/*
 * CPU frequency scaling for Broadcom BMIPS SoCs
 *
 * Copyright (c) 2017 Broadcom
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation version 2.
 *
 * This program is distributed "as is" WITHOUT ANY WARRANTY of any
 * kind, whether express or implied; without even the implied warranty
 * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 */

#include <linux/cpufreq.h>
#include <linux/module.h>
#include <linux/of_address.h>
#include <linux/slab.h>

/* for mips_hpt_frequency */
#include <asm/time.h>

#define BMIPS_CPUFREQ_PREFIX    "bmips"
#define BMIPS_CPUFREQ_NAME      BMIPS_CPUFREQ_PREFIX "-cpufreq"

#define TRANSITION_LATENCY      (25 * 1000)     /* 25 us */

#define BMIPS5_CLK_DIV_SET_SHIFT        0x7
#define BMIPS5_CLK_DIV_SHIFT            0x4
#define BMIPS5_CLK_DIV_MASK             0xf

enum bmips_type {
        BMIPS5000,
        BMIPS5200,
};

struct cpufreq_compat {
        const char *compatible;
        unsigned int bmips_type;
        unsigned int clk_mult;
        unsigned int max_freqs;
};

#define BMIPS(c, t, m, f) { \
        .compatible = c, \
        .bmips_type = (t), \
        .clk_mult = (m), \
        .max_freqs = (f), \
}

static struct cpufreq_compat bmips_cpufreq_compat[] = {
        BMIPS("brcm,bmips5000", BMIPS5000, 8, 4),
        BMIPS("brcm,bmips5200", BMIPS5200, 8, 4),
        { }
};

static struct cpufreq_compat *priv;

static int htp_freq_to_cpu_freq(unsigned int clk_mult)
{
        return mips_hpt_frequency * clk_mult / 1000;
}

static struct cpufreq_frequency_table *
bmips_cpufreq_get_freq_table(const struct cpufreq_policy *policy)
{
        struct cpufreq_frequency_table *table;
        unsigned long cpu_freq;
        int i;

        cpu_freq = htp_freq_to_cpu_freq(priv->clk_mult);

        table = kmalloc_objs(*table, priv->max_freqs + 1);
        if (!table)
                return ERR_PTR(-ENOMEM);

        for (i = 0; i < priv->max_freqs; i++) {
                table[i].frequency = cpu_freq / (1 << i);
                table[i].driver_data = i;
        }
        table[i].frequency = CPUFREQ_TABLE_END;

        return table;
}

static unsigned int bmips_cpufreq_get(unsigned int cpu)
{
        unsigned int div;
        uint32_t mode;

        switch (priv->bmips_type) {
        case BMIPS5200:
        case BMIPS5000:
                mode = read_c0_brcm_mode();
                div = ((mode >> BMIPS5_CLK_DIV_SHIFT) & BMIPS5_CLK_DIV_MASK);
                break;
        default:
                div = 0;
        }

        return htp_freq_to_cpu_freq(priv->clk_mult) / (1 << div);
}

static int bmips_cpufreq_target_index(struct cpufreq_policy *policy,
                                      unsigned int index)
{
        unsigned int div = policy->freq_table[index].driver_data;

        switch (priv->bmips_type) {
        case BMIPS5200:
        case BMIPS5000:
                change_c0_brcm_mode(BMIPS5_CLK_DIV_MASK << BMIPS5_CLK_DIV_SHIFT,
                                    (1 << BMIPS5_CLK_DIV_SET_SHIFT) |
                                    (div << BMIPS5_CLK_DIV_SHIFT));
                break;
        default:
                return -ENOTSUPP;
        }

        return 0;
}

static void bmips_cpufreq_exit(struct cpufreq_policy *policy)
{
        kfree(policy->freq_table);
}

static int bmips_cpufreq_init(struct cpufreq_policy *policy)
{
        struct cpufreq_frequency_table *freq_table;

        freq_table = bmips_cpufreq_get_freq_table(policy);
        if (IS_ERR(freq_table)) {
                pr_err("%s: couldn't determine frequency table (%ld).\n",
                        BMIPS_CPUFREQ_NAME, PTR_ERR(freq_table));
                return PTR_ERR(freq_table);
        }

        cpufreq_generic_init(policy, freq_table, TRANSITION_LATENCY);
        pr_info("%s: registered\n", BMIPS_CPUFREQ_NAME);

        return 0;
}

static struct cpufreq_driver bmips_cpufreq_driver = {
        .flags          = CPUFREQ_NEED_INITIAL_FREQ_CHECK,
        .verify         = cpufreq_generic_frequency_table_verify,
        .target_index   = bmips_cpufreq_target_index,
        .get            = bmips_cpufreq_get,
        .init           = bmips_cpufreq_init,
        .exit           = bmips_cpufreq_exit,
        .name           = BMIPS_CPUFREQ_PREFIX,
};

static int __init bmips_cpufreq_driver_init(void)
{
        struct cpufreq_compat *cc;
        struct device_node *np;

        for (cc = bmips_cpufreq_compat; cc->compatible; cc++) {
                np = of_find_compatible_node(NULL, "cpu", cc->compatible);
                if (np) {
                        of_node_put(np);
                        priv = cc;
                        break;
                }
        }

        /* We hit the guard element of the array. No compatible CPU found. */
        if (!cc->compatible)
                return -ENODEV;

        return cpufreq_register_driver(&bmips_cpufreq_driver);
}
module_init(bmips_cpufreq_driver_init);

static void __exit bmips_cpufreq_driver_exit(void)
{
        cpufreq_unregister_driver(&bmips_cpufreq_driver);
}
module_exit(bmips_cpufreq_driver_exit);

MODULE_AUTHOR("Markus Mayer <mmayer@broadcom.com>");
MODULE_DESCRIPTION("CPUfreq driver for Broadcom BMIPS SoCs");
MODULE_LICENSE("GPL");