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
  23 static struct clk *cpuclk;
  24
  25 static 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
  35 static 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
  43 static unsigned int     ref_freq;
  44 static unsigned long    loops_per_jiffy_ref;
  45
  46 static 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
  86 static 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
 109 static struct cpufreq_driver at32_driver = {
 110         .name           = "at32ap",
 111         .owner          = THIS_MODULE,
 112         .init           = at32_cpufreq_driver_init,
 113         .verify         = at32_verify_speed,
 114         .target         = at32_set_target,
 115         .get            = at32_get_speed,
 116         .flags          = CPUFREQ_STICKY,
 117 };
 118
 119 static int __init at32_cpufreq_init(void)
 120 {
 121         return cpufreq_register_driver(&at32_driver);
 122 }
 123 late_initcall(at32_cpufreq_init);