1 /*
2  * Cpufreq driver for the loongson-2 processors
3  *
4  * The 2E revision of loongson processor not support this feature.
5  *
6  * Copyright (C) 2006 - 2008 Lemote Inc. & Institute of Computing Technology
7  * Author: Yanhua, yanh@lemote.com
8  *
9  * This file is subject to the terms and conditions of the GNU General Public
10  * License.  See the file "COPYING" in the main directory of this archive
11  * for more details.
12  */
13 
14 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
15 
16 #include <linux/cpufreq.h>
17 #include <linux/module.h>
18 #include <linux/err.h>
19 #include <linux/delay.h>
20 #include <linux/platform_device.h>
21 
22 #include <asm/idle.h>
23 
24 #include <asm/mach-loongson2ef/loongson.h>
25 
26 static uint nowait;
27 
28 static void (*saved_cpu_wait) (void);
29 
30 static int loongson2_cpu_freq_notifier(struct notifier_block *nb,
31 					unsigned long val, void *data);
32 
33 static struct notifier_block loongson2_cpufreq_notifier_block = {
34 	.notifier_call = loongson2_cpu_freq_notifier
35 };
36 
37 static int loongson2_cpu_freq_notifier(struct notifier_block *nb,
38 					unsigned long val, void *data)
39 {
40 	if (val == CPUFREQ_POSTCHANGE)
41 		current_cpu_data.udelay_val = loops_per_jiffy;
42 
43 	return 0;
44 }
45 
46 /*
47  * Here we notify other drivers of the proposed change and the final change.
48  */
49 static int loongson2_cpufreq_target(struct cpufreq_policy *policy,
50 				     unsigned int index)
51 {
52 	unsigned int freq;
53 
54 	freq =
55 	    ((cpu_clock_freq / 1000) *
56 	     loongson2_clockmod_table[index].driver_data) / 8;
57 
58 	/* setting the cpu frequency */
59 	loongson2_cpu_set_rate(freq);
60 
61 	return 0;
62 }
63 
64 static int loongson2_cpufreq_cpu_init(struct cpufreq_policy *policy)
65 {
66 	int i;
67 	unsigned long rate;
68 	int ret;
69 
70 	rate = cpu_clock_freq / 1000;
71 	if (!rate)
72 		return -EINVAL;
73 
74 	/* clock table init */
75 	for (i = 2;
76 	     (loongson2_clockmod_table[i].frequency != CPUFREQ_TABLE_END);
77 	     i++)
78 		loongson2_clockmod_table[i].frequency = (rate * i) / 8;
79 
80 	ret = loongson2_cpu_set_rate(rate);
81 	if (ret)
82 		return ret;
83 
84 	cpufreq_generic_init(policy, &loongson2_clockmod_table[0], 0);
85 	return 0;
86 }
87 
88 static int loongson2_cpufreq_exit(struct cpufreq_policy *policy)
89 {
90 	return 0;
91 }
92 
93 static struct cpufreq_driver loongson2_cpufreq_driver = {
94 	.name = "loongson2",
95 	.init = loongson2_cpufreq_cpu_init,
96 	.verify = cpufreq_generic_frequency_table_verify,
97 	.target_index = loongson2_cpufreq_target,
98 	.get = cpufreq_generic_get,
99 	.exit = loongson2_cpufreq_exit,
100 	.attr = cpufreq_generic_attr,
101 };
102 
103 static const struct platform_device_id platform_device_ids[] = {
104 	{
105 		.name = "loongson2_cpufreq",
106 	},
107 	{}
108 };
109 
110 MODULE_DEVICE_TABLE(platform, platform_device_ids);
111 
112 static struct platform_driver platform_driver = {
113 	.driver = {
114 		.name = "loongson2_cpufreq",
115 	},
116 	.id_table = platform_device_ids,
117 };
118 
119 /*
120  * This is the simple version of Loongson-2 wait, Maybe we need do this in
121  * interrupt disabled context.
122  */
123 
124 static DEFINE_SPINLOCK(loongson2_wait_lock);
125 
126 static void loongson2_cpu_wait(void)
127 {
128 	unsigned long flags;
129 	u32 cpu_freq;
130 
131 	spin_lock_irqsave(&loongson2_wait_lock, flags);
132 	cpu_freq = readl(LOONGSON_CHIPCFG);
133 	/* Put CPU into wait mode */
134 	writel(readl(LOONGSON_CHIPCFG) & ~0x7, LOONGSON_CHIPCFG);
135 	/* Restore CPU state */
136 	writel(cpu_freq, LOONGSON_CHIPCFG);
137 	spin_unlock_irqrestore(&loongson2_wait_lock, flags);
138 	local_irq_enable();
139 }
140 
141 static int __init cpufreq_init(void)
142 {
143 	int ret;
144 
145 	/* Register platform stuff */
146 	ret = platform_driver_register(&platform_driver);
147 	if (ret)
148 		return ret;
149 
150 	pr_info("Loongson-2F CPU frequency driver\n");
151 
152 	cpufreq_register_notifier(&loongson2_cpufreq_notifier_block,
153 				  CPUFREQ_TRANSITION_NOTIFIER);
154 
155 	ret = cpufreq_register_driver(&loongson2_cpufreq_driver);
156 
157 	if (ret) {
158 		platform_driver_unregister(&platform_driver);
159 	} else if (!nowait) {
160 		saved_cpu_wait = cpu_wait;
161 		cpu_wait = loongson2_cpu_wait;
162 	}
163 
164 	return ret;
165 }
166 
167 static void __exit cpufreq_exit(void)
168 {
169 	if (!nowait && saved_cpu_wait)
170 		cpu_wait = saved_cpu_wait;
171 	cpufreq_unregister_driver(&loongson2_cpufreq_driver);
172 	cpufreq_unregister_notifier(&loongson2_cpufreq_notifier_block,
173 				    CPUFREQ_TRANSITION_NOTIFIER);
174 
175 	platform_driver_unregister(&platform_driver);
176 }
177 
178 module_init(cpufreq_init);
179 module_exit(cpufreq_exit);
180 
181 module_param(nowait, uint, 0644);
182 MODULE_PARM_DESC(nowait, "Disable Loongson-2F specific wait");
183 
184 MODULE_AUTHOR("Yanhua <yanh@lemote.com>");
185 MODULE_DESCRIPTION("cpufreq driver for Loongson2F");
186 MODULE_LICENSE("GPL");
187