// SPDX-License-Identifier: GPL-2.0-only
/*
 *  linux/arch/arm/common/icst307.c
 *
 *  Copyright (C) 2003 Deep Blue Solutions, Ltd, All Rights Reserved.
 *
 *  Support functions for calculating clocks/divisors for the ICST307
 *  clock generators.  See https://www.idt.com/ for more information
 *  on these devices.
 *
 *  This is an almost identical implementation to the ICST525 clock generator.
 *  The s2div and idx2s files are different
 */
#include <linux/module.h>
#include <linux/kernel.h>
#include <asm/div64.h>
#include "icst.h"

/*
 * Divisors for each OD setting.
 */
const unsigned char icst307_s2div[8] = { 10, 2, 8, 4, 5, 7, 3, 6 };
const unsigned char icst525_s2div[8] = { 10, 2, 8, 4, 5, 7, 9, 6 };
EXPORT_SYMBOL(icst307_s2div);
EXPORT_SYMBOL(icst525_s2div);

unsigned long icst_hz(const struct icst_params *p, struct icst_vco vco)
{
        u64 dividend = p->ref * 2 * (u64)(vco.v + 8);
        u32 divisor = (vco.r + 2) * p->s2div[vco.s];

        do_div(dividend, divisor);
        return (unsigned long)dividend;
}

EXPORT_SYMBOL(icst_hz);

/*
 * Ascending divisor S values.
 */
const unsigned char icst307_idx2s[8] = { 1, 6, 3, 4, 7, 5, 2, 0 };
const unsigned char icst525_idx2s[8] = { 1, 3, 4, 7, 5, 2, 6, 0 };
EXPORT_SYMBOL(icst307_idx2s);
EXPORT_SYMBOL(icst525_idx2s);

struct icst_vco
icst_hz_to_vco(const struct icst_params *p, unsigned long freq)
{
        struct icst_vco vco = { .s = 1, .v = p->vd_max, .r = p->rd_max };
        unsigned long f;
        unsigned int i = 0, rd, best = (unsigned int)-1;

        /*
         * First, find the PLL output divisor such
         * that the PLL output is within spec.
         */
        do {
                f = freq * p->s2div[p->idx2s[i]];

                if (f > p->vco_min && f <= p->vco_max)
                        break;
                i++;
        } while (i < 8);

        if (i >= 8)
                return vco;

        vco.s = p->idx2s[i];

        /*
         * Now find the closest divisor combination
         * which gives a PLL output of 'f'.
         */
        for (rd = p->rd_min; rd <= p->rd_max; rd++) {
                unsigned long fref_div, f_pll;
                unsigned int vd;
                int f_diff;

                fref_div = (2 * p->ref) / rd;

                vd = (f + fref_div / 2) / fref_div;
                if (vd < p->vd_min || vd > p->vd_max)
                        continue;

                f_pll = fref_div * vd;
                f_diff = f_pll - f;
                if (f_diff < 0)
                        f_diff = -f_diff;

                if ((unsigned)f_diff < best) {
                        vco.v = vd - 8;
                        vco.r = rd - 2;
                        if (f_diff == 0)
                                break;
                        best = f_diff;
                }
        }

        return vco;
}

EXPORT_SYMBOL(icst_hz_to_vco);