1 /*
2 * sc520_freq.c: cpufreq driver for the AMD Elan sc520
3 *
4 * Copyright (C) 2005 Sean Young <sean@mess.org>
5 *
6 * This program is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU General Public License
8 * as published by the Free Software Foundation; either version
9 * 2 of the License, or (at your option) any later version.
10 *
11 * Based on elanfreq.c
12 *
13 * 2005-03-30: - initial revision
14 */
15
16 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
17
18 #include <linux/kernel.h>
19 #include <linux/module.h>
20 #include <linux/init.h>
21
22 #include <linux/delay.h>
23 #include <linux/cpufreq.h>
24 #include <linux/timex.h>
25 #include <linux/io.h>
26
27 #include <asm/cpu_device_id.h>
28 #include <asm/msr.h>
29
30 #define MMCR_BASE 0xfffef000 /* The default base address */
31 #define OFFS_CPUCTL 0x2 /* CPU Control Register */
32
33 static __u8 __iomem *cpuctl;
34
35 static struct cpufreq_frequency_table sc520_freq_table[] = {
36 {0, 0x01, 100000},
37 {0, 0x02, 133000},
38 {0, 0, CPUFREQ_TABLE_END},
39 };
40
sc520_freq_get_cpu_frequency(unsigned int cpu)41 static unsigned int sc520_freq_get_cpu_frequency(unsigned int cpu)
42 {
43 u8 clockspeed_reg = *cpuctl;
44
45 switch (clockspeed_reg & 0x03) {
46 default:
47 pr_err("error: cpuctl register has unexpected value %02x\n",
48 clockspeed_reg);
49 case 0x01:
50 return 100000;
51 case 0x02:
52 return 133000;
53 }
54 }
55
sc520_freq_target(struct cpufreq_policy * policy,unsigned int state)56 static int sc520_freq_target(struct cpufreq_policy *policy, unsigned int state)
57 {
58
59 u8 clockspeed_reg;
60
61 local_irq_disable();
62
63 clockspeed_reg = *cpuctl & ~0x03;
64 *cpuctl = clockspeed_reg | sc520_freq_table[state].driver_data;
65
66 local_irq_enable();
67
68 return 0;
69 }
70
71 /*
72 * Module init and exit code
73 */
74
sc520_freq_cpu_init(struct cpufreq_policy * policy)75 static int sc520_freq_cpu_init(struct cpufreq_policy *policy)
76 {
77 struct cpuinfo_x86 *c = &cpu_data(0);
78
79 /* capability check */
80 if (c->x86_vendor != X86_VENDOR_AMD ||
81 c->x86 != 4 || c->x86_model != 9)
82 return -ENODEV;
83
84 /* cpuinfo and default policy values */
85 policy->cpuinfo.transition_latency = 1000000; /* 1ms */
86 policy->freq_table = sc520_freq_table;
87
88 return 0;
89 }
90
91
92 static struct cpufreq_driver sc520_freq_driver = {
93 .get = sc520_freq_get_cpu_frequency,
94 .verify = cpufreq_generic_frequency_table_verify,
95 .target_index = sc520_freq_target,
96 .init = sc520_freq_cpu_init,
97 .name = "sc520_freq",
98 .attr = cpufreq_generic_attr,
99 };
100
101 static const struct x86_cpu_id sc520_ids[] = {
102 { X86_VENDOR_AMD, 4, 9 },
103 {}
104 };
105 MODULE_DEVICE_TABLE(x86cpu, sc520_ids);
106
sc520_freq_init(void)107 static int __init sc520_freq_init(void)
108 {
109 int err;
110
111 if (!x86_match_cpu(sc520_ids))
112 return -ENODEV;
113
114 cpuctl = ioremap((unsigned long)(MMCR_BASE + OFFS_CPUCTL), 1);
115 if (!cpuctl) {
116 pr_err("sc520_freq: error: failed to remap memory\n");
117 return -ENOMEM;
118 }
119
120 err = cpufreq_register_driver(&sc520_freq_driver);
121 if (err)
122 iounmap(cpuctl);
123
124 return err;
125 }
126
127
sc520_freq_exit(void)128 static void __exit sc520_freq_exit(void)
129 {
130 cpufreq_unregister_driver(&sc520_freq_driver);
131 iounmap(cpuctl);
132 }
133
134
135 MODULE_LICENSE("GPL");
136 MODULE_AUTHOR("Sean Young <sean@mess.org>");
137 MODULE_DESCRIPTION("cpufreq driver for AMD's Elan sc520 CPU");
138
139 module_init(sc520_freq_init);
140 module_exit(sc520_freq_exit);
141
142