drivers/cpufreq/sc520_freq.c

   1 /*
   2  *      sc520_freq.c: cpufreq driver for the AMD Elan sc520
   3  *
   4  *      Copyright (C) 2005 Sean Young <sean@mess.org>
   5  *
   6  *      This program is free software; you can redistribute it and/or
   7  *      modify it under the terms of the GNU General Public License
   8  *      as published by the Free Software Foundation; either version
   9  *      2 of the License, or (at your option) any later version.
  10  *
  11  *      Based on elanfreq.c
  12  *
  13  *      2005-03-30: - initial revision
  14  */
  15
  16 #include <linux/kernel.h>
  17 #include <linux/module.h>
  18 #include <linux/init.h>
  19
  20 #include <linux/delay.h>
  21 #include <linux/cpufreq.h>
  22 #include <linux/timex.h>
  23 #include <linux/io.h>
  24
  25 #include <asm/cpu_device_id.h>
  26 #include <asm/msr.h>
  27
  28 #define MMCR_BASE       0xfffef000      /* The default base address */
  29 #define OFFS_CPUCTL     0x2   /* CPU Control Register */
  30
  31 static __u8 __iomem *cpuctl;
  32
  33 #define PFX "sc520_freq: "
  34
  35 static struct cpufreq_frequency_table sc520_freq_table[] = {
  36         {0x01,  100000},
  37         {0x02,  133000},
  38         {0,     CPUFREQ_TABLE_END},
  39 };
  40
  41 static unsigned int sc520_freq_get_cpu_frequency(unsigned int cpu)
  42 {
  43         u8 clockspeed_reg = *cpuctl;
  44
  45         switch (clockspeed_reg & 0x03) {
  46         default:
  47                 printk(KERN_ERR PFX "error: cpuctl register has unexpected "
  48                                 "value %02x\n", clockspeed_reg);
  49         case 0x01:
  50                 return 100000;
  51         case 0x02:
  52                 return 133000;
  53         }
  54 }
  55
  56 static int sc520_freq_target(struct cpufreq_policy *policy, unsigned int state)
  57 {
  58
  59         struct cpufreq_freqs    freqs;
  60         u8 clockspeed_reg;
  61
  62         freqs.old = sc520_freq_get_cpu_frequency(0);
  63         freqs.new = sc520_freq_table[state].frequency;
  64
  65         cpufreq_notify_transition(policy, &freqs, CPUFREQ_PRECHANGE);
  66
  67         pr_debug("attempting to set frequency to %i kHz\n",
  68                         sc520_freq_table[state].frequency);
  69
  70         local_irq_disable();
  71
  72         clockspeed_reg = *cpuctl & ~0x03;
  73         *cpuctl = clockspeed_reg | sc520_freq_table[state].driver_data;
  74
  75         local_irq_enable();
  76
  77         cpufreq_notify_transition(policy, &freqs, CPUFREQ_POSTCHANGE);
  78
  79         return 0;
  80 }
  81
  82 /*
  83  *      Module init and exit code
  84  */
  85
  86 static int sc520_freq_cpu_init(struct cpufreq_policy *policy)
  87 {
  88         struct cpuinfo_x86 *c = &cpu_data(0);
  89
  90         /* capability check */
  91         if (c->x86_vendor != X86_VENDOR_AMD ||
  92             c->x86 != 4 || c->x86_model != 9)
  93                 return -ENODEV;
  94
  95         /* cpuinfo and default policy values */
  96         policy->cpuinfo.transition_latency = 1000000; /* 1ms */
  97
  98         return cpufreq_table_validate_and_show(policy, sc520_freq_table);
  99 }
 100
 101
 102 static struct cpufreq_driver sc520_freq_driver = {
 103         .get    = sc520_freq_get_cpu_frequency,
 104         .verify = cpufreq_generic_frequency_table_verify,
 105         .target_index = sc520_freq_target,
 106         .init   = sc520_freq_cpu_init,
 107         .exit   = cpufreq_generic_exit,
 108         .name   = "sc520_freq",
 109         .attr   = cpufreq_generic_attr,
 110 };
 111
 112 static const struct x86_cpu_id sc520_ids[] = {
 113         { X86_VENDOR_AMD, 4, 9 },
 114         {}
 115 };
 116 MODULE_DEVICE_TABLE(x86cpu, sc520_ids);
 117
 118 static int __init sc520_freq_init(void)
 119 {
 120         int err;
 121
 122         if (!x86_match_cpu(sc520_ids))
 123                 return -ENODEV;
 124
 125         cpuctl = ioremap((unsigned long)(MMCR_BASE + OFFS_CPUCTL), 1);
 126         if (!cpuctl) {
 127                 printk(KERN_ERR "sc520_freq: error: failed to remap memory\n");
 128                 return -ENOMEM;
 129         }
 130
 131         err = cpufreq_register_driver(&sc520_freq_driver);
 132         if (err)
 133                 iounmap(cpuctl);
 134
 135         return err;
 136 }
 137
 138
 139 static void __exit sc520_freq_exit(void)
 140 {
 141         cpufreq_unregister_driver(&sc520_freq_driver);
 142         iounmap(cpuctl);
 143 }
 144
 145
 146 MODULE_LICENSE("GPL");
 147 MODULE_AUTHOR("Sean Young <sean@mess.org>");
 148 MODULE_DESCRIPTION("cpufreq driver for AMD's Elan sc520 CPU");
 149
 150 module_init(sc520_freq_init);
 151 module_exit(sc520_freq_exit);
 152