icst.c

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/*
 *  linux/arch/arm/common/icst307.c
 *
 *  Copyright (C) 2003 Deep Blue Solutions, Ltd, All Rights Reserved.
 *
 * 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.
 *
 *  Support functions for calculating clocks/divisors for the ICST307
 *  clock generators.  See http://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/hardware/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)
{
    return p->ref * 2 * (vco.v + 8) / ((vco.r + 2) * p->s2div[vco.s]);
}

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;
    } 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);