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         unsigned int old_freq, new_freq;
  41
  42         old_freq = at32_get_speed(0);
  43         new_freq = freq_table[index].frequency;
  44
  45         if (!ref_freq) {
  46                 ref_freq = old_freq;
  47                 loops_per_jiffy_ref = boot_cpu_data.loops_per_jiffy;
  48         }
  49
  50         if (old_freq < new_freq)
  51                 boot_cpu_data.loops_per_jiffy = cpufreq_scale(
  52                                 loops_per_jiffy_ref, ref_freq, new_freq);
  53         clk_set_rate(cpuclk, new_freq * 1000);
  54         if (new_freq < old_freq)
  55                 boot_cpu_data.loops_per_jiffy = cpufreq_scale(
  56                                 loops_per_jiffy_ref, ref_freq, new_freq);
  57
  58         return 0;
  59 }
  60
  61 static int at32_cpufreq_driver_init(struct cpufreq_policy *policy)
  62 {
  63         unsigned int frequency, rate, min_freq;
  64         int retval, steps, i;
  65
  66         if (policy->cpu != 0)
  67                 return -EINVAL;
  68
  69         cpuclk = clk_get(NULL, "cpu");
  70         if (IS_ERR(cpuclk)) {
  71                 pr_debug("cpufreq: could not get CPU clk\n");
  72                 retval = PTR_ERR(cpuclk);
  73                 goto out_err;
  74         }
  75
  76         min_freq = (clk_round_rate(cpuclk, 1) + 500) / 1000;
  77         frequency = (clk_round_rate(cpuclk, ~0UL) + 500) / 1000;
  78         policy->cpuinfo.transition_latency = 0;
  79
  80         /*
  81          * AVR32 CPU frequency rate scales in power of two between maximum and
  82          * minimum, also add space for the table end marker.
  83          *
  84          * Further validate that the frequency is usable, and append it to the
  85          * frequency table.
  86          */
  87         steps = fls(frequency / min_freq) + 1;
  88         freq_table = kzalloc(steps * sizeof(struct cpufreq_frequency_table),
  89                         GFP_KERNEL);
  90         if (!freq_table) {
  91                 retval = -ENOMEM;
  92                 goto out_err_put_clk;
  93         }
  94
  95         for (i = 0; i < (steps - 1); i++) {
  96                 rate = clk_round_rate(cpuclk, frequency * 1000) / 1000;
  97
  98                 if (rate != frequency)
  99                         freq_table[i].frequency = CPUFREQ_ENTRY_INVALID;
 100                 else
 101                         freq_table[i].frequency = frequency;
 102
 103                 frequency /= 2;
 104         }
 105
 106         freq_table[steps - 1].frequency = CPUFREQ_TABLE_END;
 107
 108         retval = cpufreq_table_validate_and_show(policy, freq_table);
 109         if (!retval) {
 110                 printk("cpufreq: AT32AP CPU frequency driver\n");
 111                 return 0;
 112         }
 113
 114         kfree(freq_table);
 115 out_err_put_clk:
 116         clk_put(cpuclk);
 117 out_err:
 118         return retval;
 119 }
 120
 121 static struct cpufreq_driver at32_driver = {
 122         .name           = "at32ap",
 123         .init           = at32_cpufreq_driver_init,
 124         .verify         = cpufreq_generic_frequency_table_verify,
 125         .target_index   = at32_set_target,
 126         .get            = at32_get_speed,
 127         .flags          = CPUFREQ_STICKY,
 128 };
 129
 130 static int __init at32_cpufreq_init(void)
 131 {
 132         return cpufreq_register_driver(&at32_driver);
 133 }
 134 late_initcall(at32_cpufreq_init);