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"
28 #define int_to_frac(x) ((x) << FRAC_BITS)
29 #define frac_to_int(x) ((x) >> FRAC_BITS)
32 * mul_frac() - multiply two fixed-point numbers
33 * @x: first multiplicand
34 * @y: second multiplicand
36 * Return: the result of multiplying two fixed-point numbers. The
37 * result is also a fixed-point number.
39 static inline s64
mul_frac(s64 x
, s64 y
)
41 return (x
* y
) >> FRAC_BITS
;
45 * div_frac() - divide two fixed-point numbers
49 * Return: the result of dividing two fixed-point numbers. The
50 * result is also a fixed-point number.
52 static inline s64
div_frac(s64 x
, s64 y
)
54 return div_s64(x
<< FRAC_BITS
, y
);
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
68 struct power_allocator_params
{
72 int trip_max_desired_temperature
;
76 * estimate_sustainable_power() - Estimate the sustainable power of a thermal zone
77 * @tz: thermal zone we are operating in
79 * For thermal zones that don't provide a sustainable_power in their
80 * thermal_zone_params, estimate one. Calculate it using the minimum
81 * power of all the cooling devices as that gives a valid value that
82 * can give some degree of functionality. For optimal performance of
83 * this governor, provide a sustainable_power in the thermal zone's
84 * thermal_zone_params.
86 static u32
estimate_sustainable_power(struct thermal_zone_device
*tz
)
88 u32 sustainable_power
= 0;
89 struct thermal_instance
*instance
;
90 struct power_allocator_params
*params
= tz
->governor_data
;
92 list_for_each_entry(instance
, &tz
->thermal_instances
, tz_node
) {
93 struct thermal_cooling_device
*cdev
= instance
->cdev
;
96 if (instance
->trip
!= params
->trip_max_desired_temperature
)
99 if (power_actor_get_min_power(cdev
, tz
, &min_power
))
102 sustainable_power
+= min_power
;
105 return sustainable_power
;
109 * estimate_pid_constants() - Estimate the constants for the PID controller
110 * @tz: thermal zone for which to estimate the constants
111 * @sustainable_power: sustainable power for the thermal zone
112 * @trip_switch_on: trip point number for the switch on temperature
113 * @control_temp: target temperature for the power allocator governor
114 * @force: whether to force the update of the constants
116 * This function is used to update the estimation of the PID
117 * controller constants in struct thermal_zone_parameters.
118 * Sustainable power is provided in case it was estimated. The
119 * estimated sustainable_power should not be stored in the
120 * thermal_zone_parameters so it has to be passed explicitly to this
123 * If @force is not set, the values in the thermal zone's parameters
124 * are preserved if they are not zero. If @force is set, the values
125 * in thermal zone's parameters are overwritten.
127 static void estimate_pid_constants(struct thermal_zone_device
*tz
,
128 u32 sustainable_power
, int trip_switch_on
,
129 int control_temp
, bool force
)
133 u32 temperature_threshold
;
135 ret
= tz
->ops
->get_trip_temp(tz
, trip_switch_on
, &switch_on_temp
);
139 temperature_threshold
= control_temp
- switch_on_temp
;
141 if (!tz
->tzp
->k_po
|| force
)
142 tz
->tzp
->k_po
= int_to_frac(sustainable_power
) /
143 temperature_threshold
;
145 if (!tz
->tzp
->k_pu
|| force
)
146 tz
->tzp
->k_pu
= int_to_frac(2 * sustainable_power
) /
147 temperature_threshold
;
149 if (!tz
->tzp
->k_i
|| force
)
150 tz
->tzp
->k_i
= int_to_frac(10) / 1000;
152 * The default for k_d and integral_cutoff is 0, so we can
153 * leave them as they are.
158 * pid_controller() - PID controller
159 * @tz: thermal zone we are operating in
160 * @current_temp: the current temperature in millicelsius
161 * @control_temp: the target temperature in millicelsius
162 * @max_allocatable_power: maximum allocatable power for this thermal zone
164 * This PID controller increases the available power budget so that the
165 * temperature of the thermal zone gets as close as possible to
166 * @control_temp and limits the power if it exceeds it. k_po is the
167 * proportional term when we are overshooting, k_pu is the
168 * proportional term when we are undershooting. integral_cutoff is a
169 * threshold below which we stop accumulating the error. The
170 * accumulated error is only valid if the requested power will make
171 * the system warmer. If the system is mostly idle, there's no point
172 * in accumulating positive error.
174 * Return: The power budget for the next period.
176 static u32
pid_controller(struct thermal_zone_device
*tz
,
179 u32 max_allocatable_power
)
181 s64 p
, i
, d
, power_range
;
182 s32 err
, max_power_frac
;
183 u32 sustainable_power
;
184 struct power_allocator_params
*params
= tz
->governor_data
;
186 max_power_frac
= int_to_frac(max_allocatable_power
);
188 if (tz
->tzp
->sustainable_power
) {
189 sustainable_power
= tz
->tzp
->sustainable_power
;
191 sustainable_power
= estimate_sustainable_power(tz
);
192 estimate_pid_constants(tz
, sustainable_power
,
193 params
->trip_switch_on
, control_temp
,
197 err
= control_temp
- current_temp
;
198 err
= int_to_frac(err
);
200 /* Calculate the proportional term */
201 p
= mul_frac(err
< 0 ? tz
->tzp
->k_po
: tz
->tzp
->k_pu
, err
);
204 * Calculate the integral term
206 * if the error is less than cut off allow integration (but
207 * the integral is limited to max power)
209 i
= mul_frac(tz
->tzp
->k_i
, params
->err_integral
);
211 if (err
< int_to_frac(tz
->tzp
->integral_cutoff
)) {
212 s64 i_next
= i
+ mul_frac(tz
->tzp
->k_i
, err
);
214 if (abs64(i_next
) < max_power_frac
) {
216 params
->err_integral
+= err
;
221 * Calculate the derivative term
223 * We do err - prev_err, so with a positive k_d, a decreasing
224 * error (i.e. driving closer to the line) results in less
225 * power being applied, slowing down the controller)
227 d
= mul_frac(tz
->tzp
->k_d
, err
- params
->prev_err
);
228 d
= div_frac(d
, tz
->passive_delay
);
229 params
->prev_err
= err
;
231 power_range
= p
+ i
+ d
;
233 /* feed-forward the known sustainable dissipatable power */
234 power_range
= sustainable_power
+ frac_to_int(power_range
);
236 power_range
= clamp(power_range
, (s64
)0, (s64
)max_allocatable_power
);
238 trace_thermal_power_allocator_pid(tz
, frac_to_int(err
),
239 frac_to_int(params
->err_integral
),
240 frac_to_int(p
), frac_to_int(i
),
241 frac_to_int(d
), power_range
);
247 * divvy_up_power() - divvy the allocated power between the actors
248 * @req_power: each actor's requested power
249 * @max_power: each actor's maximum available power
250 * @num_actors: size of the @req_power, @max_power and @granted_power's array
251 * @total_req_power: sum of @req_power
252 * @power_range: total allocated power
253 * @granted_power: output array: each actor's granted power
254 * @extra_actor_power: an appropriately sized array to be used in the
255 * function as temporary storage of the extra power given
258 * This function divides the total allocated power (@power_range)
259 * fairly between the actors. It first tries to give each actor a
260 * share of the @power_range according to how much power it requested
261 * compared to the rest of the actors. For example, if only one actor
262 * requests power, then it receives all the @power_range. If
263 * three actors each requests 1mW, each receives a third of the
266 * If any actor received more than their maximum power, then that
267 * surplus is re-divvied among the actors based on how far they are
268 * from their respective maximums.
270 * Granted power for each actor is written to @granted_power, which
271 * should've been allocated by the calling function.
273 static void divvy_up_power(u32
*req_power
, u32
*max_power
, int num_actors
,
274 u32 total_req_power
, u32 power_range
,
275 u32
*granted_power
, u32
*extra_actor_power
)
277 u32 extra_power
, capped_extra_power
;
281 * Prevent division by 0 if none of the actors request power.
283 if (!total_req_power
)
286 capped_extra_power
= 0;
288 for (i
= 0; i
< num_actors
; i
++) {
289 u64 req_range
= req_power
[i
] * power_range
;
291 granted_power
[i
] = DIV_ROUND_CLOSEST_ULL(req_range
,
294 if (granted_power
[i
] > max_power
[i
]) {
295 extra_power
+= granted_power
[i
] - max_power
[i
];
296 granted_power
[i
] = max_power
[i
];
299 extra_actor_power
[i
] = max_power
[i
] - granted_power
[i
];
300 capped_extra_power
+= extra_actor_power
[i
];
307 * Re-divvy the reclaimed extra among actors based on
308 * how far they are from the max
310 extra_power
= min(extra_power
, capped_extra_power
);
311 if (capped_extra_power
> 0)
312 for (i
= 0; i
< num_actors
; i
++)
313 granted_power
[i
] += (extra_actor_power
[i
] *
314 extra_power
) / capped_extra_power
;
317 static int allocate_power(struct thermal_zone_device
*tz
,
321 struct thermal_instance
*instance
;
322 struct power_allocator_params
*params
= tz
->governor_data
;
323 u32
*req_power
, *max_power
, *granted_power
, *extra_actor_power
;
324 u32
*weighted_req_power
;
325 u32 total_req_power
, max_allocatable_power
, total_weighted_req_power
;
326 u32 total_granted_power
, power_range
;
327 int i
, num_actors
, total_weight
, ret
= 0;
328 int trip_max_desired_temperature
= params
->trip_max_desired_temperature
;
330 mutex_lock(&tz
->lock
);
334 list_for_each_entry(instance
, &tz
->thermal_instances
, tz_node
) {
335 if ((instance
->trip
== trip_max_desired_temperature
) &&
336 cdev_is_power_actor(instance
->cdev
)) {
338 total_weight
+= instance
->weight
;
343 * We need to allocate five arrays of the same size:
344 * req_power, max_power, granted_power, extra_actor_power and
345 * weighted_req_power. They are going to be needed until this
346 * function returns. Allocate them all in one go to simplify
347 * the allocation and deallocation logic.
349 BUILD_BUG_ON(sizeof(*req_power
) != sizeof(*max_power
));
350 BUILD_BUG_ON(sizeof(*req_power
) != sizeof(*granted_power
));
351 BUILD_BUG_ON(sizeof(*req_power
) != sizeof(*extra_actor_power
));
352 BUILD_BUG_ON(sizeof(*req_power
) != sizeof(*weighted_req_power
));
353 req_power
= kcalloc(num_actors
* 5, sizeof(*req_power
), GFP_KERNEL
);
359 max_power
= &req_power
[num_actors
];
360 granted_power
= &req_power
[2 * num_actors
];
361 extra_actor_power
= &req_power
[3 * num_actors
];
362 weighted_req_power
= &req_power
[4 * num_actors
];
365 total_weighted_req_power
= 0;
367 max_allocatable_power
= 0;
369 list_for_each_entry(instance
, &tz
->thermal_instances
, tz_node
) {
371 struct thermal_cooling_device
*cdev
= instance
->cdev
;
373 if (instance
->trip
!= trip_max_desired_temperature
)
376 if (!cdev_is_power_actor(cdev
))
379 if (cdev
->ops
->get_requested_power(cdev
, tz
, &req_power
[i
]))
383 weight
= 1 << FRAC_BITS
;
385 weight
= instance
->weight
;
387 weighted_req_power
[i
] = frac_to_int(weight
* req_power
[i
]);
389 if (power_actor_get_max_power(cdev
, tz
, &max_power
[i
]))
392 total_req_power
+= req_power
[i
];
393 max_allocatable_power
+= max_power
[i
];
394 total_weighted_req_power
+= weighted_req_power
[i
];
399 power_range
= pid_controller(tz
, current_temp
, control_temp
,
400 max_allocatable_power
);
402 divvy_up_power(weighted_req_power
, max_power
, num_actors
,
403 total_weighted_req_power
, power_range
, granted_power
,
406 total_granted_power
= 0;
408 list_for_each_entry(instance
, &tz
->thermal_instances
, tz_node
) {
409 if (instance
->trip
!= trip_max_desired_temperature
)
412 if (!cdev_is_power_actor(instance
->cdev
))
415 power_actor_set_power(instance
->cdev
, instance
,
417 total_granted_power
+= granted_power
[i
];
422 trace_thermal_power_allocator(tz
, req_power
, total_req_power
,
423 granted_power
, total_granted_power
,
424 num_actors
, power_range
,
425 max_allocatable_power
, current_temp
,
426 control_temp
- current_temp
);
430 mutex_unlock(&tz
->lock
);
435 static int get_governor_trips(struct thermal_zone_device
*tz
,
436 struct power_allocator_params
*params
)
438 int i
, ret
, last_passive
;
439 bool found_first_passive
;
441 found_first_passive
= false;
445 for (i
= 0; i
< tz
->trips
; i
++) {
446 enum thermal_trip_type type
;
448 ret
= tz
->ops
->get_trip_type(tz
, i
, &type
);
452 if (!found_first_passive
) {
453 if (type
== THERMAL_TRIP_PASSIVE
) {
454 params
->trip_switch_on
= i
;
455 found_first_passive
= true;
457 } else if (type
== THERMAL_TRIP_PASSIVE
) {
464 if (last_passive
!= -1) {
465 params
->trip_max_desired_temperature
= last_passive
;
474 static void reset_pid_controller(struct power_allocator_params
*params
)
476 params
->err_integral
= 0;
477 params
->prev_err
= 0;
480 static void allow_maximum_power(struct thermal_zone_device
*tz
)
482 struct thermal_instance
*instance
;
483 struct power_allocator_params
*params
= tz
->governor_data
;
485 list_for_each_entry(instance
, &tz
->thermal_instances
, tz_node
) {
486 if ((instance
->trip
!= params
->trip_max_desired_temperature
) ||
487 (!cdev_is_power_actor(instance
->cdev
)))
490 instance
->target
= 0;
491 instance
->cdev
->updated
= false;
492 thermal_cdev_update(instance
->cdev
);
497 * power_allocator_bind() - bind the power_allocator governor to a thermal zone
498 * @tz: thermal zone to bind it to
500 * Check that the thermal zone is valid for this governor, that is, it
501 * has two thermal trips. If so, initialize the PID controller
502 * parameters and bind it to the thermal zone.
504 * Return: 0 on success, -EINVAL if the trips were invalid or -ENOMEM
505 * if we ran out of memory.
507 static int power_allocator_bind(struct thermal_zone_device
*tz
)
510 struct power_allocator_params
*params
;
516 params
= kzalloc(sizeof(*params
), GFP_KERNEL
);
520 if (!tz
->tzp
->sustainable_power
)
521 dev_warn(&tz
->device
, "power_allocator: sustainable_power will be estimated\n");
523 ret
= get_governor_trips(tz
, params
);
526 "thermal zone %s has wrong trip setup for power allocator\n",
531 ret
= tz
->ops
->get_trip_temp(tz
, params
->trip_max_desired_temperature
,
536 estimate_pid_constants(tz
, tz
->tzp
->sustainable_power
,
537 params
->trip_switch_on
, control_temp
, false);
538 reset_pid_controller(params
);
540 tz
->governor_data
= params
;
549 static void power_allocator_unbind(struct thermal_zone_device
*tz
)
551 dev_dbg(&tz
->device
, "Unbinding from thermal zone %d\n", tz
->id
);
552 kfree(tz
->governor_data
);
553 tz
->governor_data
= NULL
;
556 static int power_allocator_throttle(struct thermal_zone_device
*tz
, int trip
)
559 int switch_on_temp
, control_temp
, current_temp
;
560 struct power_allocator_params
*params
= tz
->governor_data
;
563 * We get called for every trip point but we only need to do
564 * our calculations once
566 if (trip
!= params
->trip_max_desired_temperature
)
569 ret
= thermal_zone_get_temp(tz
, ¤t_temp
);
571 dev_warn(&tz
->device
, "Failed to get temperature: %d\n", ret
);
575 ret
= tz
->ops
->get_trip_temp(tz
, params
->trip_switch_on
,
578 dev_warn(&tz
->device
,
579 "Failed to get switch on temperature: %d\n", ret
);
583 if (current_temp
< switch_on_temp
) {
585 reset_pid_controller(params
);
586 allow_maximum_power(tz
);
592 ret
= tz
->ops
->get_trip_temp(tz
, params
->trip_max_desired_temperature
,
595 dev_warn(&tz
->device
,
596 "Failed to get the maximum desired temperature: %d\n",
601 return allocate_power(tz
, current_temp
, control_temp
);
604 static struct thermal_governor thermal_gov_power_allocator
= {
605 .name
= "power_allocator",
606 .bind_to_tz
= power_allocator_bind
,
607 .unbind_from_tz
= power_allocator_unbind
,
608 .throttle
= power_allocator_throttle
,
611 int thermal_gov_power_allocator_register(void)
613 return thermal_register_governor(&thermal_gov_power_allocator
);
616 void thermal_gov_power_allocator_unregister(void)
618 thermal_unregister_governor(&thermal_gov_power_allocator
);