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 */
31 static int max_freq;
32
33 struct 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 */
43 static 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
54 static 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
elanfreq_get_cpu_frequency(unsigned int cpu)76 static 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
elanfreq_target(struct cpufreq_policy * policy,unsigned int state)104 static 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
elanfreq_cpu_init(struct cpufreq_policy * policy)143 static 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 */
elanfreq_setup(char * str)179 static 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
189 static 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
198 static const struct x86_cpu_id elan_id[] = {
199 X86_MATCH_VENDOR_FAM_MODEL(AMD, 4, 10, NULL),
200 {}
201 };
202 MODULE_DEVICE_TABLE(x86cpu, elan_id);
203
elanfreq_init(void)204 static 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
elanfreq_exit(void)212 static void __exit elanfreq_exit(void)
213 {
214 cpufreq_unregister_driver(&elanfreq_driver);
215 }
216
217
218 module_param(max_freq, int, 0444);
219
220 MODULE_LICENSE("GPL");
221 MODULE_AUTHOR("Robert Schwebel <r.schwebel@pengutronix.de>, "
222 "Sven Geggus <sven@geggus.net>");
223 MODULE_DESCRIPTION("cpufreq driver for AMD's Elan CPUs");
224
225 module_init(elanfreq_init);
226 module_exit(elanfreq_exit);
227