// SPDX-License-Identifier: GPL-2.0
/*
 * A power allocator to manage temperature
 *
 * Copyright (C) 2014 ARM Ltd.
 *
 */

#define pr_fmt(fmt) "Power allocator: " fmt

#include <linux/slab.h>
#include <linux/thermal.h>

#define CREATE_TRACE_POINTS
#include "thermal_trace_ipa.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_actor - internal power information for power actor
 * @req_power:          requested power value (not weighted)
 * @max_power:          max allocatable power for this actor
 * @granted_power:      granted power for this actor
 * @extra_actor_power:  extra power that this actor can receive
 * @weighted_req_power: weighted requested power as input to IPA
 */
struct power_actor {
        u32 req_power;
        u32 max_power;
        u32 granted_power;
        u32 extra_actor_power;
        u32 weighted_req_power;
};

/**
 * 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
 * @update_cdevs:       whether or not update cdevs on the next run
 * @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.
 * @sustainable_power:  Sustainable power (heat) that this thermal zone can
 *                      dissipate
 * @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 NULL.
 * @trip_max:           last passive trip point of the thermal zone. The
 *                      temperature we are controlling for.
 * @total_weight:       Sum of all thermal instances weights
 * @num_actors:         number of cooling devices supporting IPA callbacks
 * @buffer_size:        internal buffer size, to avoid runtime re-calculation
 * @power:              buffer for all power actors internal power information
 */
struct power_allocator_params {
        bool allocated_tzp;
        bool update_cdevs;
        s64 err_integral;
        s32 prev_err;
        u32 sustainable_power;
        const struct thermal_trip *trip_switch_on;
        const struct thermal_trip *trip_max;
        int total_weight;
        unsigned int num_actors;
        unsigned int buffer_size;
        struct power_actor *power;
};

static bool power_actor_is_valid(struct thermal_instance *instance)
{
        return cdev_is_power_actor(instance->cdev);
}

/**
 * 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)
{
        struct power_allocator_params *params = tz->governor_data;
        const struct thermal_trip_desc *td = trip_to_trip_desc(params->trip_max);
        struct thermal_cooling_device *cdev;
        struct thermal_instance *instance;
        u32 sustainable_power = 0;
        u32 min_power;

        list_for_each_entry(instance, &td->thermal_instances, trip_node) {
                if (!power_actor_is_valid(instance))
                        continue;

                cdev = instance->cdev;
                if (cdev->ops->state2power(cdev, instance->upper, &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 for the switch on temperature
 * @control_temp:       target temperature for the power allocator governor
 *
 * This function is used to update the estimation of the PID
 * controller constants in struct thermal_zone_parameters.
 */
static void estimate_pid_constants(struct thermal_zone_device *tz,
                                   u32 sustainable_power,
                                   const struct thermal_trip *trip_switch_on,
                                   int control_temp)
{
        u32 temperature_threshold = control_temp;
        s32 k_i;

        if (trip_switch_on)
                temperature_threshold -= trip_switch_on->temperature;

        /*
         * 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;

        tz->tzp->k_po = int_to_frac(sustainable_power) /
                temperature_threshold;

        tz->tzp->k_pu = int_to_frac(2 * sustainable_power) /
                temperature_threshold;

        k_i = tz->tzp->k_pu / 10;
        tz->tzp->k_i = k_i > 0 ? k_i : 1;

        /*
         * The default for k_d and integral_cutoff is 0, so we can
         * leave them as they are.
         */
}

/**
 * get_sustainable_power() - Get the right sustainable power
 * @tz:         thermal zone for which to estimate the constants
 * @params:     parameters for the power allocator governor
 * @control_temp:       target temperature for the power allocator governor
 *
 * This function is used for getting the proper sustainable power value based
 * on variables which might be updated by the user sysfs interface. If that
 * happen the new value is going to be estimated and updated. It is also used
 * after thermal zone binding, where the initial values where set to 0.
 */
static u32 get_sustainable_power(struct thermal_zone_device *tz,
                                 struct power_allocator_params *params,
                                 int control_temp)
{
        u32 sustainable_power;

        if (!tz->tzp->sustainable_power)
                sustainable_power = estimate_sustainable_power(tz);
        else
                sustainable_power = tz->tzp->sustainable_power;

        /* Check if it's init value 0 or there was update via sysfs */
        if (sustainable_power != params->sustainable_power) {
                estimate_pid_constants(tz, sustainable_power,
                                       params->trip_switch_on, control_temp);

                /* Do the estimation only once and make available in sysfs */
                tz->tzp->sustainable_power = sustainable_power;
                params->sustainable_power = sustainable_power;
        }

        return sustainable_power;
}

/**
 * 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)
{
        struct power_allocator_params *params = tz->governor_data;
        s64 p, i, d, power_range;
        s32 err, max_power_frac;
        u32 sustainable_power;

        max_power_frac = int_to_frac(max_allocatable_power);

        sustainable_power = get_sustainable_power(tz, params, control_temp);

        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, jiffies_to_msecs(tz->passive_delay_jiffies));
        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;
}

/**
 * power_actor_set_power() - limit the maximum power a cooling device consumes
 * @cdev:       pointer to &thermal_cooling_device
 * @instance:   thermal instance to update
 * @power:      the power in milliwatts
 *
 * Set the cooling device to consume at most @power milliwatts. The limit is
 * expected to be a cap at the maximum power consumption.
 *
 * Return: 0 on success, -EINVAL if the cooling device does not
 * implement the power actor API or -E* for other failures.
 */
static int
power_actor_set_power(struct thermal_cooling_device *cdev,
                      struct thermal_instance *instance, u32 power)
{
        unsigned long state;
        int ret;

        ret = cdev->ops->power2state(cdev, power, &state);
        if (ret)
                return ret;

        instance->target = clamp_val(state, instance->lower, instance->upper);

        thermal_cdev_update_nocheck(cdev);

        return 0;
}

/**
 * divvy_up_power() - divvy the allocated power between the actors
 * @power:              buffer for all power actors internal power information
 * @num_actors:         number of power actors in this thermal zone
 * @total_req_power:    sum of all weighted requested power for all actors
 * @power_range:        total allocated power
 *
 * 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.
 */
static void divvy_up_power(struct power_actor *power, int num_actors,
                           u32 total_req_power, u32 power_range)
{
        u32 capped_extra_power = 0;
        u32 extra_power = 0;
        int i;

        if (!total_req_power) {
                /*
                 * Nobody requested anything, just give everybody
                 * the maximum power
                 */
                for (i = 0; i < num_actors; i++) {
                        struct power_actor *pa = &power[i];

                        pa->granted_power = pa->max_power;
                }

                return;
        }

        for (i = 0; i < num_actors; i++) {
                struct power_actor *pa = &power[i];
                u64 req_range = (u64)pa->weighted_req_power * power_range;

                pa->granted_power = DIV_ROUND_CLOSEST_ULL(req_range,
                                                          total_req_power);

                if (pa->granted_power > pa->max_power) {
                        extra_power += pa->granted_power - pa->max_power;
                        pa->granted_power = pa->max_power;
                }

                pa->extra_actor_power = pa->max_power - pa->granted_power;
                capped_extra_power += pa->extra_actor_power;
        }

        if (!extra_power || !capped_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);

        for (i = 0; i < num_actors; i++) {
                struct power_actor *pa = &power[i];
                u64 extra_range = pa->extra_actor_power;

                extra_range *= extra_power;
                pa->granted_power += DIV_ROUND_CLOSEST_ULL(extra_range,
                                                capped_extra_power);
        }
}

static void allocate_power(struct thermal_zone_device *tz, int control_temp)
{
        struct power_allocator_params *params = tz->governor_data;
        const struct thermal_trip_desc *td = trip_to_trip_desc(params->trip_max);
        unsigned int num_actors = params->num_actors;
        struct power_actor *power = params->power;
        struct thermal_cooling_device *cdev;
        struct thermal_instance *instance;
        u32 total_weighted_req_power = 0;
        u32 max_allocatable_power = 0;
        u32 total_granted_power = 0;
        u32 total_req_power = 0;
        u32 power_range, weight;
        int i = 0, ret;

        if (!num_actors)
                return;

        /* Clean all buffers for new power estimations */
        memset(power, 0, params->buffer_size);

        list_for_each_entry(instance, &td->thermal_instances, trip_node) {
                struct power_actor *pa = &power[i];

                if (!power_actor_is_valid(instance))
                        continue;

                cdev = instance->cdev;

                ret = cdev->ops->get_requested_power(cdev, &pa->req_power);
                if (ret)
                        continue;

                if (!params->total_weight)
                        weight = 1 << FRAC_BITS;
                else
                        weight = instance->weight;

                pa->weighted_req_power = frac_to_int(weight * pa->req_power);

                ret = cdev->ops->state2power(cdev, instance->lower,
                                             &pa->max_power);
                if (ret)
                        continue;

                total_req_power += pa->req_power;
                max_allocatable_power += pa->max_power;
                total_weighted_req_power += pa->weighted_req_power;

                i++;
        }

        power_range = pid_controller(tz, control_temp, max_allocatable_power);

        divvy_up_power(power, num_actors, total_weighted_req_power,
                       power_range);

        i = 0;
        list_for_each_entry(instance, &td->thermal_instances, trip_node) {
                struct power_actor *pa = &power[i];

                if (!power_actor_is_valid(instance))
                        continue;

                power_actor_set_power(instance->cdev, instance,
                                      pa->granted_power);
                total_granted_power += pa->granted_power;

                trace_thermal_power_actor(tz, i, pa->req_power,
                                          pa->granted_power);
                i++;
        }

        trace_thermal_power_allocator(tz, total_req_power, total_granted_power,
                                      num_actors, power_range,
                                      max_allocatable_power, tz->temperature,
                                      control_temp - tz->temperature);
}

/**
 * get_governor_trips() - get 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)
{
        const struct thermal_trip *first_passive = NULL;
        const struct thermal_trip *last_passive = NULL;
        const struct thermal_trip *last_active = NULL;
        const struct thermal_trip_desc *td;

        for_each_trip_desc(tz, td) {
                const struct thermal_trip *trip = &td->trip;

                switch (trip->type) {
                case THERMAL_TRIP_PASSIVE:
                        if (!first_passive) {
                                first_passive = trip;
                                break;
                        }
                        last_passive = trip;
                        break;
                case THERMAL_TRIP_ACTIVE:
                        last_active = trip;
                        break;
                default:
                        break;
                }
        }

        if (last_passive) {
                params->trip_switch_on = first_passive;
                params->trip_max = last_passive;
        } else if (first_passive) {
                params->trip_switch_on = NULL;
                params->trip_max = first_passive;
        } else {
                params->trip_switch_on = NULL;
                params->trip_max = 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 power_allocator_params *params = tz->governor_data;
        const struct thermal_trip_desc *td = trip_to_trip_desc(params->trip_max);
        struct thermal_cooling_device *cdev;
        struct thermal_instance *instance;
        u32 req_power;

        list_for_each_entry(instance, &td->thermal_instances, trip_node) {
                if (!power_actor_is_valid(instance))
                        continue;

                cdev = instance->cdev;

                instance->target = 0;
                scoped_guard(cooling_dev, cdev) {
                        /*
                         * Call for updating the cooling devices local stats and
                         * avoid periods of dozen of seconds when those have not
                         * been maintained.
                         */
                        cdev->ops->get_requested_power(cdev, &req_power);

                        if (params->update_cdevs)
                                __thermal_cdev_update(cdev);
                }
        }
}

/**
 * check_power_actors() - Check all cooling devices and warn when they are
 *                      not power actors
 * @tz:         thermal zone to operate on
 * @params:     power allocator private data
 *
 * Check all cooling devices in the @tz and warn every time they are missing
 * power actor API. The warning should help to investigate the issue, which
 * could be e.g. lack of Energy Model for a given device.
 *
 * If all of the cooling devices currently attached to @tz implement the power
 * actor API, return the number of them (which may be 0, because some cooling
 * devices may be attached later). Otherwise, return -EINVAL.
 */
static int check_power_actors(struct thermal_zone_device *tz,
                              struct power_allocator_params *params)
{
        const struct thermal_trip_desc *td;
        struct thermal_instance *instance;
        int ret = 0;

        if (!params->trip_max)
                return 0;

        td = trip_to_trip_desc(params->trip_max);

        list_for_each_entry(instance, &td->thermal_instances, trip_node) {
                if (!cdev_is_power_actor(instance->cdev)) {
                        dev_warn(&tz->device, "power_allocator: %s is not a power actor\n",
                                 instance->cdev->type);
                        return -EINVAL;
                }
                ret++;
        }

        return ret;
}

static int allocate_actors_buffer(struct power_allocator_params *params,
                                  int num_actors)
{
        int ret;

        kfree(params->power);

        /* There might be no cooling devices yet. */
        if (!num_actors) {
                ret = 0;
                goto clean_state;
        }

        params->power = kzalloc_objs(struct power_actor, num_actors);
        if (!params->power) {
                ret = -ENOMEM;
                goto clean_state;
        }

        params->num_actors = num_actors;
        params->buffer_size = num_actors * sizeof(struct power_actor);

        return 0;

clean_state:
        params->num_actors = 0;
        params->buffer_size = 0;
        params->power = NULL;
        return ret;
}

static void power_allocator_update_weight(struct power_allocator_params *params)
{
        const struct thermal_trip_desc *td;
        struct thermal_instance *instance;

        if (!params->trip_max)
                return;

        td = trip_to_trip_desc(params->trip_max);

        params->total_weight = 0;
        list_for_each_entry(instance, &td->thermal_instances, trip_node)
                if (power_actor_is_valid(instance))
                        params->total_weight += instance->weight;
}

static void power_allocator_update_tz(struct thermal_zone_device *tz,
                                      enum thermal_notify_event reason)
{
        struct power_allocator_params *params = tz->governor_data;
        const struct thermal_trip_desc *td = trip_to_trip_desc(params->trip_max);
        struct thermal_instance *instance;
        int num_actors = 0;

        switch (reason) {
        case THERMAL_TZ_BIND_CDEV:
        case THERMAL_TZ_UNBIND_CDEV:
                list_for_each_entry(instance, &td->thermal_instances, trip_node)
                        if (power_actor_is_valid(instance))
                                num_actors++;

                if (num_actors != params->num_actors)
                        allocate_actors_buffer(params, num_actors);

                fallthrough;
        case THERMAL_INSTANCE_WEIGHT_CHANGED:
                power_allocator_update_weight(params);
                break;
        default:
                break;
        }
}

/**
 * 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, or -EINVAL
 * when there are unsupported cooling devices in the @tz.
 */
static int power_allocator_bind(struct thermal_zone_device *tz)
{
        struct power_allocator_params *params;
        int ret;

        params = kzalloc_obj(*params);
        if (!params)
                return -ENOMEM;

        get_governor_trips(tz, params);

        ret = check_power_actors(tz, params);
        if (ret < 0) {
                dev_warn(&tz->device, "power_allocator: binding failed\n");
                kfree(params);
                return ret;
        }

        ret = allocate_actors_buffer(params, ret);
        if (ret) {
                dev_warn(&tz->device, "power_allocator: allocation failed\n");
                kfree(params);
                return ret;
        }

        if (!tz->tzp) {
                tz->tzp = kzalloc_obj(*tz->tzp);
                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");
        else
                params->sustainable_power = tz->tzp->sustainable_power;

        if (params->trip_max)
                estimate_pid_constants(tz, tz->tzp->sustainable_power,
                                       params->trip_switch_on,
                                       params->trip_max->temperature);

        reset_pid_controller(params);

        tz->governor_data = params;

        power_allocator_update_weight(params);

        return 0;

free_params:
        kfree(params->power);
        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(params->power);
        kfree(tz->governor_data);
        tz->governor_data = NULL;
}

static void power_allocator_manage(struct thermal_zone_device *tz)
{
        struct power_allocator_params *params = tz->governor_data;
        const struct thermal_trip *trip = params->trip_switch_on;

        lockdep_assert_held(&tz->lock);

        if (trip && tz->temperature < trip->temperature) {
                reset_pid_controller(params);
                allow_maximum_power(tz);
                params->update_cdevs = false;
                return;
        }

        if (!params->trip_max)
                return;

        allocate_power(tz, params->trip_max->temperature);
        params->update_cdevs = true;
}

static struct thermal_governor thermal_gov_power_allocator = {
        .name           = "power_allocator",
        .bind_to_tz     = power_allocator_bind,
        .unbind_from_tz = power_allocator_unbind,
        .manage         = power_allocator_manage,
        .update_tz      = power_allocator_update_tz,
};
THERMAL_GOVERNOR_DECLARE(thermal_gov_power_allocator);