LXR linux/drivers/clk/versatile/icst.c

   1// SPDX-License-Identifier: GPL-2.0-only
   2/*
   3 *  linux/arch/arm/common/icst307.c
   4 *
   5 *  Copyright (C) 2003 Deep Blue Solutions, Ltd, All Rights Reserved.
   6 *
   7 *  Support functions for calculating clocks/divisors for the ICST307
   8 *  clock generators.  See https://www.idt.com/ for more information
   9 *  on these devices.
  10 *
  11 *  This is an almost identical implementation to the ICST525 clock generator.
  12 *  The s2div and idx2s files are different
  13 */
  14#include <linux/module.h>
  15#include <linux/kernel.h>
  16#include <asm/div64.h>
  17#include "icst.h"
  18
  19/*
  20 * Divisors for each OD setting.
  21 */
  22const unsigned char icst307_s2div[8] = { 10, 2, 8, 4, 5, 7, 3, 6 };
  23const unsigned char icst525_s2div[8] = { 10, 2, 8, 4, 5, 7, 9, 6 };
  24EXPORT_SYMBOL(icst307_s2div);
  25EXPORT_SYMBOL(icst525_s2div);
  26
  27unsigned long icst_hz(const struct icst_params *p, struct icst_vco vco)
  28{
  29        u64 dividend = p->ref * 2 * (u64)(vco.v + 8);
  30        u32 divisor = (vco.r + 2) * p->s2div[vco.s];
  31
  32        do_div(dividend, divisor);
  33        return (unsigned long)dividend;
  34}
  35
  36EXPORT_SYMBOL(icst_hz);
  37
  38/*
  39 * Ascending divisor S values.
  40 */
  41const unsigned char icst307_idx2s[8] = { 1, 6, 3, 4, 7, 5, 2, 0 };
  42const unsigned char icst525_idx2s[8] = { 1, 3, 4, 7, 5, 2, 6, 0 };
  43EXPORT_SYMBOL(icst307_idx2s);
  44EXPORT_SYMBOL(icst525_idx2s);
  45
  46struct icst_vco
  47icst_hz_to_vco(const struct icst_params *p, unsigned long freq)
  48{
  49        struct icst_vco vco = { .s = 1, .v = p->vd_max, .r = p->rd_max };
  50        unsigned long f;
  51        unsigned int i = 0, rd, best = (unsigned int)-1;
  52
  53        /*
  54         * First, find the PLL output divisor such
  55         * that the PLL output is within spec.
  56         */
  57        do {
  58                f = freq * p->s2div[p->idx2s[i]];
  59
  60                if (f > p->vco_min && f <= p->vco_max)
  61                        break;
  62                i++;
  63        } while (i < 8);
  64
  65        if (i >= 8)
  66                return vco;
  67
  68        vco.s = p->idx2s[i];
  69
  70        /*
  71         * Now find the closest divisor combination
  72         * which gives a PLL output of 'f'.
  73         */
  74        for (rd = p->rd_min; rd <= p->rd_max; rd++) {
  75                unsigned long fref_div, f_pll;
  76                unsigned int vd;
  77                int f_diff;
  78
  79                fref_div = (2 * p->ref) / rd;
  80
  81                vd = (f + fref_div / 2) / fref_div;
  82                if (vd < p->vd_min || vd > p->vd_max)
  83                        continue;
  84
  85                f_pll = fref_div * vd;
  86                f_diff = f_pll - f;
  87                if (f_diff < 0)
  88                        f_diff = -f_diff;
  89
  90                if ((unsigned)f_diff < best) {
  91                        vco.v = vd - 8;
  92                        vco.r = rd - 2;
  93                        if (f_diff == 0)
  94                                break;
  95                        best = f_diff;
  96                }
  97        }
  98
  99        return vco;
 100}
 101
 102EXPORT_SYMBOL(icst_hz_to_vco);
 103