arch/avr32/mach-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 <asm/system.h>
  23
  24 static struct clk *cpuclk;
  25
  26 static int at32_verify_speed(struct cpufreq_policy *policy)
  27 {
  28         if (policy->cpu != 0)
  29                 return -EINVAL;
  30
  31         cpufreq_verify_within_limits(policy, policy->cpuinfo.min_freq,
  32                         policy->cpuinfo.max_freq);
  33         return 0;
  34 }
  35
  36 static unsigned int at32_get_speed(unsigned int cpu)
  37 {
  38         /* No SMP support */
  39         if (cpu)
  40                 return 0;
  41         return (unsigned int)((clk_get_rate(cpuclk) + 500) / 1000);
  42 }
  43
  44 static unsigned int     ref_freq;
  45 static unsigned long    loops_per_jiffy_ref;
  46
  47 static int at32_set_target(struct cpufreq_policy *policy,
  48                           unsigned int target_freq,
  49                           unsigned int relation)
  50 {
  51         struct cpufreq_freqs freqs;
  52         long freq;
  53
  54         /* Convert target_freq from kHz to Hz */
  55         freq = clk_round_rate(cpuclk, target_freq * 1000);
  56
  57         /* Check if policy->min <= new_freq <= policy->max */
  58         if(freq < (policy->min * 1000) || freq > (policy->max * 1000))
  59                 return -EINVAL;
  60
  61         pr_debug("cpufreq: requested frequency %u Hz\n", target_freq * 1000);
  62
  63         freqs.old = at32_get_speed(0);
  64         freqs.new = (freq + 500) / 1000;
  65         freqs.cpu = 0;
  66         freqs.flags = 0;
  67
  68         if (!ref_freq) {
  69                 ref_freq = freqs.old;
  70                 loops_per_jiffy_ref = boot_cpu_data.loops_per_jiffy;
  71         }
  72
  73         cpufreq_notify_transition(&freqs, CPUFREQ_PRECHANGE);
  74         if (freqs.old < freqs.new)
  75                 boot_cpu_data.loops_per_jiffy = cpufreq_scale(
  76                                 loops_per_jiffy_ref, ref_freq, freqs.new);
  77         clk_set_rate(cpuclk, freq);
  78         if (freqs.new < freqs.old)
  79                 boot_cpu_data.loops_per_jiffy = cpufreq_scale(
  80                                 loops_per_jiffy_ref, ref_freq, freqs.new);
  81         cpufreq_notify_transition(&freqs, CPUFREQ_POSTCHANGE);
  82
  83         pr_debug("cpufreq: set frequency %lu Hz\n", freq);
  84
  85         return 0;
  86 }
  87
  88 static int __init at32_cpufreq_driver_init(struct cpufreq_policy *policy)
  89 {
  90         if (policy->cpu != 0)
  91                 return -EINVAL;
  92
  93         cpuclk = clk_get(NULL, "cpu");
  94         if (IS_ERR(cpuclk)) {
  95                 pr_debug("cpufreq: could not get CPU clk\n");
  96                 return PTR_ERR(cpuclk);
  97         }
  98
  99         policy->cpuinfo.min_freq = (clk_round_rate(cpuclk, 1) + 500) / 1000;
 100         policy->cpuinfo.max_freq = (clk_round_rate(cpuclk, ~0UL) + 500) / 1000;
 101         policy->cpuinfo.transition_latency = 0;
 102         policy->cur = at32_get_speed(0);
 103         policy->min = policy->cpuinfo.min_freq;
 104         policy->max = policy->cpuinfo.max_freq;
 105
 106         printk("cpufreq: AT32AP CPU frequency driver\n");
 107
 108         return 0;
 109 }
 110
 111 static struct cpufreq_driver at32_driver = {
 112         .name           = "at32ap",
 113         .owner          = THIS_MODULE,
 114         .init           = at32_cpufreq_driver_init,
 115         .verify         = at32_verify_speed,
 116         .target         = at32_set_target,
 117         .get            = at32_get_speed,
 118         .flags          = CPUFREQ_STICKY,
 119 };
 120
 121 static int __init at32_cpufreq_init(void)
 122 {
 123         return cpufreq_register_driver(&at32_driver);
 124 }
 125 late_initcall(at32_cpufreq_init);