/*
 * S3C2416/2450 CPUfreq Support
 *
 * Copyright 2011 Heiko Stuebner <heiko@sntech.de>
 *
 * based on s3c64xx_cpufreq.c
 *
 * Copyright 2009 Wolfson Microelectronics plc
 *
 * 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.
 */

#include <linux/kernel.h>
#include <linux/types.h>
#include <linux/init.h>
#include <linux/cpufreq.h>
#include <linux/clk.h>
#include <linux/err.h>
#include <linux/regulator/consumer.h>
#include <linux/reboot.h>
#include <linux/module.h>

static DEFINE_MUTEX(cpufreq_lock);

struct s3c2416_data {
        struct clk *armdiv;
        struct clk *armclk;
        struct clk *hclk;

        unsigned long regulator_latency;
#ifdef CONFIG_ARM_S3C2416_CPUFREQ_VCORESCALE
        struct regulator *vddarm;
#endif

        struct cpufreq_frequency_table *freq_table;

        bool is_dvs;
        bool disable_dvs;
};

static struct s3c2416_data s3c2416_cpufreq;

struct s3c2416_dvfs {
        unsigned int vddarm_min;
        unsigned int vddarm_max;
};

/* pseudo-frequency for dvs mode */
#define FREQ_DVS        132333

/* frequency to sleep and reboot in
 * it's essential to leave dvs, as some boards do not reconfigure the
 * regulator on reboot
 */
#define FREQ_SLEEP      133333

/* Sources for the ARMCLK */
#define SOURCE_HCLK     0
#define SOURCE_ARMDIV   1

#ifdef CONFIG_ARM_S3C2416_CPUFREQ_VCORESCALE
/* S3C2416 only supports changing the voltage in the dvs-mode.
 * Voltages down to 1.0V seem to work, so we take what the regulator
 * can get us.
 */
static struct s3c2416_dvfs s3c2416_dvfs_table[] = {
        [SOURCE_HCLK] = {  950000, 1250000 },
        [SOURCE_ARMDIV] = { 1250000, 1350000 },
};
#endif

static struct cpufreq_frequency_table s3c2416_freq_table[] = {
        { 0, SOURCE_HCLK, FREQ_DVS },
        { 0, SOURCE_ARMDIV, 133333 },
        { 0, SOURCE_ARMDIV, 266666 },
        { 0, SOURCE_ARMDIV, 400000 },
        { 0, 0, CPUFREQ_TABLE_END },
};

static struct cpufreq_frequency_table s3c2450_freq_table[] = {
        { 0, SOURCE_HCLK, FREQ_DVS },
        { 0, SOURCE_ARMDIV, 133500 },
        { 0, SOURCE_ARMDIV, 267000 },
        { 0, SOURCE_ARMDIV, 534000 },
        { 0, 0, CPUFREQ_TABLE_END },
};

static unsigned int s3c2416_cpufreq_get_speed(unsigned int cpu)
{
        struct s3c2416_data *s3c_freq = &s3c2416_cpufreq;

        if (cpu != 0)
                return 0;

        /* return our pseudo-frequency when in dvs mode */
        if (s3c_freq->is_dvs)
                return FREQ_DVS;

        return clk_get_rate(s3c_freq->armclk) / 1000;
}

static int s3c2416_cpufreq_set_armdiv(struct s3c2416_data *s3c_freq,
                                      unsigned int freq)
{
        int ret;

        if (clk_get_rate(s3c_freq->armdiv) / 1000 != freq) {
                ret = clk_set_rate(s3c_freq->armdiv, freq * 1000);
                if (ret < 0) {
                        pr_err("cpufreq: Failed to set armdiv rate %dkHz: %d\n",
                               freq, ret);
                        return ret;
                }
        }

        return 0;
}

static int s3c2416_cpufreq_enter_dvs(struct s3c2416_data *s3c_freq, int idx)
{
#ifdef CONFIG_ARM_S3C2416_CPUFREQ_VCORESCALE
        struct s3c2416_dvfs *dvfs;
#endif
        int ret;

        if (s3c_freq->is_dvs) {
                pr_debug("cpufreq: already in dvs mode, nothing to do\n");
                return 0;
        }

        pr_debug("cpufreq: switching armclk to hclk (%lukHz)\n",
                 clk_get_rate(s3c_freq->hclk) / 1000);
        ret = clk_set_parent(s3c_freq->armclk, s3c_freq->hclk);
        if (ret < 0) {
                pr_err("cpufreq: Failed to switch armclk to hclk: %d\n", ret);
                return ret;
        }

#ifdef CONFIG_ARM_S3C2416_CPUFREQ_VCORESCALE
        /* changing the core voltage is only allowed when in dvs mode */
        if (s3c_freq->vddarm) {
                dvfs = &s3c2416_dvfs_table[idx];

                pr_debug("cpufreq: setting regulator to %d-%d\n",
                         dvfs->vddarm_min, dvfs->vddarm_max);
                ret = regulator_set_voltage(s3c_freq->vddarm,
                                            dvfs->vddarm_min,
                                            dvfs->vddarm_max);

                /* when lowering the voltage failed, there is nothing to do */
                if (ret != 0)
                        pr_err("cpufreq: Failed to set VDDARM: %d\n", ret);
        }
#endif

        s3c_freq->is_dvs = 1;

        return 0;
}

static int s3c2416_cpufreq_leave_dvs(struct s3c2416_data *s3c_freq, int idx)
{
#ifdef CONFIG_ARM_S3C2416_CPUFREQ_VCORESCALE
        struct s3c2416_dvfs *dvfs;
#endif
        int ret;

        if (!s3c_freq->is_dvs) {
                pr_debug("cpufreq: not in dvs mode, so can't leave\n");
                return 0;
        }

#ifdef CONFIG_ARM_S3C2416_CPUFREQ_VCORESCALE
        if (s3c_freq->vddarm) {
                dvfs = &s3c2416_dvfs_table[idx];

                pr_debug("cpufreq: setting regulator to %d-%d\n",
                         dvfs->vddarm_min, dvfs->vddarm_max);
                ret = regulator_set_voltage(s3c_freq->vddarm,
                                            dvfs->vddarm_min,
                                            dvfs->vddarm_max);
                if (ret != 0) {
                        pr_err("cpufreq: Failed to set VDDARM: %d\n", ret);
                        return ret;
                }
        }
#endif

        /* force armdiv to hclk frequency for transition from dvs*/
        if (clk_get_rate(s3c_freq->armdiv) > clk_get_rate(s3c_freq->hclk)) {
                pr_debug("cpufreq: force armdiv to hclk frequency (%lukHz)\n",
                         clk_get_rate(s3c_freq->hclk) / 1000);
                ret = s3c2416_cpufreq_set_armdiv(s3c_freq,
                                        clk_get_rate(s3c_freq->hclk) / 1000);
                if (ret < 0) {
                        pr_err("cpufreq: Failed to set the armdiv to %lukHz: %d\n",
                               clk_get_rate(s3c_freq->hclk) / 1000, ret);
                        return ret;
                }
        }

        pr_debug("cpufreq: switching armclk parent to armdiv (%lukHz)\n",
                        clk_get_rate(s3c_freq->armdiv) / 1000);

        ret = clk_set_parent(s3c_freq->armclk, s3c_freq->armdiv);
        if (ret < 0) {
                pr_err("cpufreq: Failed to switch armclk clock parent to armdiv: %d\n",
                       ret);
                return ret;
        }

        s3c_freq->is_dvs = 0;

        return 0;
}

static int s3c2416_cpufreq_set_target(struct cpufreq_policy *policy,
                                      unsigned int index)
{
        struct s3c2416_data *s3c_freq = &s3c2416_cpufreq;
        unsigned int new_freq;
        int idx, ret, to_dvs = 0;

        mutex_lock(&cpufreq_lock);

        idx = s3c_freq->freq_table[index].driver_data;

        if (idx == SOURCE_HCLK)
                to_dvs = 1;

        /* switching to dvs when it's not allowed */
        if (to_dvs && s3c_freq->disable_dvs) {
                pr_debug("cpufreq: entering dvs mode not allowed\n");
                ret = -EINVAL;
                goto out;
        }

        /* When leavin dvs mode, always switch the armdiv to the hclk rate
         * The S3C2416 has stability issues when switching directly to
         * higher frequencies.
         */
        new_freq = (s3c_freq->is_dvs && !to_dvs)
                                ? clk_get_rate(s3c_freq->hclk) / 1000
                                : s3c_freq->freq_table[index].frequency;

        if (to_dvs) {
                pr_debug("cpufreq: enter dvs\n");
                ret = s3c2416_cpufreq_enter_dvs(s3c_freq, idx);
        } else if (s3c_freq->is_dvs) {
                pr_debug("cpufreq: leave dvs\n");
                ret = s3c2416_cpufreq_leave_dvs(s3c_freq, idx);
        } else {
                pr_debug("cpufreq: change armdiv to %dkHz\n", new_freq);
                ret = s3c2416_cpufreq_set_armdiv(s3c_freq, new_freq);
        }

out:
        mutex_unlock(&cpufreq_lock);

        return ret;
}

#ifdef CONFIG_ARM_S3C2416_CPUFREQ_VCORESCALE
static void __init s3c2416_cpufreq_cfg_regulator(struct s3c2416_data *s3c_freq)
{
        int count, v, i, found;
        struct cpufreq_frequency_table *pos;
        struct s3c2416_dvfs *dvfs;

        count = regulator_count_voltages(s3c_freq->vddarm);
        if (count < 0) {
                pr_err("cpufreq: Unable to check supported voltages\n");
                return;
        }

        if (!count)
                goto out;

        cpufreq_for_each_valid_entry(pos, s3c_freq->freq_table) {
                dvfs = &s3c2416_dvfs_table[pos->driver_data];
                found = 0;

                /* Check only the min-voltage, more is always ok on S3C2416 */
                for (i = 0; i < count; i++) {
                        v = regulator_list_voltage(s3c_freq->vddarm, i);
                        if (v >= dvfs->vddarm_min)
                                found = 1;
                }

                if (!found) {
                        pr_debug("cpufreq: %dkHz unsupported by regulator\n",
                                 pos->frequency);
                        pos->frequency = CPUFREQ_ENTRY_INVALID;
                }
        }

out:
        /* Guessed */
        s3c_freq->regulator_latency = 1 * 1000 * 1000;
}
#endif

static int s3c2416_cpufreq_reboot_notifier_evt(struct notifier_block *this,
                                               unsigned long event, void *ptr)
{
        struct s3c2416_data *s3c_freq = &s3c2416_cpufreq;
        int ret;

        mutex_lock(&cpufreq_lock);

        /* disable further changes */
        s3c_freq->disable_dvs = 1;

        mutex_unlock(&cpufreq_lock);

        /* some boards don't reconfigure the regulator on reboot, which
         * could lead to undervolting the cpu when the clock is reset.
         * Therefore we always leave the DVS mode on reboot.
         */
        if (s3c_freq->is_dvs) {
                pr_debug("cpufreq: leave dvs on reboot\n");
                ret = cpufreq_driver_target(cpufreq_cpu_get(0), FREQ_SLEEP, 0);
                if (ret < 0)
                        return NOTIFY_BAD;
        }

        return NOTIFY_DONE;
}

static struct notifier_block s3c2416_cpufreq_reboot_notifier = {
        .notifier_call = s3c2416_cpufreq_reboot_notifier_evt,
};

static int __init s3c2416_cpufreq_driver_init(struct cpufreq_policy *policy)
{
        struct s3c2416_data *s3c_freq = &s3c2416_cpufreq;
        struct cpufreq_frequency_table *pos;
        struct clk *msysclk;
        unsigned long rate;
        int ret;

        if (policy->cpu != 0)
                return -EINVAL;

        msysclk = clk_get(NULL, "msysclk");
        if (IS_ERR(msysclk)) {
                ret = PTR_ERR(msysclk);
                pr_err("cpufreq: Unable to obtain msysclk: %d\n", ret);
                return ret;
        }

        /*
         * S3C2416 and S3C2450 share the same processor-ID and also provide no
         * other means to distinguish them other than through the rate of
         * msysclk. On S3C2416 msysclk runs at 800MHz and on S3C2450 at 533MHz.
         */
        rate = clk_get_rate(msysclk);
        if (rate == 800 * 1000 * 1000) {
                pr_info("cpufreq: msysclk running at %lukHz, using S3C2416 frequency table\n",
                        rate / 1000);
                s3c_freq->freq_table = s3c2416_freq_table;
                policy->cpuinfo.max_freq = 400000;
        } else if (rate / 1000 == 534000) {
                pr_info("cpufreq: msysclk running at %lukHz, using S3C2450 frequency table\n",
                        rate / 1000);
                s3c_freq->freq_table = s3c2450_freq_table;
                policy->cpuinfo.max_freq = 534000;
        }

        /* not needed anymore */
        clk_put(msysclk);

        if (s3c_freq->freq_table == NULL) {
                pr_err("cpufreq: No frequency information for this CPU, msysclk at %lukHz\n",
                       rate / 1000);
                return -ENODEV;
        }

        s3c_freq->is_dvs = 0;

        s3c_freq->armdiv = clk_get(NULL, "armdiv");
        if (IS_ERR(s3c_freq->armdiv)) {
                ret = PTR_ERR(s3c_freq->armdiv);
                pr_err("cpufreq: Unable to obtain ARMDIV: %d\n", ret);
                return ret;
        }

        s3c_freq->hclk = clk_get(NULL, "hclk");
        if (IS_ERR(s3c_freq->hclk)) {
                ret = PTR_ERR(s3c_freq->hclk);
                pr_err("cpufreq: Unable to obtain HCLK: %d\n", ret);
                goto err_hclk;
        }

        /* chech hclk rate, we only support the common 133MHz for now
         * hclk could also run at 66MHz, but this not often used
         */
        rate = clk_get_rate(s3c_freq->hclk);
        if (rate < 133 * 1000 * 1000) {
                pr_err("cpufreq: HCLK not at 133MHz\n");
                clk_put(s3c_freq->hclk);
                ret = -EINVAL;
                goto err_armclk;
        }

        s3c_freq->armclk = clk_get(NULL, "armclk");
        if (IS_ERR(s3c_freq->armclk)) {
                ret = PTR_ERR(s3c_freq->armclk);
                pr_err("cpufreq: Unable to obtain ARMCLK: %d\n", ret);
                goto err_armclk;
        }

#ifdef CONFIG_ARM_S3C2416_CPUFREQ_VCORESCALE
        s3c_freq->vddarm = regulator_get(NULL, "vddarm");
        if (IS_ERR(s3c_freq->vddarm)) {
                ret = PTR_ERR(s3c_freq->vddarm);
                pr_err("cpufreq: Failed to obtain VDDARM: %d\n", ret);
                goto err_vddarm;
        }

        s3c2416_cpufreq_cfg_regulator(s3c_freq);
#else
        s3c_freq->regulator_latency = 0;
#endif

        cpufreq_for_each_entry(pos, s3c_freq->freq_table) {
                /* special handling for dvs mode */
                if (pos->driver_data == 0) {
                        if (!s3c_freq->hclk) {
                                pr_debug("cpufreq: %dkHz unsupported as it would need unavailable dvs mode\n",
                                         pos->frequency);
                                pos->frequency = CPUFREQ_ENTRY_INVALID;
                        } else {
                                continue;
                        }
                }

                /* Check for frequencies we can generate */
                rate = clk_round_rate(s3c_freq->armdiv,
                                      pos->frequency * 1000);
                rate /= 1000;
                if (rate != pos->frequency) {
                        pr_debug("cpufreq: %dkHz unsupported by clock (clk_round_rate return %lu)\n",
                                pos->frequency, rate);
                        pos->frequency = CPUFREQ_ENTRY_INVALID;
                }
        }

        /* Datasheet says PLL stabalisation time must be at least 300us,
         * so but add some fudge. (reference in LOCKCON0 register description)
         */
        ret = cpufreq_generic_init(policy, s3c_freq->freq_table,
                        (500 * 1000) + s3c_freq->regulator_latency);
        if (ret)
                goto err_freq_table;

        register_reboot_notifier(&s3c2416_cpufreq_reboot_notifier);

        return 0;

err_freq_table:
#ifdef CONFIG_ARM_S3C2416_CPUFREQ_VCORESCALE
        regulator_put(s3c_freq->vddarm);
err_vddarm:
#endif
        clk_put(s3c_freq->armclk);
err_armclk:
        clk_put(s3c_freq->hclk);
err_hclk:
        clk_put(s3c_freq->armdiv);

        return ret;
}

static struct cpufreq_driver s3c2416_cpufreq_driver = {
        .flags          = CPUFREQ_NEED_INITIAL_FREQ_CHECK,
        .verify         = cpufreq_generic_frequency_table_verify,
        .target_index   = s3c2416_cpufreq_set_target,
        .get            = s3c2416_cpufreq_get_speed,
        .init           = s3c2416_cpufreq_driver_init,
        .name           = "s3c2416",
        .attr           = cpufreq_generic_attr,
};

static int __init s3c2416_cpufreq_init(void)
{
        return cpufreq_register_driver(&s3c2416_cpufreq_driver);
}
module_init(s3c2416_cpufreq_init);