sam7fc/src/at91_pitc.c

/***************************************************************************
 *   sam7fc - Periodic Timer Handling                                      *
 *                                                                         *
 *   Copyright (C) 01/2008 by Olaf Rempel                                  *
 *   razzor@kopf-tisch.de                                                  *
 *                                                                         *
 *   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; version 2 of the License                *
 *                                                                         *
 *   This program 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         *
 *   GNU General Public License for more details.                          *
 *                                                                         *
 *   You should have received a copy of the GNU General Public License     *
 *   along with this program; if not, write to the                         *
 *   Free Software Foundation, Inc.,                                       *
 *   59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.             *
 ***************************************************************************/
#include "AT91SAM7S256.h"
#include "at91_pitc.h"
#include "at91_sysc.h"
#include "board.h"

#define PITC_HZ		1000

/* PIV is 20bit -> min. 3Hz @48MHz MCK */
#define HZ_TO_PIV(HZ) (MCK / (16 * HZ))

static LIST_HEAD(timer_list);
volatile static uint32_t pitc_ticks;

static void _pitc_schedule_timer(struct pitc_timer *timer)
{
	timer->nextrun = timer->interval + pitc_ticks;

	struct pitc_timer *search;
	list_for_each_entry(search, &timer_list, list)
		if (search->nextrun > timer->nextrun)
			break;

	list_add_tail(&timer->list, &search->list);
}

void pitc_schedule_timer(struct pitc_timer *timer)
{
	/* disable PITC interrupt */
	*AT91C_PITC_PIMR &= ~AT91C_PITC_PITIEN;

	/* check it timer is already running */
	if (timer->nextrun == 0 && timer->interval > 0)
		_pitc_schedule_timer(timer);

	// TODO: if timer is running, interval changes are delayed

	/* enable PITC interrupt */
	*AT91C_PITC_PIMR |= AT91C_PITC_PITIEN;
}

void pitc_remove_timer(struct pitc_timer *timer)
{
	timer->interval = 0;
}

static void pitc_isr(uint32_t status)
{
	/* get Ticks and clear interrupt */
	pitc_ticks += (*AT91C_PITC_PIVR & AT91C_PITC_PICNT) >> 20;

	struct pitc_timer *search, *tmp;
	list_for_each_entry_safe(search, tmp, &timer_list, list) {
		/* if this entry not scheduled yet, abort search */
		if (pitc_ticks < search->nextrun)
			break;

		/* remove from list */
		list_del(&search->list);

		/* exec handler */
		if ((search->interval == 0) || search->func(search) == PITC_REMOVE_TIMER) {
			/* one-shot timer, mark as completed */
			search->nextrun = 0;
			continue;
		}

		/* interval timer, reschedule it */
		_pitc_schedule_timer(search);
	}
}

uint32_t pitc_get_ticks(void)
{
	return pitc_ticks;
}

void at91_pitc_init(void)
{
	sysc_register_isr(AT91_SYSIRQ_PIT, &pitc_isr);

	*AT91C_PITC_PIMR = (AT91C_PITC_PIV & HZ_TO_PIV(PITC_HZ)) |
			   AT91C_PITC_PITEN |
			   AT91C_PITC_PITIEN;
}