// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (c) 2020 Samsung Electronics Co., Ltd.
 *            http://www.samsung.com/
 * Author: Marek Szyprowski <m.szyprowski@samsung.com>
 *
 * Simplified generic voltage coupler from regulator core.c
 * The main difference is that it keeps current regulator voltage
 * if consumers didn't apply their constraints yet.
 */

#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/of.h>
#include <linux/regulator/coupler.h>
#include <linux/regulator/driver.h>
#include <linux/regulator/machine.h>

static int regulator_get_optimal_voltage(struct regulator_dev *rdev,
                                         int *current_uV,
                                         int *min_uV, int *max_uV,
                                         suspend_state_t state)
{
        struct coupling_desc *c_desc = &rdev->coupling_desc;
        struct regulator_dev **c_rdevs = c_desc->coupled_rdevs;
        struct regulation_constraints *constraints = rdev->constraints;
        int desired_min_uV = 0, desired_max_uV = INT_MAX;
        int max_current_uV = 0, min_current_uV = INT_MAX;
        int highest_min_uV = 0, target_uV, possible_uV;
        int i, ret, max_spread, n_coupled = c_desc->n_coupled;
        bool done;

        *current_uV = -1;

        /* Find highest min desired voltage */
        for (i = 0; i < n_coupled; i++) {
                int tmp_min = 0;
                int tmp_max = INT_MAX;

                lockdep_assert_held_once(&c_rdevs[i]->mutex.base);

                ret = regulator_check_consumers(c_rdevs[i],
                                                &tmp_min,
                                                &tmp_max, state);
                if (ret < 0)
                        return ret;

                if (tmp_min == 0) {
                        ret = regulator_get_voltage_rdev(c_rdevs[i]);
                        if (ret < 0)
                                return ret;
                        tmp_min = ret;
                }

                /* apply constraints */
                ret = regulator_check_voltage(c_rdevs[i], &tmp_min, &tmp_max);
                if (ret < 0)
                        return ret;

                highest_min_uV = max(highest_min_uV, tmp_min);

                if (i == 0) {
                        desired_min_uV = tmp_min;
                        desired_max_uV = tmp_max;
                }
        }

        max_spread = constraints->max_spread[0];

        /*
         * Let target_uV be equal to the desired one if possible.
         * If not, set it to minimum voltage, allowed by other coupled
         * regulators.
         */
        target_uV = max(desired_min_uV, highest_min_uV - max_spread);

        /*
         * Find min and max voltages, which currently aren't violating
         * max_spread.
         */
        for (i = 1; i < n_coupled; i++) {
                int tmp_act;

                tmp_act = regulator_get_voltage_rdev(c_rdevs[i]);
                if (tmp_act < 0)
                        return tmp_act;

                min_current_uV = min(tmp_act, min_current_uV);
                max_current_uV = max(tmp_act, max_current_uV);
        }

        /*
         * Correct target voltage, so as it currently isn't
         * violating max_spread
         */
        possible_uV = max(target_uV, max_current_uV - max_spread);
        possible_uV = min(possible_uV, min_current_uV + max_spread);

        if (possible_uV > desired_max_uV)
                return -EINVAL;

        done = (possible_uV == target_uV);
        desired_min_uV = possible_uV;

        /* Set current_uV if wasn't done earlier in the code and if necessary */
        if (*current_uV == -1) {
                ret = regulator_get_voltage_rdev(rdev);
                if (ret < 0)
                        return ret;
                *current_uV = ret;
        }

        *min_uV = desired_min_uV;
        *max_uV = desired_max_uV;

        return done;
}

static int exynos_coupler_balance_voltage(struct regulator_coupler *coupler,
                                          struct regulator_dev *rdev,
                                          suspend_state_t state)
{
        struct regulator_dev **c_rdevs;
        struct regulator_dev *best_rdev;
        struct coupling_desc *c_desc = &rdev->coupling_desc;
        int i, ret, n_coupled, best_min_uV, best_max_uV, best_c_rdev;
        unsigned int delta, best_delta;
        unsigned long c_rdev_done = 0;
        bool best_c_rdev_done;

        c_rdevs = c_desc->coupled_rdevs;
        n_coupled = c_desc->n_coupled;

        /*
         * Find the best possible voltage change on each loop. Leave the loop
         * if there isn't any possible change.
         */
        do {
                best_c_rdev_done = false;
                best_delta = 0;
                best_min_uV = 0;
                best_max_uV = 0;
                best_c_rdev = 0;
                best_rdev = NULL;

                /*
                 * Find highest difference between optimal voltage
                 * and current voltage.
                 */
                for (i = 0; i < n_coupled; i++) {
                        /*
                         * optimal_uV is the best voltage that can be set for
                         * i-th regulator at the moment without violating
                         * max_spread constraint in order to balance
                         * the coupled voltages.
                         */
                        int optimal_uV = 0, optimal_max_uV = 0, current_uV = 0;

                        if (test_bit(i, &c_rdev_done))
                                continue;

                        ret = regulator_get_optimal_voltage(c_rdevs[i],
                                                            &current_uV,
                                                            &optimal_uV,
                                                            &optimal_max_uV,
                                                            state);
                        if (ret < 0)
                                goto out;

                        delta = abs(optimal_uV - current_uV);

                        if (delta && best_delta <= delta) {
                                best_c_rdev_done = ret;
                                best_delta = delta;
                                best_rdev = c_rdevs[i];
                                best_min_uV = optimal_uV;
                                best_max_uV = optimal_max_uV;
                                best_c_rdev = i;
                        }
                }

                /* Nothing to change, return successfully */
                if (!best_rdev) {
                        ret = 0;
                        goto out;
                }

                ret = regulator_set_voltage_rdev(best_rdev, best_min_uV,
                                                 best_max_uV, state);

                if (ret < 0)
                        goto out;

                if (best_c_rdev_done)
                        set_bit(best_c_rdev, &c_rdev_done);

        } while (n_coupled > 1);

out:
        return ret;
}

static int exynos_coupler_attach(struct regulator_coupler *coupler,
                                 struct regulator_dev *rdev)
{
        return 0;
}

static struct regulator_coupler exynos_coupler = {
        .attach_regulator = exynos_coupler_attach,
        .balance_voltage  = exynos_coupler_balance_voltage,
};

static int __init exynos_coupler_init(void)
{
        if (!of_machine_is_compatible("samsung,exynos5800"))
                return 0;

        return regulator_coupler_register(&exynos_coupler);
}
arch_initcall(exynos_coupler_init);