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 cpufreq_frequency_table *freq_table;
  25
  26 static unsigned int     ref_freq;
  27 static unsigned long    loops_per_jiffy_ref;
  28
  29 static int at32_set_target(struct cpufreq_policy *policy, unsigned int index)
  30 {
  31         unsigned int old_freq, new_freq;
  32
  33         old_freq = policy->cur;
  34         new_freq = freq_table[index].frequency;
  35
  36         if (!ref_freq) {
  37                 ref_freq = old_freq;
  38                 loops_per_jiffy_ref = boot_cpu_data.loops_per_jiffy;
  39         }
  40
  41         if (old_freq < new_freq)
  42                 boot_cpu_data.loops_per_jiffy = cpufreq_scale(
  43                                 loops_per_jiffy_ref, ref_freq, new_freq);
  44         clk_set_rate(policy->clk, new_freq * 1000);
  45         if (new_freq < old_freq)
  46                 boot_cpu_data.loops_per_jiffy = cpufreq_scale(
  47                                 loops_per_jiffy_ref, ref_freq, new_freq);
  48
  49         return 0;
  50 }
  51
  52 static int at32_cpufreq_driver_init(struct cpufreq_policy *policy)
  53 {
  54         unsigned int frequency, rate, min_freq;
  55         struct clk *cpuclk;
  56         int retval, steps, i;
  57
  58         if (policy->cpu != 0)
  59                 return -EINVAL;
  60
  61         cpuclk = clk_get(NULL, "cpu");
  62         if (IS_ERR(cpuclk)) {
  63                 pr_debug("cpufreq: could not get CPU clk\n");
  64                 retval = PTR_ERR(cpuclk);
  65                 goto out_err;
  66         }
  67
  68         min_freq = (clk_round_rate(cpuclk, 1) + 500) / 1000;
  69         frequency = (clk_round_rate(cpuclk, ~0UL) + 500) / 1000;
  70         policy->cpuinfo.transition_latency = 0;
  71
  72         /*
  73          * AVR32 CPU frequency rate scales in power of two between maximum and
  74          * minimum, also add space for the table end marker.
  75          *
  76          * Further validate that the frequency is usable, and append it to the
  77          * frequency table.
  78          */
  79         steps = fls(frequency / min_freq) + 1;
  80         freq_table = kzalloc(steps * sizeof(struct cpufreq_frequency_table),
  81                         GFP_KERNEL);
  82         if (!freq_table) {
  83                 retval = -ENOMEM;
  84                 goto out_err_put_clk;
  85         }
  86
  87         for (i = 0; i < (steps - 1); i++) {
  88                 rate = clk_round_rate(cpuclk, frequency * 1000) / 1000;
  89
  90                 if (rate != frequency)
  91                         freq_table[i].frequency = CPUFREQ_ENTRY_INVALID;
  92                 else
  93                         freq_table[i].frequency = frequency;
  94
  95                 frequency /= 2;
  96         }
  97
  98         policy->clk = cpuclk;
  99         freq_table[steps - 1].frequency = CPUFREQ_TABLE_END;
 100
 101         retval = cpufreq_table_validate_and_show(policy, freq_table);
 102         if (!retval) {
 103                 printk("cpufreq: AT32AP CPU frequency driver\n");
 104                 return 0;
 105         }
 106
 107         kfree(freq_table);
 108 out_err_put_clk:
 109         clk_put(cpuclk);
 110 out_err:
 111         return retval;
 112 }
 113
 114 static struct cpufreq_driver at32_driver = {
 115         .name           = "at32ap",
 116         .init           = at32_cpufreq_driver_init,
 117         .verify         = cpufreq_generic_frequency_table_verify,
 118         .target_index   = at32_set_target,
 119         .get            = cpufreq_generic_get,
 120         .flags          = CPUFREQ_STICKY,
 121 };
 122
 123 static int __init at32_cpufreq_init(void)
 124 {
 125         return cpufreq_register_driver(&at32_driver);
 126 }
 127 late_initcall(at32_cpufreq_init);