isa-timer.c

/*
 *  linux/arch/arm/mach-footbridge/isa-timer.c
 *
 *  Copyright (C) 1998 Russell King.
 *  Copyright (C) 1998 Phil Blundell
 */
#include <linux/clockchips.h>
#include <linux/clocksource.h>
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/irq.h>
#include <linux/io.h>
#include <linux/timex.h>

#include <asm/irq.h>

#include <asm/mach/time.h>

#include "common.h"

#define PIT_MODE	0x43
#define PIT_CH0		0x40

#define PIT_LATCH	((PIT_TICK_RATE + HZ / 2) / HZ)

static cycle_t pit_read(struct clocksource *cs)
{
	unsigned long flags;
	static int old_count;
	static u32 old_jifs;
	int count;
	u32 jifs;

	raw_local_irq_save(flags);

	jifs = jiffies;
	outb_p(0x00, PIT_MODE);		/* latch the count */
	count = inb_p(PIT_CH0);		/* read the latched count */
	count |= inb_p(PIT_CH0) << 8;

	if (count > old_count && jifs == old_jifs)
		count = old_count;

	old_count = count;
	old_jifs = jifs;

	raw_local_irq_restore(flags);

	count = (PIT_LATCH - 1) - count;

	return (cycle_t)(jifs * PIT_LATCH) + count;
}

static struct clocksource pit_cs = {
	.name		= "pit",
	.rating		= 110,
	.read		= pit_read,
	.mask		= CLOCKSOURCE_MASK(32),
};

static void pit_set_mode(enum clock_event_mode mode,
	struct clock_event_device *evt)
{
	unsigned long flags;

	raw_local_irq_save(flags);

	switch (mode) {
	case CLOCK_EVT_MODE_PERIODIC:
		outb_p(0x34, PIT_MODE);
		outb_p(PIT_LATCH & 0xff, PIT_CH0);
		outb_p(PIT_LATCH >> 8, PIT_CH0);
		break;

	case CLOCK_EVT_MODE_SHUTDOWN:
	case CLOCK_EVT_MODE_UNUSED:
		outb_p(0x30, PIT_MODE);
		outb_p(0, PIT_CH0);
		outb_p(0, PIT_CH0);
		break;

	case CLOCK_EVT_MODE_ONESHOT:
	case CLOCK_EVT_MODE_RESUME:
		break;
	}
	local_irq_restore(flags);
}

static int pit_set_next_event(unsigned long delta,
	struct clock_event_device *evt)
{
	return 0;
}

static struct clock_event_device pit_ce = {
	.name		= "pit",
	.features	= CLOCK_EVT_FEAT_PERIODIC,
	.set_mode	= pit_set_mode,
	.set_next_event	= pit_set_next_event,
	.shift		= 32,
};

static irqreturn_t pit_timer_interrupt(int irq, void *dev_id)
{
	struct clock_event_device *ce = dev_id;
	ce->event_handler(ce);
	return IRQ_HANDLED;
}

static struct irqaction pit_timer_irq = {
	.name		= "pit",
	.handler	= pit_timer_interrupt,
	.flags		= IRQF_DISABLED | IRQF_TIMER | IRQF_IRQPOLL,
	.dev_id		= &pit_ce,
};

static void __init isa_timer_init(void)
{
	pit_ce.cpumask = cpumask_of(smp_processor_id());
	pit_ce.mult = div_sc(PIT_TICK_RATE, NSEC_PER_SEC, pit_ce.shift);
	pit_ce.max_delta_ns = clockevent_delta2ns(0x7fff, &pit_ce);
	pit_ce.min_delta_ns = clockevent_delta2ns(0x000f, &pit_ce);

	clocksource_register_hz(&pit_cs, PIT_TICK_RATE);

	setup_irq(pit_ce.irq, &pit_timer_irq);
	clockevents_register_device(&pit_ce);
}

struct sys_timer isa_timer = {
	.init		= isa_timer_init,
};