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 void sc520_freq_set_cpu_state(struct cpufreq_policy *policy,
  57                 unsigned int state)
  58 {
  59
  60         struct cpufreq_freqs    freqs;
  61         u8 clockspeed_reg;
  62
  63         freqs.old = sc520_freq_get_cpu_frequency(0);
  64         freqs.new = sc520_freq_table[state].frequency;
  65
  66         cpufreq_notify_transition(policy, &freqs, CPUFREQ_PRECHANGE);
  67
  68         pr_debug("attempting to set frequency to %i kHz\n",
  69                         sc520_freq_table[state].frequency);
  70
  71         local_irq_disable();
  72
  73         clockspeed_reg = *cpuctl & ~0x03;
  74         *cpuctl = clockspeed_reg | sc520_freq_table[state].driver_data;
  75
  76         local_irq_enable();
  77
  78         cpufreq_notify_transition(policy, &freqs, CPUFREQ_POSTCHANGE);
  79 };
  80
  81 static int sc520_freq_target(struct cpufreq_policy *policy,
  82                             unsigned int target_freq,
  83                             unsigned int relation)
  84 {
  85         unsigned int newstate = 0;
  86
  87         if (cpufreq_frequency_table_target(policy, sc520_freq_table,
  88                                 target_freq, relation, &newstate))
  89                 return -EINVAL;
  90
  91         sc520_freq_set_cpu_state(policy, newstate);
  92
  93         return 0;
  94 }
  95
  96
  97 /*
  98  *      Module init and exit code
  99  */
 100
 101 static int sc520_freq_cpu_init(struct cpufreq_policy *policy)
 102 {
 103         struct cpuinfo_x86 *c = &cpu_data(0);
 104
 105         /* capability check */
 106         if (c->x86_vendor != X86_VENDOR_AMD ||
 107             c->x86 != 4 || c->x86_model != 9)
 108                 return -ENODEV;
 109
 110         /* cpuinfo and default policy values */
 111         policy->cpuinfo.transition_latency = 1000000; /* 1ms */
 112
 113         return cpufreq_table_validate_and_show(policy, sc520_freq_table);
 114 }
 115
 116
 117 static struct cpufreq_driver sc520_freq_driver = {
 118         .get    = sc520_freq_get_cpu_frequency,
 119         .verify = cpufreq_generic_frequency_table_verify,
 120         .target = sc520_freq_target,
 121         .init   = sc520_freq_cpu_init,
 122         .exit   = cpufreq_generic_exit,
 123         .name   = "sc520_freq",
 124         .attr   = cpufreq_generic_attr,
 125 };
 126
 127 static const struct x86_cpu_id sc520_ids[] = {
 128         { X86_VENDOR_AMD, 4, 9 },
 129         {}
 130 };
 131 MODULE_DEVICE_TABLE(x86cpu, sc520_ids);
 132
 133 static int __init sc520_freq_init(void)
 134 {
 135         int err;
 136
 137         if (!x86_match_cpu(sc520_ids))
 138                 return -ENODEV;
 139
 140         cpuctl = ioremap((unsigned long)(MMCR_BASE + OFFS_CPUCTL), 1);
 141         if (!cpuctl) {
 142                 printk(KERN_ERR "sc520_freq: error: failed to remap memory\n");
 143                 return -ENOMEM;
 144         }
 145
 146         err = cpufreq_register_driver(&sc520_freq_driver);
 147         if (err)
 148                 iounmap(cpuctl);
 149
 150         return err;
 151 }
 152
 153
 154 static void __exit sc520_freq_exit(void)
 155 {
 156         cpufreq_unregister_driver(&sc520_freq_driver);
 157         iounmap(cpuctl);
 158 }
 159
 160
 161 MODULE_LICENSE("GPL");
 162 MODULE_AUTHOR("Sean Young <sean@mess.org>");
 163 MODULE_DESCRIPTION("cpufreq driver for AMD's Elan sc520 CPU");
 164
 165 module_init(sc520_freq_init);
 166 module_exit(sc520_freq_exit);
 167