LXR linux/drivers/cpufreq/at32ap-cpufreq.c

   1/*
   2 * Copyright (C) 2004-2007 Atmel Corporation
   3 *
   4 * Based on MIPS implementation arch/mips/kernel/time.c
   5 *   Copyright 2001 MontaVista Software Inc.
   6 *
   7 * This program is free software; you can redistribute it and/or modify
   8 * it under the terms of the GNU General Public License version 2 as
   9 * published by the Free Software Foundation.
  10 */
  11
  12/*#define DEBUG*/
  13
  14#include <linux/kernel.h>
  15#include <linux/types.h>
  16#include <linux/init.h>
  17#include <linux/cpufreq.h>
  18#include <linux/io.h>
  19#include <linux/clk.h>
  20#include <linux/err.h>
  21#include <linux/export.h>
  22#include <linux/slab.h>
  23
  24static struct cpufreq_frequency_table *freq_table;
  25
  26static unsigned int     ref_freq;
  27static unsigned long    loops_per_jiffy_ref;
  28
  29static int at32_set_target(struct cpufreq_policy *policy, unsigned int index)
  30{
  31        unsigned int old_freq, new_freq;
  32
  33        old_freq = policy->cur;
  34        new_freq = freq_table[index].frequency;
  35
  36        if (!ref_freq) {
  37                ref_freq = old_freq;
  38                loops_per_jiffy_ref = boot_cpu_data.loops_per_jiffy;
  39        }
  40
  41        if (old_freq < new_freq)
  42                boot_cpu_data.loops_per_jiffy = cpufreq_scale(
  43                                loops_per_jiffy_ref, ref_freq, new_freq);
  44        clk_set_rate(policy->clk, new_freq * 1000);
  45        if (new_freq < old_freq)
  46                boot_cpu_data.loops_per_jiffy = cpufreq_scale(
  47                                loops_per_jiffy_ref, ref_freq, new_freq);
  48
  49        return 0;
  50}
  51
  52static int at32_cpufreq_driver_init(struct cpufreq_policy *policy)
  53{
  54        unsigned int frequency, rate, min_freq;
  55        struct clk *cpuclk;
  56        int retval, steps, i;
  57
  58        if (policy->cpu != 0)
  59                return -EINVAL;
  60
  61        cpuclk = clk_get(NULL, "cpu");
  62        if (IS_ERR(cpuclk)) {
  63                pr_debug("cpufreq: could not get CPU clk\n");
  64                retval = PTR_ERR(cpuclk);
  65                goto out_err;
  66        }
  67
  68        min_freq = (clk_round_rate(cpuclk, 1) + 500) / 1000;
  69        frequency = (clk_round_rate(cpuclk, ~0UL) + 500) / 1000;
  70        policy->cpuinfo.transition_latency = 0;
  71
  72        /*
  73         * AVR32 CPU frequency rate scales in power of two between maximum and
  74         * minimum, also add space for the table end marker.
  75         *
  76         * Further validate that the frequency is usable, and append it to the
  77         * frequency table.
  78         */
  79        steps = fls(frequency / min_freq) + 1;
  80        freq_table = kzalloc(steps * sizeof(struct cpufreq_frequency_table),
  81                        GFP_KERNEL);
  82        if (!freq_table) {
  83                retval = -ENOMEM;
  84                goto out_err_put_clk;
  85        }
  86
  87        for (i = 0; i < (steps - 1); i++) {
  88                rate = clk_round_rate(cpuclk, frequency * 1000) / 1000;
  89
  90                if (rate != frequency)
  91                        freq_table[i].frequency = CPUFREQ_ENTRY_INVALID;
  92                else
  93                        freq_table[i].frequency = frequency;
  94
  95                frequency /= 2;
  96        }
  97
  98        policy->clk = cpuclk;
  99        freq_table[steps - 1].frequency = CPUFREQ_TABLE_END;
 100
 101        retval = cpufreq_table_validate_and_show(policy, freq_table);
 102        if (!retval) {
 103                printk("cpufreq: AT32AP CPU frequency driver\n");
 104                return 0;
 105        }
 106
 107        kfree(freq_table);
 108out_err_put_clk:
 109        clk_put(cpuclk);
 110out_err:
 111        return retval;
 112}
 113
 114static struct cpufreq_driver at32_driver = {
 115        .name           = "at32ap",
 116        .init           = at32_cpufreq_driver_init,
 117        .verify         = cpufreq_generic_frequency_table_verify,
 118        .target_index   = at32_set_target,
 119        .get            = cpufreq_generic_get,
 120        .flags          = CPUFREQ_STICKY,
 121};
 122
 123static int __init at32_cpufreq_init(void)
 124{
 125        return cpufreq_register_driver(&at32_driver);
 126}
 127late_initcall(at32_cpufreq_init);
 128