/*
 * Copyright (c) 2015 Linaro Ltd.
 * Author: Pi-Cheng Chen <pi-cheng.chen@linaro.org>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 */

#include <linux/clk.h>
#include <linux/cpu.h>
#include <linux/cpu_cooling.h>
#include <linux/cpufreq.h>
#include <linux/cpumask.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/platform_device.h>
#include <linux/pm_opp.h>
#include <linux/regulator/consumer.h>
#include <linux/slab.h>
#include <linux/thermal.h>

#define MIN_VOLT_SHIFT          (100000)
#define MAX_VOLT_SHIFT          (200000)
#define MAX_VOLT_LIMIT          (1150000)
#define VOLT_TOL                (10000)

/*
 * The struct mtk_cpu_dvfs_info holds necessary information for doing CPU DVFS
 * on each CPU power/clock domain of Mediatek SoCs. Each CPU cluster in
 * Mediatek SoCs has two voltage inputs, Vproc and Vsram. In some cases the two
 * voltage inputs need to be controlled under a hardware limitation:
 * 100mV < Vsram - Vproc < 200mV
 *
 * When scaling the clock frequency of a CPU clock domain, the clock source
 * needs to be switched to another stable PLL clock temporarily until
 * the original PLL becomes stable at target frequency.
 */
struct mtk_cpu_dvfs_info {
        struct cpumask cpus;
        struct device *cpu_dev;
        struct regulator *proc_reg;
        struct regulator *sram_reg;
        struct clk *cpu_clk;
        struct clk *inter_clk;
        struct thermal_cooling_device *cdev;
        struct list_head list_head;
        int intermediate_voltage;
        bool need_voltage_tracking;
};

static LIST_HEAD(dvfs_info_list);

static struct mtk_cpu_dvfs_info *mtk_cpu_dvfs_info_lookup(int cpu)
{
        struct mtk_cpu_dvfs_info *info;
        struct list_head *list;

        list_for_each(list, &dvfs_info_list) {
                info = list_entry(list, struct mtk_cpu_dvfs_info, list_head);

                if (cpumask_test_cpu(cpu, &info->cpus))
                        return info;
        }

        return NULL;
}

static int mtk_cpufreq_voltage_tracking(struct mtk_cpu_dvfs_info *info,
                                        int new_vproc)
{
        struct regulator *proc_reg = info->proc_reg;
        struct regulator *sram_reg = info->sram_reg;
        int old_vproc, old_vsram, new_vsram, vsram, vproc, ret;

        old_vproc = regulator_get_voltage(proc_reg);
        if (old_vproc < 0) {
                pr_err("%s: invalid Vproc value: %d\n", __func__, old_vproc);
                return old_vproc;
        }
        /* Vsram should not exceed the maximum allowed voltage of SoC. */
        new_vsram = min(new_vproc + MIN_VOLT_SHIFT, MAX_VOLT_LIMIT);

        if (old_vproc < new_vproc) {
                /*
                 * When scaling up voltages, Vsram and Vproc scale up step
                 * by step. At each step, set Vsram to (Vproc + 200mV) first,
                 * then set Vproc to (Vsram - 100mV).
                 * Keep doing it until Vsram and Vproc hit target voltages.
                 */
                do {
                        old_vsram = regulator_get_voltage(sram_reg);
                        if (old_vsram < 0) {
                                pr_err("%s: invalid Vsram value: %d\n",
                                       __func__, old_vsram);
                                return old_vsram;
                        }
                        old_vproc = regulator_get_voltage(proc_reg);
                        if (old_vproc < 0) {
                                pr_err("%s: invalid Vproc value: %d\n",
                                       __func__, old_vproc);
                                return old_vproc;
                        }

                        vsram = min(new_vsram, old_vproc + MAX_VOLT_SHIFT);

                        if (vsram + VOLT_TOL >= MAX_VOLT_LIMIT) {
                                vsram = MAX_VOLT_LIMIT;

                                /*
                                 * If the target Vsram hits the maximum voltage,
                                 * try to set the exact voltage value first.
                                 */
                                ret = regulator_set_voltage(sram_reg, vsram,
                                                            vsram);
                                if (ret)
                                        ret = regulator_set_voltage(sram_reg,
                                                        vsram - VOLT_TOL,
                                                        vsram);

                                vproc = new_vproc;
                        } else {
                                ret = regulator_set_voltage(sram_reg, vsram,
                                                            vsram + VOLT_TOL);

                                vproc = vsram - MIN_VOLT_SHIFT;
                        }
                        if (ret)
                                return ret;

                        ret = regulator_set_voltage(proc_reg, vproc,
                                                    vproc + VOLT_TOL);
                        if (ret) {
                                regulator_set_voltage(sram_reg, old_vsram,
                                                      old_vsram);
                                return ret;
                        }
                } while (vproc < new_vproc || vsram < new_vsram);
        } else if (old_vproc > new_vproc) {
                /*
                 * When scaling down voltages, Vsram and Vproc scale down step
                 * by step. At each step, set Vproc to (Vsram - 200mV) first,
                 * then set Vproc to (Vproc + 100mV).
                 * Keep doing it until Vsram and Vproc hit target voltages.
                 */
                do {
                        old_vproc = regulator_get_voltage(proc_reg);
                        if (old_vproc < 0) {
                                pr_err("%s: invalid Vproc value: %d\n",
                                       __func__, old_vproc);
                                return old_vproc;
                        }
                        old_vsram = regulator_get_voltage(sram_reg);
                        if (old_vsram < 0) {
                                pr_err("%s: invalid Vsram value: %d\n",
                                       __func__, old_vsram);
                                return old_vsram;
                        }

                        vproc = max(new_vproc, old_vsram - MAX_VOLT_SHIFT);
                        ret = regulator_set_voltage(proc_reg, vproc,
                                                    vproc + VOLT_TOL);
                        if (ret)
                                return ret;

                        if (vproc == new_vproc)
                                vsram = new_vsram;
                        else
                                vsram = max(new_vsram, vproc + MIN_VOLT_SHIFT);

                        if (vsram + VOLT_TOL >= MAX_VOLT_LIMIT) {
                                vsram = MAX_VOLT_LIMIT;

                                /*
                                 * If the target Vsram hits the maximum voltage,
                                 * try to set the exact voltage value first.
                                 */
                                ret = regulator_set_voltage(sram_reg, vsram,
                                                            vsram);
                                if (ret)
                                        ret = regulator_set_voltage(sram_reg,
                                                        vsram - VOLT_TOL,
                                                        vsram);
                        } else {
                                ret = regulator_set_voltage(sram_reg, vsram,
                                                            vsram + VOLT_TOL);
                        }

                        if (ret) {
                                regulator_set_voltage(proc_reg, old_vproc,
                                                      old_vproc);
                                return ret;
                        }
                } while (vproc > new_vproc + VOLT_TOL ||
                         vsram > new_vsram + VOLT_TOL);
        }

        return 0;
}

static int mtk_cpufreq_set_voltage(struct mtk_cpu_dvfs_info *info, int vproc)
{
        if (info->need_voltage_tracking)
                return mtk_cpufreq_voltage_tracking(info, vproc);
        else
                return regulator_set_voltage(info->proc_reg, vproc,
                                             vproc + VOLT_TOL);
}

static int mtk_cpufreq_set_target(struct cpufreq_policy *policy,
                                  unsigned int index)
{
        struct cpufreq_frequency_table *freq_table = policy->freq_table;
        struct clk *cpu_clk = policy->clk;
        struct clk *armpll = clk_get_parent(cpu_clk);
        struct mtk_cpu_dvfs_info *info = policy->driver_data;
        struct device *cpu_dev = info->cpu_dev;
        struct dev_pm_opp *opp;
        long freq_hz, old_freq_hz;
        int vproc, old_vproc, inter_vproc, target_vproc, ret;

        inter_vproc = info->intermediate_voltage;

        old_freq_hz = clk_get_rate(cpu_clk);
        old_vproc = regulator_get_voltage(info->proc_reg);
        if (old_vproc < 0) {
                pr_err("%s: invalid Vproc value: %d\n", __func__, old_vproc);
                return old_vproc;
        }

        freq_hz = freq_table[index].frequency * 1000;

        rcu_read_lock();
        opp = dev_pm_opp_find_freq_ceil(cpu_dev, &freq_hz);
        if (IS_ERR(opp)) {
                rcu_read_unlock();
                pr_err("cpu%d: failed to find OPP for %ld\n",
                       policy->cpu, freq_hz);
                return PTR_ERR(opp);
        }
        vproc = dev_pm_opp_get_voltage(opp);
        rcu_read_unlock();

        /*
         * If the new voltage or the intermediate voltage is higher than the
         * current voltage, scale up voltage first.
         */
        target_vproc = (inter_vproc > vproc) ? inter_vproc : vproc;
        if (old_vproc < target_vproc) {
                ret = mtk_cpufreq_set_voltage(info, target_vproc);
                if (ret) {
                        pr_err("cpu%d: failed to scale up voltage!\n",
                               policy->cpu);
                        mtk_cpufreq_set_voltage(info, old_vproc);
                        return ret;
                }
        }

        /* Reparent the CPU clock to intermediate clock. */
        ret = clk_set_parent(cpu_clk, info->inter_clk);
        if (ret) {
                pr_err("cpu%d: failed to re-parent cpu clock!\n",
                       policy->cpu);
                mtk_cpufreq_set_voltage(info, old_vproc);
                WARN_ON(1);
                return ret;
        }

        /* Set the original PLL to target rate. */
        ret = clk_set_rate(armpll, freq_hz);
        if (ret) {
                pr_err("cpu%d: failed to scale cpu clock rate!\n",
                       policy->cpu);
                clk_set_parent(cpu_clk, armpll);
                mtk_cpufreq_set_voltage(info, old_vproc);
                return ret;
        }

        /* Set parent of CPU clock back to the original PLL. */
        ret = clk_set_parent(cpu_clk, armpll);
        if (ret) {
                pr_err("cpu%d: failed to re-parent cpu clock!\n",
                       policy->cpu);
                mtk_cpufreq_set_voltage(info, inter_vproc);
                WARN_ON(1);
                return ret;
        }

        /*
         * If the new voltage is lower than the intermediate voltage or the
         * original voltage, scale down to the new voltage.
         */
        if (vproc < inter_vproc || vproc < old_vproc) {
                ret = mtk_cpufreq_set_voltage(info, vproc);
                if (ret) {
                        pr_err("cpu%d: failed to scale down voltage!\n",
                               policy->cpu);
                        clk_set_parent(cpu_clk, info->inter_clk);
                        clk_set_rate(armpll, old_freq_hz);
                        clk_set_parent(cpu_clk, armpll);
                        return ret;
                }
        }

        return 0;
}

static void mtk_cpufreq_ready(struct cpufreq_policy *policy)
{
        struct mtk_cpu_dvfs_info *info = policy->driver_data;
        struct device_node *np = of_node_get(info->cpu_dev->of_node);

        if (WARN_ON(!np))
                return;

        if (of_find_property(np, "#cooling-cells", NULL)) {
                info->cdev = of_cpufreq_cooling_register(np,
                                                         policy->related_cpus);

                if (IS_ERR(info->cdev)) {
                        dev_err(info->cpu_dev,
                                "running cpufreq without cooling device: %ld\n",
                                PTR_ERR(info->cdev));

                        info->cdev = NULL;
                }
        }

        of_node_put(np);
}

static int mtk_cpu_dvfs_info_init(struct mtk_cpu_dvfs_info *info, int cpu)
{
        struct device *cpu_dev;
        struct regulator *proc_reg = ERR_PTR(-ENODEV);
        struct regulator *sram_reg = ERR_PTR(-ENODEV);
        struct clk *cpu_clk = ERR_PTR(-ENODEV);
        struct clk *inter_clk = ERR_PTR(-ENODEV);
        struct dev_pm_opp *opp;
        unsigned long rate;
        int ret;

        cpu_dev = get_cpu_device(cpu);
        if (!cpu_dev) {
                pr_err("failed to get cpu%d device\n", cpu);
                return -ENODEV;
        }

        cpu_clk = clk_get(cpu_dev, "cpu");
        if (IS_ERR(cpu_clk)) {
                if (PTR_ERR(cpu_clk) == -EPROBE_DEFER)
                        pr_warn("cpu clk for cpu%d not ready, retry.\n", cpu);
                else
                        pr_err("failed to get cpu clk for cpu%d\n", cpu);

                ret = PTR_ERR(cpu_clk);
                return ret;
        }

        inter_clk = clk_get(cpu_dev, "intermediate");
        if (IS_ERR(inter_clk)) {
                if (PTR_ERR(inter_clk) == -EPROBE_DEFER)
                        pr_warn("intermediate clk for cpu%d not ready, retry.\n",
                                cpu);
                else
                        pr_err("failed to get intermediate clk for cpu%d\n",
                               cpu);

                ret = PTR_ERR(inter_clk);
                goto out_free_resources;
        }

        proc_reg = regulator_get_exclusive(cpu_dev, "proc");
        if (IS_ERR(proc_reg)) {
                if (PTR_ERR(proc_reg) == -EPROBE_DEFER)
                        pr_warn("proc regulator for cpu%d not ready, retry.\n",
                                cpu);
                else
                        pr_err("failed to get proc regulator for cpu%d\n",
                               cpu);

                ret = PTR_ERR(proc_reg);
                goto out_free_resources;
        }

        /* Both presence and absence of sram regulator are valid cases. */
        sram_reg = regulator_get_exclusive(cpu_dev, "sram");

        /* Get OPP-sharing information from "operating-points-v2" bindings */
        ret = dev_pm_opp_of_get_sharing_cpus(cpu_dev, &info->cpus);
        if (ret) {
                pr_err("failed to get OPP-sharing information for cpu%d\n",
                       cpu);
                goto out_free_resources;
        }

        ret = dev_pm_opp_of_cpumask_add_table(&info->cpus);
        if (ret) {
                pr_warn("no OPP table for cpu%d\n", cpu);
                goto out_free_resources;
        }

        /* Search a safe voltage for intermediate frequency. */
        rate = clk_get_rate(inter_clk);
        rcu_read_lock();
        opp = dev_pm_opp_find_freq_ceil(cpu_dev, &rate);
        if (IS_ERR(opp)) {
                rcu_read_unlock();
                pr_err("failed to get intermediate opp for cpu%d\n", cpu);
                ret = PTR_ERR(opp);
                goto out_free_opp_table;
        }
        info->intermediate_voltage = dev_pm_opp_get_voltage(opp);
        rcu_read_unlock();

        info->cpu_dev = cpu_dev;
        info->proc_reg = proc_reg;
        info->sram_reg = IS_ERR(sram_reg) ? NULL : sram_reg;
        info->cpu_clk = cpu_clk;
        info->inter_clk = inter_clk;

        /*
         * If SRAM regulator is present, software "voltage tracking" is needed
         * for this CPU power domain.
         */
        info->need_voltage_tracking = !IS_ERR(sram_reg);

        return 0;

out_free_opp_table:
        dev_pm_opp_of_cpumask_remove_table(&info->cpus);

out_free_resources:
        if (!IS_ERR(proc_reg))
                regulator_put(proc_reg);
        if (!IS_ERR(sram_reg))
                regulator_put(sram_reg);
        if (!IS_ERR(cpu_clk))
                clk_put(cpu_clk);
        if (!IS_ERR(inter_clk))
                clk_put(inter_clk);

        return ret;
}

static void mtk_cpu_dvfs_info_release(struct mtk_cpu_dvfs_info *info)
{
        if (!IS_ERR(info->proc_reg))
                regulator_put(info->proc_reg);
        if (!IS_ERR(info->sram_reg))
                regulator_put(info->sram_reg);
        if (!IS_ERR(info->cpu_clk))
                clk_put(info->cpu_clk);
        if (!IS_ERR(info->inter_clk))
                clk_put(info->inter_clk);

        dev_pm_opp_of_cpumask_remove_table(&info->cpus);
}

static int mtk_cpufreq_init(struct cpufreq_policy *policy)
{
        struct mtk_cpu_dvfs_info *info;
        struct cpufreq_frequency_table *freq_table;
        int ret;

        info = mtk_cpu_dvfs_info_lookup(policy->cpu);
        if (!info) {
                pr_err("dvfs info for cpu%d is not initialized.\n",
                       policy->cpu);
                return -EINVAL;
        }

        ret = dev_pm_opp_init_cpufreq_table(info->cpu_dev, &freq_table);
        if (ret) {
                pr_err("failed to init cpufreq table for cpu%d: %d\n",
                       policy->cpu, ret);
                return ret;
        }

        ret = cpufreq_table_validate_and_show(policy, freq_table);
        if (ret) {
                pr_err("%s: invalid frequency table: %d\n", __func__, ret);
                goto out_free_cpufreq_table;
        }

        cpumask_copy(policy->cpus, &info->cpus);
        policy->driver_data = info;
        policy->clk = info->cpu_clk;

        return 0;

out_free_cpufreq_table:
        dev_pm_opp_free_cpufreq_table(info->cpu_dev, &freq_table);
        return ret;
}

static int mtk_cpufreq_exit(struct cpufreq_policy *policy)
{
        struct mtk_cpu_dvfs_info *info = policy->driver_data;

        cpufreq_cooling_unregister(info->cdev);
        dev_pm_opp_free_cpufreq_table(info->cpu_dev, &policy->freq_table);

        return 0;
}

static struct cpufreq_driver mt8173_cpufreq_driver = {
        .flags = CPUFREQ_STICKY | CPUFREQ_NEED_INITIAL_FREQ_CHECK |
                 CPUFREQ_HAVE_GOVERNOR_PER_POLICY,
        .verify = cpufreq_generic_frequency_table_verify,
        .target_index = mtk_cpufreq_set_target,
        .get = cpufreq_generic_get,
        .init = mtk_cpufreq_init,
        .exit = mtk_cpufreq_exit,
        .ready = mtk_cpufreq_ready,
        .name = "mtk-cpufreq",
        .attr = cpufreq_generic_attr,
};

static int mt8173_cpufreq_probe(struct platform_device *pdev)
{
        struct mtk_cpu_dvfs_info *info;
        struct list_head *list, *tmp;
        int cpu, ret;

        for_each_possible_cpu(cpu) {
                info = mtk_cpu_dvfs_info_lookup(cpu);
                if (info)
                        continue;

                info = devm_kzalloc(&pdev->dev, sizeof(*info), GFP_KERNEL);
                if (!info) {
                        ret = -ENOMEM;
                        goto release_dvfs_info_list;
                }

                ret = mtk_cpu_dvfs_info_init(info, cpu);
                if (ret) {
                        dev_err(&pdev->dev,
                                "failed to initialize dvfs info for cpu%d\n",
                                cpu);
                        goto release_dvfs_info_list;
                }

                list_add(&info->list_head, &dvfs_info_list);
        }

        ret = cpufreq_register_driver(&mt8173_cpufreq_driver);
        if (ret) {
                dev_err(&pdev->dev, "failed to register mtk cpufreq driver\n");
                goto release_dvfs_info_list;
        }

        return 0;

release_dvfs_info_list:
        list_for_each_safe(list, tmp, &dvfs_info_list) {
                info = list_entry(list, struct mtk_cpu_dvfs_info, list_head);

                mtk_cpu_dvfs_info_release(info);
                list_del(list);
        }

        return ret;
}

static struct platform_driver mt8173_cpufreq_platdrv = {
        .driver = {
                .name   = "mt8173-cpufreq",
        },
        .probe          = mt8173_cpufreq_probe,
};

static int mt8173_cpufreq_driver_init(void)
{
        struct platform_device *pdev;
        int err;

        if (!of_machine_is_compatible("mediatek,mt8173"))
                return -ENODEV;

        err = platform_driver_register(&mt8173_cpufreq_platdrv);
        if (err)
                return err;

        /*
         * Since there's no place to hold device registration code and no
         * device tree based way to match cpufreq driver yet, both the driver
         * and the device registration codes are put here to handle defer
         * probing.
         */
        pdev = platform_device_register_simple("mt8173-cpufreq", -1, NULL, 0);
        if (IS_ERR(pdev)) {
                pr_err("failed to register mtk-cpufreq platform device\n");
                return PTR_ERR(pdev);
        }

        return 0;
}
device_initcall(mt8173_cpufreq_driver_init);