cpufreq.c

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/*
 *  linux/kernel/cpufreq.c
 *
 *  Copyright (C) 2001 Russell King
 *
 *  $Id: cpufreq.c,v 1.17.2.2 2002/05/03 13:26:27 rmk Exp $
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * CPU speed changing core functionality.  We provide the following
 * services to the system:
 *  - notifier lists to inform other code of the freq change both
 *    before and after the freq change.
 *  - the ability to change the freq speed
 *
 * ** You'll need to add CTL_CPU = 10 to include/linux/sysctl.h if
 * it's not already present.
 *
 * When this appears in the kernel, the sysctl enums will move to
 * include/linux/sysctl.h
 */
#include <linux/config.h>
#include <linux/types.h>
#include <linux/module.h>
#include <linux/notifier.h>
#include <linux/cpufreq.h>
#include <linux/kernel.h>
#include <linux/delay.h>
#include <linux/init.h>
#include <linux/smp.h>
#include <linux/fs.h>
#include <linux/sysctl.h>

#include <asm/semaphore.h>
#include <asm/system.h>
#include <asm/uaccess.h>
#include <linux/interrupt.h>	/* requires system.h */

/*
 * This list is for kernel code that needs to handle
 * changes to devices when the CPU clock speed changes.
 */
static struct notifier_block *cpufreq_notifier_list;
static DECLARE_MUTEX_LOCKED(cpufreq_sem);
static unsigned long cpufreq_ref_loops;
static unsigned int cpufreq_ref_freq;
static int cpufreq_initialised;
static unsigned int (*cpufreq_validatespeed)(unsigned int);
static void (*cpufreq_setspeed)(unsigned int);

#ifndef CONFIG_SMP
static unsigned int __cpufreq_max;
static unsigned int __cpufreq_min;
static unsigned int __cpufreq_cur;
#endif

static unsigned long scale(unsigned long ref, u_int div, u_int mult)
{
	unsigned long new_jiffy_l, new_jiffy_h;

	/*
	 * Recalculate loops_per_jiffy.  We do it this way to
	 * avoid math overflow on 32-bit machines.  Maybe we
	 * should make this architecture dependent?  If you have
	 * a better way of doing this, please replace!
	 *
	 *    new = old * mult / div
	 */
	new_jiffy_h = ref / div;
	new_jiffy_l = (ref % div) / 100;
	new_jiffy_h *= mult;
	new_jiffy_l = new_jiffy_l * mult / div;

	return new_jiffy_h + new_jiffy_l * 100;
}

/*
 * cpufreq_max command line parameter.  Use:
 *  cpufreq=59000-221000
 * to set the CPU frequency to 59 to 221MHz.
 */
static int __init cpufreq_setup(char *str)
{
	unsigned int min, max;
	int i;

	min = 0;
	max = simple_strtoul(str, &str, 0);
	if (*str == '-') {
		min = max;
		max = simple_strtoul(str + 1, NULL, 0);
	}

	for (i = 0; i < smp_num_cpus; i++) {
		cpufreq_max(i) = max;
		cpufreq_min(i) = min;
	}

	return 1;
}

__setup("cpufreq=", cpufreq_setup);

/**
 *	cpufreq_register_notifier - register a driver with cpufreq
 *	@nb: notifier function to register
 *
 *	Add a driver to the list of drivers that which to be notified about
 *	CPU clock rate changes. The driver will be called three times on
 *	clock change.
 *
 *	This function may sleep, and has the same return conditions as
 *	notifier_chain_register.
 */
int cpufreq_register_notifier(struct notifier_block *nb)
{
	int ret;

	down(&cpufreq_sem);
	ret = notifier_chain_register(&cpufreq_notifier_list, nb);
	up(&cpufreq_sem);

	return ret;
}

EXPORT_SYMBOL(cpufreq_register_notifier);

/**
 *	cpufreq_unregister_notifier - unregister a driver with cpufreq
 *	@nb: notifier block to be unregistered
 *
 *	Remove a driver from the CPU frequency notifier lists.
 *
 *	This function may sleep, and has the same return conditions as
 *	notifier_chain_unregister.
 */
int cpufreq_unregister_notifier(struct notifier_block *nb)
{
	int ret;

	down(&cpufreq_sem);
	ret = notifier_chain_unregister(&cpufreq_notifier_list, nb);
	up(&cpufreq_sem);

	return ret;
}

EXPORT_SYMBOL(cpufreq_unregister_notifier);

/*
 * This notifier alters the system "loops_per_jiffy" for the clock
 * speed change.  We ignore CPUFREQ_MINMAX here.
 */
static void adjust_jiffies(unsigned long val, struct cpufreq_info *ci)
{
	if ((val == CPUFREQ_PRECHANGE  && ci->old_freq < ci->new_freq) ||
	    (val == CPUFREQ_POSTCHANGE && ci->old_freq > ci->new_freq))
	    	loops_per_jiffy = scale(cpufreq_ref_loops, cpufreq_ref_freq,
					ci->new_freq);
}

#ifdef CONFIG_PM
/**
 *	cpufreq_restore - restore the CPU clock frequency after resume
 *
 *	Restore the CPU clock frequency so that our idea of the current
 *	frequency reflects the actual hardware.
 */
int cpufreq_restore(void)
{
	unsigned long old_cpus;
	int cpu = smp_processor_id();
	int ret;

	if (!cpufreq_initialised)
		panic("cpufreq_restore() called before initialisation!");
	if (in_interrupt())
		panic("cpufreq_restore() called from interrupt context!");

	/*
	 * Bind to the current CPU.
	 */
	old_cpus = current->cpus_allowed;
	current->cpus_allowed = 1UL << cpu_logical_map(cpu);

	down(&cpufreq_sem);

	ret = -ENXIO;
	if (cpufreq_setspeed) {
		cpufreq_setspeed(cpufreq_current(cpu));
		ret = 0;
	}

	up(&cpufreq_sem);

	current->cpus_allowed = old_cpus;

	return ret;
}

EXPORT_SYMBOL_GPL(cpufreq_restore);
#endif

/**
 *	cpu_setfreq - change the CPU clock frequency.
 *	@freq: frequency (in kHz) at which we should run.
 *
 *	Set the CPU clock frequency, informing all registered users of
 *	the change. We bound the frequency according to the cpufreq_max
 *	command line parameter, and the parameters the registered users
 *	will allow.
 *
 *	This function must be called from process context, and on the
 *	cpu that we wish to change the frequency of.
 *
 *	We return 0 if successful. (we are currently always successful).
 */
int cpufreq_set(unsigned int freq)
{
	unsigned long old_cpus;
	struct cpufreq_info clkinfo;
	struct cpufreq_minmax minmax;
	int cpu = smp_processor_id();
	int ret;

	if (!cpufreq_initialised)
		panic("cpufreq_set() called before initialisation!");
	if (in_interrupt())
		panic("cpufreq_set() called from interrupt context!");

	/*
	 * Bind to the current CPU.
	 */
	old_cpus = current->cpus_allowed;
	current->cpus_allowed = 1UL << cpu_logical_map(cpu);

	down(&cpufreq_sem);
	ret = -ENXIO;
	if (!cpufreq_setspeed || !cpufreq_validatespeed)
		goto out;

	/*
	 * Don't allow the CPU to be clocked over the limit.
	 */
	minmax.min_freq = cpufreq_min(cpu);
	minmax.max_freq = cpufreq_max(cpu);
	minmax.cur_freq = cpufreq_current(cpu);
	minmax.new_freq = freq;

	/*
	 * Find out what the registered devices will currently tolerate,
	 * and limit the requested clock rate to these values.  Drivers
	 * must not rely on the 'new_freq' value - it is only a guide.
	 */
	notifier_call_chain(&cpufreq_notifier_list, CPUFREQ_MINMAX, &minmax);
	if (freq < minmax.min_freq)
		freq = minmax.min_freq;
	if (freq > minmax.max_freq)
		freq = minmax.max_freq;

	/*
	 * Ask the CPU specific code to validate the speed.  If the speed
	 * is not acceptable, make it acceptable.  Current policy is to
	 * round the frequency down to the value the processor actually
	 * supports.
	 */
	freq = cpufreq_validatespeed(freq);

	if (cpufreq_current(cpu) != freq) {
		clkinfo.old_freq = cpufreq_current(cpu);
		clkinfo.new_freq = freq;

		notifier_call_chain(&cpufreq_notifier_list, CPUFREQ_PRECHANGE,
				    &clkinfo);

		adjust_jiffies(CPUFREQ_PRECHANGE, &clkinfo);

		/*
		 * Actually set the CPU frequency.
		 */
		cpufreq_setspeed(freq);
		cpufreq_current(cpu) = freq;
		adjust_jiffies(CPUFREQ_POSTCHANGE, &clkinfo);

		notifier_call_chain(&cpufreq_notifier_list, CPUFREQ_POSTCHANGE,
				    &clkinfo);
	}

	ret = 0;

 out:
	up(&cpufreq_sem);

	current->cpus_allowed = old_cpus;

	return ret;
}

EXPORT_SYMBOL_GPL(cpufreq_set);

/**
 *	cpufreq_setmax - set the CPU to maximum frequency
 *
 *	Sets the CPU this function is executed on to maximum frequency.
 */
int cpufreq_setmax(void)
{
	return cpufreq_set(cpufreq_max(smp_processor_id()));
}

EXPORT_SYMBOL_GPL(cpufreq_setmax);

/**
 *	cpufreq_get - return the current CPU clock frequency in 1kHz
 *	@cpu: cpu number to obtain frequency for
 *
 *	Returns the specified CPUs frequency in kHz.
 */
unsigned int cpufreq_get(int cpu)
{
	if (!cpufreq_initialised)
		panic("cpufreq_get() called before initialisation!");
	return cpufreq_current(cpu);
}

EXPORT_SYMBOL(cpufreq_get);

#ifdef CONFIG_SYSCTL

static int
cpufreq_procctl(ctl_table *ctl, int write, struct file *filp,
		void *buffer, size_t *lenp)
{
	char buf[16], *p;
	int cpu = 0, len, left = *lenp;

	if (!left || (filp->f_pos && !write)) {
		*lenp = 0;
		return 0;
	}

	if (write) {
		unsigned int freq;

		len = left;
		if (left > sizeof(buf))
			left = sizeof(buf);
		if (copy_from_user(buf, buffer, left))
			return -EFAULT;
		buf[sizeof(buf) - 1] = '\0';

		freq = simple_strtoul(buf, &p, 0);
		cpufreq_set(freq);
	} else {
		len = sprintf(buf, "%d\n", cpufreq_get(cpu));
		if (len > left)
			len = left;
		if (copy_to_user(buffer, buf, len))
			return -EFAULT;
	}

	*lenp = len;
	filp->f_pos += len;
	return 0;
}

static int
cpufreq_sysctl(ctl_table *table, int *name, int nlen,
	       void *oldval, size_t *oldlenp,
	       void *newval, size_t newlen, void **context)
{
	int cpu = 0;

	if (oldval && oldlenp) {
		size_t oldlen;

		if (get_user(oldlen, oldlenp))
			return -EFAULT;

		if (oldlen != sizeof(unsigned int))
			return -EINVAL;

		if (put_user(cpufreq_get(cpu), (unsigned int *)oldval) ||
		    put_user(sizeof(unsigned int), oldlenp))
			return -EFAULT;
	}
	if (newval && newlen) {
		unsigned int freq;

		if (newlen != sizeof(unsigned int))
			return -EINVAL;

		if (get_user(freq, (unsigned int *)newval))
			return -EFAULT;

		cpufreq_set(freq);
	}
	return 1;
}

enum {
	CPU_NR_FREQ_MAX = 1,
	CPU_NR_FREQ_MIN = 2,
	CPU_NR_FREQ = 3
};

static ctl_table ctl_cpu_vars[4] = {
	{
		ctl_name:	CPU_NR_FREQ_MAX,
		procname:	"speed-max",
		data:		&cpufreq_max(0),
		maxlen:		sizeof(cpufreq_max(0)),
		mode:		0444,
		proc_handler:	proc_dointvec,
	},
	{
		ctl_name:	CPU_NR_FREQ_MIN,
		procname:	"speed-min",
		data:		&cpufreq_min(0),
		maxlen:		sizeof(cpufreq_min(0)),
		mode:		0444,
		proc_handler:	proc_dointvec,
	},
	{
		ctl_name:	CPU_NR_FREQ,
		procname:	"speed",
		mode:		0644,
		proc_handler:	cpufreq_procctl,
		strategy:	cpufreq_sysctl,
	},
	{
		ctl_name:	0,
	}
};

enum {
	CPU_NR = 1,
};

static ctl_table ctl_cpu_nr[2] = {
	{
		ctl_name:	CPU_NR,
		procname:	"0",
		mode:		0555,
		child:		ctl_cpu_vars,
	},
	{
		ctl_name:	0,
	}
};

static ctl_table ctl_cpu[2] = {
	{
		ctl_name:	CTL_CPU,
		procname:	"cpu",
		mode:		0555,
		child:		ctl_cpu_nr,
	},
	{
		ctl_name:	0,
	}
};

static inline void cpufreq_sysctl_init(void)
{
	register_sysctl_table(ctl_cpu, 0);
}

#else
#define cpufreq_sysctl_init()
#endif

/**
 *	cpufreq_setfunctions - Set CPU clock functions
 *	@validate: pointer to validation function
 *	@setspeed: pointer to setspeed function
 */
void
cpufreq_setfunctions(unsigned int (*validate)(unsigned int),
		     void (*setspeed)(unsigned int))
{
	down(&cpufreq_sem);
	cpufreq_validatespeed = validate;
	cpufreq_setspeed = setspeed;
	up(&cpufreq_sem);
}

EXPORT_SYMBOL_GPL(cpufreq_setfunctions);

/**
 *	cpufreq_init - Initialise the cpufreq core
 *	@freq: current CPU clock speed.
 *	@min_freq: minimum CPU clock speed.
 *	@max_freq: maximum CPU clock speed.
 *
 *	Initialise the cpufreq core. If the cpufreq_max command line
 *	parameter has not been specified, we set the maximum clock rate
 *	to the current CPU clock rate.
 */
void cpufreq_init(unsigned int freq,
		  unsigned int min_freq,
		  unsigned int max_freq)
{
	/*
	 * If the user doesn't tell us their maximum frequency,
	 * or if it is invalid, use the values determined 
	 * by the cpufreq-arch-specific initialization functions.
	 * The validatespeed code is responsible for limiting
	 * this further.
	 */
	if (max_freq && ((cpufreq_max(0) == 0) || (cpufreq_max(0) > max_freq)))
		cpufreq_max(0) = max_freq;
	if (min_freq && ((cpufreq_min(0) == 0) || (cpufreq_min(0) < min_freq)))
		cpufreq_min(0) = min_freq;

	if (cpufreq_max(0) == 0)
		cpufreq_max(0) = freq;

	printk(KERN_INFO "CPU clock: %d.%03d MHz (%d.%03d-%d.%03d MHz)\n",
		freq / 1000, freq % 1000,
		cpufreq_min(0) / 1000, cpufreq_min(0) % 1000,
		cpufreq_max(0) / 1000, cpufreq_max(0) % 1000);

	cpufreq_ref_loops = loops_per_jiffy;
	cpufreq_ref_freq = freq;
	cpufreq_current(smp_processor_id()) = freq;

	cpufreq_initialised = 1;
	up(&cpufreq_sem);

	cpufreq_sysctl_init();
}

EXPORT_SYMBOL_GPL(cpufreq_init);