// SPDX-License-Identifier: GPL-2.0+
/*
 * Voltage regulators coupler for NVIDIA Tegra20
 * Copyright (C) 2019 GRATE-DRIVER project
 *
 * Voltage constraints borrowed from downstream kernel sources
 * Copyright (C) 2010-2011 NVIDIA Corporation
 */

#define pr_fmt(fmt)     "tegra voltage-coupler: " fmt

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

#include <soc/tegra/fuse.h>
#include <soc/tegra/pmc.h>

struct tegra_regulator_coupler {
        struct regulator_coupler coupler;
        struct regulator_dev *core_rdev;
        struct regulator_dev *cpu_rdev;
        struct regulator_dev *rtc_rdev;
        struct notifier_block reboot_notifier;
        struct notifier_block suspend_notifier;
        int core_min_uV, cpu_min_uV;
        bool sys_reboot_mode_req;
        bool sys_reboot_mode;
        bool sys_suspend_mode_req;
        bool sys_suspend_mode;
};

static inline struct tegra_regulator_coupler *
to_tegra_coupler(struct regulator_coupler *coupler)
{
        return container_of(coupler, struct tegra_regulator_coupler, coupler);
}

static int tegra20_core_limit(struct tegra_regulator_coupler *tegra,
                              struct regulator_dev *core_rdev)
{
        int core_min_uV = 0;
        int core_max_uV;
        int core_cur_uV;
        int err;

        /*
         * Tegra20 SoC has critical DVFS-capable devices that are
         * permanently-active or active at a boot time, like EMC
         * (DRAM controller) or Display controller for example.
         *
         * The voltage of a CORE SoC power domain shall not be dropped below
         * a minimum level, which is determined by device's clock rate.
         * This means that we can't fully allow CORE voltage scaling until
         * the state of all DVFS-critical CORE devices is synced.
         */
        if (tegra_pmc_core_domain_state_synced() && !tegra->sys_reboot_mode) {
                pr_info_once("voltage state synced\n");
                return 0;
        }

        if (tegra->core_min_uV > 0)
                return tegra->core_min_uV;

        core_cur_uV = regulator_get_voltage_rdev(core_rdev);
        if (core_cur_uV < 0)
                return core_cur_uV;

        core_max_uV = max(core_cur_uV, 1200000);

        err = regulator_check_voltage(core_rdev, &core_min_uV, &core_max_uV);
        if (err)
                return err;

        /*
         * Limit minimum CORE voltage to a value left from bootloader or,
         * if it's unreasonably low value, to the most common 1.2v or to
         * whatever maximum value defined via board's device-tree.
         */
        tegra->core_min_uV = core_max_uV;

        pr_info("core voltage initialized to %duV\n", tegra->core_min_uV);

        return tegra->core_min_uV;
}

static int tegra20_core_rtc_max_spread(struct regulator_dev *core_rdev,
                                       struct regulator_dev *rtc_rdev)
{
        struct coupling_desc *c_desc = &core_rdev->coupling_desc;
        struct regulator_dev *rdev;
        int max_spread;
        unsigned int i;

        for (i = 1; i < c_desc->n_coupled; i++) {
                max_spread = core_rdev->constraints->max_spread[i - 1];
                rdev = c_desc->coupled_rdevs[i];

                if (rdev == rtc_rdev && max_spread)
                        return max_spread;
        }

        pr_err_once("rtc-core max-spread is undefined in device-tree\n");

        return 150000;
}

static int tegra20_cpu_nominal_uV(void)
{
        switch (tegra_sku_info.soc_speedo_id) {
        case 0:
                return 1100000;
        case 1:
                return 1025000;
        default:
                return 1125000;
        }
}

static int tegra20_core_nominal_uV(void)
{
        switch (tegra_sku_info.soc_speedo_id) {
        default:
                return 1225000;
        case 2:
                return 1300000;
        }
}

static int tegra20_core_rtc_update(struct tegra_regulator_coupler *tegra,
                                   struct regulator_dev *core_rdev,
                                   struct regulator_dev *rtc_rdev,
                                   int cpu_uV, int cpu_min_uV)
{
        int core_min_uV, core_max_uV = INT_MAX;
        int rtc_min_uV, rtc_max_uV = INT_MAX;
        int core_target_uV;
        int rtc_target_uV;
        int max_spread;
        int core_uV;
        int rtc_uV;
        int err;

        /*
         * RTC and CORE voltages should be no more than 170mV from each other,
         * CPU should be below RTC and CORE by at least 120mV. This applies
         * to all Tegra20 SoC's.
         */
        max_spread = tegra20_core_rtc_max_spread(core_rdev, rtc_rdev);

        /*
         * The core voltage scaling is currently not hooked up in drivers,
         * hence we will limit the minimum core voltage to a reasonable value.
         * This should be good enough for the time being.
         */
        core_min_uV = tegra20_core_limit(tegra, core_rdev);
        if (core_min_uV < 0)
                return core_min_uV;

        err = regulator_check_voltage(core_rdev, &core_min_uV, &core_max_uV);
        if (err)
                return err;

        err = regulator_check_consumers(core_rdev, &core_min_uV, &core_max_uV,
                                        PM_SUSPEND_ON);
        if (err)
                return err;

        /* prepare voltage level for suspend */
        if (tegra->sys_suspend_mode)
                core_min_uV = clamp(tegra20_core_nominal_uV(),
                                    core_min_uV, core_max_uV);

        core_uV = regulator_get_voltage_rdev(core_rdev);
        if (core_uV < 0)
                return core_uV;

        core_min_uV = max(cpu_min_uV + 125000, core_min_uV);
        if (core_min_uV > core_max_uV)
                return -EINVAL;

        if (cpu_uV + 120000 > core_uV)
                pr_err("core-cpu voltage constraint violated: %d %d\n",
                       core_uV, cpu_uV + 120000);

        rtc_uV = regulator_get_voltage_rdev(rtc_rdev);
        if (rtc_uV < 0)
                return rtc_uV;

        if (cpu_uV + 120000 > rtc_uV)
                pr_err("rtc-cpu voltage constraint violated: %d %d\n",
                       rtc_uV, cpu_uV + 120000);

        if (abs(core_uV - rtc_uV) > 170000)
                pr_err("core-rtc voltage constraint violated: %d %d\n",
                       core_uV, rtc_uV);

        rtc_min_uV = max(cpu_min_uV + 125000, core_min_uV - max_spread);

        err = regulator_check_voltage(rtc_rdev, &rtc_min_uV, &rtc_max_uV);
        if (err)
                return err;

        while (core_uV != core_min_uV || rtc_uV != rtc_min_uV) {
                if (core_uV < core_min_uV) {
                        core_target_uV = min(core_uV + max_spread, core_min_uV);
                        core_target_uV = min(rtc_uV + max_spread, core_target_uV);
                } else {
                        core_target_uV = max(core_uV - max_spread, core_min_uV);
                        core_target_uV = max(rtc_uV - max_spread, core_target_uV);
                }

                if (core_uV == core_target_uV)
                        goto update_rtc;

                err = regulator_set_voltage_rdev(core_rdev,
                                                 core_target_uV,
                                                 core_max_uV,
                                                 PM_SUSPEND_ON);
                if (err)
                        return err;

                core_uV = core_target_uV;
update_rtc:
                if (rtc_uV < rtc_min_uV) {
                        rtc_target_uV = min(rtc_uV + max_spread, rtc_min_uV);
                        rtc_target_uV = min(core_uV + max_spread, rtc_target_uV);
                } else {
                        rtc_target_uV = max(rtc_uV - max_spread, rtc_min_uV);
                        rtc_target_uV = max(core_uV - max_spread, rtc_target_uV);
                }

                if (rtc_uV == rtc_target_uV)
                        continue;

                err = regulator_set_voltage_rdev(rtc_rdev,
                                                 rtc_target_uV,
                                                 rtc_max_uV,
                                                 PM_SUSPEND_ON);
                if (err)
                        return err;

                rtc_uV = rtc_target_uV;
        }

        return 0;
}

static int tegra20_core_voltage_update(struct tegra_regulator_coupler *tegra,
                                       struct regulator_dev *cpu_rdev,
                                       struct regulator_dev *core_rdev,
                                       struct regulator_dev *rtc_rdev)
{
        int cpu_uV;

        cpu_uV = regulator_get_voltage_rdev(cpu_rdev);
        if (cpu_uV < 0)
                return cpu_uV;

        return tegra20_core_rtc_update(tegra, core_rdev, rtc_rdev,
                                       cpu_uV, cpu_uV);
}

static int tegra20_cpu_voltage_update(struct tegra_regulator_coupler *tegra,
                                      struct regulator_dev *cpu_rdev,
                                      struct regulator_dev *core_rdev,
                                      struct regulator_dev *rtc_rdev)
{
        int cpu_min_uV_consumers = 0;
        int cpu_max_uV = INT_MAX;
        int cpu_min_uV = 0;
        int cpu_uV;
        int err;

        err = regulator_check_voltage(cpu_rdev, &cpu_min_uV, &cpu_max_uV);
        if (err)
                return err;

        err = regulator_check_consumers(cpu_rdev, &cpu_min_uV, &cpu_max_uV,
                                        PM_SUSPEND_ON);
        if (err)
                return err;

        err = regulator_check_consumers(cpu_rdev, &cpu_min_uV_consumers,
                                        &cpu_max_uV, PM_SUSPEND_ON);
        if (err)
                return err;

        cpu_uV = regulator_get_voltage_rdev(cpu_rdev);
        if (cpu_uV < 0)
                return cpu_uV;

        /* store boot voltage level */
        if (!tegra->cpu_min_uV)
                tegra->cpu_min_uV = cpu_uV;

        /*
         * CPU's regulator may not have any consumers, hence the voltage
         * must not be changed in that case because CPU simply won't
         * survive the voltage drop if it's running on a higher frequency.
         */
        if (!cpu_min_uV_consumers)
                cpu_min_uV = cpu_uV;

        /* restore boot voltage level */
        if (tegra->sys_reboot_mode)
                cpu_min_uV = max(cpu_min_uV, tegra->cpu_min_uV);

        /* prepare voltage level for suspend */
        if (tegra->sys_suspend_mode)
                cpu_min_uV = clamp(tegra20_cpu_nominal_uV(),
                                   cpu_min_uV, cpu_max_uV);

        if (cpu_min_uV > cpu_uV) {
                err = tegra20_core_rtc_update(tegra, core_rdev, rtc_rdev,
                                              cpu_uV, cpu_min_uV);
                if (err)
                        return err;

                err = regulator_set_voltage_rdev(cpu_rdev, cpu_min_uV,
                                                 cpu_max_uV, PM_SUSPEND_ON);
                if (err)
                        return err;
        } else if (cpu_min_uV < cpu_uV)  {
                err = regulator_set_voltage_rdev(cpu_rdev, cpu_min_uV,
                                                 cpu_max_uV, PM_SUSPEND_ON);
                if (err)
                        return err;

                err = tegra20_core_rtc_update(tegra, core_rdev, rtc_rdev,
                                              cpu_uV, cpu_min_uV);
                if (err)
                        return err;
        }

        return 0;
}

static int tegra20_regulator_balance_voltage(struct regulator_coupler *coupler,
                                             struct regulator_dev *rdev,
                                             suspend_state_t state)
{
        struct tegra_regulator_coupler *tegra = to_tegra_coupler(coupler);
        struct regulator_dev *core_rdev = tegra->core_rdev;
        struct regulator_dev *cpu_rdev = tegra->cpu_rdev;
        struct regulator_dev *rtc_rdev = tegra->rtc_rdev;

        if ((core_rdev != rdev && cpu_rdev != rdev && rtc_rdev != rdev) ||
            state != PM_SUSPEND_ON) {
                pr_err("regulators are not coupled properly\n");
                return -EINVAL;
        }

        tegra->sys_reboot_mode = READ_ONCE(tegra->sys_reboot_mode_req);
        tegra->sys_suspend_mode = READ_ONCE(tegra->sys_suspend_mode_req);

        if (rdev == cpu_rdev)
                return tegra20_cpu_voltage_update(tegra, cpu_rdev,
                                                  core_rdev, rtc_rdev);

        if (rdev == core_rdev)
                return tegra20_core_voltage_update(tegra, cpu_rdev,
                                                   core_rdev, rtc_rdev);

        pr_err("changing %s voltage not permitted\n", rdev_get_name(rtc_rdev));

        return -EPERM;
}

static int tegra20_regulator_prepare_suspend(struct tegra_regulator_coupler *tegra,
                                             bool sys_suspend_mode)
{
        int err;

        if (!tegra->core_rdev || !tegra->rtc_rdev || !tegra->cpu_rdev)
                return 0;

        /*
         * All power domains are enabled early during resume from suspend
         * by GENPD core.  Domains like VENC may require a higher voltage
         * when enabled during resume from suspend.  This also prepares
         * hardware for resuming from LP0.
         */

        WRITE_ONCE(tegra->sys_suspend_mode_req, sys_suspend_mode);

        err = regulator_sync_voltage_rdev(tegra->cpu_rdev);
        if (err)
                return err;

        err = regulator_sync_voltage_rdev(tegra->core_rdev);
        if (err)
                return err;

        return 0;
}

static int tegra20_regulator_suspend(struct notifier_block *notifier,
                                     unsigned long mode, void *arg)
{
        struct tegra_regulator_coupler *tegra;
        int ret = 0;

        tegra = container_of(notifier, struct tegra_regulator_coupler,
                             suspend_notifier);

        switch (mode) {
        case PM_HIBERNATION_PREPARE:
        case PM_RESTORE_PREPARE:
        case PM_SUSPEND_PREPARE:
                ret = tegra20_regulator_prepare_suspend(tegra, true);
                break;

        case PM_POST_HIBERNATION:
        case PM_POST_RESTORE:
        case PM_POST_SUSPEND:
                ret = tegra20_regulator_prepare_suspend(tegra, false);
                break;
        }

        if (ret)
                pr_err("failed to prepare regulators: %d\n", ret);

        return notifier_from_errno(ret);
}

static int tegra20_regulator_prepare_reboot(struct tegra_regulator_coupler *tegra,
                                            bool sys_reboot_mode)
{
        int err;

        if (!tegra->core_rdev || !tegra->rtc_rdev || !tegra->cpu_rdev)
                return 0;

        WRITE_ONCE(tegra->sys_reboot_mode_req, true);

        /*
         * Some devices use CPU soft-reboot method and in this case we
         * should ensure that voltages are sane for the reboot by restoring
         * the minimum boot levels.
         */
        err = regulator_sync_voltage_rdev(tegra->cpu_rdev);
        if (err)
                return err;

        err = regulator_sync_voltage_rdev(tegra->core_rdev);
        if (err)
                return err;

        WRITE_ONCE(tegra->sys_reboot_mode_req, sys_reboot_mode);

        return 0;
}

static int tegra20_regulator_reboot(struct notifier_block *notifier,
                                    unsigned long event, void *cmd)
{
        struct tegra_regulator_coupler *tegra;
        int ret;

        if (event != SYS_RESTART)
                return NOTIFY_DONE;

        tegra = container_of(notifier, struct tegra_regulator_coupler,
                             reboot_notifier);

        ret = tegra20_regulator_prepare_reboot(tegra, true);

        return notifier_from_errno(ret);
}

static int tegra20_regulator_attach(struct regulator_coupler *coupler,
                                    struct regulator_dev *rdev)
{
        struct tegra_regulator_coupler *tegra = to_tegra_coupler(coupler);
        struct device_node *np = rdev->dev.of_node;

        if (of_property_read_bool(np, "nvidia,tegra-core-regulator") &&
            !tegra->core_rdev) {
                tegra->core_rdev = rdev;
                return 0;
        }

        if (of_property_read_bool(np, "nvidia,tegra-rtc-regulator") &&
            !tegra->rtc_rdev) {
                tegra->rtc_rdev = rdev;
                return 0;
        }

        if (of_property_read_bool(np, "nvidia,tegra-cpu-regulator") &&
            !tegra->cpu_rdev) {
                tegra->cpu_rdev = rdev;
                return 0;
        }

        return -EINVAL;
}

static int tegra20_regulator_detach(struct regulator_coupler *coupler,
                                    struct regulator_dev *rdev)
{
        struct tegra_regulator_coupler *tegra = to_tegra_coupler(coupler);

        /*
         * We don't expect regulators to be decoupled during reboot,
         * this may race with the reboot handler and shouldn't ever
         * happen in practice.
         */
        if (WARN_ON_ONCE(system_state > SYSTEM_RUNNING))
                return -EPERM;

        if (tegra->core_rdev == rdev) {
                tegra->core_rdev = NULL;
                return 0;
        }

        if (tegra->rtc_rdev == rdev) {
                tegra->rtc_rdev = NULL;
                return 0;
        }

        if (tegra->cpu_rdev == rdev) {
                tegra->cpu_rdev = NULL;
                return 0;
        }

        return -EINVAL;
}

static struct tegra_regulator_coupler tegra20_coupler = {
        .coupler = {
                .attach_regulator = tegra20_regulator_attach,
                .detach_regulator = tegra20_regulator_detach,
                .balance_voltage = tegra20_regulator_balance_voltage,
        },
        .reboot_notifier.notifier_call = tegra20_regulator_reboot,
        .suspend_notifier.notifier_call = tegra20_regulator_suspend,
};

static int __init tegra_regulator_coupler_init(void)
{
        int err;

        if (!of_machine_is_compatible("nvidia,tegra20"))
                return 0;

        err = register_reboot_notifier(&tegra20_coupler.reboot_notifier);
        WARN_ON(err);

        err = register_pm_notifier(&tegra20_coupler.suspend_notifier);
        WARN_ON(err);

        return regulator_coupler_register(&tegra20_coupler.coupler);
}
arch_initcall(tegra_regulator_coupler_init);