// SPDX-License-Identifier: GPL-2.0-only
/*
 *  gov_bang_bang.c - A simple thermal throttling governor using hysteresis
 *
 *  Copyright (C) 2014 Peter Kaestle <peter@piie.net>
 *
 *  Based on step_wise.c with following Copyrights:
 *  Copyright (C) 2012 Intel Corp
 *  Copyright (C) 2012 Durgadoss R <durgadoss.r@intel.com>
 *
 * Regulation Logic: a two point regulation, deliver cooling state depending
 * on the previous state shown in this diagram:
 *
 *                Fan:   OFF    ON
 *
 *                              |
 *                              |
 *          trip_temp:    +---->+
 *                        |     |        ^
 *                        |     |        |
 *                        |     |   Temperature
 * (trip_temp - hyst):    +<----+
 *                        |
 *                        |
 *                        |
 *
 *   * If the fan is not running and temperature exceeds trip_temp, the fan
 *     gets turned on.
 *   * In case the fan is running, temperature must fall below
 *     (trip_temp - hyst) so that the fan gets turned off again.
 */

#include <linux/thermal.h>

#include "thermal_core.h"

static void bang_bang_set_instance_target(struct thermal_instance *instance,
                                          unsigned int target)
{
        if (instance->target != 0 && instance->target != 1 &&
            instance->target != THERMAL_NO_TARGET)
                pr_debug("Unexpected state %ld of thermal instance %s in bang-bang\n",
                         instance->target, instance->name);

        /*
         * Enable the fan when the trip is crossed on the way up and disable it
         * when the trip is crossed on the way down.
         */
        instance->target = target;
        instance->initialized = true;

        dev_dbg(&instance->cdev->device, "target=%ld\n", instance->target);

        thermal_cdev_update_nocheck(instance->cdev);
}

/**
 * bang_bang_trip_crossed - controls devices associated with the given zone
 * @tz: thermal_zone_device
 * @trip: the trip point
 * @upward: whether or not the trip has been crossed on the way up
 */
static void bang_bang_trip_crossed(struct thermal_zone_device *tz,
                                   const struct thermal_trip *trip,
                                   bool upward)
{
        const struct thermal_trip_desc *td = trip_to_trip_desc(trip);
        struct thermal_instance *instance;

        lockdep_assert_held(&tz->lock);

        dev_dbg(&tz->device, "Trip%d[temp=%d]:temp=%d:hyst=%d\n",
                thermal_zone_trip_id(tz, trip), trip->temperature,
                tz->temperature, trip->hysteresis);

        list_for_each_entry(instance, &td->thermal_instances, trip_node)
                bang_bang_set_instance_target(instance, upward);
}

static void bang_bang_manage(struct thermal_zone_device *tz)
{
        const struct thermal_trip_desc *td;
        struct thermal_instance *instance;

        /* If the code below has run already, nothing needs to be done. */
        if (tz->governor_data)
                return;

        for_each_trip_desc(tz, td) {
                const struct thermal_trip *trip = &td->trip;
                bool turn_on;

                if (trip->temperature == THERMAL_TEMP_INVALID ||
                    trip->type == THERMAL_TRIP_CRITICAL ||
                    trip->type == THERMAL_TRIP_HOT)
                        continue;

                /*
                 * Adjust the target states for uninitialized thermal instances
                 * to the thermal zone temperature and the trip point threshold.
                 */
                turn_on = tz->temperature >= td->threshold;
                list_for_each_entry(instance, &td->thermal_instances, trip_node) {
                        if (!instance->initialized)
                                bang_bang_set_instance_target(instance, turn_on);
                }
        }

        tz->governor_data = (void *)true;
}

static void bang_bang_update_tz(struct thermal_zone_device *tz,
                                enum thermal_notify_event reason)
{
        /*
         * Let bang_bang_manage() know that it needs to walk trips after binding
         * a new cdev and after system resume.
         */
        if (reason == THERMAL_TZ_BIND_CDEV || reason == THERMAL_TZ_RESUME)
                tz->governor_data = NULL;
}

static struct thermal_governor thermal_gov_bang_bang = {
        .name           = "bang_bang",
        .trip_crossed   = bang_bang_trip_crossed,
        .manage         = bang_bang_manage,
        .update_tz      = bang_bang_update_tz,
};
THERMAL_GOVERNOR_DECLARE(thermal_gov_bang_bang);