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-loongson2ef/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 	cpufreq_generic_init(policy, &loongson2_clockmod_table[0], 0);
99 	return 0;
100 }
101 
102 static int loongson2_cpufreq_exit(struct cpufreq_policy *policy)
103 {
104 	clk_put(policy->clk);
105 	return 0;
106 }
107 
108 static struct cpufreq_driver loongson2_cpufreq_driver = {
109 	.name = "loongson2",
110 	.init = loongson2_cpufreq_cpu_init,
111 	.verify = cpufreq_generic_frequency_table_verify,
112 	.target_index = loongson2_cpufreq_target,
113 	.get = cpufreq_generic_get,
114 	.exit = loongson2_cpufreq_exit,
115 	.attr = cpufreq_generic_attr,
116 };
117 
118 static const struct platform_device_id platform_device_ids[] = {
119 	{
120 		.name = "loongson2_cpufreq",
121 	},
122 	{}
123 };
124 
125 MODULE_DEVICE_TABLE(platform, platform_device_ids);
126 
127 static struct platform_driver platform_driver = {
128 	.driver = {
129 		.name = "loongson2_cpufreq",
130 	},
131 	.id_table = platform_device_ids,
132 };
133 
134 /*
135  * This is the simple version of Loongson-2 wait, Maybe we need do this in
136  * interrupt disabled context.
137  */
138 
139 static DEFINE_SPINLOCK(loongson2_wait_lock);
140 
141 static void loongson2_cpu_wait(void)
142 {
143 	unsigned long flags;
144 	u32 cpu_freq;
145 
146 	spin_lock_irqsave(&loongson2_wait_lock, flags);
147 	cpu_freq = readl(LOONGSON_CHIPCFG);
148 	/* Put CPU into wait mode */
149 	writel(readl(LOONGSON_CHIPCFG) & ~0x7, LOONGSON_CHIPCFG);
150 	/* Restore CPU state */
151 	writel(cpu_freq, LOONGSON_CHIPCFG);
152 	spin_unlock_irqrestore(&loongson2_wait_lock, flags);
153 	local_irq_enable();
154 }
155 
156 static int __init cpufreq_init(void)
157 {
158 	int ret;
159 
160 	/* Register platform stuff */
161 	ret = platform_driver_register(&platform_driver);
162 	if (ret)
163 		return ret;
164 
165 	pr_info("Loongson-2F CPU frequency driver\n");
166 
167 	cpufreq_register_notifier(&loongson2_cpufreq_notifier_block,
168 				  CPUFREQ_TRANSITION_NOTIFIER);
169 
170 	ret = cpufreq_register_driver(&loongson2_cpufreq_driver);
171 
172 	if (!ret && !nowait) {
173 		saved_cpu_wait = cpu_wait;
174 		cpu_wait = loongson2_cpu_wait;
175 	}
176 
177 	return ret;
178 }
179 
180 static void __exit cpufreq_exit(void)
181 {
182 	if (!nowait && saved_cpu_wait)
183 		cpu_wait = saved_cpu_wait;
184 	cpufreq_unregister_driver(&loongson2_cpufreq_driver);
185 	cpufreq_unregister_notifier(&loongson2_cpufreq_notifier_block,
186 				    CPUFREQ_TRANSITION_NOTIFIER);
187 
188 	platform_driver_unregister(&platform_driver);
189 }
190 
191 module_init(cpufreq_init);
192 module_exit(cpufreq_exit);
193 
194 module_param(nowait, uint, 0644);
195 MODULE_PARM_DESC(nowait, "Disable Loongson-2F specific wait");
196 
197 MODULE_AUTHOR("Yanhua <yanh@lemote.com>");
198 MODULE_DESCRIPTION("cpufreq driver for Loongson2F");
199 MODULE_LICENSE("GPL");
200