// SPDX-License-Identifier: GPL-2.0-only
/*
 *  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.
 *
 *  BIG FAT DISCLAIMER: Work in progress code. Possibly *dangerous*
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#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 */

static unsigned int                     busfreq;   /* FSB, in 10 kHz */
static unsigned int                     max_multiplier;

static unsigned int                     param_busfreq = 0;
static unsigned int                     param_max_multiplier = 0;

module_param_named(max_multiplier, param_max_multiplier, uint, S_IRUGO);
MODULE_PARM_DESC(max_multiplier, "Maximum multiplier (allowed values: 20 30 35 40 45 50 55 60)");

module_param_named(bus_frequency, param_busfreq, uint, S_IRUGO);
MODULE_PARM_DESC(bus_frequency, "Bus frequency in kHz");

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

static const u8 index_to_register[8] = { 6, 3, 1, 0, 2, 7, 5, 4 };
static const u8 register_to_index[8] = { 3, 2, 4, 1, 7, 6, 0, 5 };

static const struct {
        unsigned freq;
        unsigned mult;
} usual_frequency_table[] = {
        { 350000, 35 }, // 100   * 3.5
        { 400000, 40 }, // 100   * 4
        { 450000, 45 }, // 100   * 4.5
        { 475000, 50 }, //  95   * 5
        { 500000, 50 }, // 100   * 5
        { 506250, 45 }, // 112.5 * 4.5
        { 533500, 55 }, //  97   * 5.5
        { 550000, 55 }, // 100   * 5.5
        { 562500, 50 }, // 112.5 * 5
        { 570000, 60 }, //  95   * 6
        { 600000, 60 }, // 100   * 6
        { 618750, 55 }, // 112.5 * 5.5
        { 660000, 55 }, // 120   * 5.5
        { 675000, 60 }, // 112.5 * 6
        { 720000, 60 }, // 120   * 6
};

#define FREQ_RANGE              3000

/**
 * 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)
{
        unsigned long invalue = 0;
        u32 msrval;

        local_irq_disable();

        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 */

        local_irq_enable();

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

static void powernow_k6_set_cpu_multiplier(unsigned int best_i)
{
        unsigned long outvalue, invalue;
        unsigned long msrval;
        unsigned long cr0;

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

        /*
         * The processor doesn't respond to inquiry cycles while changing the
         * frequency, so we must disable cache.
         */
        local_irq_disable();
        cr0 = read_cr0();
        write_cr0(cr0 | X86_CR0_CD);
        wbinvd();

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

        msrval = POWERNOW_IOPORT + 0x1;
        wrmsr(MSR_K6_EPMR, msrval, 0); /* enable the PowerNow port */
        invalue = inl(POWERNOW_IOPORT + 0x8);
        invalue = invalue & 0x1f;
        outvalue = outvalue | invalue;
        outl(outvalue, (POWERNOW_IOPORT + 0x8));
        msrval = POWERNOW_IOPORT + 0x0;
        wrmsr(MSR_K6_EPMR, msrval, 0); /* disable it again */

        write_cr0(cr0);
        local_irq_enable();
}

/**
 * powernow_k6_target - set the PowerNow! multiplier
 * @best_i: clock_ratio[best_i] is the target multiplier
 *
 *   Tries to change the PowerNow! multiplier
 */
static int powernow_k6_target(struct cpufreq_policy *policy,
                unsigned int best_i)
{

        if (clock_ratio[best_i].driver_data > max_multiplier) {
                pr_err("invalid target frequency\n");
                return -EINVAL;
        }

        powernow_k6_set_cpu_multiplier(best_i);

        return 0;
}

static int powernow_k6_cpu_init(struct cpufreq_policy *policy)
{
        struct cpufreq_frequency_table *pos;
        unsigned int i, f;
        unsigned khz;

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

        max_multiplier = 0;
        khz = cpu_khz;
        for (i = 0; i < ARRAY_SIZE(usual_frequency_table); i++) {
                if (khz >= usual_frequency_table[i].freq - FREQ_RANGE &&
                    khz <= usual_frequency_table[i].freq + FREQ_RANGE) {
                        khz = usual_frequency_table[i].freq;
                        max_multiplier = usual_frequency_table[i].mult;
                        break;
                }
        }
        if (param_max_multiplier) {
                cpufreq_for_each_entry(pos, clock_ratio)
                        if (pos->driver_data == param_max_multiplier) {
                                max_multiplier = param_max_multiplier;
                                goto have_max_multiplier;
                        }
                pr_err("invalid max_multiplier parameter, valid parameters 20, 30, 35, 40, 45, 50, 55, 60\n");
                return -EINVAL;
        }

        if (!max_multiplier) {
                pr_warn("unknown frequency %u, cannot determine current multiplier\n",
                        khz);
                pr_warn("use module parameters max_multiplier and bus_frequency\n");
                return -EOPNOTSUPP;
        }

have_max_multiplier:
        param_max_multiplier = max_multiplier;

        if (param_busfreq) {
                if (param_busfreq >= 50000 && param_busfreq <= 150000) {
                        busfreq = param_busfreq / 10;
                        goto have_busfreq;
                }
                pr_err("invalid bus_frequency parameter, allowed range 50000 - 150000 kHz\n");
                return -EINVAL;
        }

        busfreq = khz / max_multiplier;
have_busfreq:
        param_busfreq = busfreq * 10;

        /* table init */
        cpufreq_for_each_entry(pos, clock_ratio) {
                f = pos->driver_data;
                if (f > max_multiplier)
                        pos->frequency = CPUFREQ_ENTRY_INVALID;
                else
                        pos->frequency = busfreq * f;
        }

        /* cpuinfo and default policy values */
        policy->cpuinfo.transition_latency = 500000;
        policy->freq_table = clock_ratio;

        return 0;
}


static void powernow_k6_cpu_exit(struct cpufreq_policy *policy)
{
        unsigned int i;

        for (i = 0; (clock_ratio[i].frequency != CPUFREQ_TABLE_END); i++) {
                if (clock_ratio[i].driver_data == max_multiplier) {
                        struct cpufreq_freqs freqs;

                        freqs.old = policy->cur;
                        freqs.new = clock_ratio[i].frequency;
                        freqs.flags = 0;

                        cpufreq_freq_transition_begin(policy, &freqs);
                        powernow_k6_target(policy, i);
                        cpufreq_freq_transition_end(policy, &freqs, 0);
                        return;
                }
        }
}

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

static struct cpufreq_driver powernow_k6_driver = {
        .verify         = cpufreq_generic_frequency_table_verify,
        .target_index   = powernow_k6_target,
        .init           = powernow_k6_cpu_init,
        .exit           = powernow_k6_cpu_exit,
        .get            = powernow_k6_get,
        .name           = "powernow-k6",
};

static const struct x86_cpu_id powernow_k6_ids[] = {
        X86_MATCH_VENDOR_FAM_MODEL(AMD, 5, 12, NULL),
        X86_MATCH_VENDOR_FAM_MODEL(AMD, 5, 13, NULL),
        {}
};
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!")) {
                pr_info("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, "
                "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);