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#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#include <linux/timex.h>
23#include <linux/io.h>
24
25#include <asm/cpu_device_id.h>
26#include <asm/msr.h>
27
28#define MMCR_BASE	0xfffef000	/* The default base address */
29#define OFFS_CPUCTL	0x2   /* CPU Control Register */
30
31static __u8 __iomem *cpuctl;
32
33#define PFX "sc520_freq: "
34
35static struct cpufreq_frequency_table sc520_freq_table[] = {
36	{0, 0x01,	100000},
37	{0, 0x02,	133000},
38	{0, 0,	CPUFREQ_TABLE_END},
39};
40
41static 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		printk(KERN_ERR PFX "error: cpuctl register has unexpected "
48				"value %02x\n", clockspeed_reg);
49	case 0x01:
50		return 100000;
51	case 0x02:
52		return 133000;
53	}
54}
55
56static 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
75static 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
87	return cpufreq_table_validate_and_show(policy, sc520_freq_table);
88}
89
90
91static struct cpufreq_driver sc520_freq_driver = {
92	.get	= sc520_freq_get_cpu_frequency,
93	.verify	= cpufreq_generic_frequency_table_verify,
94	.target_index = sc520_freq_target,
95	.init	= sc520_freq_cpu_init,
96	.name	= "sc520_freq",
97	.attr	= cpufreq_generic_attr,
98};
99
100static const struct x86_cpu_id sc520_ids[] = {
101	{ X86_VENDOR_AMD, 4, 9 },
102	{}
103};
104MODULE_DEVICE_TABLE(x86cpu, sc520_ids);
105
106static int __init sc520_freq_init(void)
107{
108	int err;
109
110	if (!x86_match_cpu(sc520_ids))
111		return -ENODEV;
112
113	cpuctl = ioremap((unsigned long)(MMCR_BASE + OFFS_CPUCTL), 1);
114	if (!cpuctl) {
115		printk(KERN_ERR "sc520_freq: error: failed to remap memory\n");
116		return -ENOMEM;
117	}
118
119	err = cpufreq_register_driver(&sc520_freq_driver);
120	if (err)
121		iounmap(cpuctl);
122
123	return err;
124}
125
126
127static void __exit sc520_freq_exit(void)
128{
129	cpufreq_unregister_driver(&sc520_freq_driver);
130	iounmap(cpuctl);
131}
132
133
134MODULE_LICENSE("GPL");
135MODULE_AUTHOR("Sean Young <sean@mess.org>");
136MODULE_DESCRIPTION("cpufreq driver for AMD's Elan sc520 CPU");
137
138module_init(sc520_freq_init);
139module_exit(sc520_freq_exit);
140
141