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// SPDX-License-Identifier: GPL-2.0-or-later
/*
* elanfreq: cpufreq driver for the AMD ELAN family
*
* (c) Copyright 2002 Robert Schwebel <r.schwebel@pengutronix.de>
*
* Parts of this code are (c) Sven Geggus <sven@geggus.net>
*
* All Rights Reserved.
*
* 2002-02-13: - initial revision for 2.4.18-pre9 by Robert Schwebel
*/
#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 <asm/cpu_device_id.h>
#include <asm/msr.h>
#include <linux/timex.h>
#include <linux/io.h>
#define REG_CSCIR 0x22 /* Chip Setup and Control Index Register */
#define REG_CSCDR 0x23 /* Chip Setup and Control Data Register */
/* Module parameter */
static int max_freq;
struct s_elan_multiplier {
int clock; /* frequency in kHz */
int val40h; /* PMU Force Mode register */
int val80h; /* CPU Clock Speed Register */
};
/*
* It is important that the frequencies
* are listed in ascending order here!
*/
static struct s_elan_multiplier elan_multiplier[] = {
{1000, 0x02, 0x18},
{2000, 0x02, 0x10},
{4000, 0x02, 0x08},
{8000, 0x00, 0x00},
{16000, 0x00, 0x02},
{33000, 0x00, 0x04},
{66000, 0x01, 0x04},
{99000, 0x01, 0x05}
};
static struct cpufreq_frequency_table elanfreq_table[] = {
{0, 0, 1000},
{0, 1, 2000},
{0, 2, 4000},
{0, 3, 8000},
{0, 4, 16000},
{0, 5, 33000},
{0, 6, 66000},
{0, 7, 99000},
{0, 0, CPUFREQ_TABLE_END},
};
/**
* elanfreq_get_cpu_frequency: determine current cpu speed
*
* Finds out at which frequency the CPU of the Elan SOC runs
* at the moment. Frequencies from 1 to 33 MHz are generated
* the normal way, 66 and 99 MHz are called "Hyperspeed Mode"
* and have the rest of the chip running with 33 MHz.
*/
static unsigned int elanfreq_get_cpu_frequency(unsigned int cpu)
{
u8 clockspeed_reg; /* Clock Speed Register */
local_irq_disable();
outb_p(0x80, REG_CSCIR);
clockspeed_reg = inb_p(REG_CSCDR);
local_irq_enable();
if ((clockspeed_reg & 0xE0) == 0xE0)
return 0;
/* Are we in CPU clock multiplied mode (66/99 MHz)? */
if ((clockspeed_reg & 0xE0) == 0xC0) {
if ((clockspeed_reg & 0x01) == 0)
return 66000;
else
return 99000;
}
/* 33 MHz is not 32 MHz... */
if ((clockspeed_reg & 0xE0) == 0xA0)
return 33000;
return (1<<((clockspeed_reg & 0xE0) >> 5)) * 1000;
}
static int elanfreq_target(struct cpufreq_policy *policy,
unsigned int state)
{
/*
* Access to the Elan's internal registers is indexed via
* 0x22: Chip Setup & Control Register Index Register (CSCI)
* 0x23: Chip Setup & Control Register Data Register (CSCD)
*
*/
/*
* 0x40 is the Power Management Unit's Force Mode Register.
* Bit 6 enables Hyperspeed Mode (66/100 MHz core frequency)
*/
local_irq_disable();
outb_p(0x40, REG_CSCIR); /* Disable hyperspeed mode */
outb_p(0x00, REG_CSCDR);
local_irq_enable(); /* wait till internal pipelines and */
udelay(1000); /* buffers have cleaned up */
local_irq_disable();
/* now, set the CPU clock speed register (0x80) */
outb_p(0x80, REG_CSCIR);
outb_p(elan_multiplier[state].val80h, REG_CSCDR);
/* now, the hyperspeed bit in PMU Force Mode Register (0x40) */
outb_p(0x40, REG_CSCIR);
outb_p(elan_multiplier[state].val40h, REG_CSCDR);
udelay(10000);
local_irq_enable();
return 0;
}
/*
* Module init and exit code
*/
static int elanfreq_cpu_init(struct cpufreq_policy *policy)
{
struct cpuinfo_x86 *c = &cpu_data(0);
struct cpufreq_frequency_table *pos;
/* capability check */
if ((c->x86_vendor != X86_VENDOR_AMD) ||
(c->x86 != 4) || (c->x86_model != 10))
return -ENODEV;
/* max freq */
if (!max_freq)
max_freq = elanfreq_get_cpu_frequency(0);
/* table init */
cpufreq_for_each_entry(pos, elanfreq_table)
if (pos->frequency > max_freq)
pos->frequency = CPUFREQ_ENTRY_INVALID;
policy->freq_table = elanfreq_table;
return 0;
}
#ifndef MODULE
/**
* elanfreq_setup - elanfreq command line parameter parsing
*
* elanfreq command line parameter. Use:
* elanfreq=66000
* to set the maximum CPU frequency to 66 MHz. Note that in
* case you do not give this boot parameter, the maximum
* frequency will fall back to _current_ CPU frequency which
* might be lower. If you build this as a module, use the
* max_freq module parameter instead.
*/
static int __init elanfreq_setup(char *str)
{
max_freq = simple_strtoul(str, &str, 0);
pr_warn("You're using the deprecated elanfreq command line option. Use elanfreq.max_freq instead, please!\n");
return 1;
}
__setup("elanfreq=", elanfreq_setup);
#endif
static struct cpufreq_driver elanfreq_driver = {
.get = elanfreq_get_cpu_frequency,
.flags = CPUFREQ_NO_AUTO_DYNAMIC_SWITCHING,
.verify = cpufreq_generic_frequency_table_verify,
.target_index = elanfreq_target,
.init = elanfreq_cpu_init,
.name = "elanfreq",
.attr = cpufreq_generic_attr,
};
static const struct x86_cpu_id elan_id[] = {
{ X86_VENDOR_AMD, 4, 10, },
{}
};
MODULE_DEVICE_TABLE(x86cpu, elan_id);
static int __init elanfreq_init(void)
{
if (!x86_match_cpu(elan_id))
return -ENODEV;
return cpufreq_register_driver(&elanfreq_driver);
}
static void __exit elanfreq_exit(void)
{
cpufreq_unregister_driver(&elanfreq_driver);
}
module_param(max_freq, int, 0444);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Robert Schwebel <r.schwebel@pengutronix.de>, "
"Sven Geggus <sven@geggus.net>");
MODULE_DESCRIPTION("cpufreq driver for AMD's Elan CPUs");
module_init(elanfreq_init);
module_exit(elanfreq_exit);
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