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/*
 * Copyright (c) 1999 University of Utah and the Flux Group.
 * All rights reserved.
 *
 * This file is part of the Flux OSKit.  The OSKit is free software, also known
 * as "open source;" you can redistribute it and/or modify it under the terms
 * of the GNU General Public License (GPL), version 2, as published by the Free
 * Software Foundation (FSF).  To explore alternate licensing terms, contact
 * the University of Utah at [email protected] or +1-801-585-3271.
 *
 * The OSKit is distributed in the hope that it will be useful, but WITHOUT ANY
 * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
 * FOR A PARTICULAR PURPOSE.  See the GPL for more details.  You should have
 * received a copy of the GPL along with the OSKit; see the file COPYING.  If
 * not, write to the FSF, 59 Temple Place #330, Boston, MA 02111-1307, USA.
 */
/*
 * Timer interrupt support.
 */

#include <oskit/dev/dev.h>

#include <oskit/machine/pc/pit.h>

#include <machine/mach_param.h>	/* HZ */
#include <machine/spl.h>

#include "../ds_oskit.h"


#define NTIMERS		4
#define TIMER_FREQ	HZ
#define TIMER_VALUE	(PIT_HZ / TIMER_FREQ)

struct timer_handler {
	void	(*func)(void);
	struct	timer_handler *next;
};

static struct timer_handler *timer_head, *timer_free;
static struct timer_handler timer_data[NTIMERS];


/*
 * This is called on every Mach clock tick, at splsoftclock.
 * These handlers want to be called with interrupts disabled,
 * but then reenable and redisable them before returning.
 */
void
softclock_oskit (void)
{
	struct timer_handler *th;
	osenv_intr_disable();
	for (th = timer_head; th; th = th->next)
		(*th->func)();
	osenv_intr_enable();

	oskit_softint();
}

/*
 * Initialize timers.
 */
void
osenv_timer_init()
{
	static int initialized = 0;  /* guard against multiple invocations */
	int i;

	if (initialized)
		return;

	initialized = 1;

	for (i = 0; i < NTIMERS; i++)
		timer_data[i].next = &timer_data[i + 1];
	timer_data[NTIMERS - 1].next = 0;
	timer_free = &timer_data[0];
}

/*
 * Turn all timers off.
 */
void
osenv_timer_shutdown()
{
	osenv_log(OSENV_LOG_DEBUG, "Shutting down timer\n");
	osenv_timer_pit_shutdown();
}

/*
 * Register a timer handler to be called at the specified frequency.
 */
void
osenv_timer_register(void (*func)(void), int freq)
{
	struct timer_handler *th;
	spl_t s;

	/* XXX */
	osenv_timer_init();

	if (timer_free == 0)
		osenv_panic("%s:%d: ran out of entries", __FILE__, __LINE__);
	/*
	 * XXX
	 */
	if (freq != TIMER_FREQ)
		osenv_panic("%s:%d: bad freq", __FILE__, __LINE__);
	if (func == 0)
		osenv_panic("%s:%d: null function", __FILE__, __LINE__);

	s = splio ();

	th = timer_free;
	timer_free = th->next;
	th->next = timer_head;
	timer_head = th;
	th->func = func;

	splx (s);
}


/*
 * Frequency and function address uniquely identify which to remove since
 * equal values are equivelent.
 */
void
osenv_timer_unregister(void (*func)(void), int freq)
{
	spl_t s;
	struct timer_handler *th, **prev;

	if (freq != TIMER_FREQ)
		osenv_panic("%s:%d: bad freq", __FILE__, __LINE__);

	s = splio ();

	/* move the timer from the run-queue to the unused-queue */
	prev = &timer_head;
	th = timer_head;

	while (th && (th->func != func)) {
		prev = &th->next;
		th = th->next;
	}
	if (!th) {
		osenv_log(OSENV_LOG_WARNING, "Timer handler not found\n");
	} else {
		/* have the active list skip over it */
		*prev = th->next;

		/* place in inactive queue */
		th->next = timer_free;
		timer_free = th;
	}

	splx (s);
}


/*
 * Spin for a small amount of time, specified in nanoseconds,
 * without blocking or enabling interrupts.
 */
void
osenv_timer_spin(long nanosec)
{
	int prev_val = osenv_timer_pit_read();

	while (nanosec > 0) {
		int val = osenv_timer_pit_read();
		if (val > prev_val)
			prev_val += TIMER_VALUE;
		nanosec -= (prev_val - val) * PIT_NS;
		prev_val = val;
	}
}

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