cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
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gov_bang_bang.c (3410B)

      1// SPDX-License-Identifier: GPL-2.0-only
      2/*
      3 *  gov_bang_bang.c - A simple thermal throttling governor using hysteresis
      4 *
      5 *  Copyright (C) 2014 Peter Kaestle <peter@piie.net>
      6 *
      7 *  Based on step_wise.c with following Copyrights:
      8 *  Copyright (C) 2012 Intel Corp
      9 *  Copyright (C) 2012 Durgadoss R <durgadoss.r@intel.com>
     10 */
     11
     12#include <linux/thermal.h>
     13
     14#include "thermal_core.h"
     15
     16static void thermal_zone_trip_update(struct thermal_zone_device *tz, int trip)
     17{
     18	int trip_temp, trip_hyst;
     19	struct thermal_instance *instance;
     20
     21	tz->ops->get_trip_temp(tz, trip, &trip_temp);
     22
     23	if (!tz->ops->get_trip_hyst) {
     24		pr_warn_once("Undefined get_trip_hyst for thermal zone %s - "
     25				"running with default hysteresis zero\n", tz->type);
     26		trip_hyst = 0;
     27	} else
     28		tz->ops->get_trip_hyst(tz, trip, &trip_hyst);
     29
     30	dev_dbg(&tz->device, "Trip%d[temp=%d]:temp=%d:hyst=%d\n",
     31				trip, trip_temp, tz->temperature,
     32				trip_hyst);
     33
     34	mutex_lock(&tz->lock);
     35
     36	list_for_each_entry(instance, &tz->thermal_instances, tz_node) {
     37		if (instance->trip != trip)
     38			continue;
     39
     40		/* in case fan is in initial state, switch the fan off */
     41		if (instance->target == THERMAL_NO_TARGET)
     42			instance->target = 0;
     43
     44		/* in case fan is neither on nor off set the fan to active */
     45		if (instance->target != 0 && instance->target != 1) {
     46			pr_warn("Thermal instance %s controlled by bang-bang has unexpected state: %ld\n",
     47					instance->name, instance->target);
     48			instance->target = 1;
     49		}
     50
     51		/*
     52		 * enable fan when temperature exceeds trip_temp and disable
     53		 * the fan in case it falls below trip_temp minus hysteresis
     54		 */
     55		if (instance->target == 0 && tz->temperature >= trip_temp)
     56			instance->target = 1;
     57		else if (instance->target == 1 &&
     58				tz->temperature <= trip_temp - trip_hyst)
     59			instance->target = 0;
     60
     61		dev_dbg(&instance->cdev->device, "target=%d\n",
     62					(int)instance->target);
     63
     64		mutex_lock(&instance->cdev->lock);
     65		instance->cdev->updated = false; /* cdev needs update */
     66		mutex_unlock(&instance->cdev->lock);
     67	}
     68
     69	mutex_unlock(&tz->lock);
     70}
     71
     72/**
     73 * bang_bang_control - controls devices associated with the given zone
     74 * @tz: thermal_zone_device
     75 * @trip: the trip point
     76 *
     77 * Regulation Logic: a two point regulation, deliver cooling state depending
     78 * on the previous state shown in this diagram:
     79 *
     80 *                Fan:   OFF    ON
     81 *
     82 *                              |
     83 *                              |
     84 *          trip_temp:    +---->+
     85 *                        |     |        ^
     86 *                        |     |        |
     87 *                        |     |   Temperature
     88 * (trip_temp - hyst):    +<----+
     89 *                        |
     90 *                        |
     91 *                        |
     92 *
     93 *   * If the fan is not running and temperature exceeds trip_temp, the fan
     94 *     gets turned on.
     95 *   * In case the fan is running, temperature must fall below
     96 *     (trip_temp - hyst) so that the fan gets turned off again.
     97 *
     98 */
     99static int bang_bang_control(struct thermal_zone_device *tz, int trip)
    100{
    101	struct thermal_instance *instance;
    102
    103	thermal_zone_trip_update(tz, trip);
    104
    105	mutex_lock(&tz->lock);
    106
    107	list_for_each_entry(instance, &tz->thermal_instances, tz_node)
    108		thermal_cdev_update(instance->cdev);
    109
    110	mutex_unlock(&tz->lock);
    111
    112	return 0;
    113}
    114
    115static struct thermal_governor thermal_gov_bang_bang = {
    116	.name		= "bang_bang",
    117	.throttle	= bang_bang_control,
    118};
    119THERMAL_GOVERNOR_DECLARE(thermal_gov_bang_bang);