// SPDX-License-Identifier: GPL-2.0-only
/*
 *  CPU frequency scaling for OMAP using OPP information
 *
 *  Copyright (C) 2005 Nokia Corporation
 *  Written by Tony Lindgren <tony@atomide.com>
 *
 *  Based on cpu-sa1110.c, Copyright (C) 2001 Russell King
 *
 * Copyright (C) 2007-2011 Texas Instruments, Inc.
 * - OMAP3/4 support by Rajendra Nayak, Santosh Shilimkar
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/cpufreq.h>
#include <linux/delay.h>
#include <linux/init.h>
#include <linux/err.h>
#include <linux/clk.h>
#include <linux/io.h>
#include <linux/pm_opp.h>
#include <linux/cpu.h>
#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/regulator/consumer.h>

#include <asm/smp_plat.h>
#include <asm/cpu.h>

/* OPP tolerance in percentage */
#define OPP_TOLERANCE   4

static struct cpufreq_frequency_table *freq_table;
static atomic_t freq_table_users = ATOMIC_INIT(0);
static struct device *mpu_dev;
static struct regulator *mpu_reg;

static int omap_target(struct cpufreq_policy *policy, unsigned int index)
{
        int r, ret;
        struct dev_pm_opp *opp;
        unsigned long freq, volt = 0, volt_old = 0, tol = 0;
        unsigned int old_freq, new_freq;

        old_freq = policy->cur;
        new_freq = freq_table[index].frequency;

        freq = new_freq * 1000;
        ret = clk_round_rate(policy->clk, freq);
        if (ret < 0) {
                dev_warn(mpu_dev,
                         "CPUfreq: Cannot find matching frequency for %lu\n",
                         freq);
                return ret;
        }
        freq = ret;

        if (mpu_reg) {
                opp = dev_pm_opp_find_freq_ceil(mpu_dev, &freq);
                if (IS_ERR(opp)) {
                        dev_err(mpu_dev, "%s: unable to find MPU OPP for %d\n",
                                __func__, new_freq);
                        return -EINVAL;
                }
                volt = dev_pm_opp_get_voltage(opp);
                dev_pm_opp_put(opp);
                tol = volt * OPP_TOLERANCE / 100;
                volt_old = regulator_get_voltage(mpu_reg);
        }

        dev_dbg(mpu_dev, "cpufreq-omap: %u MHz, %ld mV --> %u MHz, %ld mV\n", 
                old_freq / 1000, volt_old ? volt_old / 1000 : -1,
                new_freq / 1000, volt ? volt / 1000 : -1);

        /* scaling up?  scale voltage before frequency */
        if (mpu_reg && (new_freq > old_freq)) {
                r = regulator_set_voltage(mpu_reg, volt - tol, volt + tol);
                if (r < 0) {
                        dev_warn(mpu_dev, "%s: unable to scale voltage up.\n",
                                 __func__);
                        return r;
                }
        }

        ret = clk_set_rate(policy->clk, new_freq * 1000);

        /* scaling down?  scale voltage after frequency */
        if (mpu_reg && (new_freq < old_freq)) {
                r = regulator_set_voltage(mpu_reg, volt - tol, volt + tol);
                if (r < 0) {
                        dev_warn(mpu_dev, "%s: unable to scale voltage down.\n",
                                 __func__);
                        clk_set_rate(policy->clk, old_freq * 1000);
                        return r;
                }
        }

        return ret;
}

static inline void freq_table_free(void)
{
        if (atomic_dec_and_test(&freq_table_users))
                dev_pm_opp_free_cpufreq_table(mpu_dev, &freq_table);
}

static int omap_cpu_init(struct cpufreq_policy *policy)
{
        int result;

        policy->clk = clk_get(NULL, "cpufreq_ck");
        if (IS_ERR(policy->clk))
                return PTR_ERR(policy->clk);

        if (!freq_table) {
                result = dev_pm_opp_init_cpufreq_table(mpu_dev, &freq_table);
                if (result) {
                        dev_err(mpu_dev,
                                "%s: cpu%d: failed creating freq table[%d]\n",
                                __func__, policy->cpu, result);
                        clk_put(policy->clk);
                        return result;
                }
        }

        atomic_inc_return(&freq_table_users);

        /* FIXME: what's the actual transition time? */
        cpufreq_generic_init(policy, freq_table, 300 * 1000);
        dev_pm_opp_of_register_em(policy->cpus);

        return 0;
}

static int omap_cpu_exit(struct cpufreq_policy *policy)
{
        freq_table_free();
        clk_put(policy->clk);
        return 0;
}

static struct cpufreq_driver omap_driver = {
        .flags          = CPUFREQ_STICKY | CPUFREQ_NEED_INITIAL_FREQ_CHECK,
        .verify         = cpufreq_generic_frequency_table_verify,
        .target_index   = omap_target,
        .get            = cpufreq_generic_get,
        .init           = omap_cpu_init,
        .exit           = omap_cpu_exit,
        .name           = "omap",
        .attr           = cpufreq_generic_attr,
};

static int omap_cpufreq_probe(struct platform_device *pdev)
{
        mpu_dev = get_cpu_device(0);
        if (!mpu_dev) {
                pr_warn("%s: unable to get the MPU device\n", __func__);
                return -EINVAL;
        }

        mpu_reg = regulator_get(mpu_dev, "vcc");
        if (IS_ERR(mpu_reg)) {
                pr_warn("%s: unable to get MPU regulator\n", __func__);
                mpu_reg = NULL;
        } else {
                /* 
                 * Ensure physical regulator is present.
                 * (e.g. could be dummy regulator.)
                 */
                if (regulator_get_voltage(mpu_reg) < 0) {
                        pr_warn("%s: physical regulator not present for MPU\n",
                                __func__);
                        regulator_put(mpu_reg);
                        mpu_reg = NULL;
                }
        }

        return cpufreq_register_driver(&omap_driver);
}

static int omap_cpufreq_remove(struct platform_device *pdev)
{
        return cpufreq_unregister_driver(&omap_driver);
}

static struct platform_driver omap_cpufreq_platdrv = {
        .driver = {
                .name   = "omap-cpufreq",
        },
        .probe          = omap_cpufreq_probe,
        .remove         = omap_cpufreq_remove,
};
module_platform_driver(omap_cpufreq_platdrv);

MODULE_DESCRIPTION("cpufreq driver for OMAP SoCs");
MODULE_LICENSE("GPL");