LXR linux/drivers/cpufreq/sc520

   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
  29static __u8 __iomem *cpuctl;
  30
  31static struct cpufreq_frequency_table sc520_freq_table[] = {
  32        {0, 0x01,       100000},
  33        {0, 0x02,       133000},
  34        {0, 0,  CPUFREQ_TABLE_END},
  35};
  36
  37static 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        case 0x01:
  46                return 100000;
  47        case 0x02:
  48                return 133000;
  49        }
  50}
  51
  52static int sc520_freq_target(struct cpufreq_policy *policy, unsigned int state)
  53{
  54
  55        u8 clockspeed_reg;
  56
  57        local_irq_disable();
  58
  59        clockspeed_reg = *cpuctl & ~0x03;
  60        *cpuctl = clockspeed_reg | sc520_freq_table[state].driver_data;
  61
  62        local_irq_enable();
  63
  64        return 0;
  65}
  66
  67/*
  68 *      Module init and exit code
  69 */
  70
  71static int sc520_freq_cpu_init(struct cpufreq_policy *policy)
  72{
  73        struct cpuinfo_x86 *c = &cpu_data(0);
  74
  75        /* capability check */
  76        if (c->x86_vendor != X86_VENDOR_AMD ||
  77            c->x86 != 4 || c->x86_model != 9)
  78                return -ENODEV;
  79
  80        /* cpuinfo and default policy values */
  81        policy->cpuinfo.transition_latency = 1000000; /* 1ms */
  82        policy->freq_table = sc520_freq_table;
  83
  84        return 0;
  85}
  86
  87
  88static struct cpufreq_driver sc520_freq_driver = {
  89        .get    = sc520_freq_get_cpu_frequency,
  90        .verify = cpufreq_generic_frequency_table_verify,
  91        .target_index = sc520_freq_target,
  92        .init   = sc520_freq_cpu_init,
  93        .name   = "sc520_freq",
  94        .attr   = cpufreq_generic_attr,
  95};
  96
  97static const struct x86_cpu_id sc520_ids[] = {
  98        X86_MATCH_VENDOR_FAM_MODEL(AMD, 4, 9, NULL),
  99        {}
 100};
 101MODULE_DEVICE_TABLE(x86cpu, sc520_ids);
 102
 103static int __init sc520_freq_init(void)
 104{
 105        int err;
 106
 107        if (!x86_match_cpu(sc520_ids))
 108                return -ENODEV;
 109
 110        cpuctl = ioremap((unsigned long)(MMCR_BASE + OFFS_CPUCTL), 1);
 111        if (!cpuctl) {
 112                pr_err("sc520_freq: error: failed to remap memory\n");
 113                return -ENOMEM;
 114        }
 115
 116        err = cpufreq_register_driver(&sc520_freq_driver);
 117        if (err)
 118                iounmap(cpuctl);
 119
 120        return err;
 121}
 122
 123
 124static void __exit sc520_freq_exit(void)
 125{
 126        cpufreq_unregister_driver(&sc520_freq_driver);
 127        iounmap(cpuctl);
 128}
 129
 130
 131MODULE_LICENSE("GPL");
 132MODULE_AUTHOR("Sean Young <sean@mess.org>");
 133MODULE_DESCRIPTION("cpufreq driver for AMD's Elan sc520 CPU");
 134
 135module_init(sc520_freq_init);
 136module_exit(sc520_freq_exit);
 137
 138