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,
  39                           unsigned int target_freq,
  40                           unsigned int relation)
  41 {
  42         struct cpufreq_freqs freqs;
  43         long freq;
  44
  45         /* Convert target_freq from kHz to Hz */
  46         freq = clk_round_rate(cpuclk, target_freq * 1000);
  47
  48         /* Check if policy->min <= new_freq <= policy->max */
  49         if(freq < (policy->min * 1000) || freq > (policy->max * 1000))
  50                 return -EINVAL;
  51
  52         pr_debug("cpufreq: requested frequency %u Hz\n", target_freq * 1000);
  53
  54         freqs.old = at32_get_speed(0);
  55         freqs.new = (freq + 500) / 1000;
  56         freqs.flags = 0;
  57
  58         if (!ref_freq) {
  59                 ref_freq = freqs.old;
  60                 loops_per_jiffy_ref = boot_cpu_data.loops_per_jiffy;
  61         }
  62
  63         cpufreq_notify_transition(policy, &freqs, CPUFREQ_PRECHANGE);
  64         if (freqs.old < freqs.new)
  65                 boot_cpu_data.loops_per_jiffy = cpufreq_scale(
  66                                 loops_per_jiffy_ref, ref_freq, freqs.new);
  67         clk_set_rate(cpuclk, freq);
  68         if (freqs.new < freqs.old)
  69                 boot_cpu_data.loops_per_jiffy = cpufreq_scale(
  70                                 loops_per_jiffy_ref, ref_freq, freqs.new);
  71         cpufreq_notify_transition(policy, &freqs, CPUFREQ_POSTCHANGE);
  72
  73         pr_debug("cpufreq: set frequency %lu Hz\n", freq);
  74
  75         return 0;
  76 }
  77
  78 static int __init at32_cpufreq_driver_init(struct cpufreq_policy *policy)
  79 {
  80         unsigned int frequency, rate, min_freq;
  81         int retval, steps, i;
  82
  83         if (policy->cpu != 0)
  84                 return -EINVAL;
  85
  86         cpuclk = clk_get(NULL, "cpu");
  87         if (IS_ERR(cpuclk)) {
  88                 pr_debug("cpufreq: could not get CPU clk\n");
  89                 retval = PTR_ERR(cpuclk);
  90                 goto out_err;
  91         }
  92
  93         min_freq = (clk_round_rate(cpuclk, 1) + 500) / 1000;
  94         frequency = (clk_round_rate(cpuclk, ~0UL) + 500) / 1000;
  95         policy->cpuinfo.transition_latency = 0;
  96
  97         /*
  98          * AVR32 CPU frequency rate scales in power of two between maximum and
  99          * minimum, also add space for the table end marker.
 100          *
 101          * Further validate that the frequency is usable, and append it to the
 102          * frequency table.
 103          */
 104         steps = fls(frequency / min_freq) + 1;
 105         freq_table = kzalloc(steps * sizeof(struct cpufreq_frequency_table),
 106                         GFP_KERNEL);
 107         if (!freq_table) {
 108                 retval = -ENOMEM;
 109                 goto out_err_put_clk;
 110         }
 111
 112         for (i = 0; i < (steps - 1); i++) {
 113                 rate = clk_round_rate(cpuclk, frequency * 1000) / 1000;
 114
 115                 if (rate != frequency)
 116                         freq_table[i].frequency = CPUFREQ_ENTRY_INVALID;
 117                 else
 118                         freq_table[i].frequency = frequency;
 119
 120                 frequency /= 2;
 121         }
 122
 123         freq_table[steps - 1].frequency = CPUFREQ_TABLE_END;
 124
 125         retval = cpufreq_table_validate_and_show(policy, freq_table);
 126         if (!retval) {
 127                 printk("cpufreq: AT32AP CPU frequency driver\n");
 128                 return 0;
 129         }
 130
 131         kfree(freq_table);
 132 out_err_put_clk:
 133         clk_put(cpuclk);
 134 out_err:
 135         return retval;
 136 }
 137
 138 static struct cpufreq_driver at32_driver = {
 139         .name           = "at32ap",
 140         .init           = at32_cpufreq_driver_init,
 141         .verify         = cpufreq_generic_frequency_table_verify,
 142         .target         = at32_set_target,
 143         .get            = at32_get_speed,
 144         .flags          = CPUFREQ_STICKY,
 145 };
 146
 147 static int __init at32_cpufreq_init(void)
 148 {
 149         return cpufreq_register_driver(&at32_driver);
 150 }
 151 late_initcall(at32_cpufreq_init);