drivers/cpufreq/sc520_freq.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  *      sc520_freq.c: cpufreq driver for the AMD Elan sc520
   4  *
   5  *      Copyright (C) 2005 Sean Young <sean@mess.org>
   6  *
   7  *      Based on elanfreq.c
   8  *
   9  *      2005-03-30: - initial revision
  10  */
  11
  12 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  13
  14 #include <linux/kernel.h>
  15 #include <linux/module.h>
  16 #include <linux/init.h>
  17
  18 #include <linux/delay.h>
  19 #include <linux/cpufreq.h>
  20 #include <linux/timex.h>
  21 #include <linux/io.h>
  22
  23 #include <asm/cpu_device_id.h>
  24 #include <asm/msr.h>
  25
  26 #define MMCR_BASE       0xfffef000      /* The default base address */
  27 #define OFFS_CPUCTL     0x2   /* CPU Control Register */
  28
  29 static __u8 __iomem *cpuctl;
  30
  31 static struct cpufreq_frequency_table sc520_freq_table[] = {
  32         {0, 0x01,       100000},
  33         {0, 0x02,       133000},
  34         {0, 0,  CPUFREQ_TABLE_END},
  35 };
  36
  37 static unsigned int sc520_freq_get_cpu_frequency(unsigned int cpu)
  38 {
  39         u8 clockspeed_reg = *cpuctl;
  40
  41         switch (clockspeed_reg & 0x03) {
  42         default:
  43                 pr_err("error: cpuctl register has unexpected value %02x\n",
  44                        clockspeed_reg);
  45                 fallthrough;
  46         case 0x01:
  47                 return 100000;
  48         case 0x02:
  49                 return 133000;
  50         }
  51 }
  52
  53 static int sc520_freq_target(struct cpufreq_policy *policy, unsigned int state)
  54 {
  55
  56         u8 clockspeed_reg;
  57
  58         local_irq_disable();
  59
  60         clockspeed_reg = *cpuctl & ~0x03;
  61         *cpuctl = clockspeed_reg | sc520_freq_table[state].driver_data;
  62
  63         local_irq_enable();
  64
  65         return 0;
  66 }
  67
  68 /*
  69  *      Module init and exit code
  70  */
  71
  72 static int sc520_freq_cpu_init(struct cpufreq_policy *policy)
  73 {
  74         struct cpuinfo_x86 *c = &cpu_data(0);
  75
  76         /* capability check */
  77         if (c->x86_vendor != X86_VENDOR_AMD ||
  78             c->x86 != 4 || c->x86_model != 9)
  79                 return -ENODEV;
  80
  81         /* cpuinfo and default policy values */
  82         policy->cpuinfo.transition_latency = 1000000; /* 1ms */
  83         policy->freq_table = sc520_freq_table;
  84
  85         return 0;
  86 }
  87
  88
  89 static struct cpufreq_driver sc520_freq_driver = {
  90         .get    = sc520_freq_get_cpu_frequency,
  91         .verify = cpufreq_generic_frequency_table_verify,
  92         .target_index = sc520_freq_target,
  93         .init   = sc520_freq_cpu_init,
  94         .name   = "sc520_freq",
  95         .attr   = cpufreq_generic_attr,
  96 };
  97
  98 static const struct x86_cpu_id sc520_ids[] = {
  99         X86_MATCH_VENDOR_FAM_MODEL(AMD, 4, 9, NULL),
 100         {}
 101 };
 102 MODULE_DEVICE_TABLE(x86cpu, sc520_ids);
 103
 104 static int __init sc520_freq_init(void)
 105 {
 106         int err;
 107
 108         if (!x86_match_cpu(sc520_ids))
 109                 return -ENODEV;
 110
 111         cpuctl = ioremap((unsigned long)(MMCR_BASE + OFFS_CPUCTL), 1);
 112         if (!cpuctl) {
 113                 pr_err("sc520_freq: error: failed to remap memory\n");
 114                 return -ENOMEM;
 115         }
 116
 117         err = cpufreq_register_driver(&sc520_freq_driver);
 118         if (err)
 119                 iounmap(cpuctl);
 120
 121         return err;
 122 }
 123
 124
 125 static void __exit sc520_freq_exit(void)
 126 {
 127         cpufreq_unregister_driver(&sc520_freq_driver);
 128         iounmap(cpuctl);
 129 }
 130
 131
 132 MODULE_LICENSE("GPL");
 133 MODULE_AUTHOR("Sean Young <sean@mess.org>");
 134 MODULE_DESCRIPTION("cpufreq driver for AMD's Elan sc520 CPU");
 135
 136 module_init(sc520_freq_init);
 137 module_exit(sc520_freq_exit);
 138