arch/arm/common/icst307.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.icst.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
  20 #include <asm/hardware/icst307.h>
  21
  22 /*
  23  * Divisors for each OD setting.
  24  */
  25 static unsigned char s2div[8] = { 10, 2, 8, 4, 5, 7, 3, 6 };
  26
  27 unsigned long icst307_khz(const struct icst_params *p, struct icst_vco vco)
  28 {
  29         return p->ref * 2 * (vco.v + 8) / ((vco.r + 2) * s2div[vco.s]);
  30 }
  31
  32 EXPORT_SYMBOL(icst307_khz);
  33
  34 /*
  35  * Ascending divisor S values.
  36  */
  37 static unsigned char idx2s[8] = { 1, 6, 3, 4, 7, 5, 2, 0 };
  38
  39 struct icst_vco
  40 icst307_khz_to_vco(const struct icst_params *p, unsigned long freq)
  41 {
  42         struct icst_vco vco = { .s = 1, .v = p->vd_max, .r = p->rd_max };
  43         unsigned long f;
  44         unsigned int i = 0, rd, best = (unsigned int)-1;
  45
  46         /*
  47          * First, find the PLL output divisor such
  48          * that the PLL output is within spec.
  49          */
  50         do {
  51                 f = freq * s2div[idx2s[i]];
  52
  53                 /*
  54                  * f must be between 6MHz and 200MHz (3.3 or 5V)
  55                  */
  56                 if (f > 6000 && f <= p->vco_max)
  57                         break;
  58         } while (i < ARRAY_SIZE(idx2s));
  59
  60         if (i >= ARRAY_SIZE(idx2s))
  61                 return vco;
  62
  63         vco.s = idx2s[i];
  64
  65         /*
  66          * Now find the closest divisor combination
  67          * which gives a PLL output of 'f'.
  68          */
  69         for (rd = p->rd_min; rd <= p->rd_max; rd++) {
  70                 unsigned long fref_div, f_pll;
  71                 unsigned int vd;
  72                 int f_diff;
  73
  74                 fref_div = (2 * p->ref) / rd;
  75
  76                 vd = (f + fref_div / 2) / fref_div;
  77                 if (vd < p->vd_min || vd > p->vd_max)
  78                         continue;
  79
  80                 f_pll = fref_div * vd;
  81                 f_diff = f_pll - f;
  82                 if (f_diff < 0)
  83                         f_diff = -f_diff;
  84
  85                 if ((unsigned)f_diff < best) {
  86                         vco.v = vd - 8;
  87                         vco.r = rd - 2;
  88                         if (f_diff == 0)
  89                                 break;
  90                         best = f_diff;
  91                 }
  92         }
  93
  94         return vco;
  95 }
  96
  97 EXPORT_SYMBOL(icst307_khz_to_vco);