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 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  17
  18 #include <linux/kernel.h>
  19 #include <linux/module.h>
  20 #include <linux/init.h>
  21
  22 #include <linux/delay.h>
  23 #include <linux/cpufreq.h>
  24 #include <linux/timex.h>
  25 #include <linux/io.h>
  26
  27 #include <asm/cpu_device_id.h>
  28 #include <asm/msr.h>
  29
  30 #define MMCR_BASE       0xfffef000      /* The default base address */
  31 #define OFFS_CPUCTL     0x2   /* CPU Control Register */
  32
  33 static __u8 __iomem *cpuctl;
  34
  35 static struct cpufreq_frequency_table sc520_freq_table[] = {
  36         {0, 0x01,       100000},
  37         {0, 0x02,       133000},
  38         {0, 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                 pr_err("error: cpuctl register has unexpected value %02x\n",
  48                        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         u8 clockspeed_reg;
  60
  61         local_irq_disable();
  62
  63         clockspeed_reg = *cpuctl & ~0x03;
  64         *cpuctl = clockspeed_reg | sc520_freq_table[state].driver_data;
  65
  66         local_irq_enable();
  67
  68         return 0;
  69 }
  70
  71 /*
  72  *      Module init and exit code
  73  */
  74
  75 static int sc520_freq_cpu_init(struct cpufreq_policy *policy)
  76 {
  77         struct cpuinfo_x86 *c = &cpu_data(0);
  78
  79         /* capability check */
  80         if (c->x86_vendor != X86_VENDOR_AMD ||
  81             c->x86 != 4 || c->x86_model != 9)
  82                 return -ENODEV;
  83
  84         /* cpuinfo and default policy values */
  85         policy->cpuinfo.transition_latency = 1000000; /* 1ms */
  86
  87         return cpufreq_table_validate_and_show(policy, sc520_freq_table);
  88 }
  89
  90
  91 static struct cpufreq_driver sc520_freq_driver = {
  92         .get    = sc520_freq_get_cpu_frequency,
  93         .verify = cpufreq_generic_frequency_table_verify,
  94         .target_index = sc520_freq_target,
  95         .init   = sc520_freq_cpu_init,
  96         .name   = "sc520_freq",
  97         .attr   = cpufreq_generic_attr,
  98 };
  99
 100 static const struct x86_cpu_id sc520_ids[] = {
 101         { X86_VENDOR_AMD, 4, 9 },
 102         {}
 103 };
 104 MODULE_DEVICE_TABLE(x86cpu, sc520_ids);
 105
 106 static int __init sc520_freq_init(void)
 107 {
 108         int err;
 109
 110         if (!x86_match_cpu(sc520_ids))
 111                 return -ENODEV;
 112
 113         cpuctl = ioremap((unsigned long)(MMCR_BASE + OFFS_CPUCTL), 1);
 114         if (!cpuctl) {
 115                 pr_err("sc520_freq: error: failed to remap memory\n");
 116                 return -ENOMEM;
 117         }
 118
 119         err = cpufreq_register_driver(&sc520_freq_driver);
 120         if (err)
 121                 iounmap(cpuctl);
 122
 123         return err;
 124 }
 125
 126
 127 static void __exit sc520_freq_exit(void)
 128 {
 129         cpufreq_unregister_driver(&sc520_freq_driver);
 130         iounmap(cpuctl);
 131 }
 132
 133
 134 MODULE_LICENSE("GPL");
 135 MODULE_AUTHOR("Sean Young <sean@mess.org>");
 136 MODULE_DESCRIPTION("cpufreq driver for AMD's Elan sc520 CPU");
 137
 138 module_init(sc520_freq_init);
 139 module_exit(sc520_freq_exit);
 140