/*
 * Copyright (c) 2006 Jakub Jermar
 * 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.
 * - The name of the author may not be used to endorse or promote products
 *   derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 AUTHOR 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.
 */

/** @addtogroup genericddi
 * @{
 */
/**
 * @file
 * @brief	IRQ dispatcher.
 *
 * This file provides means of connecting IRQs with particular
 * devices and logic for dispatching interrupts to IRQ handlers
 * defined by those devices.
 *
 * This code is designed to support:
 * - multiple devices sharing single IRQ
 * - multiple IRQs per signle device
 *
 *
 * Note about architectures.
 *
 * Some architectures has the term IRQ well defined. Examples
 * of such architectures include amd64, ia32 and mips32. Some
 * other architectures, such as sparc64, don't use the term
 * at all. In those cases, we boldly step forward and define what
 * an IRQ is.
 *
 * The implementation is generic enough and still allows the
 * architectures to use the hardware layout effectively.
 * For instance, on amd64 and ia32, where there is only 16
 * IRQs, the irq_hash_table can be optimized to a one-dimensional
 * array. Next, when it is known that the IRQ numbers (aka INR's)
 * are unique, the claim functions can always return IRQ_ACCEPT.
 *
 *
 * Note about the irq_hash_table.
 *
 * The hash table is configured to use two keys: inr and devno.
 * However, the hash index is computed only from inr. Moreover,
 * if devno is -1, the match is based on the return value of
 * the claim() function instead of on devno.
 */

#include <ddi/irq.h>
#include <adt/hash_table.h>
#include <arch/types.h>
#include <synch/spinlock.h>
#include <arch.h>

#define KEY_INR		0
#define KEY_DEVNO	1

/**
 * Spinlock protecting the hash table.
 * This lock must be taken only when interrupts are disabled.
 */
SPINLOCK_INITIALIZE(irq_hash_table_lock);
static hash_table_t irq_hash_table;

/**
 * Hash table operations for cases when we know that
 * there will be collisions between different keys.
 */
static index_t irq_ht_hash(unative_t *key);
static bool irq_ht_compare(unative_t *key, count_t keys, link_t *item);

static hash_table_operations_t irq_ht_ops = {
	.hash = irq_ht_hash,
	.compare = irq_ht_compare,
	.remove_callback = NULL		/* not used */
};

/**
 * Hash table operations for cases when we know that
 * there will be no collisions between different keys.
 * However, there might be still collisions among
 * elements with single key (sharing of one IRQ).
 */
static index_t irq_lin_hash(unative_t *key);
static bool irq_lin_compare(unative_t *key, count_t keys, link_t *item);

static hash_table_operations_t irq_lin_ops = {
	.hash = irq_lin_hash,
	.compare = irq_lin_compare,
	.remove_callback = NULL		/* not used */
};

/** Initialize IRQ subsystem.
 *
 * @param inrs Numbers of unique IRQ numbers or INRs.
 * @param chains Number of chains in the hash table.
 */
void irq_init(count_t inrs, count_t chains)
{
	/*
	 * Be smart about the choice of the hash table operations.
	 * In cases in which inrs equals the requested number of
	 * chains (i.e. where there is no collision between
	 * different keys), we can use optimized set of operations.
	 */
	if (inrs == chains)
		hash_table_create(&irq_hash_table, chains, 2, &irq_lin_ops);
	else
		hash_table_create(&irq_hash_table, chains, 2, &irq_ht_ops);
}

/** Initialize one IRQ structure.
 *
 * @param irq Pointer to the IRQ structure to be initialized.
 *
 */
void irq_initialize(irq_t *irq)
{
	link_initialize(&irq->link);
	spinlock_initialize(&irq->lock, "irq.lock");
	irq->preack = false;
	irq->inr = -1;
	irq->devno = -1;
	irq->trigger = (irq_trigger_t) 0;
	irq->claim = NULL;
	irq->handler = NULL;
	irq->arg = NULL;
	irq->notif_cfg.notify = false;
	irq->notif_cfg.answerbox = NULL;
	irq->notif_cfg.code = NULL;
	irq->notif_cfg.method = 0;
	irq->notif_cfg.counter = 0;
	link_initialize(&irq->notif_cfg.link);
}

/** Register IRQ for device.
 *
 * The irq structure must be filled with information
 * about the interrupt source and with the claim()
 * function pointer and irq_handler() function pointer.
 *
 * @param irq IRQ structure belonging to a device.
 */
void irq_register(irq_t *irq)
{
	ipl_t ipl;
	unative_t key[] = {
		(unative_t) irq->inr,
		(unative_t) irq->devno
	};
	
	ipl = interrupts_disable();
	spinlock_lock(&irq_hash_table_lock);
	hash_table_insert(&irq_hash_table, key, &irq->link);
	spinlock_unlock(&irq_hash_table_lock);
	interrupts_restore(ipl);
}

/** Dispatch the IRQ.
 *
 * We assume this function is only called from interrupt
 * context (i.e. that interrupts are disabled prior to
 * this call).
 *
 * This function attempts to lookup a fitting IRQ
 * structure. In case of success, return with interrupts
 * disabled and holding the respective structure.
 *
 * @param inr Interrupt number (aka inr or irq).
 *
 * @return IRQ structure of the respective device or NULL.
 */
irq_t *irq_dispatch_and_lock(inr_t inr)
{
	link_t *lnk;
	unative_t key[] = {
		(unative_t) inr,
		(unative_t) -1		/* search will use claim() instead of devno */
	};
	
	spinlock_lock(&irq_hash_table_lock);

	lnk = hash_table_find(&irq_hash_table, key);
	if (lnk) {
		irq_t *irq;
		
		irq = hash_table_get_instance(lnk, irq_t, link);

		spinlock_unlock(&irq_hash_table_lock);
		return irq;
	}
	
	spinlock_unlock(&irq_hash_table_lock);

	return NULL;	
}

/** Find the IRQ structure corresponding to inr and devno.
 *
 * This functions attempts to lookup the IRQ structure
 * corresponding to its arguments. On success, this
 * function returns with interrups disabled, holding
 * the lock of the respective IRQ structure.
 *
 * This function assumes interrupts are already disabled.
 *
 * @param inr INR being looked up.
 * @param devno Devno being looked up.
 *
 * @return Locked IRQ structure on success or NULL on failure.
 */
irq_t *irq_find_and_lock(inr_t inr, devno_t devno)
{
	link_t *lnk;
	unative_t keys[] = {
		(unative_t) inr,
		(unative_t) devno
	};
	
	spinlock_lock(&irq_hash_table_lock);

	lnk = hash_table_find(&irq_hash_table, keys);
	if (lnk) {
		irq_t *irq;
		
		irq = hash_table_get_instance(lnk, irq_t, link);

		spinlock_unlock(&irq_hash_table_lock);
		return irq;
	}
	
	spinlock_unlock(&irq_hash_table_lock);

	return NULL;	
}

/** Compute hash index for the key.
 *
 * This function computes hash index into
 * the IRQ hash table for which there
 * can be collisions between different
 * INRs.
 *
 * The devno is not used to compute the hash.
 *
 * @param key The first of the keys is inr and the second is devno or -1.
 *
 * @return Index into the hash table.
 */
index_t irq_ht_hash(unative_t key[])
{
	inr_t inr = (inr_t) key[KEY_INR];
	return inr % irq_hash_table.entries;
}

/** Compare hash table element with a key.
 *
 * There are two things to note about this function.
 * First, it is used for the more complex architecture setup
 * in which there are way too many interrupt numbers (i.e. inr's)
 * to arrange the hash table so that collisions occur only
 * among same inrs of different devnos. So the explicit check
 * for inr match must be done.
 * Second, if devno is -1, the second key (i.e. devno) is not
 * used for the match and the result of the claim() function
 * is used instead.
 *
 * This function assumes interrupts are already disabled.
 *
 * @param key Keys (i.e. inr and devno).
 * @param keys This is 2.
 * @param item The item to compare the key with.
 *
 * @return True on match or false otherwise.
 */
bool irq_ht_compare(unative_t key[], count_t keys, link_t *item)
{
	irq_t *irq = hash_table_get_instance(item, irq_t, link);
	inr_t inr = (inr_t) key[KEY_INR];
	devno_t devno = (devno_t) key[KEY_DEVNO];

	bool rv;
	
	spinlock_lock(&irq->lock);
	if (devno == -1) {
		/* Invoked by irq_dispatch_and_lock(). */
		rv = ((irq->inr == inr) && (irq->claim() == IRQ_ACCEPT));
	} else {
		/* Invoked by irq_find_and_lock(). */
		rv = ((irq->inr == inr) && (irq->devno == devno));
	}
	
	/* unlock only on non-match */
	if (!rv)
		spinlock_unlock(&irq->lock);

	return rv;
}

/** Compute hash index for the key.
 *
 * This function computes hash index into
 * the IRQ hash table for which there
 * are no collisions between different
 * INRs.
 *
 * @param key The first of the keys is inr and the second is devno or -1.
 *
 * @return Index into the hash table.
 */
index_t irq_lin_hash(unative_t key[])
{
	inr_t inr = (inr_t) key[KEY_INR];
	return inr;
}

/** Compare hash table element with a key.
 *
 * There are two things to note about this function.
 * First, it is used for the less complex architecture setup
 * in which there are not too many interrupt numbers (i.e. inr's)
 * to arrange the hash table so that collisions occur only
 * among same inrs of different devnos. So the explicit check
 * for inr match is not done.
 * Second, if devno is -1, the second key (i.e. devno) is not
 * used for the match and the result of the claim() function
 * is used instead.
 *
 * This function assumes interrupts are already disabled.
 *
 * @param key Keys (i.e. inr and devno).
 * @param keys This is 2.
 * @param item The item to compare the key with.
 *
 * @return True on match or false otherwise.
 */
bool irq_lin_compare(unative_t key[], count_t keys, link_t *item)
{
	irq_t *irq = list_get_instance(item, irq_t, link);
	devno_t devno = (devno_t) key[KEY_DEVNO];
	bool rv;
	
	spinlock_lock(&irq->lock);
	if (devno == -1) {
		/* Invoked by irq_dispatch_and_lock() */
		rv = (irq->claim() == IRQ_ACCEPT);
	} else {
		/* Invoked by irq_find_and_lock() */
		rv = (irq->devno == devno);
	}
	
	/* unlock only on non-match */
	if (!rv)
		spinlock_unlock(&irq->lock);
	
	return rv;
}

/** @}
 */