540 lines
15 KiB
C
540 lines
15 KiB
C
/*
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* A power allocator to manage temperature
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*
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* Copyright (C) 2014 ARM Ltd.
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*
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* This program is distributed "as is" WITHOUT ANY WARRANTY of any
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* kind, whether express or implied; without even the implied warranty
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* of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*/
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#define pr_fmt(fmt) "Power allocator: " fmt
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#include <linux/rculist.h>
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#include <linux/slab.h>
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#include <linux/thermal.h>
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#define CREATE_TRACE_POINTS
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#include <trace/events/thermal_power_allocator.h>
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#include "thermal_core.h"
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#define FRAC_BITS 10
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#define int_to_frac(x) ((x) << FRAC_BITS)
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#define frac_to_int(x) ((x) >> FRAC_BITS)
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/**
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* mul_frac() - multiply two fixed-point numbers
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* @x: first multiplicand
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* @y: second multiplicand
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*
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* Return: the result of multiplying two fixed-point numbers. The
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* result is also a fixed-point number.
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*/
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static inline s64 mul_frac(s64 x, s64 y)
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{
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return (x * y) >> FRAC_BITS;
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}
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/**
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* div_frac() - divide two fixed-point numbers
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* @x: the dividend
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* @y: the divisor
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*
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* Return: the result of dividing two fixed-point numbers. The
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* result is also a fixed-point number.
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*/
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static inline s64 div_frac(s64 x, s64 y)
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{
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return div_s64(x << FRAC_BITS, y);
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}
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/**
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* struct power_allocator_params - parameters for the power allocator governor
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* @err_integral: accumulated error in the PID controller.
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* @prev_err: error in the previous iteration of the PID controller.
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* Used to calculate the derivative term.
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* @trip_switch_on: first passive trip point of the thermal zone. The
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* governor switches on when this trip point is crossed.
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* @trip_max_desired_temperature: last passive trip point of the thermal
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* zone. The temperature we are
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* controlling for.
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*/
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struct power_allocator_params {
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s64 err_integral;
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s32 prev_err;
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int trip_switch_on;
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int trip_max_desired_temperature;
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};
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/**
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* pid_controller() - PID controller
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* @tz: thermal zone we are operating in
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* @current_temp: the current temperature in millicelsius
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* @control_temp: the target temperature in millicelsius
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* @max_allocatable_power: maximum allocatable power for this thermal zone
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*
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* This PID controller increases the available power budget so that the
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* temperature of the thermal zone gets as close as possible to
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* @control_temp and limits the power if it exceeds it. k_po is the
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* proportional term when we are overshooting, k_pu is the
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* proportional term when we are undershooting. integral_cutoff is a
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* threshold below which we stop accumulating the error. The
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* accumulated error is only valid if the requested power will make
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* the system warmer. If the system is mostly idle, there's no point
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* in accumulating positive error.
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*
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* Return: The power budget for the next period.
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*/
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static u32 pid_controller(struct thermal_zone_device *tz,
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int current_temp,
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int control_temp,
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u32 max_allocatable_power)
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{
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s64 p, i, d, power_range;
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s32 err, max_power_frac;
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struct power_allocator_params *params = tz->governor_data;
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max_power_frac = int_to_frac(max_allocatable_power);
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err = control_temp - current_temp;
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err = int_to_frac(err);
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/* Calculate the proportional term */
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p = mul_frac(err < 0 ? tz->tzp->k_po : tz->tzp->k_pu, err);
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/*
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* Calculate the integral term
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*
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* if the error is less than cut off allow integration (but
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* the integral is limited to max power)
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*/
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i = mul_frac(tz->tzp->k_i, params->err_integral);
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if (err < int_to_frac(tz->tzp->integral_cutoff)) {
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s64 i_next = i + mul_frac(tz->tzp->k_i, err);
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if (abs64(i_next) < max_power_frac) {
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i = i_next;
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params->err_integral += err;
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}
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}
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/*
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* Calculate the derivative term
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*
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* We do err - prev_err, so with a positive k_d, a decreasing
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* error (i.e. driving closer to the line) results in less
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* power being applied, slowing down the controller)
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*/
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d = mul_frac(tz->tzp->k_d, err - params->prev_err);
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d = div_frac(d, tz->passive_delay);
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params->prev_err = err;
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power_range = p + i + d;
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/* feed-forward the known sustainable dissipatable power */
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power_range = tz->tzp->sustainable_power + frac_to_int(power_range);
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power_range = clamp(power_range, (s64)0, (s64)max_allocatable_power);
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trace_thermal_power_allocator_pid(tz, frac_to_int(err),
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frac_to_int(params->err_integral),
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frac_to_int(p), frac_to_int(i),
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frac_to_int(d), power_range);
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return power_range;
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}
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/**
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* divvy_up_power() - divvy the allocated power between the actors
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* @req_power: each actor's requested power
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* @max_power: each actor's maximum available power
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* @num_actors: size of the @req_power, @max_power and @granted_power's array
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* @total_req_power: sum of @req_power
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* @power_range: total allocated power
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* @granted_power: output array: each actor's granted power
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* @extra_actor_power: an appropriately sized array to be used in the
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* function as temporary storage of the extra power given
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* to the actors
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*
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* This function divides the total allocated power (@power_range)
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* fairly between the actors. It first tries to give each actor a
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* share of the @power_range according to how much power it requested
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* compared to the rest of the actors. For example, if only one actor
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* requests power, then it receives all the @power_range. If
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* three actors each requests 1mW, each receives a third of the
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* @power_range.
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*
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* If any actor received more than their maximum power, then that
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* surplus is re-divvied among the actors based on how far they are
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* from their respective maximums.
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*
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* Granted power for each actor is written to @granted_power, which
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* should've been allocated by the calling function.
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*/
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static void divvy_up_power(u32 *req_power, u32 *max_power, int num_actors,
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u32 total_req_power, u32 power_range,
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u32 *granted_power, u32 *extra_actor_power)
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{
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u32 extra_power, capped_extra_power;
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int i;
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/*
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* Prevent division by 0 if none of the actors request power.
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*/
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if (!total_req_power)
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total_req_power = 1;
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capped_extra_power = 0;
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extra_power = 0;
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for (i = 0; i < num_actors; i++) {
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u64 req_range = req_power[i] * power_range;
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granted_power[i] = DIV_ROUND_CLOSEST_ULL(req_range,
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total_req_power);
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if (granted_power[i] > max_power[i]) {
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extra_power += granted_power[i] - max_power[i];
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granted_power[i] = max_power[i];
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}
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extra_actor_power[i] = max_power[i] - granted_power[i];
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capped_extra_power += extra_actor_power[i];
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}
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if (!extra_power)
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return;
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/*
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* Re-divvy the reclaimed extra among actors based on
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* how far they are from the max
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*/
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extra_power = min(extra_power, capped_extra_power);
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if (capped_extra_power > 0)
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for (i = 0; i < num_actors; i++)
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granted_power[i] += (extra_actor_power[i] *
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extra_power) / capped_extra_power;
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}
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static int allocate_power(struct thermal_zone_device *tz,
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int current_temp,
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int control_temp)
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{
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struct thermal_instance *instance;
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struct power_allocator_params *params = tz->governor_data;
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u32 *req_power, *max_power, *granted_power, *extra_actor_power;
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u32 total_req_power, max_allocatable_power;
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u32 total_granted_power, power_range;
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int i, num_actors, total_weight, ret = 0;
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int trip_max_desired_temperature = params->trip_max_desired_temperature;
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mutex_lock(&tz->lock);
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num_actors = 0;
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total_weight = 0;
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list_for_each_entry(instance, &tz->thermal_instances, tz_node) {
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if ((instance->trip == trip_max_desired_temperature) &&
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cdev_is_power_actor(instance->cdev)) {
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num_actors++;
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total_weight += instance->weight;
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}
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}
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/*
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* We need to allocate three arrays of the same size:
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* req_power, max_power and granted_power. They are going to
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* be needed until this function returns. Allocate them all
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* in one go to simplify the allocation and deallocation
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* logic.
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*/
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BUILD_BUG_ON(sizeof(*req_power) != sizeof(*max_power));
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BUILD_BUG_ON(sizeof(*req_power) != sizeof(*granted_power));
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BUILD_BUG_ON(sizeof(*req_power) != sizeof(*extra_actor_power));
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req_power = devm_kcalloc(&tz->device, num_actors * 4,
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sizeof(*req_power), GFP_KERNEL);
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if (!req_power) {
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ret = -ENOMEM;
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goto unlock;
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}
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max_power = &req_power[num_actors];
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granted_power = &req_power[2 * num_actors];
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extra_actor_power = &req_power[3 * num_actors];
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i = 0;
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total_req_power = 0;
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max_allocatable_power = 0;
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list_for_each_entry(instance, &tz->thermal_instances, tz_node) {
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int weight;
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struct thermal_cooling_device *cdev = instance->cdev;
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if (instance->trip != trip_max_desired_temperature)
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continue;
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if (!cdev_is_power_actor(cdev))
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continue;
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if (cdev->ops->get_requested_power(cdev, tz, &req_power[i]))
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continue;
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if (!total_weight)
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weight = 1 << FRAC_BITS;
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else
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weight = instance->weight;
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req_power[i] = frac_to_int(weight * req_power[i]);
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if (power_actor_get_max_power(cdev, tz, &max_power[i]))
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continue;
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total_req_power += req_power[i];
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max_allocatable_power += max_power[i];
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i++;
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}
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power_range = pid_controller(tz, current_temp, control_temp,
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max_allocatable_power);
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divvy_up_power(req_power, max_power, num_actors, total_req_power,
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power_range, granted_power, extra_actor_power);
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total_granted_power = 0;
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i = 0;
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list_for_each_entry(instance, &tz->thermal_instances, tz_node) {
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if (instance->trip != trip_max_desired_temperature)
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continue;
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if (!cdev_is_power_actor(instance->cdev))
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continue;
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power_actor_set_power(instance->cdev, instance,
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granted_power[i]);
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total_granted_power += granted_power[i];
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i++;
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}
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trace_thermal_power_allocator(tz, req_power, total_req_power,
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granted_power, total_granted_power,
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num_actors, power_range,
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max_allocatable_power, current_temp,
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control_temp - current_temp);
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devm_kfree(&tz->device, req_power);
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unlock:
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mutex_unlock(&tz->lock);
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return ret;
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}
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static int get_governor_trips(struct thermal_zone_device *tz,
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struct power_allocator_params *params)
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{
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int i, ret, last_passive;
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bool found_first_passive;
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found_first_passive = false;
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last_passive = -1;
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ret = -EINVAL;
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for (i = 0; i < tz->trips; i++) {
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enum thermal_trip_type type;
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ret = tz->ops->get_trip_type(tz, i, &type);
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if (ret)
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return ret;
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if (!found_first_passive) {
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if (type == THERMAL_TRIP_PASSIVE) {
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params->trip_switch_on = i;
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found_first_passive = true;
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}
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} else if (type == THERMAL_TRIP_PASSIVE) {
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last_passive = i;
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} else {
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break;
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}
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}
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if (last_passive != -1) {
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params->trip_max_desired_temperature = last_passive;
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ret = 0;
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} else {
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ret = -EINVAL;
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}
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return ret;
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}
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static void reset_pid_controller(struct power_allocator_params *params)
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{
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params->err_integral = 0;
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params->prev_err = 0;
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}
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static void allow_maximum_power(struct thermal_zone_device *tz)
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{
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struct thermal_instance *instance;
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struct power_allocator_params *params = tz->governor_data;
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list_for_each_entry(instance, &tz->thermal_instances, tz_node) {
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if ((instance->trip != params->trip_max_desired_temperature) ||
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(!cdev_is_power_actor(instance->cdev)))
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continue;
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instance->target = 0;
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instance->cdev->updated = false;
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thermal_cdev_update(instance->cdev);
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}
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}
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/**
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* power_allocator_bind() - bind the power_allocator governor to a thermal zone
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* @tz: thermal zone to bind it to
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*
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* Check that the thermal zone is valid for this governor, that is, it
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* has two thermal trips. If so, initialize the PID controller
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* parameters and bind it to the thermal zone.
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*
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* Return: 0 on success, -EINVAL if the trips were invalid or -ENOMEM
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* if we ran out of memory.
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*/
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static int power_allocator_bind(struct thermal_zone_device *tz)
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{
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int ret;
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struct power_allocator_params *params;
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int switch_on_temp, control_temp;
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u32 temperature_threshold;
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if (!tz->tzp || !tz->tzp->sustainable_power) {
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dev_err(&tz->device,
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"power_allocator: missing sustainable_power\n");
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return -EINVAL;
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}
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params = devm_kzalloc(&tz->device, sizeof(*params), GFP_KERNEL);
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if (!params)
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return -ENOMEM;
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ret = get_governor_trips(tz, params);
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if (ret) {
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dev_err(&tz->device,
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"thermal zone %s has wrong trip setup for power allocator\n",
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tz->type);
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goto free;
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}
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ret = tz->ops->get_trip_temp(tz, params->trip_switch_on,
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&switch_on_temp);
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if (ret)
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goto free;
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ret = tz->ops->get_trip_temp(tz, params->trip_max_desired_temperature,
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&control_temp);
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if (ret)
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goto free;
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temperature_threshold = control_temp - switch_on_temp;
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tz->tzp->k_po = tz->tzp->k_po ?:
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int_to_frac(tz->tzp->sustainable_power) / temperature_threshold;
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tz->tzp->k_pu = tz->tzp->k_pu ?:
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int_to_frac(2 * tz->tzp->sustainable_power) /
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temperature_threshold;
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tz->tzp->k_i = tz->tzp->k_i ?: int_to_frac(10) / 1000;
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/*
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* The default for k_d and integral_cutoff is 0, so we can
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* leave them as they are.
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*/
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reset_pid_controller(params);
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tz->governor_data = params;
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return 0;
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free:
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devm_kfree(&tz->device, params);
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return ret;
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}
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static void power_allocator_unbind(struct thermal_zone_device *tz)
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{
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dev_dbg(&tz->device, "Unbinding from thermal zone %d\n", tz->id);
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devm_kfree(&tz->device, tz->governor_data);
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tz->governor_data = NULL;
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}
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static int power_allocator_throttle(struct thermal_zone_device *tz, int trip)
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{
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int ret;
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int switch_on_temp, control_temp, current_temp;
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struct power_allocator_params *params = tz->governor_data;
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/*
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* We get called for every trip point but we only need to do
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* our calculations once
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*/
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if (trip != params->trip_max_desired_temperature)
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return 0;
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ret = thermal_zone_get_temp(tz, ¤t_temp);
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if (ret) {
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dev_warn(&tz->device, "Failed to get temperature: %d\n", ret);
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return ret;
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}
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ret = tz->ops->get_trip_temp(tz, params->trip_switch_on,
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&switch_on_temp);
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if (ret) {
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dev_warn(&tz->device,
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"Failed to get switch on temperature: %d\n", ret);
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return ret;
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}
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if (current_temp < switch_on_temp) {
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tz->passive = 0;
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reset_pid_controller(params);
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allow_maximum_power(tz);
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return 0;
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}
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tz->passive = 1;
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ret = tz->ops->get_trip_temp(tz, params->trip_max_desired_temperature,
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&control_temp);
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if (ret) {
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dev_warn(&tz->device,
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"Failed to get the maximum desired temperature: %d\n",
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ret);
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return ret;
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|
}
|
|
|
|
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);
|
|
}
|