/*
   * 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
  ", 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
  ");

  	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
  ", 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
  ",
  			 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);
  }