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 <asm/msr.h>
25 #include <linux/timex.h>
26 #include <linux/io.h>
27
28 #define REG_CSCIR 0x22 /* Chip Setup and Control Index Register */
29 #define REG_CSCDR 0x23 /* Chip Setup and Control Data Register */
30
31 /* Module parameter */
32 static int max_freq;
33
34 struct s_elan_multiplier {
35 int clock; /* frequency in kHz */
36 int val40h; /* PMU Force Mode register */
37 int val80h; /* CPU Clock Speed Register */
38 };
39
40 /*
41 * It is important that the frequencies
42 * are listed in ascending order here!
43 */
44 static struct s_elan_multiplier elan_multiplier[] = {
45 {1000, 0x02, 0x18},
46 {2000, 0x02, 0x10},
47 {4000, 0x02, 0x08},
48 {8000, 0x00, 0x00},
49 {16000, 0x00, 0x02},
50 {33000, 0x00, 0x04},
51 {66000, 0x01, 0x04},
52 {99000, 0x01, 0x05}
53 };
54
55 static struct cpufreq_frequency_table elanfreq_table[] = {
56 {0, 0, 1000},
57 {0, 1, 2000},
58 {0, 2, 4000},
59 {0, 3, 8000},
60 {0, 4, 16000},
61 {0, 5, 33000},
62 {0, 6, 66000},
63 {0, 7, 99000},
64 {0, 0, CPUFREQ_TABLE_END},
65 };
66
67
68 /**
69 * elanfreq_get_cpu_frequency: determine current cpu speed
70 *
71 * Finds out at which frequency the CPU of the Elan SOC runs
72 * at the moment. Frequencies from 1 to 33 MHz are generated
73 * the normal way, 66 and 99 MHz are called "Hyperspeed Mode"
74 * and have the rest of the chip running with 33 MHz.
75 */
76
elanfreq_get_cpu_frequency(unsigned int cpu)77 static unsigned int elanfreq_get_cpu_frequency(unsigned int cpu)
78 {
79 u8 clockspeed_reg; /* Clock Speed Register */
80
81 local_irq_disable();
82 outb_p(0x80, REG_CSCIR);
83 clockspeed_reg = inb_p(REG_CSCDR);
84 local_irq_enable();
85
86 if ((clockspeed_reg & 0xE0) == 0xE0)
87 return 0;
88
89 /* Are we in CPU clock multiplied mode (66/99 MHz)? */
90 if ((clockspeed_reg & 0xE0) == 0xC0) {
91 if ((clockspeed_reg & 0x01) == 0)
92 return 66000;
93 else
94 return 99000;
95 }
96
97 /* 33 MHz is not 32 MHz... */
98 if ((clockspeed_reg & 0xE0) == 0xA0)
99 return 33000;
100
101 return (1<<((clockspeed_reg & 0xE0) >> 5)) * 1000;
102 }
103
104
elanfreq_target(struct cpufreq_policy * policy,unsigned int state)105 static int elanfreq_target(struct cpufreq_policy *policy,
106 unsigned int state)
107 {
108 /*
109 * Access to the Elan's internal registers is indexed via
110 * 0x22: Chip Setup & Control Register Index Register (CSCI)
111 * 0x23: Chip Setup & Control Register Data Register (CSCD)
112 *
113 */
114
115 /*
116 * 0x40 is the Power Management Unit's Force Mode Register.
117 * Bit 6 enables Hyperspeed Mode (66/100 MHz core frequency)
118 */
119
120 local_irq_disable();
121 outb_p(0x40, REG_CSCIR); /* Disable hyperspeed mode */
122 outb_p(0x00, REG_CSCDR);
123 local_irq_enable(); /* wait till internal pipelines and */
124 udelay(1000); /* buffers have cleaned up */
125
126 local_irq_disable();
127
128 /* now, set the CPU clock speed register (0x80) */
129 outb_p(0x80, REG_CSCIR);
130 outb_p(elan_multiplier[state].val80h, REG_CSCDR);
131
132 /* now, the hyperspeed bit in PMU Force Mode Register (0x40) */
133 outb_p(0x40, REG_CSCIR);
134 outb_p(elan_multiplier[state].val40h, REG_CSCDR);
135 udelay(10000);
136 local_irq_enable();
137
138 return 0;
139 }
140 /*
141 * Module init and exit code
142 */
143
elanfreq_cpu_init(struct cpufreq_policy * policy)144 static int elanfreq_cpu_init(struct cpufreq_policy *policy)
145 {
146 struct cpuinfo_x86 *c = &cpu_data(0);
147 struct cpufreq_frequency_table *pos;
148
149 /* capability check */
150 if ((c->x86_vendor != X86_VENDOR_AMD) ||
151 (c->x86 != 4) || (c->x86_model != 10))
152 return -ENODEV;
153
154 /* max freq */
155 if (!max_freq)
156 max_freq = elanfreq_get_cpu_frequency(0);
157
158 /* table init */
159 cpufreq_for_each_entry(pos, elanfreq_table)
160 if (pos->frequency > max_freq)
161 pos->frequency = CPUFREQ_ENTRY_INVALID;
162
163 policy->freq_table = elanfreq_table;
164 return 0;
165 }
166
167
168 #ifndef MODULE
169 /**
170 * elanfreq_setup - elanfreq command line parameter parsing
171 *
172 * elanfreq command line parameter. Use:
173 * elanfreq=66000
174 * to set the maximum CPU frequency to 66 MHz. Note that in
175 * case you do not give this boot parameter, the maximum
176 * frequency will fall back to _current_ CPU frequency which
177 * might be lower. If you build this as a module, use the
178 * max_freq module parameter instead.
179 */
elanfreq_setup(char * str)180 static int __init elanfreq_setup(char *str)
181 {
182 max_freq = simple_strtoul(str, &str, 0);
183 pr_warn("You're using the deprecated elanfreq command line option. Use elanfreq.max_freq instead, please!\n");
184 return 1;
185 }
186 __setup("elanfreq=", elanfreq_setup);
187 #endif
188
189
190 static struct cpufreq_driver elanfreq_driver = {
191 .get = elanfreq_get_cpu_frequency,
192 .flags = CPUFREQ_NO_AUTO_DYNAMIC_SWITCHING,
193 .verify = cpufreq_generic_frequency_table_verify,
194 .target_index = elanfreq_target,
195 .init = elanfreq_cpu_init,
196 .name = "elanfreq",
197 .attr = cpufreq_generic_attr,
198 };
199
200 static const struct x86_cpu_id elan_id[] = {
201 X86_MATCH_VENDOR_FAM_MODEL(AMD, 4, 10, NULL),
202 {}
203 };
204 MODULE_DEVICE_TABLE(x86cpu, elan_id);
205
elanfreq_init(void)206 static int __init elanfreq_init(void)
207 {
208 if (!x86_match_cpu(elan_id))
209 return -ENODEV;
210 return cpufreq_register_driver(&elanfreq_driver);
211 }
212
213
elanfreq_exit(void)214 static void __exit elanfreq_exit(void)
215 {
216 cpufreq_unregister_driver(&elanfreq_driver);
217 }
218
219
220 module_param(max_freq, int, 0444);
221
222 MODULE_LICENSE("GPL");
223 MODULE_AUTHOR("Robert Schwebel <r.schwebel@pengutronix.de>, "
224 "Sven Geggus <sven@geggus.net>");
225 MODULE_DESCRIPTION("cpufreq driver for AMD's Elan CPUs");
226
227 module_init(elanfreq_init);
228 module_exit(elanfreq_exit);
229