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/sched.h>	/* set_cpus_allowed() */
20 #include <linux/delay.h>
21 #include <linux/platform_device.h>
22 
23 #include <asm/clock.h>
24 #include <asm/idle.h>
25 
26 #include <asm/mach-loongson64/loongson.h>
27 
28 static uint nowait;
29 
30 static void (*saved_cpu_wait) (void);
31 
32 static int loongson2_cpu_freq_notifier(struct notifier_block *nb,
33 					unsigned long val, void *data);
34 
35 static struct notifier_block loongson2_cpufreq_notifier_block = {
36 	.notifier_call = loongson2_cpu_freq_notifier
37 };
38 
39 static int loongson2_cpu_freq_notifier(struct notifier_block *nb,
40 					unsigned long val, void *data)
41 {
42 	if (val == CPUFREQ_POSTCHANGE)
43 		current_cpu_data.udelay_val = loops_per_jiffy;
44 
45 	return 0;
46 }
47 
48 /*
49  * Here we notify other drivers of the proposed change and the final change.
50  */
51 static int loongson2_cpufreq_target(struct cpufreq_policy *policy,
52 				     unsigned int index)
53 {
54 	unsigned int freq;
55 
56 	freq =
57 	    ((cpu_clock_freq / 1000) *
58 	     loongson2_clockmod_table[index].driver_data) / 8;
59 
60 	/* setting the cpu frequency */
61 	clk_set_rate(policy->clk, freq * 1000);
62 
63 	return 0;
64 }
65 
66 static int loongson2_cpufreq_cpu_init(struct cpufreq_policy *policy)
67 {
68 	struct clk *cpuclk;
69 	int i;
70 	unsigned long rate;
71 	int ret;
72 
73 	cpuclk = clk_get(NULL, "cpu_clk");
74 	if (IS_ERR(cpuclk)) {
75 		pr_err("couldn't get CPU clk\n");
76 		return PTR_ERR(cpuclk);
77 	}
78 
79 	rate = cpu_clock_freq / 1000;
80 	if (!rate) {
81 		clk_put(cpuclk);
82 		return -EINVAL;
83 	}
84 
85 	/* clock table init */
86 	for (i = 2;
87 	     (loongson2_clockmod_table[i].frequency != CPUFREQ_TABLE_END);
88 	     i++)
89 		loongson2_clockmod_table[i].frequency = (rate * i) / 8;
90 
91 	ret = clk_set_rate(cpuclk, rate * 1000);
92 	if (ret) {
93 		clk_put(cpuclk);
94 		return ret;
95 	}
96 
97 	policy->clk = cpuclk;
98 	return cpufreq_generic_init(policy, &loongson2_clockmod_table[0], 0);
99 }
100 
101 static int loongson2_cpufreq_exit(struct cpufreq_policy *policy)
102 {
103 	clk_put(policy->clk);
104 	return 0;
105 }
106 
107 static struct cpufreq_driver loongson2_cpufreq_driver = {
108 	.name = "loongson2",
109 	.init = loongson2_cpufreq_cpu_init,
110 	.verify = cpufreq_generic_frequency_table_verify,
111 	.target_index = loongson2_cpufreq_target,
112 	.get = cpufreq_generic_get,
113 	.exit = loongson2_cpufreq_exit,
114 	.attr = cpufreq_generic_attr,
115 };
116 
117 static struct platform_device_id platform_device_ids[] = {
118 	{
119 		.name = "loongson2_cpufreq",
120 	},
121 	{}
122 };
123 
124 MODULE_DEVICE_TABLE(platform, platform_device_ids);
125 
126 static struct platform_driver platform_driver = {
127 	.driver = {
128 		.name = "loongson2_cpufreq",
129 	},
130 	.id_table = platform_device_ids,
131 };
132 
133 /*
134  * This is the simple version of Loongson-2 wait, Maybe we need do this in
135  * interrupt disabled context.
136  */
137 
138 static DEFINE_SPINLOCK(loongson2_wait_lock);
139 
140 static void loongson2_cpu_wait(void)
141 {
142 	unsigned long flags;
143 	u32 cpu_freq;
144 
145 	spin_lock_irqsave(&loongson2_wait_lock, flags);
146 	cpu_freq = LOONGSON_CHIPCFG(0);
147 	LOONGSON_CHIPCFG(0) &= ~0x7;	/* Put CPU into wait mode */
148 	LOONGSON_CHIPCFG(0) = cpu_freq;	/* Restore CPU state */
149 	spin_unlock_irqrestore(&loongson2_wait_lock, flags);
150 	local_irq_enable();
151 }
152 
153 static int __init cpufreq_init(void)
154 {
155 	int ret;
156 
157 	/* Register platform stuff */
158 	ret = platform_driver_register(&platform_driver);
159 	if (ret)
160 		return ret;
161 
162 	pr_info("Loongson-2F CPU frequency driver\n");
163 
164 	cpufreq_register_notifier(&loongson2_cpufreq_notifier_block,
165 				  CPUFREQ_TRANSITION_NOTIFIER);
166 
167 	ret = cpufreq_register_driver(&loongson2_cpufreq_driver);
168 
169 	if (!ret && !nowait) {
170 		saved_cpu_wait = cpu_wait;
171 		cpu_wait = loongson2_cpu_wait;
172 	}
173 
174 	return ret;
175 }
176 
177 static void __exit cpufreq_exit(void)
178 {
179 	if (!nowait && saved_cpu_wait)
180 		cpu_wait = saved_cpu_wait;
181 	cpufreq_unregister_driver(&loongson2_cpufreq_driver);
182 	cpufreq_unregister_notifier(&loongson2_cpufreq_notifier_block,
183 				    CPUFREQ_TRANSITION_NOTIFIER);
184 
185 	platform_driver_unregister(&platform_driver);
186 }
187 
188 module_init(cpufreq_init);
189 module_exit(cpufreq_exit);
190 
191 module_param(nowait, uint, 0644);
192 MODULE_PARM_DESC(nowait, "Disable Loongson-2F specific wait");
193 
194 MODULE_AUTHOR("Yanhua <yanh@lemote.com>");
195 MODULE_DESCRIPTION("cpufreq driver for Loongson2F");
196 MODULE_LICENSE("GPL");
197