_allocator_register(void)
{
	return thermal_register_governor(&thermal_gov_power_allocator);
}

void thermal_gov_power_allocator_unregister(void)
{
	thermal_unregister_governor(&thermal_gov_power_allocator);
}