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
  24 static struct clk *cpuclk;
  25 static struct cpufreq_frequency_table *freq_table;
  26
  27 static unsigned int at32_get_speed(unsigned int cpu)
  28 {
  29         /* No SMP support */
  30         if (cpu)
  31                 return 0;
  32         return (unsigned int)((clk_get_rate(cpuclk) + 500) / 1000);
  33 }
  34
  35 static unsigned int     ref_freq;
  36 static unsigned long    loops_per_jiffy_ref;
  37
  38 static int at32_set_target(struct cpufreq_policy *policy, unsigned int index)
  39 {
  40         struct cpufreq_freqs freqs;
  41
  42         freqs.old = at32_get_speed(0);
  43         freqs.new = freq_table[index].frequency;
  44
  45         if (!ref_freq) {
  46                 ref_freq = freqs.old;
  47                 loops_per_jiffy_ref = boot_cpu_data.loops_per_jiffy;
  48         }
  49
  50         cpufreq_notify_transition(policy, &freqs, CPUFREQ_PRECHANGE);
  51         if (freqs.old < freqs.new)
  52                 boot_cpu_data.loops_per_jiffy = cpufreq_scale(
  53                                 loops_per_jiffy_ref, ref_freq, freqs.new);
  54         clk_set_rate(cpuclk, freqs.new * 1000);
  55         if (freqs.new < freqs.old)
  56                 boot_cpu_data.loops_per_jiffy = cpufreq_scale(
  57                                 loops_per_jiffy_ref, ref_freq, freqs.new);
  58         cpufreq_notify_transition(policy, &freqs, CPUFREQ_POSTCHANGE);
  59
  60         pr_debug("cpufreq: set frequency %u Hz\n", freqs.new * 1000);
  61
  62         return 0;
  63 }
  64
  65 static int __init at32_cpufreq_driver_init(struct cpufreq_policy *policy)
  66 {
  67         unsigned int frequency, rate, min_freq;
  68         int retval, steps, i;
  69
  70         if (policy->cpu != 0)
  71                 return -EINVAL;
  72
  73         cpuclk = clk_get(NULL, "cpu");
  74         if (IS_ERR(cpuclk)) {
  75                 pr_debug("cpufreq: could not get CPU clk\n");
  76                 retval = PTR_ERR(cpuclk);
  77                 goto out_err;
  78         }
  79
  80         min_freq = (clk_round_rate(cpuclk, 1) + 500) / 1000;
  81         frequency = (clk_round_rate(cpuclk, ~0UL) + 500) / 1000;
  82         policy->cpuinfo.transition_latency = 0;
  83
  84         /*
  85          * AVR32 CPU frequency rate scales in power of two between maximum and
  86          * minimum, also add space for the table end marker.
  87          *
  88          * Further validate that the frequency is usable, and append it to the
  89          * frequency table.
  90          */
  91         steps = fls(frequency / min_freq) + 1;
  92         freq_table = kzalloc(steps * sizeof(struct cpufreq_frequency_table),
  93                         GFP_KERNEL);
  94         if (!freq_table) {
  95                 retval = -ENOMEM;
  96                 goto out_err_put_clk;
  97         }
  98
  99         for (i = 0; i < (steps - 1); i++) {
 100                 rate = clk_round_rate(cpuclk, frequency * 1000) / 1000;
 101
 102                 if (rate != frequency)
 103                         freq_table[i].frequency = CPUFREQ_ENTRY_INVALID;
 104                 else
 105                         freq_table[i].frequency = frequency;
 106
 107                 frequency /= 2;
 108         }
 109
 110         freq_table[steps - 1].frequency = CPUFREQ_TABLE_END;
 111
 112         retval = cpufreq_table_validate_and_show(policy, freq_table);
 113         if (!retval) {
 114                 printk("cpufreq: AT32AP CPU frequency driver\n");
 115                 return 0;
 116         }
 117
 118         kfree(freq_table);
 119 out_err_put_clk:
 120         clk_put(cpuclk);
 121 out_err:
 122         return retval;
 123 }
 124
 125 static struct cpufreq_driver at32_driver = {
 126         .name           = "at32ap",
 127         .init           = at32_cpufreq_driver_init,
 128         .verify         = cpufreq_generic_frequency_table_verify,
 129         .target_index   = at32_set_target,
 130         .get            = at32_get_speed,
 131         .flags          = CPUFREQ_STICKY,
 132 };
 133
 134 static int __init at32_cpufreq_init(void)
 135 {
 136         return cpufreq_register_driver(&at32_driver);
 137 }
 138 late_initcall(at32_cpufreq_init);