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/msr.h>
  26
  27 #define MMCR_BASE       0xfffef000      /* The default base address */
  28 #define OFFS_CPUCTL     0x2   /* CPU Control Register */
  29
  30 static __u8 __iomem *cpuctl;
  31
  32 #define PFX "sc520_freq: "
  33
  34 static struct cpufreq_frequency_table sc520_freq_table[] = {
  35         {0x01,  100000},
  36         {0x02,  133000},
  37         {0,     CPUFREQ_TABLE_END},
  38 };
  39
  40 static unsigned int sc520_freq_get_cpu_frequency(unsigned int cpu)
  41 {
  42         u8 clockspeed_reg = *cpuctl;
  43
  44         switch (clockspeed_reg & 0x03) {
  45         default:
  46                 printk(KERN_ERR PFX "error: cpuctl register has unexpected "
  47                                 "value %02x\n", clockspeed_reg);
  48         case 0x01:
  49                 return 100000;
  50         case 0x02:
  51                 return 133000;
  52         }
  53 }
  54
  55 static void sc520_freq_set_cpu_state(unsigned int state)
  56 {
  57
  58         struct cpufreq_freqs    freqs;
  59         u8 clockspeed_reg;
  60
  61         freqs.old = sc520_freq_get_cpu_frequency(0);
  62         freqs.new = sc520_freq_table[state].frequency;
  63         freqs.cpu = 0; /* AMD Elan is UP */
  64
  65         cpufreq_notify_transition(&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].index;
  74
  75         local_irq_enable();
  76
  77         cpufreq_notify_transition(&freqs, CPUFREQ_POSTCHANGE);
  78 };
  79
  80 static int sc520_freq_verify(struct cpufreq_policy *policy)
  81 {
  82         return cpufreq_frequency_table_verify(policy, &sc520_freq_table[0]);
  83 }
  84
  85 static int sc520_freq_target(struct cpufreq_policy *policy,
  86                             unsigned int target_freq,
  87                             unsigned int relation)
  88 {
  89         unsigned int newstate = 0;
  90
  91         if (cpufreq_frequency_table_target(policy, sc520_freq_table,
  92                                 target_freq, relation, &newstate))
  93                 return -EINVAL;
  94
  95         sc520_freq_set_cpu_state(newstate);
  96
  97         return 0;
  98 }
  99
 100
 101 /*
 102  *      Module init and exit code
 103  */
 104
 105 static int sc520_freq_cpu_init(struct cpufreq_policy *policy)
 106 {
 107         struct cpuinfo_x86 *c = &cpu_data(0);
 108         int result;
 109
 110         /* capability check */
 111         if (c->x86_vendor != X86_VENDOR_AMD ||
 112             c->x86 != 4 || c->x86_model != 9)
 113                 return -ENODEV;
 114
 115         /* cpuinfo and default policy values */
 116         policy->cpuinfo.transition_latency = 1000000; /* 1ms */
 117         policy->cur = sc520_freq_get_cpu_frequency(0);
 118
 119         result = cpufreq_frequency_table_cpuinfo(policy, sc520_freq_table);
 120         if (result)
 121                 return result;
 122
 123         cpufreq_frequency_table_get_attr(sc520_freq_table, policy->cpu);
 124
 125         return 0;
 126 }
 127
 128
 129 static int sc520_freq_cpu_exit(struct cpufreq_policy *policy)
 130 {
 131         cpufreq_frequency_table_put_attr(policy->cpu);
 132         return 0;
 133 }
 134
 135
 136 static struct freq_attr *sc520_freq_attr[] = {
 137         &cpufreq_freq_attr_scaling_available_freqs,
 138         NULL,
 139 };
 140
 141
 142 static struct cpufreq_driver sc520_freq_driver = {
 143         .get    = sc520_freq_get_cpu_frequency,
 144         .verify = sc520_freq_verify,
 145         .target = sc520_freq_target,
 146         .init   = sc520_freq_cpu_init,
 147         .exit   = sc520_freq_cpu_exit,
 148         .name   = "sc520_freq",
 149         .owner  = THIS_MODULE,
 150         .attr   = sc520_freq_attr,
 151 };
 152
 153
 154 static int __init sc520_freq_init(void)
 155 {
 156         struct cpuinfo_x86 *c = &cpu_data(0);
 157         int err;
 158
 159         /* Test if we have the right hardware */
 160         if (c->x86_vendor != X86_VENDOR_AMD ||
 161             c->x86 != 4 || c->x86_model != 9) {
 162                 pr_debug("no Elan SC520 processor found!\n");
 163                 return -ENODEV;
 164         }
 165         cpuctl = ioremap((unsigned long)(MMCR_BASE + OFFS_CPUCTL), 1);
 166         if (!cpuctl) {
 167                 printk(KERN_ERR "sc520_freq: error: failed to remap memory\n");
 168                 return -ENOMEM;
 169         }
 170
 171         err = cpufreq_register_driver(&sc520_freq_driver);
 172         if (err)
 173                 iounmap(cpuctl);
 174
 175         return err;
 176 }
 177
 178
 179 static void __exit sc520_freq_exit(void)
 180 {
 181         cpufreq_unregister_driver(&sc520_freq_driver);
 182         iounmap(cpuctl);
 183 }
 184
 185
 186 MODULE_LICENSE("GPL");
 187 MODULE_AUTHOR("Sean Young <sean@mess.org>");
 188 MODULE_DESCRIPTION("cpufreq driver for AMD's Elan sc520 CPU");
 189
 190 module_init(sc520_freq_init);
 191 module_exit(sc520_freq_exit);
 192