loongson2_cpufreq.c

  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
 26static uint nowait;
 27
 28static void (*saved_cpu_wait) (void);
 29
 30static int loongson2_cpu_freq_notifier(struct notifier_block *nb,
 31					unsigned long val, void *data);
 32
 33static struct notifier_block loongson2_cpufreq_notifier_block = {
 34	.notifier_call = loongson2_cpu_freq_notifier
 35};
 36
 37static 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 */
 49static 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
 64static 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
 88static struct cpufreq_driver loongson2_cpufreq_driver = {
 89	.name = "loongson2",
 90	.init = loongson2_cpufreq_cpu_init,
 91	.verify = cpufreq_generic_frequency_table_verify,
 92	.target_index = loongson2_cpufreq_target,
 93	.get = cpufreq_generic_get,
 94};
 95
 96static const struct platform_device_id platform_device_ids[] = {
 97	{
 98		.name = "loongson2_cpufreq",
 99	},
100	{}
101};
102
103MODULE_DEVICE_TABLE(platform, platform_device_ids);
104
105static struct platform_driver platform_driver = {
106	.driver = {
107		.name = "loongson2_cpufreq",
108	},
109	.id_table = platform_device_ids,
110};
111
112/*
113 * This is the simple version of Loongson-2 wait, Maybe we need do this in
114 * interrupt disabled context.
115 */
116
117static DEFINE_SPINLOCK(loongson2_wait_lock);
118
119static void loongson2_cpu_wait(void)
120{
121	unsigned long flags;
122	u32 cpu_freq;
123
124	spin_lock_irqsave(&loongson2_wait_lock, flags);
125	cpu_freq = readl(LOONGSON_CHIPCFG);
126	/* Put CPU into wait mode */
127	writel(readl(LOONGSON_CHIPCFG) & ~0x7, LOONGSON_CHIPCFG);
128	/* Restore CPU state */
129	writel(cpu_freq, LOONGSON_CHIPCFG);
130	spin_unlock_irqrestore(&loongson2_wait_lock, flags);
131	local_irq_enable();
132}
133
134static int __init cpufreq_init(void)
135{
136	int ret;
137
138	/* Register platform stuff */
139	ret = platform_driver_register(&platform_driver);
140	if (ret)
141		return ret;
142
143	pr_info("Loongson-2F CPU frequency driver\n");
144
145	cpufreq_register_notifier(&loongson2_cpufreq_notifier_block,
146				  CPUFREQ_TRANSITION_NOTIFIER);
147
148	ret = cpufreq_register_driver(&loongson2_cpufreq_driver);
149
150	if (ret) {
151		platform_driver_unregister(&platform_driver);
152	} else if (!nowait) {
153		saved_cpu_wait = cpu_wait;
154		cpu_wait = loongson2_cpu_wait;
155	}
156
157	return ret;
158}
159
160static void __exit cpufreq_exit(void)
161{
162	if (!nowait && saved_cpu_wait)
163		cpu_wait = saved_cpu_wait;
164	cpufreq_unregister_driver(&loongson2_cpufreq_driver);
165	cpufreq_unregister_notifier(&loongson2_cpufreq_notifier_block,
166				    CPUFREQ_TRANSITION_NOTIFIER);
167
168	platform_driver_unregister(&platform_driver);
169}
170
171module_init(cpufreq_init);
172module_exit(cpufreq_exit);
173
174module_param(nowait, uint, 0644);
175MODULE_PARM_DESC(nowait, "Disable Loongson-2F specific wait");
176
177MODULE_AUTHOR("Yanhua <yanh@lemote.com>");
178MODULE_DESCRIPTION("cpufreq driver for Loongson2F");
179MODULE_LICENSE("GPL");