loongson2_cpufreq.c

/*
 * Cpufreq driver for the loongson-2 processors
 *
 * The 2E revision of loongson processor not support this feature.
 *
 * Copyright (C) 2006 - 2008 Lemote Inc. & Institute of Computing Technology
 * Author: Yanhua, yanh@lemote.com
 *
 * This file is subject to the terms and conditions of the GNU General Public
 * License.  See the file "COPYING" in the main directory of this archive
 * for more details.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/cpufreq.h>
#include <linux/module.h>
#include <linux/err.h>
#include <linux/delay.h>
#include <linux/platform_device.h>

#include <asm/idle.h>

#include <asm/mach-loongson2ef/loongson.h>

static uint nowait;

static void (*saved_cpu_wait) (void);

static int loongson2_cpu_freq_notifier(struct notifier_block *nb,
					unsigned long val, void *data);

static struct notifier_block loongson2_cpufreq_notifier_block = {
	.notifier_call = loongson2_cpu_freq_notifier
};

static int loongson2_cpu_freq_notifier(struct notifier_block *nb,
					unsigned long val, void *data)
{
	if (val == CPUFREQ_POSTCHANGE)
		current_cpu_data.udelay_val = loops_per_jiffy;

	return 0;
}

/*
 * Here we notify other drivers of the proposed change and the final change.
 */
static int loongson2_cpufreq_target(struct cpufreq_policy *policy,
				     unsigned int index)
{
	unsigned int freq;

	freq =
	    ((cpu_clock_freq / 1000) *
	     loongson2_clockmod_table[index].driver_data) / 8;

	/* setting the cpu frequency */
	loongson2_cpu_set_rate(freq);

	return 0;
}

static int loongson2_cpufreq_cpu_init(struct cpufreq_policy *policy)
{
	int i;
	unsigned long rate;
	int ret;

	rate = cpu_clock_freq / 1000;
	if (!rate)
		return -EINVAL;

	/* clock table init */
	for (i = 2;
	     (loongson2_clockmod_table[i].frequency != CPUFREQ_TABLE_END);
	     i++)
		loongson2_clockmod_table[i].frequency = (rate * i) / 8;

	ret = loongson2_cpu_set_rate(rate);
	if (ret)
		return ret;

	cpufreq_generic_init(policy, &loongson2_clockmod_table[0], 0);
	return 0;
}

static int loongson2_cpufreq_exit(struct cpufreq_policy *policy)
{
	return 0;
}

static struct cpufreq_driver loongson2_cpufreq_driver = {
	.name = "loongson2",
	.init = loongson2_cpufreq_cpu_init,
	.verify = cpufreq_generic_frequency_table_verify,
	.target_index = loongson2_cpufreq_target,
	.get = cpufreq_generic_get,
	.exit = loongson2_cpufreq_exit,
	.attr = cpufreq_generic_attr,
};

static const struct platform_device_id platform_device_ids[] = {
	{
		.name = "loongson2_cpufreq",
	},
	{}
};

MODULE_DEVICE_TABLE(platform, platform_device_ids);

static struct platform_driver platform_driver = {
	.driver = {
		.name = "loongson2_cpufreq",
	},
	.id_table = platform_device_ids,
};

/*
 * This is the simple version of Loongson-2 wait, Maybe we need do this in
 * interrupt disabled context.
 */

static DEFINE_SPINLOCK(loongson2_wait_lock);

static void loongson2_cpu_wait(void)
{
	unsigned long flags;
	u32 cpu_freq;

	spin_lock_irqsave(&loongson2_wait_lock, flags);
	cpu_freq = readl(LOONGSON_CHIPCFG);
	/* Put CPU into wait mode */
	writel(readl(LOONGSON_CHIPCFG) & ~0x7, LOONGSON_CHIPCFG);
	/* Restore CPU state */
	writel(cpu_freq, LOONGSON_CHIPCFG);
	spin_unlock_irqrestore(&loongson2_wait_lock, flags);
	local_irq_enable();
}

static int __init cpufreq_init(void)
{
	int ret;

	/* Register platform stuff */
	ret = platform_driver_register(&platform_driver);
	if (ret)
		return ret;

	pr_info("Loongson-2F CPU frequency driver\n");

	cpufreq_register_notifier(&loongson2_cpufreq_notifier_block,
				  CPUFREQ_TRANSITION_NOTIFIER);

	ret = cpufreq_register_driver(&loongson2_cpufreq_driver);

	if (!ret && !nowait) {
		saved_cpu_wait = cpu_wait;
		cpu_wait = loongson2_cpu_wait;
	}

	return ret;
}

static void __exit cpufreq_exit(void)
{
	if (!nowait && saved_cpu_wait)
		cpu_wait = saved_cpu_wait;
	cpufreq_unregister_driver(&loongson2_cpufreq_driver);
	cpufreq_unregister_notifier(&loongson2_cpufreq_notifier_block,
				    CPUFREQ_TRANSITION_NOTIFIER);

	platform_driver_unregister(&platform_driver);
}

module_init(cpufreq_init);
module_exit(cpufreq_exit);

module_param(nowait, uint, 0644);
MODULE_PARM_DESC(nowait, "Disable Loongson-2F specific wait");

MODULE_AUTHOR("Yanhua <yanh@lemote.com>");
MODULE_DESCRIPTION("cpufreq driver for Loongson2F");
MODULE_LICENSE("GPL");