/*
* 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 INVALID_TRIP -1
#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
* @allocated_tzp: whether we have allocated tzp for this thermal zone and
* it needs to be freed on unbind
* @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.
* If the thermal zone only has one passive trip point,
* @trip_switch_on should be INVALID_TRIP.
* @trip_max_desired_temperature: last passive trip point of the thermal
* zone. The temperature we are
* controlling for.
*/
struct power_allocator_params {
bool allocated_tzp;
s64 err_integral;
s32 prev_err;
int trip_switch_on;
int trip_max_desired_temperature;
};
/**
* estimate_sustainable_power() - Estimate the sustainable power of a thermal zone
* @tz: thermal zone we are operating in
*
* For thermal zones that don't provide a sustainable_power in their
* thermal_zone_params, estimate one. Calculate it using the minimum
* power of all the cooling devices as that gives a valid value that
* can give some degree of functionality. For optimal performance of
* this governor, provide a sustainable_power in the thermal zone's
* thermal_zone_params.
*/
static u32 estimate_sustainable_power(struct thermal_zone_device *tz)
{
u32 sustainable_power = 0;
struct thermal_instance *instance;
struct power_allocator_params *params = tz->governor_data;
list_for_each_entry(instance, &tz->thermal_instances, tz_node) {
struct thermal_cooling_device *cdev = instance->cdev;
u32 min_power;
if (instance->trip != params->trip_max_desired_temperature)
continue;
if (power_actor_get_min_power(cdev, tz, &min_power))
continue;
sustainable_power += min_power;
}
return sustainable_power;
}
/**
* estimate_pid_constants() - Estimate the constants for the PID controller
* @tz: thermal zone for which to estimate the constants
* @sustainable_power: sustainable power for the thermal zone
* @trip_switch_on: trip point number for the switch on temperature
* @control_temp: target temperature for the power allocator governor
* @force: whether to force the update of the constants
*
* This function is used to update the estimation of the PID
* controller constants in struct thermal_zone_parameters.
* Sustainable power is provided in case it was estimated. The
* estimated sustainable_power should not be stored in the
* thermal_zone_parameters so it has to be passed explicitly to this
* function.
*
* If @force is not set, the values in the thermal zone's parameters
* are preserved if they are not zero. If @force is set, the values
* in thermal zone's parameters are overwritten.
*/
static void estimate_pid_constants(struct thermal_zone_device *tz,
u32 sustainable_power, int trip_switch_on,
int control_temp, bool force)
{
int ret;
int switch_on_temp;
u32 temperature_threshold;
ret = tz->ops->get_trip_temp(tz, trip_switch_on, &switch_on_temp);
if (ret)
switch_on_temp = 0;
temperature_threshold = control_temp - switch_on_temp;
/*
* estimate_pid_constants() tries to find appropriate default
* values for thermal zones that don't provide them. If a
* system integrator has configured a thermal zone with two
* passive trip points at the same temperature, that person
* hasn't put any effort to set up the thermal zone properly
* so just give up.
*/
if (!temperature_threshold)
return;
if (!tz->tzp->k_po || force)
tz->tzp->k_po = int_to_frac(sustainable_power) /
temperature_threshold;
if (!tz->tzp->k_pu || force)
tz->tzp->k_pu = int_to_frac(2 * sustainable_power) /
temperature_threshold;
if (!tz->tzp->k_i || force)
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.
*/
}
/**
* pid_controller() - PID controller
* @tz: thermal zone we are operating in
* @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 control_temp,
u32 max_allocatable_power)
{
s64 p, i, d, power_range;
s32 err, max_power_frac;
u32 sustainable_power;
struct power_allocator_params *params = tz->governor_data;
max_power_frac = int_to_frac(max_allocatable_power);
if (tz->tzp->sustainable_power) {
sustainable_power = tz->tzp->sustainable_power;
} else {
sustainable_power = estimate_sustainable_power(tz);
estimate_pid_constants(tz, sustainable_power,
params->trip_switch_on, control_temp,
true);
}
err = control_temp - tz->temperature;
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 (abs(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 = 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 = (u64)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 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;
}
}
if (!num_actors) {
ret = -ENODEV;
goto unlock;
}
/*
* 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, 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, tz->temperature,
control_temp - tz->temperature);
kfree(req_power);
unlock:
mutex_unlock(&tz->lock);
return ret;
}
/**
* get_governor_trips() - get the number of the two trip points that are key for this governor
* @tz: thermal zone to operate on
* @params: pointer to private data for this governor
*
* The power allocator governor works optimally with two trips points:
* a "switch on" trip point and a "maximum desired temperature". These
* are defined as the first and last passive trip points.
*
* If there is only one trip point, then that's considered to be the
* "maximum desired temperature" trip point and the governor is always
* on. If there are no passive or active trip points, then the
* governor won't do anything. In fact, its throttle function
* won't be called at all.
*/
static void get_governor_trips(struct thermal_zone_device *tz,
struct power_allocator_params *params)
{
int i, last_active, last_passive;
bool found_first_passive;
found_first_passive = false;
last_active = INVALID_TRIP;
last_passive = INVALID_TRIP;
for (i = 0; i < tz->trips; i++) {
enum thermal_trip_type type;
int ret;
ret = tz->ops->get_trip_type(tz, i, &type);
if (ret) {
dev_warn(&tz->device,
"Failed to get trip point %d type: %d\n", i,
ret);
continue;
}
if (type == THERMAL_TRIP_PASSIVE) {
if (!found_first_passive) {
params->trip_switch_on = i;
found_first_passive = true;
} else {
last_passive = i;
}
} else if (type == THERMAL_TRIP_ACTIVE) {
last_active = i;
} else {
break;
}
}
if (last_passive != INVALID_TRIP) {
params->trip_max_desired_temperature = last_passive;
} else if (found_first_passive) {
params->trip_max_desired_temperature = params->trip_switch_on;
params->trip_switch_on = INVALID_TRIP;
} else {
params->trip_switch_on = INVALID_TRIP;
params->trip_max_desired_temperature = last_active;
}
}
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;
mutex_lock(&tz->lock);
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;
mutex_lock(&instance->cdev->lock);
instance->cdev->updated = false;
mutex_unlock(&instance->cdev->lock);
thermal_cdev_update(instance->cdev);
}
mutex_unlock(&tz->lock);
}
/**
* power_allocator_bind() - bind the power_allocator governor to a thermal zone
* @tz: thermal zone to bind it to
*
* Initialize the PID controller parameters and bind it to the thermal
* zone.
*
* Return: 0 on success, 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 control_temp;
params = kzalloc(sizeof(*params), GFP_KERNEL);
if (!params)
return -ENOMEM;
if (!tz->tzp) {
tz->tzp = kzalloc(sizeof(*tz->tzp), GFP_KERNEL);
if (!tz->tzp) {
ret = -ENOMEM;
goto free_params;
}
params->allocated_tzp = true;
}
if (!tz->tzp->sustainable_power)
dev_warn(&tz->device, "power_allocator: sustainable_power will be estimated\n");
get_governor_trips(tz, params);
if (tz->trips > 0) {
ret = tz->ops->get_trip_temp(tz,
params->trip_max_desired_temperature,
&control_temp);
if (!ret)
estimate_pid_constants(tz, tz->tzp->sustainable_power,
params->trip_switch_on,
control_temp, false);
}
reset_pid_controller(params);
tz->governor_data = params;
return 0;
free_params:
kfree(params);
return ret;
}
static void power_allocator_unbind(struct thermal_zone_device *tz)
{
struct power_allocator_params *params = tz->governor_data;
dev_dbg(&tz->device, "Unbinding from thermal zone %d\n", tz->id);
if (params->allocated_tzp) {
kfree(tz->tzp);
tz->tzp = NULL;
}
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;
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 = tz->ops->get_trip_temp(tz, params->trip_switch_on,
&switch_on_temp);
if (!ret && (tz->temperature < 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, 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);
}
