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![Michele Di Giorgio](/assets/img/avatar_default.png)
When multiple thermal zones are bound to the same cooling device, multiple kernel threads may want to update the cooling device state by calling thermal_cdev_update(). Having cdev not protected by a mutex can lead to a race condition. Consider the following situation with two kernel threads k1 and k2: Thread k1 Thread k2 || || call thermal_cdev_update() || ... || set_cur_state(cdev, target); call power_actor_set_power() || ... || instance->target = state; || cdev->updated = false; || || cdev->updated = true; || // completes execution call thermal_cdev_update() || // cdev->updated == true || return; || \/ time k2 has already looped through the thermal instances looking for the deepest cooling device state and is preempted right before setting cdev->updated to true. Now, k1 runs, modifies the thermal instance state and sets cdev->updated to false. Then, k1 is preempted and k2 continues the execution by setting cdev->updated to true, therefore preventing k1 from performing the update. Notice that this is not an issue if k2 looks at the instance->target modified by k1 "after" it is assigned by k1. In fact, in this case the update will happen anyway and k1 can safely return immediately from thermal_cdev_update(). This may lead to a situation where a thermal governor never updates the cooling device. For example, this is the case for the step_wise governor: when calling the function thermal_zone_trip_update(), the governor may always get a new state equal to the old one (which, however, wasn't notified to the cooling device) and will therefore skip the update. CC: Zhang Rui <rui.zhang@intel.com> CC: Eduardo Valentin <edubezval@gmail.com> CC: Peter Feuerer <peter@piie.net> Reported-by: Toby Huang <toby.huang@arm.com> Signed-off-by: Michele Di Giorgio <michele.digiorgio@arm.com> Reviewed-by: Javi Merino <javi.merino@arm.com> Signed-off-by: Zhang Rui <rui.zhang@intel.com>
661 lines
19 KiB
C
661 lines
19 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 INVALID_TRIP -1
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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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* @allocated_tzp: whether we have allocated tzp for this thermal zone and
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* it needs to be freed on unbind
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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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* If the thermal zone only has one passive trip point,
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* @trip_switch_on should be INVALID_TRIP.
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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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bool allocated_tzp;
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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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* estimate_sustainable_power() - Estimate the sustainable power of a thermal zone
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* @tz: thermal zone we are operating in
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*
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* For thermal zones that don't provide a sustainable_power in their
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* thermal_zone_params, estimate one. Calculate it using the minimum
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* power of all the cooling devices as that gives a valid value that
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* can give some degree of functionality. For optimal performance of
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* this governor, provide a sustainable_power in the thermal zone's
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* thermal_zone_params.
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*/
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static u32 estimate_sustainable_power(struct thermal_zone_device *tz)
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{
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u32 sustainable_power = 0;
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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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struct thermal_cooling_device *cdev = instance->cdev;
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u32 min_power;
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if (instance->trip != params->trip_max_desired_temperature)
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continue;
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if (power_actor_get_min_power(cdev, tz, &min_power))
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continue;
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sustainable_power += min_power;
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}
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return sustainable_power;
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}
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/**
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* estimate_pid_constants() - Estimate the constants for the PID controller
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* @tz: thermal zone for which to estimate the constants
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* @sustainable_power: sustainable power for the thermal zone
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* @trip_switch_on: trip point number for the switch on temperature
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* @control_temp: target temperature for the power allocator governor
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* @force: whether to force the update of the constants
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*
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* This function is used to update the estimation of the PID
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* controller constants in struct thermal_zone_parameters.
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* Sustainable power is provided in case it was estimated. The
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* estimated sustainable_power should not be stored in the
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* thermal_zone_parameters so it has to be passed explicitly to this
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* function.
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*
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* If @force is not set, the values in the thermal zone's parameters
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* are preserved if they are not zero. If @force is set, the values
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* in thermal zone's parameters are overwritten.
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*/
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static void estimate_pid_constants(struct thermal_zone_device *tz,
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u32 sustainable_power, int trip_switch_on,
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int control_temp, bool force)
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{
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int ret;
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int switch_on_temp;
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u32 temperature_threshold;
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ret = tz->ops->get_trip_temp(tz, trip_switch_on, &switch_on_temp);
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if (ret)
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switch_on_temp = 0;
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temperature_threshold = control_temp - switch_on_temp;
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/*
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* estimate_pid_constants() tries to find appropriate default
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* values for thermal zones that don't provide them. If a
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* system integrator has configured a thermal zone with two
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* passive trip points at the same temperature, that person
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* hasn't put any effort to set up the thermal zone properly
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* so just give up.
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*/
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if (!temperature_threshold)
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return;
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if (!tz->tzp->k_po || force)
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tz->tzp->k_po = int_to_frac(sustainable_power) /
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temperature_threshold;
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if (!tz->tzp->k_pu || force)
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tz->tzp->k_pu = int_to_frac(2 * sustainable_power) /
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temperature_threshold;
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if (!tz->tzp->k_i || force)
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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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}
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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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* @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 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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u32 sustainable_power;
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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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if (tz->tzp->sustainable_power) {
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sustainable_power = tz->tzp->sustainable_power;
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} else {
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sustainable_power = estimate_sustainable_power(tz);
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estimate_pid_constants(tz, sustainable_power,
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params->trip_switch_on, control_temp,
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true);
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}
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err = control_temp - tz->temperature;
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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 (abs(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 = 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 = (u64)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 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 *weighted_req_power;
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u32 total_req_power, max_allocatable_power, total_weighted_req_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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if (!num_actors) {
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ret = -ENODEV;
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goto unlock;
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}
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/*
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* We need to allocate five arrays of the same size:
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* req_power, max_power, granted_power, extra_actor_power and
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* weighted_req_power. They are going to be needed until this
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* function returns. Allocate them all in one go to simplify
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* the allocation and deallocation 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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BUILD_BUG_ON(sizeof(*req_power) != sizeof(*weighted_req_power));
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req_power = kcalloc(num_actors * 5, 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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weighted_req_power = &req_power[4 * num_actors];
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i = 0;
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total_weighted_req_power = 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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weighted_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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total_weighted_req_power += weighted_req_power[i];
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i++;
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}
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power_range = pid_controller(tz, control_temp, max_allocatable_power);
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divvy_up_power(weighted_req_power, max_power, num_actors,
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total_weighted_req_power, power_range, granted_power,
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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, tz->temperature,
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control_temp - tz->temperature);
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kfree(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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/**
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* get_governor_trips() - get the number of the two trip points that are key for this governor
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* @tz: thermal zone to operate on
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* @params: pointer to private data for this governor
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*
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* The power allocator governor works optimally with two trips points:
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* a "switch on" trip point and a "maximum desired temperature". These
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* are defined as the first and last passive trip points.
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*
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* If there is only one trip point, then that's considered to be the
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* "maximum desired temperature" trip point and the governor is always
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* on. If there are no passive or active trip points, then the
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* 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;
|
|
|
|
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);
|
|
}
|
|
}
|
|
|
|
/**
|
|
* 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);
|
|
}
|