/*
 *  This file was based upon code in Powertweak Linux (http://powertweak.sf.net)
 *  (C) 2000-2003  Dave Jones, Arjan van de Ven, Janne Pänkälä,
 *                 Dominik Brodowski.
 *
 *  Licensed under the terms of the GNU GPL License version 2.
 *
 *  BIG FAT DISCLAIMER: Work in progress code. Possibly *dangerous*
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/cpufreq.h>
#include <linux/ioport.h>
#include <linux/timex.h>
#include <linux/io.h>

#include <asm/cpu_device_id.h>
#include <asm/msr.h>

#define POWERNOW_IOPORT 0xfff0          /* it doesn't matter where, as long
                                           as it is unused */

#define PFX "powernow-k6: "
static unsigned int                     busfreq;   /* FSB, in 10 kHz */
static unsigned int                     max_multiplier;


/* Clock ratio multiplied by 10 - see table 27 in AMD#23446 */
static struct cpufreq_frequency_table clock_ratio[] = {
        {45,  /* 000 -> 4.5x */ 0},
        {50,  /* 001 -> 5.0x */ 0},
        {40,  /* 010 -> 4.0x */ 0},
        {55,  /* 011 -> 5.5x */ 0},
        {20,  /* 100 -> 2.0x */ 0},
        {30,  /* 101 -> 3.0x */ 0},
        {60,  /* 110 -> 6.0x */ 0},
        {35,  /* 111 -> 3.5x */ 0},
        {0, CPUFREQ_TABLE_END}
};


/**
 * powernow_k6_get_cpu_multiplier - returns the current FSB multiplier
 *
 *   Returns the current setting of the frequency multiplier. Core clock
 * speed is frequency of the Front-Side Bus multiplied with this value.
 */
static int powernow_k6_get_cpu_multiplier(void)
{
        u64 invalue = 0;
        u32 msrval;

        msrval = POWERNOW_IOPORT + 0x1;
        wrmsr(MSR_K6_EPMR, msrval, 0); /* enable the PowerNow port */
        invalue = inl(POWERNOW_IOPORT + 0x8);
        msrval = POWERNOW_IOPORT + 0x0;
        wrmsr(MSR_K6_EPMR, msrval, 0); /* disable it again */

        return clock_ratio[(invalue >> 5)&7].driver_data;
}


/**
 * powernow_k6_set_state - set the PowerNow! multiplier
 * @best_i: clock_ratio[best_i] is the target multiplier
 *
 *   Tries to change the PowerNow! multiplier
 */
static void powernow_k6_set_state(struct cpufreq_policy *policy,
                unsigned int best_i)
{
        unsigned long outvalue = 0, invalue = 0;
        unsigned long msrval;
        struct cpufreq_freqs freqs;

        if (clock_ratio[best_i].driver_data > max_multiplier) {
                printk(KERN_ERR PFX "invalid target frequency\n");
                return;
        }

        freqs.old = busfreq * powernow_k6_get_cpu_multiplier();
        freqs.new = busfreq * clock_ratio[best_i].driver_data;

        cpufreq_notify_transition(policy, &freqs, CPUFREQ_PRECHANGE);

        /* we now need to transform best_i to the BVC format, see AMD#23446 */

        outvalue = (1<<12) | (1<<10) | (1<<9) | (best_i<<5);

        msrval = POWERNOW_IOPORT + 0x1;
        wrmsr(MSR_K6_EPMR, msrval, 0); /* enable the PowerNow port */
        invalue = inl(POWERNOW_IOPORT + 0x8);
        invalue = invalue & 0xf;
        outvalue = outvalue | invalue;
        outl(outvalue , (POWERNOW_IOPORT + 0x8));
        msrval = POWERNOW_IOPORT + 0x0;
        wrmsr(MSR_K6_EPMR, msrval, 0); /* disable it again */

        cpufreq_notify_transition(policy, &freqs, CPUFREQ_POSTCHANGE);

        return;
}


/**
 * powernow_k6_verify - verifies a new CPUfreq policy
 * @policy: new policy
 *
 * Policy must be within lowest and highest possible CPU Frequency,
 * and at least one possible state must be within min and max.
 */
static int powernow_k6_verify(struct cpufreq_policy *policy)
{
        return cpufreq_frequency_table_verify(policy, &clock_ratio[0]);
}


/**
 * powernow_k6_setpolicy - sets a new CPUFreq policy
 * @policy: new policy
 * @target_freq: the target frequency
 * @relation: how that frequency relates to achieved frequency
 *  (CPUFREQ_RELATION_L or CPUFREQ_RELATION_H)
 *
 * sets a new CPUFreq policy
 */
static int powernow_k6_target(struct cpufreq_policy *policy,
                               unsigned int target_freq,
                               unsigned int relation)
{
        unsigned int newstate = 0;

        if (cpufreq_frequency_table_target(policy, &clock_ratio[0],
                                target_freq, relation, &newstate))
                return -EINVAL;

        powernow_k6_set_state(policy, newstate);

        return 0;
}


static int powernow_k6_cpu_init(struct cpufreq_policy *policy)
{
        unsigned int i, f;
        int result;

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

        /* get frequencies */
        max_multiplier = powernow_k6_get_cpu_multiplier();
        busfreq = cpu_khz / max_multiplier;

        /* table init */
        for (i = 0; (clock_ratio[i].frequency != CPUFREQ_TABLE_END); i++) {
                f = clock_ratio[i].driver_data;
                if (f > max_multiplier)
                        clock_ratio[i].frequency = CPUFREQ_ENTRY_INVALID;
                else
                        clock_ratio[i].frequency = busfreq * f;
        }

        /* cpuinfo and default policy values */
        policy->cpuinfo.transition_latency = 200000;
        policy->cur = busfreq * max_multiplier;

        result = cpufreq_frequency_table_cpuinfo(policy, clock_ratio);
        if (result)
                return result;

        cpufreq_frequency_table_get_attr(clock_ratio, policy->cpu);

        return 0;
}


static int powernow_k6_cpu_exit(struct cpufreq_policy *policy)
{
        unsigned int i;
        for (i = 0; i < 8; i++) {
                if (i == max_multiplier)
                        powernow_k6_set_state(policy, i);
        }
        cpufreq_frequency_table_put_attr(policy->cpu);
        return 0;
}

static unsigned int powernow_k6_get(unsigned int cpu)
{
        unsigned int ret;
        ret = (busfreq * powernow_k6_get_cpu_multiplier());
        return ret;
}

static struct freq_attr *powernow_k6_attr[] = {
        &cpufreq_freq_attr_scaling_available_freqs,
        NULL,
};

static struct cpufreq_driver powernow_k6_driver = {
        .verify         = powernow_k6_verify,
        .target         = powernow_k6_target,
        .init           = powernow_k6_cpu_init,
        .exit           = powernow_k6_cpu_exit,
        .get            = powernow_k6_get,
        .name           = "powernow-k6",
        .attr           = powernow_k6_attr,
};

static const struct x86_cpu_id powernow_k6_ids[] = {
        { X86_VENDOR_AMD, 5, 12 },
        { X86_VENDOR_AMD, 5, 13 },
        {}
};
MODULE_DEVICE_TABLE(x86cpu, powernow_k6_ids);

/**
 * powernow_k6_init - initializes the k6 PowerNow! CPUFreq driver
 *
 *   Initializes the K6 PowerNow! support. Returns -ENODEV on unsupported
 * devices, -EINVAL or -ENOMEM on problems during initiatization, and zero
 * on success.
 */
static int __init powernow_k6_init(void)
{
        if (!x86_match_cpu(powernow_k6_ids))
                return -ENODEV;

        if (!request_region(POWERNOW_IOPORT, 16, "PowerNow!")) {
                printk(KERN_INFO PFX "PowerNow IOPORT region already used.\n");
                return -EIO;
        }

        if (cpufreq_register_driver(&powernow_k6_driver)) {
                release_region(POWERNOW_IOPORT, 16);
                return -EINVAL;
        }

        return 0;
}


/**
 * powernow_k6_exit - unregisters AMD K6-2+/3+ PowerNow! support
 *
 *   Unregisters AMD K6-2+ / K6-3+ PowerNow! support.
 */
static void __exit powernow_k6_exit(void)
{
        cpufreq_unregister_driver(&powernow_k6_driver);
        release_region(POWERNOW_IOPORT, 16);
}


MODULE_AUTHOR("Arjan van de Ven, Dave Jones <davej@redhat.com>, "
                "Dominik Brodowski <linux@brodo.de>");
MODULE_DESCRIPTION("PowerNow! driver for AMD K6-2+ / K6-3+ processors.");
MODULE_LICENSE("GPL");

module_init(powernow_k6_init);
module_exit(powernow_k6_exit);