linux-imx

/*

 * 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.

 */