/*
 * Copyright (c) 2006-2009 Simtec Electronics
 *      http://armlinux.simtec.co.uk/
 *      Ben Dooks <ben@simtec.co.uk>
 *      Vincent Sanders <vince@simtec.co.uk>
 *
 * S3C2440/S3C2442 CPU Frequency scaling
 *
 * 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.
*/

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/init.h>
#include <linux/module.h>
#include <linux/interrupt.h>
#include <linux/ioport.h>
#include <linux/cpufreq.h>
#include <linux/device.h>
#include <linux/delay.h>
#include <linux/clk.h>
#include <linux/err.h>
#include <linux/io.h>

#include <asm/mach/arch.h>
#include <asm/mach/map.h>

#include <mach/regs-clock.h>

#include <plat/cpu.h>
#include <plat/cpu-freq-core.h>

static struct clk *xtal;
static struct clk *fclk;
static struct clk *hclk;
static struct clk *armclk;

/* HDIV: 1, 2, 3, 4, 6, 8 */

static inline int within_khz(unsigned long a, unsigned long b)
{
        long diff = a - b;

        return (diff >= -1000 && diff <= 1000);
}

/**
 * s3c2440_cpufreq_calcdivs - calculate divider settings
 * @cfg: The cpu frequency settings.
 *
 * Calcualte the divider values for the given frequency settings
 * specified in @cfg. The values are stored in @cfg for later use
 * by the relevant set routine if the request settings can be reached.
 */
static int s3c2440_cpufreq_calcdivs(struct s3c_cpufreq_config *cfg)
{
        unsigned int hdiv, pdiv;
        unsigned long hclk, fclk, armclk;
        unsigned long hclk_max;

        fclk = cfg->freq.fclk;
        armclk = cfg->freq.armclk;
        hclk_max = cfg->max.hclk;

        s3c_freq_dbg("%s: fclk is %lu, armclk %lu, max hclk %lu\n",
                     __func__, fclk, armclk, hclk_max);

        if (armclk > fclk) {
                pr_warn("%s: armclk > fclk\n", __func__);
                armclk = fclk;
        }

        /* if we are in DVS, we need HCLK to be <= ARMCLK */
        if (armclk < fclk && armclk < hclk_max)
                hclk_max = armclk;

        for (hdiv = 1; hdiv < 9; hdiv++) {
                if (hdiv == 5 || hdiv == 7)
                        hdiv++;

                hclk = (fclk / hdiv);
                if (hclk <= hclk_max || within_khz(hclk, hclk_max))
                        break;
        }

        s3c_freq_dbg("%s: hclk %lu, div %d\n", __func__, hclk, hdiv);

        if (hdiv > 8)
                goto invalid;

        pdiv = (hclk > cfg->max.pclk) ? 2 : 1;

        if ((hclk / pdiv) > cfg->max.pclk)
                pdiv++;

        s3c_freq_dbg("%s: pdiv %d\n", __func__, pdiv);

        if (pdiv > 2)
                goto invalid;

        pdiv *= hdiv;

        /* calculate a valid armclk */

        if (armclk < hclk)
                armclk = hclk;

        /* if we're running armclk lower than fclk, this really means
         * that the system should go into dvs mode, which means that
         * armclk is connected to hclk. */
        if (armclk < fclk) {
                cfg->divs.dvs = 1;
                armclk = hclk;
        } else
                cfg->divs.dvs = 0;

        cfg->freq.armclk = armclk;

        /* store the result, and then return */

        cfg->divs.h_divisor = hdiv;
        cfg->divs.p_divisor = pdiv;

        return 0;

 invalid:
        return -EINVAL;
}

#define CAMDIVN_HCLK_HALF (S3C2440_CAMDIVN_HCLK3_HALF | \
                           S3C2440_CAMDIVN_HCLK4_HALF)

/**
 * s3c2440_cpufreq_setdivs - set the cpu frequency divider settings
 * @cfg: The cpu frequency settings.
 *
 * Set the divisors from the settings in @cfg, which where generated
 * during the calculation phase by s3c2440_cpufreq_calcdivs().
 */
static void s3c2440_cpufreq_setdivs(struct s3c_cpufreq_config *cfg)
{
        unsigned long clkdiv, camdiv;

        s3c_freq_dbg("%s: divsiors: h=%d, p=%d\n", __func__,
                     cfg->divs.h_divisor, cfg->divs.p_divisor);

        clkdiv = __raw_readl(S3C2410_CLKDIVN);
        camdiv = __raw_readl(S3C2440_CAMDIVN);

        clkdiv &= ~(S3C2440_CLKDIVN_HDIVN_MASK | S3C2440_CLKDIVN_PDIVN);
        camdiv &= ~CAMDIVN_HCLK_HALF;

        switch (cfg->divs.h_divisor) {
        case 1:
                clkdiv |= S3C2440_CLKDIVN_HDIVN_1;
                break;

        case 2:
                clkdiv |= S3C2440_CLKDIVN_HDIVN_2;
                break;

        case 6:
                camdiv |= S3C2440_CAMDIVN_HCLK3_HALF;
        case 3:
                clkdiv |= S3C2440_CLKDIVN_HDIVN_3_6;
                break;

        case 8:
                camdiv |= S3C2440_CAMDIVN_HCLK4_HALF;
        case 4:
                clkdiv |= S3C2440_CLKDIVN_HDIVN_4_8;
                break;

        default:
                BUG();  /* we don't expect to get here. */
        }

        if (cfg->divs.p_divisor != cfg->divs.h_divisor)
                clkdiv |= S3C2440_CLKDIVN_PDIVN;

        /* todo - set pclk. */

        /* Write the divisors first with hclk intentionally halved so that
         * when we write clkdiv we will under-frequency instead of over. We
         * then make a short delay and remove the hclk halving if necessary.
         */

        __raw_writel(camdiv | CAMDIVN_HCLK_HALF, S3C2440_CAMDIVN);
        __raw_writel(clkdiv, S3C2410_CLKDIVN);

        ndelay(20);
        __raw_writel(camdiv, S3C2440_CAMDIVN);

        clk_set_parent(armclk, cfg->divs.dvs ? hclk : fclk);
}

static int run_freq_for(unsigned long max_hclk, unsigned long fclk,
                        int *divs,
                        struct cpufreq_frequency_table *table,
                        size_t table_size)
{
        unsigned long freq;
        int index = 0;
        int div;

        for (div = *divs; div > 0; div = *divs++) {
                freq = fclk / div;

                if (freq > max_hclk && div != 1)
                        continue;

                freq /= 1000; /* table is in kHz */
                index = s3c_cpufreq_addfreq(table, index, table_size, freq);
                if (index < 0)
                        break;
        }

        return index;
}

static int hclk_divs[] = { 1, 2, 3, 4, 6, 8, -1 };

static int s3c2440_cpufreq_calctable(struct s3c_cpufreq_config *cfg,
                                     struct cpufreq_frequency_table *table,
                                     size_t table_size)
{
        int ret;

        WARN_ON(cfg->info == NULL);
        WARN_ON(cfg->board == NULL);

        ret = run_freq_for(cfg->info->max.hclk,
                           cfg->info->max.fclk,
                           hclk_divs,
                           table, table_size);

        s3c_freq_dbg("%s: returning %d\n", __func__, ret);

        return ret;
}

static struct s3c_cpufreq_info s3c2440_cpufreq_info = {
        .max            = {
                .fclk   = 400000000,
                .hclk   = 133333333,
                .pclk   =  66666666,
        },

        .locktime_m     = 300,
        .locktime_u     = 300,
        .locktime_bits  = 16,

        .name           = "s3c244x",
        .calc_iotiming  = s3c2410_iotiming_calc,
        .set_iotiming   = s3c2410_iotiming_set,
        .get_iotiming   = s3c2410_iotiming_get,
        .set_fvco       = s3c2410_set_fvco,

        .set_refresh    = s3c2410_cpufreq_setrefresh,
        .set_divs       = s3c2440_cpufreq_setdivs,
        .calc_divs      = s3c2440_cpufreq_calcdivs,
        .calc_freqtable = s3c2440_cpufreq_calctable,

        .debug_io_show  = s3c_cpufreq_debugfs_call(s3c2410_iotiming_debugfs),
};

static int s3c2440_cpufreq_add(struct device *dev,
                               struct subsys_interface *sif)
{
        xtal = s3c_cpufreq_clk_get(NULL, "xtal");
        hclk = s3c_cpufreq_clk_get(NULL, "hclk");
        fclk = s3c_cpufreq_clk_get(NULL, "fclk");
        armclk = s3c_cpufreq_clk_get(NULL, "armclk");

        if (IS_ERR(xtal) || IS_ERR(hclk) || IS_ERR(fclk) || IS_ERR(armclk)) {
                pr_err("%s: failed to get clocks\n", __func__);
                return -ENOENT;
        }

        return s3c_cpufreq_register(&s3c2440_cpufreq_info);
}

static struct subsys_interface s3c2440_cpufreq_interface = {
        .name           = "s3c2440_cpufreq",
        .subsys         = &s3c2440_subsys,
        .add_dev        = s3c2440_cpufreq_add,
};

static int s3c2440_cpufreq_init(void)
{
        return subsys_interface_register(&s3c2440_cpufreq_interface);
}

/* arch_initcall adds the clocks we need, so use subsys_initcall. */
subsys_initcall(s3c2440_cpufreq_init);

static struct subsys_interface s3c2442_cpufreq_interface = {
        .name           = "s3c2442_cpufreq",
        .subsys         = &s3c2442_subsys,
        .add_dev        = s3c2440_cpufreq_add,
};

static int s3c2442_cpufreq_init(void)
{
        return subsys_interface_register(&s3c2442_cpufreq_interface);
}
subsys_initcall(s3c2442_cpufreq_init);