elanfreq.c

// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *	elanfreq:	cpufreq driver for the AMD ELAN family
 *
 *	(c) Copyright 2002 Robert Schwebel <[email protected]>
 *
 *	Parts of this code are (c) Sven Geggus <[email protected]>
 *
 *      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 <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",
};

static const struct x86_cpu_id elan_id[] = {
	X86_MATCH_VENDOR_FAM_MODEL(AMD, 4, 10, NULL),
	{}
};
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 <[email protected]>, "
		"Sven Geggus <[email protected]>");
MODULE_DESCRIPTION("cpufreq driver for AMD's Elan CPUs");

module_init(elanfreq_init);
module_exit(elanfreq_exit);