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// SPDX-License-Identifier: GPL-2.0-or-later
/*
* sc520_freq.c: cpufreq driver for the AMD Elan sc520
*
* Copyright (C) 2005 Sean Young <sean@mess.org>
*
* Based on elanfreq.c
*
* 2005-03-30: - initial revision
*/
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/delay.h>
#include <linux/cpufreq.h>
#include <linux/timex.h>
#include <linux/io.h>
#include <asm/cpu_device_id.h>
#include <asm/msr.h>
#define MMCR_BASE 0xfffef000 /* The default base address */
#define OFFS_CPUCTL 0x2 /* CPU Control Register */
static __u8 __iomem *cpuctl;
static struct cpufreq_frequency_table sc520_freq_table[] = {
{0, 0x01, 100000},
{0, 0x02, 133000},
{0, 0, CPUFREQ_TABLE_END},
};
static unsigned int sc520_freq_get_cpu_frequency(unsigned int cpu)
{
u8 clockspeed_reg = *cpuctl;
switch (clockspeed_reg & 0x03) {
default:
pr_err("error: cpuctl register has unexpected value %02x\n",
clockspeed_reg);
case 0x01:
return 100000;
case 0x02:
return 133000;
}
}
static int sc520_freq_target(struct cpufreq_policy *policy, unsigned int state)
{
u8 clockspeed_reg;
local_irq_disable();
clockspeed_reg = *cpuctl & ~0x03;
*cpuctl = clockspeed_reg | sc520_freq_table[state].driver_data;
local_irq_enable();
return 0;
}
/*
* Module init and exit code
*/
static int sc520_freq_cpu_init(struct cpufreq_policy *policy)
{
struct cpuinfo_x86 *c = &cpu_data(0);
/* capability check */
if (c->x86_vendor != X86_VENDOR_AMD ||
c->x86 != 4 || c->x86_model != 9)
return -ENODEV;
/* cpuinfo and default policy values */
policy->cpuinfo.transition_latency = 1000000; /* 1ms */
policy->freq_table = sc520_freq_table;
return 0;
}
static struct cpufreq_driver sc520_freq_driver = {
.get = sc520_freq_get_cpu_frequency,
.verify = cpufreq_generic_frequency_table_verify,
.target_index = sc520_freq_target,
.init = sc520_freq_cpu_init,
.name = "sc520_freq",
.attr = cpufreq_generic_attr,
};
static const struct x86_cpu_id sc520_ids[] = {
{ X86_VENDOR_AMD, 4, 9 },
{}
};
MODULE_DEVICE_TABLE(x86cpu, sc520_ids);
static int __init sc520_freq_init(void)
{
int err;
if (!x86_match_cpu(sc520_ids))
return -ENODEV;
cpuctl = ioremap((unsigned long)(MMCR_BASE + OFFS_CPUCTL), 1);
if (!cpuctl) {
pr_err("sc520_freq: error: failed to remap memory\n");
return -ENOMEM;
}
err = cpufreq_register_driver(&sc520_freq_driver);
if (err)
iounmap(cpuctl);
return err;
}
static void __exit sc520_freq_exit(void)
{
cpufreq_unregister_driver(&sc520_freq_driver);
iounmap(cpuctl);
}
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Sean Young <sean@mess.org>");
MODULE_DESCRIPTION("cpufreq driver for AMD's Elan sc520 CPU");
module_init(sc520_freq_init);
module_exit(sc520_freq_exit);
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