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 * 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
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.
92 * Return: The power budget for the next period.
94 static u32
pid_controller(struct thermal_zone_device
*tz
,
95 unsigned long current_temp
,
96 unsigned long control_temp
,
97 u32 max_allocatable_power
)
99 s64 p
, i
, d
, power_range
;
100 s32 err
, max_power_frac
;
101 struct power_allocator_params
*params
= tz
->governor_data
;
103 max_power_frac
= int_to_frac(max_allocatable_power
);
105 err
= ((s32
)control_temp
- (s32
)current_temp
);
106 err
= int_to_frac(err
);
108 /* Calculate the proportional term */
109 p
= mul_frac(err
< 0 ? tz
->tzp
->k_po
: tz
->tzp
->k_pu
, err
);
112 * Calculate the integral term
114 * if the error is less than cut off allow integration (but
115 * the integral is limited to max power)
117 i
= mul_frac(tz
->tzp
->k_i
, params
->err_integral
);
119 if (err
< int_to_frac(tz
->tzp
->integral_cutoff
)) {
120 s64 i_next
= i
+ mul_frac(tz
->tzp
->k_i
, err
);
122 if (abs64(i_next
) < max_power_frac
) {
124 params
->err_integral
+= err
;
129 * Calculate the derivative term
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)
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
;
139 power_range
= p
+ i
+ d
;
141 /* feed-forward the known sustainable dissipatable power */
142 power_range
= tz
->tzp
->sustainable_power
+ frac_to_int(power_range
);
144 power_range
= clamp(power_range
, (s64
)0, (s64
)max_allocatable_power
);
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
);
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
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
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.
178 * Granted power for each actor is written to @granted_power, which
179 * should've been allocated by the calling function.
181 static 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
)
185 u32 extra_power
, capped_extra_power
;
189 * Prevent division by 0 if none of the actors request power.
191 if (!total_req_power
)
194 capped_extra_power
= 0;
196 for (i
= 0; i
< num_actors
; i
++) {
197 u64 req_range
= req_power
[i
] * power_range
;
199 granted_power
[i
] = DIV_ROUND_CLOSEST_ULL(req_range
,
202 if (granted_power
[i
] > max_power
[i
]) {
203 extra_power
+= granted_power
[i
] - max_power
[i
];
204 granted_power
[i
] = max_power
[i
];
207 extra_actor_power
[i
] = max_power
[i
] - granted_power
[i
];
208 capped_extra_power
+= extra_actor_power
[i
];
215 * Re-divvy the reclaimed extra among actors based on
216 * how far they are from the max
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
;
225 static int allocate_power(struct thermal_zone_device
*tz
,
226 unsigned long current_temp
,
227 unsigned long control_temp
)
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
;
232 u32 total_req_power
, max_allocatable_power
;
233 u32 total_granted_power
, power_range
;
234 int i
, num_actors
, total_weight
, ret
= 0;
235 int trip_max_desired_temperature
= params
->trip_max_desired_temperature
;
237 mutex_lock(&tz
->lock
);
241 list_for_each_entry(instance
, &tz
->thermal_instances
, tz_node
) {
242 if ((instance
->trip
== trip_max_desired_temperature
) &&
243 cdev_is_power_actor(instance
->cdev
)) {
245 total_weight
+= instance
->weight
;
250 * We need to allocate three arrays of the same size:
251 * req_power, max_power and granted_power. They are going to
252 * be needed until this function returns. Allocate them all
253 * in one go to simplify the allocation and deallocation
256 BUILD_BUG_ON(sizeof(*req_power
) != sizeof(*max_power
));
257 BUILD_BUG_ON(sizeof(*req_power
) != sizeof(*granted_power
));
258 BUILD_BUG_ON(sizeof(*req_power
) != sizeof(*extra_actor_power
));
259 req_power
= devm_kcalloc(&tz
->device
, num_actors
* 4,
260 sizeof(*req_power
), GFP_KERNEL
);
266 max_power
= &req_power
[num_actors
];
267 granted_power
= &req_power
[2 * num_actors
];
268 extra_actor_power
= &req_power
[3 * num_actors
];
272 max_allocatable_power
= 0;
274 list_for_each_entry(instance
, &tz
->thermal_instances
, tz_node
) {
276 struct thermal_cooling_device
*cdev
= instance
->cdev
;
278 if (instance
->trip
!= trip_max_desired_temperature
)
281 if (!cdev_is_power_actor(cdev
))
284 if (cdev
->ops
->get_requested_power(cdev
, tz
, &req_power
[i
]))
288 weight
= 1 << FRAC_BITS
;
290 weight
= instance
->weight
;
292 req_power
[i
] = frac_to_int(weight
* req_power
[i
]);
294 if (power_actor_get_max_power(cdev
, tz
, &max_power
[i
]))
297 total_req_power
+= req_power
[i
];
298 max_allocatable_power
+= max_power
[i
];
303 power_range
= pid_controller(tz
, current_temp
, control_temp
,
304 max_allocatable_power
);
306 divvy_up_power(req_power
, max_power
, num_actors
, total_req_power
,
307 power_range
, granted_power
, extra_actor_power
);
309 total_granted_power
= 0;
311 list_for_each_entry(instance
, &tz
->thermal_instances
, tz_node
) {
312 if (instance
->trip
!= trip_max_desired_temperature
)
315 if (!cdev_is_power_actor(instance
->cdev
))
318 power_actor_set_power(instance
->cdev
, instance
,
320 total_granted_power
+= granted_power
[i
];
325 trace_thermal_power_allocator(tz
, req_power
, total_req_power
,
326 granted_power
, total_granted_power
,
327 num_actors
, power_range
,
328 max_allocatable_power
, current_temp
,
329 (s32
)control_temp
- (s32
)current_temp
);
331 devm_kfree(&tz
->device
, req_power
);
333 mutex_unlock(&tz
->lock
);
338 static int get_governor_trips(struct thermal_zone_device
*tz
,
339 struct power_allocator_params
*params
)
341 int i
, ret
, last_passive
;
342 bool found_first_passive
;
344 found_first_passive
= false;
348 for (i
= 0; i
< tz
->trips
; i
++) {
349 enum thermal_trip_type type
;
351 ret
= tz
->ops
->get_trip_type(tz
, i
, &type
);
355 if (!found_first_passive
) {
356 if (type
== THERMAL_TRIP_PASSIVE
) {
357 params
->trip_switch_on
= i
;
358 found_first_passive
= true;
360 } else if (type
== THERMAL_TRIP_PASSIVE
) {
367 if (last_passive
!= -1) {
368 params
->trip_max_desired_temperature
= last_passive
;
377 static void reset_pid_controller(struct power_allocator_params
*params
)
379 params
->err_integral
= 0;
380 params
->prev_err
= 0;
383 static void allow_maximum_power(struct thermal_zone_device
*tz
)
385 struct thermal_instance
*instance
;
386 struct power_allocator_params
*params
= tz
->governor_data
;
388 list_for_each_entry(instance
, &tz
->thermal_instances
, tz_node
) {
389 if ((instance
->trip
!= params
->trip_max_desired_temperature
) ||
390 (!cdev_is_power_actor(instance
->cdev
)))
393 instance
->target
= 0;
394 instance
->cdev
->updated
= false;
395 thermal_cdev_update(instance
->cdev
);
400 * power_allocator_bind() - bind the power_allocator governor to a thermal zone
401 * @tz: thermal zone to bind it to
403 * Check that the thermal zone is valid for this governor, that is, it
404 * has two thermal trips. If so, initialize the PID controller
405 * parameters and bind it to the thermal zone.
407 * Return: 0 on success, -EINVAL if the trips were invalid or -ENOMEM
408 * if we ran out of memory.
410 static int power_allocator_bind(struct thermal_zone_device
*tz
)
413 struct power_allocator_params
*params
;
414 unsigned long switch_on_temp
, control_temp
;
415 u32 temperature_threshold
;
417 if (!tz
->tzp
|| !tz
->tzp
->sustainable_power
) {
419 "power_allocator: missing sustainable_power\n");
423 params
= devm_kzalloc(&tz
->device
, sizeof(*params
), GFP_KERNEL
);
427 ret
= get_governor_trips(tz
, params
);
430 "thermal zone %s has wrong trip setup for power allocator\n",
435 ret
= tz
->ops
->get_trip_temp(tz
, params
->trip_switch_on
,
440 ret
= tz
->ops
->get_trip_temp(tz
, params
->trip_max_desired_temperature
,
445 temperature_threshold
= control_temp
- switch_on_temp
;
447 tz
->tzp
->k_po
= tz
->tzp
->k_po
?:
448 int_to_frac(tz
->tzp
->sustainable_power
) / temperature_threshold
;
449 tz
->tzp
->k_pu
= tz
->tzp
->k_pu
?:
450 int_to_frac(2 * tz
->tzp
->sustainable_power
) /
451 temperature_threshold
;
452 tz
->tzp
->k_i
= tz
->tzp
->k_i
?: int_to_frac(10) / 1000;
454 * The default for k_d and integral_cutoff is 0, so we can
455 * leave them as they are.
458 reset_pid_controller(params
);
460 tz
->governor_data
= params
;
465 devm_kfree(&tz
->device
, params
);
469 static void power_allocator_unbind(struct thermal_zone_device
*tz
)
471 dev_dbg(&tz
->device
, "Unbinding from thermal zone %d\n", tz
->id
);
472 devm_kfree(&tz
->device
, tz
->governor_data
);
473 tz
->governor_data
= NULL
;
476 static int power_allocator_throttle(struct thermal_zone_device
*tz
, int trip
)
479 unsigned long switch_on_temp
, control_temp
, current_temp
;
480 struct power_allocator_params
*params
= tz
->governor_data
;
483 * We get called for every trip point but we only need to do
484 * our calculations once
486 if (trip
!= params
->trip_max_desired_temperature
)
489 ret
= thermal_zone_get_temp(tz
, ¤t_temp
);
491 dev_warn(&tz
->device
, "Failed to get temperature: %d\n", ret
);
495 ret
= tz
->ops
->get_trip_temp(tz
, params
->trip_switch_on
,
498 dev_warn(&tz
->device
,
499 "Failed to get switch on temperature: %d\n", ret
);
503 if (current_temp
< switch_on_temp
) {
505 reset_pid_controller(params
);
506 allow_maximum_power(tz
);
512 ret
= tz
->ops
->get_trip_temp(tz
, params
->trip_max_desired_temperature
,
515 dev_warn(&tz
->device
,
516 "Failed to get the maximum desired temperature: %d\n",
521 return allocate_power(tz
, current_temp
, control_temp
);
524 static struct thermal_governor thermal_gov_power_allocator
= {
525 .name
= "power_allocator",
526 .bind_to_tz
= power_allocator_bind
,
527 .unbind_from_tz
= power_allocator_unbind
,
528 .throttle
= power_allocator_throttle
,
531 int thermal_gov_power_allocator_register(void)
533 return thermal_register_governor(&thermal_gov_power_allocator
);
536 void thermal_gov_power_allocator_unregister(void)
538 thermal_unregister_governor(&thermal_gov_power_allocator
);