elanfreq.c

  1// SPDX-License-Identifier: GPL-2.0-or-later
  2/*
  3 *	elanfreq:	cpufreq driver for the AMD ELAN family
  4 *
  5 *	(c) Copyright 2002 Robert Schwebel <r.schwebel@pengutronix.de>
  6 *
  7 *	Parts of this code are (c) Sven Geggus <sven@geggus.net>
  8 *
  9 *      All Rights Reserved.
 10 *
 11 *	2002-02-13: - initial revision for 2.4.18-pre9 by Robert Schwebel
 12 */
 13
 14#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
 15
 16#include <linux/kernel.h>
 17#include <linux/module.h>
 18#include <linux/init.h>
 19
 20#include <linux/delay.h>
 21#include <linux/cpufreq.h>
 22
 23#include <asm/cpu_device_id.h>
 24#include <linux/timex.h>
 25#include <linux/io.h>
 26
 27#define REG_CSCIR 0x22		/* Chip Setup and Control Index Register    */
 28#define REG_CSCDR 0x23		/* Chip Setup and Control Data  Register    */
 29
 30/* Module parameter */
 31static int max_freq;
 32
 33struct s_elan_multiplier {
 34	int clock;		/* frequency in kHz                         */
 35	int val40h;		/* PMU Force Mode register                  */
 36	int val80h;		/* CPU Clock Speed Register                 */
 37};
 38
 39/*
 40 * It is important that the frequencies
 41 * are listed in ascending order here!
 42 */
 43static struct s_elan_multiplier elan_multiplier[] = {
 44	{1000,	0x02,	0x18},
 45	{2000,	0x02,	0x10},
 46	{4000,	0x02,	0x08},
 47	{8000,	0x00,	0x00},
 48	{16000,	0x00,	0x02},
 49	{33000,	0x00,	0x04},
 50	{66000,	0x01,	0x04},
 51	{99000,	0x01,	0x05}
 52};
 53
 54static struct cpufreq_frequency_table elanfreq_table[] = {
 55	{0, 0,	1000},
 56	{0, 1,	2000},
 57	{0, 2,	4000},
 58	{0, 3,	8000},
 59	{0, 4,	16000},
 60	{0, 5,	33000},
 61	{0, 6,	66000},
 62	{0, 7,	99000},
 63	{0, 0,	CPUFREQ_TABLE_END},
 64};
 65
 66
 67/**
 68 *	elanfreq_get_cpu_frequency: determine current cpu speed
 69 *
 70 *	Finds out at which frequency the CPU of the Elan SOC runs
 71 *	at the moment. Frequencies from 1 to 33 MHz are generated
 72 *	the normal way, 66 and 99 MHz are called "Hyperspeed Mode"
 73 *	and have the rest of the chip running with 33 MHz.
 74 */
 75
 76static unsigned int elanfreq_get_cpu_frequency(unsigned int cpu)
 77{
 78	u8 clockspeed_reg;    /* Clock Speed Register */
 79
 80	local_irq_disable();
 81	outb_p(0x80, REG_CSCIR);
 82	clockspeed_reg = inb_p(REG_CSCDR);
 83	local_irq_enable();
 84
 85	if ((clockspeed_reg & 0xE0) == 0xE0)
 86		return 0;
 87
 88	/* Are we in CPU clock multiplied mode (66/99 MHz)? */
 89	if ((clockspeed_reg & 0xE0) == 0xC0) {
 90		if ((clockspeed_reg & 0x01) == 0)
 91			return 66000;
 92		else
 93			return 99000;
 94	}
 95
 96	/* 33 MHz is not 32 MHz... */
 97	if ((clockspeed_reg & 0xE0) == 0xA0)
 98		return 33000;
 99
100	return (1<<((clockspeed_reg & 0xE0) >> 5)) * 1000;
101}
102
103
104static int elanfreq_target(struct cpufreq_policy *policy,
105			    unsigned int state)
106{
107	/*
108	 * Access to the Elan's internal registers is indexed via
109	 * 0x22: Chip Setup & Control Register Index Register (CSCI)
110	 * 0x23: Chip Setup & Control Register Data  Register (CSCD)
111	 *
112	 */
113
114	/*
115	 * 0x40 is the Power Management Unit's Force Mode Register.
116	 * Bit 6 enables Hyperspeed Mode (66/100 MHz core frequency)
117	 */
118
119	local_irq_disable();
120	outb_p(0x40, REG_CSCIR);		/* Disable hyperspeed mode */
121	outb_p(0x00, REG_CSCDR);
122	local_irq_enable();		/* wait till internal pipelines and */
123	udelay(1000);			/* buffers have cleaned up          */
124
125	local_irq_disable();
126
127	/* now, set the CPU clock speed register (0x80) */
128	outb_p(0x80, REG_CSCIR);
129	outb_p(elan_multiplier[state].val80h, REG_CSCDR);
130
131	/* now, the hyperspeed bit in PMU Force Mode Register (0x40) */
132	outb_p(0x40, REG_CSCIR);
133	outb_p(elan_multiplier[state].val40h, REG_CSCDR);
134	udelay(10000);
135	local_irq_enable();
136
137	return 0;
138}
139/*
140 *	Module init and exit code
141 */
142
143static int elanfreq_cpu_init(struct cpufreq_policy *policy)
144{
145	struct cpuinfo_x86 *c = &cpu_data(0);
146	struct cpufreq_frequency_table *pos;
147
148	/* capability check */
149	if ((c->x86_vendor != X86_VENDOR_AMD) ||
150	    (c->x86 != 4) || (c->x86_model != 10))
151		return -ENODEV;
152
153	/* max freq */
154	if (!max_freq)
155		max_freq = elanfreq_get_cpu_frequency(0);
156
157	/* table init */
158	cpufreq_for_each_entry(pos, elanfreq_table)
159		if (pos->frequency > max_freq)
160			pos->frequency = CPUFREQ_ENTRY_INVALID;
161
162	policy->freq_table = elanfreq_table;
163	return 0;
164}
165
166
167#ifndef MODULE
168/**
169 * elanfreq_setup - elanfreq command line parameter parsing
170 *
171 * elanfreq command line parameter.  Use:
172 *  elanfreq=66000
173 * to set the maximum CPU frequency to 66 MHz. Note that in
174 * case you do not give this boot parameter, the maximum
175 * frequency will fall back to _current_ CPU frequency which
176 * might be lower. If you build this as a module, use the
177 * max_freq module parameter instead.
178 */
179static int __init elanfreq_setup(char *str)
180{
181	max_freq = simple_strtoul(str, &str, 0);
182	pr_warn("You're using the deprecated elanfreq command line option. Use elanfreq.max_freq instead, please!\n");
183	return 1;
184}
185__setup("elanfreq=", elanfreq_setup);
186#endif
187
188
189static struct cpufreq_driver elanfreq_driver = {
190	.get		= elanfreq_get_cpu_frequency,
191	.flags		= CPUFREQ_NO_AUTO_DYNAMIC_SWITCHING,
192	.verify		= cpufreq_generic_frequency_table_verify,
193	.target_index	= elanfreq_target,
194	.init		= elanfreq_cpu_init,
195	.name		= "elanfreq",
196};
197
198static const struct x86_cpu_id elan_id[] = {
199	X86_MATCH_VENDOR_FAM_MODEL(AMD, 4, 10, NULL),
200	{}
201};
202MODULE_DEVICE_TABLE(x86cpu, elan_id);
203
204static int __init elanfreq_init(void)
205{
206	if (!x86_match_cpu(elan_id))
207		return -ENODEV;
208	return cpufreq_register_driver(&elanfreq_driver);
209}
210
211
212static void __exit elanfreq_exit(void)
213{
214	cpufreq_unregister_driver(&elanfreq_driver);
215}
216
217
218module_param(max_freq, int, 0444);
219
220MODULE_LICENSE("GPL");
221MODULE_AUTHOR("Robert Schwebel <r.schwebel@pengutronix.de>, "
222		"Sven Geggus <sven@geggus.net>");
223MODULE_DESCRIPTION("cpufreq driver for AMD's Elan CPUs");
224
225module_init(elanfreq_init);
226module_exit(elanfreq_exit);