diff options
Diffstat (limited to 'drivers/thermal/power_allocator.c')
| -rw-r--r-- | drivers/thermal/power_allocator.c | 520 |
1 files changed, 520 insertions, 0 deletions
diff --git a/drivers/thermal/power_allocator.c b/drivers/thermal/power_allocator.c new file mode 100644 index 000000000000..67982d79b76c --- /dev/null +++ b/drivers/thermal/power_allocator.c @@ -0,0 +1,520 @@ +/* + * 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> + +#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, + unsigned long current_temp, + unsigned long 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 = ((s32)control_temp - (s32)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); + + return clamp(power_range, (s64)0, (s64)max_allocatable_power); +} + +/** + * 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_u64(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, + unsigned long current_temp, + unsigned long 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 total_req_power, max_allocatable_power; + u32 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 three arrays of the same size: + * req_power, max_power and granted_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)); + req_power = devm_kcalloc(&tz->device, num_actors * 4, + 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]; + + i = 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; + + 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]; + + i++; + } + + power_range = pid_controller(tz, current_temp, control_temp, + max_allocatable_power); + + divvy_up_power(req_power, max_power, num_actors, total_req_power, + power_range, granted_power, extra_actor_power); + + 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]); + + i++; + } + + devm_kfree(&tz->device, 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; + unsigned long 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 = devm_kzalloc(&tz->device, 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: + devm_kfree(&tz->device, 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); + devm_kfree(&tz->device, tz->governor_data); + tz->governor_data = NULL; +} + +static int power_allocator_throttle(struct thermal_zone_device *tz, int trip) +{ + int ret; + unsigned long 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, ¤t_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); +} |
