linux/drivers/cpufreq/at32ap-cpufreq.c
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   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
  23static struct clk *cpuclk;
  24
  25static int at32_verify_speed(struct cpufreq_policy *policy)
  26{
  27        if (policy->cpu != 0)
  28                return -EINVAL;
  29
  30        cpufreq_verify_within_limits(policy, policy->cpuinfo.min_freq,
  31                        policy->cpuinfo.max_freq);
  32        return 0;
  33}
  34
  35static unsigned int at32_get_speed(unsigned int cpu)
  36{
  37        /* No SMP support */
  38        if (cpu)
  39                return 0;
  40        return (unsigned int)((clk_get_rate(cpuclk) + 500) / 1000);
  41}
  42
  43static unsigned int     ref_freq;
  44static unsigned long    loops_per_jiffy_ref;
  45
  46static int at32_set_target(struct cpufreq_policy *policy,
  47                          unsigned int target_freq,
  48                          unsigned int relation)
  49{
  50        struct cpufreq_freqs freqs;
  51        long freq;
  52
  53        /* Convert target_freq from kHz to Hz */
  54        freq = clk_round_rate(cpuclk, target_freq * 1000);
  55
  56        /* Check if policy->min <= new_freq <= policy->max */
  57        if(freq < (policy->min * 1000) || freq > (policy->max * 1000))
  58                return -EINVAL;
  59
  60        pr_debug("cpufreq: requested frequency %u Hz\n", target_freq * 1000);
  61
  62        freqs.old = at32_get_speed(0);
  63        freqs.new = (freq + 500) / 1000;
  64        freqs.flags = 0;
  65
  66        if (!ref_freq) {
  67                ref_freq = freqs.old;
  68                loops_per_jiffy_ref = boot_cpu_data.loops_per_jiffy;
  69        }
  70
  71        cpufreq_notify_transition(policy, &freqs, CPUFREQ_PRECHANGE);
  72        if (freqs.old < freqs.new)
  73                boot_cpu_data.loops_per_jiffy = cpufreq_scale(
  74                                loops_per_jiffy_ref, ref_freq, freqs.new);
  75        clk_set_rate(cpuclk, freq);
  76        if (freqs.new < freqs.old)
  77                boot_cpu_data.loops_per_jiffy = cpufreq_scale(
  78                                loops_per_jiffy_ref, ref_freq, freqs.new);
  79        cpufreq_notify_transition(policy, &freqs, CPUFREQ_POSTCHANGE);
  80
  81        pr_debug("cpufreq: set frequency %lu Hz\n", freq);
  82
  83        return 0;
  84}
  85
  86static int __init at32_cpufreq_driver_init(struct cpufreq_policy *policy)
  87{
  88        if (policy->cpu != 0)
  89                return -EINVAL;
  90
  91        cpuclk = clk_get(NULL, "cpu");
  92        if (IS_ERR(cpuclk)) {
  93                pr_debug("cpufreq: could not get CPU clk\n");
  94                return PTR_ERR(cpuclk);
  95        }
  96
  97        policy->cpuinfo.min_freq = (clk_round_rate(cpuclk, 1) + 500) / 1000;
  98        policy->cpuinfo.max_freq = (clk_round_rate(cpuclk, ~0UL) + 500) / 1000;
  99        policy->cpuinfo.transition_latency = 0;
 100        policy->cur = at32_get_speed(0);
 101        policy->min = policy->cpuinfo.min_freq;
 102        policy->max = policy->cpuinfo.max_freq;
 103
 104        printk("cpufreq: AT32AP CPU frequency driver\n");
 105
 106        return 0;
 107}
 108
 109static struct cpufreq_driver at32_driver = {
 110        .name           = "at32ap",
 111        .init           = at32_cpufreq_driver_init,
 112        .verify         = at32_verify_speed,
 113        .target         = at32_set_target,
 114        .get            = at32_get_speed,
 115        .flags          = CPUFREQ_STICKY,
 116};
 117
 118static int __init at32_cpufreq_init(void)
 119{
 120        return cpufreq_register_driver(&at32_driver);
 121}
 122late_initcall(at32_cpufreq_init);
 123
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