arch/mips/kernel/time.c

/*
 * Copyright 2001 MontaVista Software Inc.
 * Author: Jun Sun, jsun@mvista.com or jsun@junsun.net
 * Copyright (c) 2003, 2004  Maciej W. Rozycki
 *
 * Common time service routines for MIPS machines. See
 * Documentation/mips/time.README.
 *
 * This program is free software; you can redistribute  it and/or modify it
 * under  the terms of  the GNU General  Public License as published by the
 * Free Software Foundation;  either version 2 of the  License, or (at your
 * option) any later version.
 */
#include <linux/clockchips.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/sched.h>
#include <linux/param.h>
#include <linux/profile.h>
#include <linux/time.h>
#include <linux/timex.h>
#include <linux/smp.h>
#include <linux/kernel_stat.h>
#include <linux/spinlock.h>
#include <linux/interrupt.h>
#include <linux/module.h>

#include <asm/bootinfo.h>
#include <asm/cache.h>
#include <asm/compiler.h>
#include <asm/cpu.h>
#include <asm/cpu-features.h>
#include <asm/div64.h>
#include <asm/sections.h>
#include <asm/time.h>

#include <irq.h>

/*
 * The integer part of the number of usecs per jiffy is taken from tick,
 * but the fractional part is not recorded, so we calculate it using the
 * initial value of HZ.  This aids systems where tick isn't really an
 * integer (e.g. for HZ = 128).
 */
#define USECS_PER_JIFFY		TICK_SIZE
#define USECS_PER_JIFFY_FRAC	((unsigned long)(u32)((1000000ULL << 32) / HZ))

#define TICK_SIZE	(tick_nsec / 1000)

/*
 * forward reference
 */
DEFINE_SPINLOCK(rtc_lock);
EXPORT_SYMBOL(rtc_lock);

int __weak rtc_mips_set_time(unsigned long sec)
{
	return 0;
}
EXPORT_SYMBOL(rtc_mips_set_time);

int __weak rtc_mips_set_mmss(unsigned long nowtime)
{
	return rtc_mips_set_time(nowtime);
}

int update_persistent_clock(struct timespec now)
{
	return rtc_mips_set_mmss(now.tv_sec);
}

/* how many counter cycles in a jiffy */
static unsigned long cycles_per_jiffy __read_mostly;

/*
 * Null timer ack for systems not needing one (e.g. i8254).
 */
static void null_timer_ack(void) { /* nothing */ }

/*
 * Null high precision timer functions for systems lacking one.
 */
static cycle_t null_hpt_read(void)
{
	return 0;
}

/*
 * Timer ack for an R4k-compatible timer of a known frequency.
 */
static void c0_timer_ack(void)
{
	write_c0_compare(read_c0_compare());
}

/*
 * High precision timer functions for a R4k-compatible timer.
 */
static cycle_t c0_hpt_read(void)
{
	return read_c0_count();
}

int (*mips_timer_state)(void);
void (*mips_timer_ack)(void);

/*
 * local_timer_interrupt() does profiling and process accounting
 * on a per-CPU basis.
 *
 * In UP mode, it is invoked from the (global) timer_interrupt.
 *
 * In SMP mode, it might invoked by per-CPU timer interrupt, or
 * a broadcasted inter-processor interrupt which itself is triggered
 * by the global timer interrupt.
 */
void local_timer_interrupt(int irq, void *dev_id)
{
	profile_tick(CPU_PROFILING);
	update_process_times(user_mode(get_irq_regs()));
}

int null_perf_irq(void)
{
	return 0;
}

EXPORT_SYMBOL(null_perf_irq);

int (*perf_irq)(void) = null_perf_irq;

EXPORT_SYMBOL(perf_irq);

/*
 * Timer interrupt
 */
int cp0_compare_irq;

/*
 * Performance counter IRQ or -1 if shared with timer
 */
int cp0_perfcount_irq;
EXPORT_SYMBOL_GPL(cp0_perfcount_irq);

/*
 * Possibly handle a performance counter interrupt.
 * Return true if the timer interrupt should not be checked
 */
static inline int handle_perf_irq (int r2)
{
	/*
	 * The performance counter overflow interrupt may be shared with the
	 * timer interrupt (cp0_perfcount_irq < 0). If it is and a
	 * performance counter has overflowed (perf_irq() == IRQ_HANDLED)
	 * and we can't reliably determine if a counter interrupt has also
	 * happened (!r2) then don't check for a timer interrupt.
	 */
	return (cp0_perfcount_irq < 0) &&
		perf_irq() == IRQ_HANDLED &&
		!r2;
}

/*
 * time_init() - it does the following things.
 *
 * 1) plat_time_init() -
 * 	a) (optional) set up RTC routines,
 *      b) (optional) calibrate and set the mips_hpt_frequency
 *	    (only needed if you intended to use cpu counter as timer interrupt
 *	     source)
 * 2) calculate a couple of cached variables for later usage
 * 3) plat_timer_setup() -
 *	a) (optional) over-write any choices made above by time_init().
 *	b) machine specific code should setup the timer irqaction.
 *	c) enable the timer interrupt
 */

unsigned int mips_hpt_frequency;

static unsigned int __init calibrate_hpt(void)
{
	cycle_t frequency, hpt_start, hpt_end, hpt_count, hz;

	const int loops = HZ / 10;
	int log_2_loops = 0;
	int i;

	/*
	 * We want to calibrate for 0.1s, but to avoid a 64-bit
	 * division we round the number of loops up to the nearest
	 * power of 2.
	 */
	while (loops > 1 << log_2_loops)
		log_2_loops++;
	i = 1 << log_2_loops;

	/*
	 * Wait for a rising edge of the timer interrupt.
	 */
	while (mips_timer_state());
	while (!mips_timer_state());

	/*
	 * Now see how many high precision timer ticks happen
	 * during the calculated number of periods between timer
	 * interrupts.
	 */
	hpt_start = clocksource_mips.read();
	do {
		while (mips_timer_state());
		while (!mips_timer_state());
	} while (--i);
	hpt_end = clocksource_mips.read();

	hpt_count = (hpt_end - hpt_start) & clocksource_mips.mask;
	hz = HZ;
	frequency = hpt_count * hz;

	return frequency >> log_2_loops;
}

struct clocksource clocksource_mips = {
	.name		= "MIPS",
	.mask		= CLOCKSOURCE_MASK(32),
	.flags		= CLOCK_SOURCE_IS_CONTINUOUS,
};

static int mips_next_event(unsigned long delta,
                           struct clock_event_device *evt)
{
	unsigned int cnt;

	cnt = read_c0_count();
	cnt += delta;
	write_c0_compare(cnt);

	return ((long)(read_c0_count() - cnt ) > 0) ? -ETIME : 0;
}

static void mips_set_mode(enum clock_event_mode mode,
                          struct clock_event_device *evt)
{
	/* Nothing to do ...  */
}

struct clock_event_device mips_clockevent;

static struct clock_event_device *global_cd[NR_CPUS];
static int cp0_timer_irq_installed;

static irqreturn_t timer_interrupt(int irq, void *dev_id)
{
	const int r2 = cpu_has_mips_r2;
	struct clock_event_device *cd;
	int cpu = smp_processor_id();

	/*
	 * Suckage alert:
	 * Before R2 of the architecture there was no way to see if a
	 * performance counter interrupt was pending, so we have to run
	 * the performance counter interrupt handler anyway.
	 */
	if (handle_perf_irq(r2))
		goto out;

	/*
	 * The same applies to performance counter interrupts.  But with the
	 * above we now know that the reason we got here must be a timer
	 * interrupt.  Being the paranoiacs we are we check anyway.
	 */
	if (!r2 || (read_c0_cause() & (1 << 30))) {
		c0_timer_ack();
		cd = global_cd[cpu];
		cd->event_handler(cd);
	}

out:
	return IRQ_HANDLED;
}

static struct irqaction timer_irqaction = {
	.handler = timer_interrupt,
	.flags = IRQF_DISABLED | IRQF_PERCPU,
	.name = "timer",
};

static void __init init_mips_clocksource(void)
{
	u64 temp;
	u32 shift;

	if (!mips_hpt_frequency || clocksource_mips.read == null_hpt_read)
		return;

	/* Calclate a somewhat reasonable rating value */
	clocksource_mips.rating = 200 + mips_hpt_frequency / 10000000;
	/* Find a shift value */
	for (shift = 32; shift > 0; shift--) {
		temp = (u64) NSEC_PER_SEC << shift;
		do_div(temp, mips_hpt_frequency);
		if ((temp >> 32) == 0)
			break;
	}
	clocksource_mips.shift = shift;
	clocksource_mips.mult = (u32)temp;

	clocksource_register(&clocksource_mips);
}

void __init __weak plat_time_init(void)
{
}

void __init __weak plat_timer_setup(struct irqaction *irq)
{
}

void __cpuinit mips_clockevent_init(void)
{
	uint64_t mips_freq = mips_hpt_frequency;
	unsigned int cpu = smp_processor_id();
	struct clock_event_device *cd;
	unsigned int irq = MIPS_CPU_IRQ_BASE + 7;

	if (!cpu_has_counter)
		return;

	if (cpu == 0)
		cd = &mips_clockevent;
	else
		cd = kzalloc(sizeof(*cd), GFP_ATOMIC);
	if (!cd)
		return;		/* We're probably roadkill ...  */

	cd->name		= "MIPS";
	cd->features		= CLOCK_EVT_FEAT_ONESHOT;

	/* Calculate the min / max delta */
	cd->mult	= div_sc((unsigned long) mips_freq, NSEC_PER_SEC, 32);
	cd->shift		= 32;
	cd->max_delta_ns	= clockevent_delta2ns(0x7fffffff, cd);
	cd->min_delta_ns	= clockevent_delta2ns(0x30, cd);

	cd->rating		= 300;
	cd->irq			= irq;
	cd->cpumask		= cpumask_of_cpu(cpu);
	cd->set_next_event	= mips_next_event;
	cd->set_mode		= mips_set_mode;

	global_cd[cpu] = cd;
	clockevents_register_device(cd);

	if (!cp0_timer_irq_installed) {
#ifdef CONFIG_MIPS_MT_SMTC
#define CPUCTR_IMASKBIT (0x100 << cp0_compare_irq)
		setup_irq_smtc(irq, &timer_irqaction, CPUCTR_IMASKBIT);
#else
		setup_irq(irq, &timer_irqaction);
#endif /* CONFIG_MIPS_MT_SMTC */
		cp0_timer_irq_installed = 1;
	}
}

void __init time_init(void)
{
	plat_time_init();

	/* Choose appropriate high precision timer routines.  */
	if (!cpu_has_counter && !clocksource_mips.read)
		/* No high precision timer -- sorry.  */
		clocksource_mips.read = null_hpt_read;
	else if (!mips_hpt_frequency && !mips_timer_state) {
		/* A high precision timer of unknown frequency.  */
		if (!clocksource_mips.read)
			/* No external high precision timer -- use R4k.  */
			clocksource_mips.read = c0_hpt_read;
	} else {
		/* We know counter frequency.  Or we can get it.  */
		if (!clocksource_mips.read) {
			/* No external high precision timer -- use R4k.  */
			clocksource_mips.read = c0_hpt_read;

			if (!mips_timer_state) {
				/* No external timer interrupt -- use R4k.  */
				mips_timer_ack = c0_timer_ack;
				/* Calculate cache parameters.  */
				cycles_per_jiffy =
					(mips_hpt_frequency + HZ / 2) / HZ;
			}
		}
		if (!mips_hpt_frequency)
			mips_hpt_frequency = calibrate_hpt();

		/* Report the high precision timer rate for a reference.  */
		printk("Using %u.%03u MHz high precision timer.\n",
		       ((mips_hpt_frequency + 500) / 1000) / 1000,
		       ((mips_hpt_frequency + 500) / 1000) % 1000);

#ifdef CONFIG_IRQ_CPU
		setup_irq(MIPS_CPU_IRQ_BASE + 7, &timer_irqaction);
#endif
	}

	if (!mips_timer_ack)
		/* No timer interrupt ack (e.g. i8254).  */
		mips_timer_ack = null_timer_ack;

	/*
	 * Call board specific timer interrupt setup.
	 *
	 * this pointer must be setup in machine setup routine.
	 *
	 * Even if a machine chooses to use a low-level timer interrupt,
	 * it still needs to setup the timer_irqaction.
	 * In that case, it might be better to set timer_irqaction.handler
	 * to be NULL function so that we are sure the high-level code
	 * is not invoked accidentally.
	 */
	plat_timer_setup(&timer_irqaction);

	init_mips_clocksource();
	mips_clockevent_init();
}