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1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * sc520_freq.c: cpufreq driver for the AMD Elan sc520
4 *
5 * Copyright (C) 2005 Sean Young <sean@mess.org>
6 *
7 * Based on elanfreq.c
8 *
9 * 2005-03-30: - initial revision
10 */
11
12#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
13
14#include <linux/kernel.h>
15#include <linux/module.h>
16#include <linux/init.h>
17
18#include <linux/delay.h>
19#include <linux/cpufreq.h>
20#include <linux/timex.h>
21#include <linux/io.h>
22
23#include <asm/cpu_device_id.h>
24
25#define MMCR_BASE 0xfffef000 /* The default base address */
26#define OFFS_CPUCTL 0x2 /* CPU Control Register */
27
28static __u8 __iomem *cpuctl;
29
30static struct cpufreq_frequency_table sc520_freq_table[] = {
31 {0, 0x01, 100000},
32 {0, 0x02, 133000},
33 {0, 0, CPUFREQ_TABLE_END},
34};
35
36static unsigned int sc520_freq_get_cpu_frequency(unsigned int cpu)
37{
38 u8 clockspeed_reg = *cpuctl;
39
40 switch (clockspeed_reg & 0x03) {
41 default:
42 pr_err("error: cpuctl register has unexpected value %02x\n",
43 clockspeed_reg);
44 fallthrough;
45 case 0x01:
46 return 100000;
47 case 0x02:
48 return 133000;
49 }
50}
51
52static int sc520_freq_target(struct cpufreq_policy *policy, unsigned int state)
53{
54
55 u8 clockspeed_reg;
56
57 local_irq_disable();
58
59 clockspeed_reg = *cpuctl & ~0x03;
60 *cpuctl = clockspeed_reg | sc520_freq_table[state].driver_data;
61
62 local_irq_enable();
63
64 return 0;
65}
66
67/*
68 * Module init and exit code
69 */
70
71static int sc520_freq_cpu_init(struct cpufreq_policy *policy)
72{
73 struct cpuinfo_x86 *c = &cpu_data(0);
74
75 /* capability check */
76 if (c->x86_vendor != X86_VENDOR_AMD ||
77 c->x86 != 4 || c->x86_model != 9)
78 return -ENODEV;
79
80 /* cpuinfo and default policy values */
81 policy->cpuinfo.transition_latency = 1000000; /* 1ms */
82 policy->freq_table = sc520_freq_table;
83
84 return 0;
85}
86
87
88static struct cpufreq_driver sc520_freq_driver = {
89 .get = sc520_freq_get_cpu_frequency,
90 .verify = cpufreq_generic_frequency_table_verify,
91 .target_index = sc520_freq_target,
92 .init = sc520_freq_cpu_init,
93 .name = "sc520_freq",
94};
95
96static const struct x86_cpu_id sc520_ids[] = {
97 X86_MATCH_VENDOR_FAM_MODEL(AMD, 4, 9, NULL),
98 {}
99};
100MODULE_DEVICE_TABLE(x86cpu, sc520_ids);
101
102static int __init sc520_freq_init(void)
103{
104 int err;
105
106 if (!x86_match_cpu(sc520_ids))
107 return -ENODEV;
108
109 cpuctl = ioremap((unsigned long)(MMCR_BASE + OFFS_CPUCTL), 1);
110 if (!cpuctl) {
111 pr_err("sc520_freq: error: failed to remap memory\n");
112 return -ENOMEM;
113 }
114
115 err = cpufreq_register_driver(&sc520_freq_driver);
116 if (err)
117 iounmap(cpuctl);
118
119 return err;
120}
121
122
123static void __exit sc520_freq_exit(void)
124{
125 cpufreq_unregister_driver(&sc520_freq_driver);
126 iounmap(cpuctl);
127}
128
129
130MODULE_LICENSE("GPL");
131MODULE_AUTHOR("Sean Young <sean@mess.org>");
132MODULE_DESCRIPTION("cpufreq driver for AMD's Elan sc520 CPU");
133
134module_init(sc520_freq_init);
135module_exit(sc520_freq_exit);
136