2 * A power allocator to manage temperature
4 * Copyright (C) 2014 ARM Ltd.
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.
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.
16 #define pr_fmt(fmt) "Power allocator: " fmt
18 #include <linux/rculist.h>
19 #include <linux/slab.h>
20 #include <linux/thermal.h>
22 #define CREATE_TRACE_POINTS
23 #include <trace/events/thermal_power_allocator.h>
25 #include "thermal_core.h"
27 #define INVALID_TRIP -1
30 #define int_to_frac(x) ((x) << FRAC_BITS)
31 #define frac_to_int(x) ((x) >> FRAC_BITS)
34 * mul_frac() - multiply two fixed-point numbers
35 * @x: first multiplicand
36 * @y: second multiplicand
38 * Return: the result of multiplying two fixed-point numbers. The
39 * result is also a fixed-point number.
41 static inline s64
mul_frac(s64 x
, s64 y
)
43 return (x
* y
) >> FRAC_BITS
;
47 * div_frac() - divide two fixed-point numbers
51 * Return: the result of dividing two fixed-point numbers. The
52 * result is also a fixed-point number.
54 static inline s64
div_frac(s64 x
, s64 y
)
56 return div_s64(x
<< FRAC_BITS
, y
);
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
74 struct power_allocator_params
{
79 int trip_max_desired_temperature
;
83 * estimate_sustainable_power() - Estimate the sustainable power of a thermal zone
84 * @tz: thermal zone we are operating in
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.
93 static u32
estimate_sustainable_power(struct thermal_zone_device
*tz
)
95 u32 sustainable_power
= 0;
96 struct thermal_instance
*instance
;
97 struct power_allocator_params
*params
= tz
->governor_data
;
99 list_for_each_entry(instance
, &tz
->thermal_instances
, tz_node
) {
100 struct thermal_cooling_device
*cdev
= instance
->cdev
;
103 if (instance
->trip
!= params
->trip_max_desired_temperature
)
106 if (power_actor_get_min_power(cdev
, tz
, &min_power
))
109 sustainable_power
+= min_power
;
112 return sustainable_power
;
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
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
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.
134 static void estimate_pid_constants(struct thermal_zone_device
*tz
,
135 u32 sustainable_power
, int trip_switch_on
,
136 int control_temp
, bool force
)
140 u32 temperature_threshold
;
142 ret
= tz
->ops
->get_trip_temp(tz
, trip_switch_on
, &switch_on_temp
);
146 temperature_threshold
= control_temp
- switch_on_temp
;
148 if (!tz
->tzp
->k_po
|| force
)
149 tz
->tzp
->k_po
= int_to_frac(sustainable_power
) /
150 temperature_threshold
;
152 if (!tz
->tzp
->k_pu
|| force
)
153 tz
->tzp
->k_pu
= int_to_frac(2 * sustainable_power
) /
154 temperature_threshold
;
156 if (!tz
->tzp
->k_i
|| force
)
157 tz
->tzp
->k_i
= int_to_frac(10) / 1000;
159 * The default for k_d and integral_cutoff is 0, so we can
160 * leave them as they are.
165 * pid_controller() - PID controller
166 * @tz: thermal zone we are operating in
167 * @current_temp: the current temperature in millicelsius
168 * @control_temp: the target temperature in millicelsius
169 * @max_allocatable_power: maximum allocatable power for this thermal zone
171 * This PID controller increases the available power budget so that the
172 * temperature of the thermal zone gets as close as possible to
173 * @control_temp and limits the power if it exceeds it. k_po is the
174 * proportional term when we are overshooting, k_pu is the
175 * proportional term when we are undershooting. integral_cutoff is a
176 * threshold below which we stop accumulating the error. The
177 * accumulated error is only valid if the requested power will make
178 * the system warmer. If the system is mostly idle, there's no point
179 * in accumulating positive error.
181 * Return: The power budget for the next period.
183 static u32
pid_controller(struct thermal_zone_device
*tz
,
186 u32 max_allocatable_power
)
188 s64 p
, i
, d
, power_range
;
189 s32 err
, max_power_frac
;
190 u32 sustainable_power
;
191 struct power_allocator_params
*params
= tz
->governor_data
;
193 max_power_frac
= int_to_frac(max_allocatable_power
);
195 if (tz
->tzp
->sustainable_power
) {
196 sustainable_power
= tz
->tzp
->sustainable_power
;
198 sustainable_power
= estimate_sustainable_power(tz
);
199 estimate_pid_constants(tz
, sustainable_power
,
200 params
->trip_switch_on
, control_temp
,
204 err
= control_temp
- current_temp
;
205 err
= int_to_frac(err
);
207 /* Calculate the proportional term */
208 p
= mul_frac(err
< 0 ? tz
->tzp
->k_po
: tz
->tzp
->k_pu
, err
);
211 * Calculate the integral term
213 * if the error is less than cut off allow integration (but
214 * the integral is limited to max power)
216 i
= mul_frac(tz
->tzp
->k_i
, params
->err_integral
);
218 if (err
< int_to_frac(tz
->tzp
->integral_cutoff
)) {
219 s64 i_next
= i
+ mul_frac(tz
->tzp
->k_i
, err
);
221 if (abs64(i_next
) < max_power_frac
) {
223 params
->err_integral
+= err
;
228 * Calculate the derivative term
230 * We do err - prev_err, so with a positive k_d, a decreasing
231 * error (i.e. driving closer to the line) results in less
232 * power being applied, slowing down the controller)
234 d
= mul_frac(tz
->tzp
->k_d
, err
- params
->prev_err
);
235 d
= div_frac(d
, tz
->passive_delay
);
236 params
->prev_err
= err
;
238 power_range
= p
+ i
+ d
;
240 /* feed-forward the known sustainable dissipatable power */
241 power_range
= sustainable_power
+ frac_to_int(power_range
);
243 power_range
= clamp(power_range
, (s64
)0, (s64
)max_allocatable_power
);
245 trace_thermal_power_allocator_pid(tz
, frac_to_int(err
),
246 frac_to_int(params
->err_integral
),
247 frac_to_int(p
), frac_to_int(i
),
248 frac_to_int(d
), power_range
);
254 * divvy_up_power() - divvy the allocated power between the actors
255 * @req_power: each actor's requested power
256 * @max_power: each actor's maximum available power
257 * @num_actors: size of the @req_power, @max_power and @granted_power's array
258 * @total_req_power: sum of @req_power
259 * @power_range: total allocated power
260 * @granted_power: output array: each actor's granted power
261 * @extra_actor_power: an appropriately sized array to be used in the
262 * function as temporary storage of the extra power given
265 * This function divides the total allocated power (@power_range)
266 * fairly between the actors. It first tries to give each actor a
267 * share of the @power_range according to how much power it requested
268 * compared to the rest of the actors. For example, if only one actor
269 * requests power, then it receives all the @power_range. If
270 * three actors each requests 1mW, each receives a third of the
273 * If any actor received more than their maximum power, then that
274 * surplus is re-divvied among the actors based on how far they are
275 * from their respective maximums.
277 * Granted power for each actor is written to @granted_power, which
278 * should've been allocated by the calling function.
280 static void divvy_up_power(u32
*req_power
, u32
*max_power
, int num_actors
,
281 u32 total_req_power
, u32 power_range
,
282 u32
*granted_power
, u32
*extra_actor_power
)
284 u32 extra_power
, capped_extra_power
;
288 * Prevent division by 0 if none of the actors request power.
290 if (!total_req_power
)
293 capped_extra_power
= 0;
295 for (i
= 0; i
< num_actors
; i
++) {
296 u64 req_range
= req_power
[i
] * power_range
;
298 granted_power
[i
] = DIV_ROUND_CLOSEST_ULL(req_range
,
301 if (granted_power
[i
] > max_power
[i
]) {
302 extra_power
+= granted_power
[i
] - max_power
[i
];
303 granted_power
[i
] = max_power
[i
];
306 extra_actor_power
[i
] = max_power
[i
] - granted_power
[i
];
307 capped_extra_power
+= extra_actor_power
[i
];
314 * Re-divvy the reclaimed extra among actors based on
315 * how far they are from the max
317 extra_power
= min(extra_power
, capped_extra_power
);
318 if (capped_extra_power
> 0)
319 for (i
= 0; i
< num_actors
; i
++)
320 granted_power
[i
] += (extra_actor_power
[i
] *
321 extra_power
) / capped_extra_power
;
324 static int allocate_power(struct thermal_zone_device
*tz
,
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
;
337 mutex_lock(&tz
->lock
);
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
)) {
345 total_weight
+= instance
->weight
;
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.
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
);
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
];
377 total_weighted_req_power
= 0;
379 max_allocatable_power
= 0;
381 list_for_each_entry(instance
, &tz
->thermal_instances
, tz_node
) {
383 struct thermal_cooling_device
*cdev
= instance
->cdev
;
385 if (instance
->trip
!= trip_max_desired_temperature
)
388 if (!cdev_is_power_actor(cdev
))
391 if (cdev
->ops
->get_requested_power(cdev
, tz
, &req_power
[i
]))
395 weight
= 1 << FRAC_BITS
;
397 weight
= instance
->weight
;
399 weighted_req_power
[i
] = frac_to_int(weight
* req_power
[i
]);
401 if (power_actor_get_max_power(cdev
, tz
, &max_power
[i
]))
404 total_req_power
+= req_power
[i
];
405 max_allocatable_power
+= max_power
[i
];
406 total_weighted_req_power
+= weighted_req_power
[i
];
411 power_range
= pid_controller(tz
, current_temp
, control_temp
,
412 max_allocatable_power
);
414 divvy_up_power(weighted_req_power
, max_power
, num_actors
,
415 total_weighted_req_power
, power_range
, granted_power
,
418 total_granted_power
= 0;
420 list_for_each_entry(instance
, &tz
->thermal_instances
, tz_node
) {
421 if (instance
->trip
!= trip_max_desired_temperature
)
424 if (!cdev_is_power_actor(instance
->cdev
))
427 power_actor_set_power(instance
->cdev
, instance
,
429 total_granted_power
+= granted_power
[i
];
434 trace_thermal_power_allocator(tz
, req_power
, total_req_power
,
435 granted_power
, total_granted_power
,
436 num_actors
, power_range
,
437 max_allocatable_power
, current_temp
,
438 control_temp
- current_temp
);
442 mutex_unlock(&tz
->lock
);
448 * get_governor_trips() - get the number of the two trip points that are key for this governor
449 * @tz: thermal zone to operate on
450 * @params: pointer to private data for this governor
452 * The power allocator governor works optimally with two trips points:
453 * a "switch on" trip point and a "maximum desired temperature". These
454 * are defined as the first and last passive trip points.
456 * If there is only one trip point, then that's considered to be the
457 * "maximum desired temperature" trip point and the governor is always
458 * on. If there are no passive or active trip points, then the
459 * governor won't do anything. In fact, its throttle function
460 * won't be called at all.
462 static void get_governor_trips(struct thermal_zone_device
*tz
,
463 struct power_allocator_params
*params
)
465 int i
, last_active
, last_passive
;
466 bool found_first_passive
;
468 found_first_passive
= false;
469 last_active
= INVALID_TRIP
;
470 last_passive
= INVALID_TRIP
;
472 for (i
= 0; i
< tz
->trips
; i
++) {
473 enum thermal_trip_type type
;
476 ret
= tz
->ops
->get_trip_type(tz
, i
, &type
);
478 dev_warn(&tz
->device
,
479 "Failed to get trip point %d type: %d\n", i
,
484 if (type
== THERMAL_TRIP_PASSIVE
) {
485 if (!found_first_passive
) {
486 params
->trip_switch_on
= i
;
487 found_first_passive
= true;
491 } else if (type
== THERMAL_TRIP_ACTIVE
) {
498 if (last_passive
!= INVALID_TRIP
) {
499 params
->trip_max_desired_temperature
= last_passive
;
500 } else if (found_first_passive
) {
501 params
->trip_max_desired_temperature
= params
->trip_switch_on
;
502 params
->trip_switch_on
= INVALID_TRIP
;
504 params
->trip_switch_on
= INVALID_TRIP
;
505 params
->trip_max_desired_temperature
= last_active
;
509 static void reset_pid_controller(struct power_allocator_params
*params
)
511 params
->err_integral
= 0;
512 params
->prev_err
= 0;
515 static void allow_maximum_power(struct thermal_zone_device
*tz
)
517 struct thermal_instance
*instance
;
518 struct power_allocator_params
*params
= tz
->governor_data
;
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
)))
525 instance
->target
= 0;
526 instance
->cdev
->updated
= false;
527 thermal_cdev_update(instance
->cdev
);
532 * power_allocator_bind() - bind the power_allocator governor to a thermal zone
533 * @tz: thermal zone to bind it to
535 * Initialize the PID controller parameters and bind it to the thermal
538 * Return: 0 on success, or -ENOMEM if we ran out of memory.
540 static int power_allocator_bind(struct thermal_zone_device
*tz
)
543 struct power_allocator_params
*params
;
546 params
= kzalloc(sizeof(*params
), GFP_KERNEL
);
551 tz
->tzp
= kzalloc(sizeof(*tz
->tzp
), GFP_KERNEL
);
557 params
->allocated_tzp
= true;
560 if (!tz
->tzp
->sustainable_power
)
561 dev_warn(&tz
->device
, "power_allocator: sustainable_power will be estimated\n");
563 get_governor_trips(tz
, params
);
566 ret
= tz
->ops
->get_trip_temp(tz
,
567 params
->trip_max_desired_temperature
,
570 estimate_pid_constants(tz
, tz
->tzp
->sustainable_power
,
571 params
->trip_switch_on
,
572 control_temp
, false);
575 reset_pid_controller(params
);
577 tz
->governor_data
= params
;
587 static void power_allocator_unbind(struct thermal_zone_device
*tz
)
589 struct power_allocator_params
*params
= tz
->governor_data
;
591 dev_dbg(&tz
->device
, "Unbinding from thermal zone %d\n", tz
->id
);
593 if (params
->allocated_tzp
) {
598 kfree(tz
->governor_data
);
599 tz
->governor_data
= NULL
;
602 static int power_allocator_throttle(struct thermal_zone_device
*tz
, int trip
)
605 int switch_on_temp
, control_temp
, current_temp
;
606 struct power_allocator_params
*params
= tz
->governor_data
;
609 * We get called for every trip point but we only need to do
610 * our calculations once
612 if (trip
!= params
->trip_max_desired_temperature
)
615 ret
= thermal_zone_get_temp(tz
, ¤t_temp
);
617 dev_warn(&tz
->device
, "Failed to get temperature: %d\n", ret
);
621 ret
= tz
->ops
->get_trip_temp(tz
, params
->trip_switch_on
,
623 if (!ret
&& (current_temp
< switch_on_temp
)) {
625 reset_pid_controller(params
);
626 allow_maximum_power(tz
);
632 ret
= tz
->ops
->get_trip_temp(tz
, params
->trip_max_desired_temperature
,
635 dev_warn(&tz
->device
,
636 "Failed to get the maximum desired temperature: %d\n",
641 return allocate_power(tz
, current_temp
, control_temp
);
644 static struct thermal_governor thermal_gov_power_allocator
= {
645 .name
= "power_allocator",
646 .bind_to_tz
= power_allocator_bind
,
647 .unbind_from_tz
= power_allocator_unbind
,
648 .throttle
= power_allocator_throttle
,
651 int thermal_gov_power_allocator_register(void)
653 return thermal_register_governor(&thermal_gov_power_allocator
);
656 void thermal_gov_power_allocator_unregister(void)
658 thermal_unregister_governor(&thermal_gov_power_allocator
);