LXR linux/arch/arm/common/icst.c

   1/*
   2 *  linux/arch/arm/common/icst307.c
   3 *
   4 *  Copyright (C) 2003 Deep Blue Solutions, Ltd, All Rights Reserved.
   5 *
   6 * This program is free software; you can redistribute it and/or modify
   7 * it under the terms of the GNU General Public License version 2 as
   8 * published by the Free Software Foundation.
   9 *
  10 *  Support functions for calculating clocks/divisors for the ICST307
  11 *  clock generators.  See http://www.idt.com/ for more information
  12 *  on these devices.
  13 *
  14 *  This is an almost identical implementation to the ICST525 clock generator.
  15 *  The s2div and idx2s files are different
  16 */
  17#include <linux/module.h>
  18#include <linux/kernel.h>
  19#include <asm/div64.h>
  20#include <asm/hardware/icst.h>
  21
  22/*
  23 * Divisors for each OD setting.
  24 */
  25const unsigned char icst307_s2div[8] = { 10, 2, 8, 4, 5, 7, 3, 6 };
  26const unsigned char icst525_s2div[8] = { 10, 2, 8, 4, 5, 7, 9, 6 };
  27EXPORT_SYMBOL(icst307_s2div);
  28EXPORT_SYMBOL(icst525_s2div);
  29
  30unsigned long icst_hz(const struct icst_params *p, struct icst_vco vco)
  31{
  32        u64 dividend = p->ref * 2 * (u64)(vco.v + 8);
  33        u32 divisor = (vco.r + 2) * p->s2div[vco.s];
  34
  35        do_div(dividend, divisor);
  36        return (unsigned long)dividend;
  37}
  38
  39EXPORT_SYMBOL(icst_hz);
  40
  41/*
  42 * Ascending divisor S values.
  43 */
  44const unsigned char icst307_idx2s[8] = { 1, 6, 3, 4, 7, 5, 2, 0 };
  45const unsigned char icst525_idx2s[8] = { 1, 3, 4, 7, 5, 2, 6, 0 };
  46EXPORT_SYMBOL(icst307_idx2s);
  47EXPORT_SYMBOL(icst525_idx2s);
  48
  49struct icst_vco
  50icst_hz_to_vco(const struct icst_params *p, unsigned long freq)
  51{
  52        struct icst_vco vco = { .s = 1, .v = p->vd_max, .r = p->rd_max };
  53        unsigned long f;
  54        unsigned int i = 0, rd, best = (unsigned int)-1;
  55
  56        /*
  57         * First, find the PLL output divisor such
  58         * that the PLL output is within spec.
  59         */
  60        do {
  61                f = freq * p->s2div[p->idx2s[i]];
  62
  63                if (f > p->vco_min && f <= p->vco_max)
  64                        break;
  65                i++;
  66        } while (i < 8);
  67
  68        if (i >= 8)
  69                return vco;
  70
  71        vco.s = p->idx2s[i];
  72
  73        /*
  74         * Now find the closest divisor combination
  75         * which gives a PLL output of 'f'.
  76         */
  77        for (rd = p->rd_min; rd <= p->rd_max; rd++) {
  78                unsigned long fref_div, f_pll;
  79                unsigned int vd;
  80                int f_diff;
  81
  82                fref_div = (2 * p->ref) / rd;
  83
  84                vd = (f + fref_div / 2) / fref_div;
  85                if (vd < p->vd_min || vd > p->vd_max)
  86                        continue;
  87
  88                f_pll = fref_div * vd;
  89                f_diff = f_pll - f;
  90                if (f_diff < 0)
  91                        f_diff = -f_diff;
  92
  93                if ((unsigned)f_diff < best) {
  94                        vco.v = vd - 8;
  95                        vco.r = rd - 2;
  96                        if (f_diff == 0)
  97                                break;
  98                        best = f_diff;
  99                }
 100        }
 101
 102        return vco;
 103}
 104
 105EXPORT_SYMBOL(icst_hz_to_vco);
 106