/*
 *  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
 *
 * 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/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/opp.h>
#include <linux/cpu.h>
#include <linux/module.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 clk *mpu_clk;
static struct device *mpu_dev;
static struct regulator *mpu_reg;

static int omap_verify_speed(struct cpufreq_policy *policy)
{
        if (!freq_table)
                return -EINVAL;
        return cpufreq_frequency_table_verify(policy, freq_table);
}

static unsigned int omap_getspeed(unsigned int cpu)
{
        unsigned long rate;

        if (cpu >= NR_CPUS)
                return 0;

        rate = clk_get_rate(mpu_clk) / 1000;
        return rate;
}

static int omap_target(struct cpufreq_policy *policy,
                       unsigned int target_freq,
                       unsigned int relation)
{
        unsigned int i;
        int r, ret = 0;
        struct cpufreq_freqs freqs;
        struct opp *opp;
        unsigned long freq, volt = 0, volt_old = 0, tol = 0;

        if (!freq_table) {
                dev_err(mpu_dev, "%s: cpu%d: no freq table!\n", __func__,
                                policy->cpu);
                return -EINVAL;
        }

        ret = cpufreq_frequency_table_target(policy, freq_table, target_freq,
                        relation, &i);
        if (ret) {
                dev_dbg(mpu_dev, "%s: cpu%d: no freq match for %d(ret=%d)\n",
                        __func__, policy->cpu, target_freq, ret);
                return ret;
        }
        freqs.new = freq_table[i].frequency;
        if (!freqs.new) {
                dev_err(mpu_dev, "%s: cpu%d: no match for freq %d\n", __func__,
                        policy->cpu, target_freq);
                return -EINVAL;
        }

        freqs.old = omap_getspeed(policy->cpu);
        freqs.cpu = policy->cpu;

        if (freqs.old == freqs.new && policy->cur == freqs.new)
                return ret;

        /* notifiers */
        for_each_cpu(i, policy->cpus) {
                freqs.cpu = i;
                cpufreq_notify_transition(&freqs, CPUFREQ_PRECHANGE);
        }

        freq = freqs.new * 1000;
        ret = clk_round_rate(mpu_clk, freq);
        if (IS_ERR_VALUE(ret)) {
                dev_warn(mpu_dev,
                         "CPUfreq: Cannot find matching frequency for %lu\n",
                         freq);
                return ret;
        }
        freq = ret;

        if (mpu_reg) {
                rcu_read_lock();
                opp = opp_find_freq_ceil(mpu_dev, &freq);
                if (IS_ERR(opp)) {
                        rcu_read_unlock();
                        dev_err(mpu_dev, "%s: unable to find MPU OPP for %d\n",
                                __func__, freqs.new);
                        return -EINVAL;
                }
                volt = opp_get_voltage(opp);
                rcu_read_unlock();
                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", 
                freqs.old / 1000, volt_old ? volt_old / 1000 : -1,
                freqs.new / 1000, volt ? volt / 1000 : -1);

        /* scaling up?  scale voltage before frequency */
        if (mpu_reg && (freqs.new > freqs.old)) {
                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__);
                        freqs.new = freqs.old;
                        goto done;
                }
        }

        ret = clk_set_rate(mpu_clk, freqs.new * 1000);

        /* scaling down?  scale voltage after frequency */
        if (mpu_reg && (freqs.new < freqs.old)) {
                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__);
                        ret = clk_set_rate(mpu_clk, freqs.old * 1000);
                        freqs.new = freqs.old;
                        goto done;
                }
        }

        freqs.new = omap_getspeed(policy->cpu);

done:
        /* notifiers */
        for_each_cpu(i, policy->cpus) {
                freqs.cpu = i;
                cpufreq_notify_transition(&freqs, CPUFREQ_POSTCHANGE);
        }

        return ret;
}

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

static int __cpuinit omap_cpu_init(struct cpufreq_policy *policy)
{
        int result = 0;

        mpu_clk = clk_get(NULL, "cpufreq_ck");
        if (IS_ERR(mpu_clk))
                return PTR_ERR(mpu_clk);

        if (policy->cpu >= NR_CPUS) {
                result = -EINVAL;
                goto fail_ck;
        }

        policy->cur = policy->min = policy->max = omap_getspeed(policy->cpu);

        if (!freq_table)
                result = 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);
                goto fail_ck;
        }

        atomic_inc_return(&freq_table_users);

        result = cpufreq_frequency_table_cpuinfo(policy, freq_table);
        if (result)
                goto fail_table;

        cpufreq_frequency_table_get_attr(freq_table, policy->cpu);

        policy->min = policy->cpuinfo.min_freq;
        policy->max = policy->cpuinfo.max_freq;
        policy->cur = omap_getspeed(policy->cpu);

        /*
         * On OMAP SMP configuartion, both processors share the voltage
         * and clock. So both CPUs needs to be scaled together and hence
         * needs software co-ordination. Use cpufreq affected_cpus
         * interface to handle this scenario. Additional is_smp() check
         * is to keep SMP_ON_UP build working.
         */
        if (is_smp()) {
                policy->shared_type = CPUFREQ_SHARED_TYPE_ANY;
                cpumask_setall(policy->cpus);
        }

        /* FIXME: what's the actual transition time? */
        policy->cpuinfo.transition_latency = 300 * 1000;

        return 0;

fail_table:
        freq_table_free();
fail_ck:
        clk_put(mpu_clk);
        return result;
}

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

static struct freq_attr *omap_cpufreq_attr[] = {
        &cpufreq_freq_attr_scaling_available_freqs,
        NULL,
};

static struct cpufreq_driver omap_driver = {
        .flags          = CPUFREQ_STICKY,
        .verify         = omap_verify_speed,
        .target         = omap_target,
        .get            = omap_getspeed,
        .init           = omap_cpu_init,
        .exit           = omap_cpu_exit,
        .name           = "omap",
        .attr           = omap_cpufreq_attr,
};

static int __init omap_cpufreq_init(void)
{
        mpu_dev = get_cpu_device(0);
        if (!mpu_dev) {
                pr_warning("%s: unable to get the mpu device\n", __func__);
                return -EINVAL;
        }

        mpu_reg = regulator_get(mpu_dev, "vcc");
        if (IS_ERR(mpu_reg)) {
                pr_warning("%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 void __exit omap_cpufreq_exit(void)
{
        cpufreq_unregister_driver(&omap_driver);
}

MODULE_DESCRIPTION("cpufreq driver for OMAP SoCs");
MODULE_LICENSE("GPL");
module_init(omap_cpufreq_init);
module_exit(omap_cpufreq_exit);