/*
 * Copyright (c) 2014, ARM Limited and Contributors. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * Redistributions of source code must retain the above copyright notice, this
 * list of conditions and the following disclaimer.
 *
 * Redistributions in binary form must reproduce the above copyright notice,
 * this list of conditions and the following disclaimer in the documentation
 * and/or other materials provided with the distribution.
 *
 * Neither the name of ARM nor the names of its contributors may be used
 * to endorse or promote products derived from this software without specific
 * prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

#ifndef __EVENTS_H__
#define __EVENTS_H__

#include <spinlock.h>

typedef struct {
	/*
	 * Counter that keeps track of the minimum number of recipients of the
	 * event. When the event is sent, this counter is incremented. When it
	 * is received, it is decremented. Therefore, a zero value means that
	 * the event hasn't been sent yet, or that all recipients have already
	 * received it.
	 *
	 * Volatile is needed as it will enforce ordering relatively to
	 * accesses to the lock.
	 */
	volatile unsigned int cnt;

	/* Lock used to avoid concurrent accesses to the counter */
	spinlock_t lock;
} event_t;

/*
 * Initialise an event.
 *   event: Address of the event to initialise
 *
 * This function can be used either to initialise a newly created event
 * structure or to recycle one.
 *
 * Note: This function is not MP-safe. It can't use the event lock as it is
 * responsible for initialising it. Care must be taken to ensure this function
 * is called in the right circumstances.
 */
void tftf_init_event(event_t *event);

/*
 * Send an event to a CPU.
 *   event: Address of the variable that acts as a synchronisation object.
 *
 * Which CPU receives the event is determined on a first-come, first-served
 * basis. If several CPUs are waiting for the same event then the first CPU
 * which takes the event will reflect that in the event structure.
 *
 * Note: This is equivalent to calling:
 *   tftf_send_event_to(event, 1);
 */
void tftf_send_event(event_t *event);

/*
 * Send an event to all CPUs.
 *   event: Address of the variable that acts as a synchronisation object.
 *
 * Note: This is equivalent to calling:
 *   tftf_send_event_to(event, PLATFORM_CORE_COUNT);
 */
void tftf_send_event_to_all(event_t *event);

/*
 * Send an event to a given number of CPUs.
 *   event: Address of the variable that acts as a synchronisation object.
 *   cpus_count: Number of CPUs to send the event to.
 *
 * Which CPUs receive the event is determined on a first-come, first-served
 * basis. If more than 'cpus_count' CPUs are waiting for the same event then the
 * first 'cpus_count' CPUs which take the event will reflect that in the event
 * structure.
 */
void tftf_send_event_to(event_t *event, unsigned int cpus_count);

/*
 * Wait for an event.
 *   event: Address of the variable that acts as a synchronisation object.
 */
void tftf_wait_for_event(event_t *event);

#endif /* __EVENTS_H__ */