/*
 * Copyright © 2006-2009, Intel Corporation.
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms and conditions of the GNU General Public License,
 * version 2, as published by the Free Software Foundation.
 *
 * This program is distributed in the hope 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.
 *
 * Author: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
 */

#include <linux/iova.h>

void
init_iova_domain(struct iova_domain *iovad, unsigned long pfn_32bit)
{
        spin_lock_init(&iovad->iova_rbtree_lock);
        iovad->rbroot = RB_ROOT;
        iovad->cached32_node = NULL;
        iovad->dma_32bit_pfn = pfn_32bit;
}

static struct rb_node *
__get_cached_rbnode(struct iova_domain *iovad, unsigned long *limit_pfn)
{
        if ((*limit_pfn != iovad->dma_32bit_pfn) ||
                (iovad->cached32_node == NULL))
                return rb_last(&iovad->rbroot);
        else {
                struct rb_node *prev_node = rb_prev(iovad->cached32_node);
                struct iova *curr_iova =
                        container_of(iovad->cached32_node, struct iova, node);
                *limit_pfn = curr_iova->pfn_lo - 1;
                return prev_node;
        }
}

static void
__cached_rbnode_insert_update(struct iova_domain *iovad,
        unsigned long limit_pfn, struct iova *new)
{
        if (limit_pfn != iovad->dma_32bit_pfn)
                return;
        iovad->cached32_node = &new->node;
}

static void
__cached_rbnode_delete_update(struct iova_domain *iovad, struct iova *free)
{
        struct iova *cached_iova;
        struct rb_node *curr;

        if (!iovad->cached32_node)
                return;
        curr = iovad->cached32_node;
        cached_iova = container_of(curr, struct iova, node);

        if (free->pfn_lo >= cached_iova->pfn_lo)
                iovad->cached32_node = rb_next(&free->node);
}

/* Computes the padding size required, to make the
 * the start address naturally aligned on its size
 */
static int
iova_get_pad_size(int size, unsigned int limit_pfn)
{
        unsigned int pad_size = 0;
        unsigned int order = ilog2(size);

        if (order)
                pad_size = (limit_pfn + 1) % (1 << order);

        return pad_size;
}

static int __alloc_and_insert_iova_range(struct iova_domain *iovad,
                unsigned long size, unsigned long limit_pfn,
                        struct iova *new, bool size_aligned)
{
        struct rb_node *prev, *curr = NULL;
        unsigned long flags;
        unsigned long saved_pfn;
        unsigned int pad_size = 0;

        /* Walk the tree backwards */
        spin_lock_irqsave(&iovad->iova_rbtree_lock, flags);
        saved_pfn = limit_pfn;
        curr = __get_cached_rbnode(iovad, &limit_pfn);
        prev = curr;
        while (curr) {
                struct iova *curr_iova = container_of(curr, struct iova, node);

                if (limit_pfn < curr_iova->pfn_lo)
                        goto move_left;
                else if (limit_pfn < curr_iova->pfn_hi)
                        goto adjust_limit_pfn;
                else {
                        if (size_aligned)
                                pad_size = iova_get_pad_size(size, limit_pfn);
                        if ((curr_iova->pfn_hi + size + pad_size) <= limit_pfn)
                                break;  /* found a free slot */
                }
adjust_limit_pfn:
                limit_pfn = curr_iova->pfn_lo - 1;
move_left:
                prev = curr;
                curr = rb_prev(curr);
        }

        if (!curr) {
                if (size_aligned)
                        pad_size = iova_get_pad_size(size, limit_pfn);
                if ((IOVA_START_PFN + size + pad_size) > limit_pfn) {
                        spin_unlock_irqrestore(&iovad->iova_rbtree_lock, flags);
                        return -ENOMEM;
                }
        }

        /* pfn_lo will point to size aligned address if size_aligned is set */
        new->pfn_lo = limit_pfn - (size + pad_size) + 1;
        new->pfn_hi = new->pfn_lo + size - 1;

        /* Insert the new_iova into domain rbtree by holding writer lock */
        /* Add new node and rebalance tree. */
        {
                struct rb_node **entry, *parent = NULL;

                /* If we have 'prev', it's a valid place to start the
                   insertion. Otherwise, start from the root. */
                if (prev)
                        entry = &prev;
                else
                        entry = &iovad->rbroot.rb_node;

                /* Figure out where to put new node */
                while (*entry) {
                        struct iova *this = container_of(*entry,
                                                        struct iova, node);
                        parent = *entry;

                        if (new->pfn_lo < this->pfn_lo)
                                entry = &((*entry)->rb_left);
                        else if (new->pfn_lo > this->pfn_lo)
                                entry = &((*entry)->rb_right);
                        else
                                BUG(); /* this should not happen */
                }

                /* Add new node and rebalance tree. */
                rb_link_node(&new->node, parent, entry);
                rb_insert_color(&new->node, &iovad->rbroot);
        }
        __cached_rbnode_insert_update(iovad, saved_pfn, new);

        spin_unlock_irqrestore(&iovad->iova_rbtree_lock, flags);


        return 0;
}

static void
iova_insert_rbtree(struct rb_root *root, struct iova *iova)
{
        struct rb_node **new = &(root->rb_node), *parent = NULL;
        /* Figure out where to put new node */
        while (*new) {
                struct iova *this = container_of(*new, struct iova, node);
                parent = *new;

                if (iova->pfn_lo < this->pfn_lo)
                        new = &((*new)->rb_left);
                else if (iova->pfn_lo > this->pfn_lo)
                        new = &((*new)->rb_right);
                else
                        BUG(); /* this should not happen */
        }
        /* Add new node and rebalance tree. */
        rb_link_node(&iova->node, parent, new);
        rb_insert_color(&iova->node, root);
}

/**
 * alloc_iova - allocates an iova
 * @iovad - iova domain in question
 * @size - size of page frames to allocate
 * @limit_pfn - max limit address
 * @size_aligned - set if size_aligned address range is required
 * This function allocates an iova in the range limit_pfn to IOVA_START_PFN
 * looking from limit_pfn instead from IOVA_START_PFN. If the size_aligned
 * flag is set then the allocated address iova->pfn_lo will be naturally
 * aligned on roundup_power_of_two(size).
 */
struct iova *
alloc_iova(struct iova_domain *iovad, unsigned long size,
        unsigned long limit_pfn,
        bool size_aligned)
{
        struct iova *new_iova;
        int ret;

        new_iova = alloc_iova_mem();
        if (!new_iova)
                return NULL;

        /* If size aligned is set then round the size to
         * to next power of two.
         */
        if (size_aligned)
                size = __roundup_pow_of_two(size);

        ret = __alloc_and_insert_iova_range(iovad, size, limit_pfn,
                        new_iova, size_aligned);

        if (ret) {
                free_iova_mem(new_iova);
                return NULL;
        }

        return new_iova;
}

/**
 * find_iova - find's an iova for a given pfn
 * @iovad - iova domain in question.
 * pfn - page frame number
 * This function finds and returns an iova belonging to the
 * given doamin which matches the given pfn.
 */
struct iova *find_iova(struct iova_domain *iovad, unsigned long pfn)
{
        unsigned long flags;
        struct rb_node *node;

        /* Take the lock so that no other thread is manipulating the rbtree */
        spin_lock_irqsave(&iovad->iova_rbtree_lock, flags);
        node = iovad->rbroot.rb_node;
        while (node) {
                struct iova *iova = container_of(node, struct iova, node);

                /* If pfn falls within iova's range, return iova */
                if ((pfn >= iova->pfn_lo) && (pfn <= iova->pfn_hi)) {
                        spin_unlock_irqrestore(&iovad->iova_rbtree_lock, flags);
                        /* We are not holding the lock while this iova
                         * is referenced by the caller as the same thread
                         * which called this function also calls __free_iova()
                         * and it is by desing that only one thread can possibly
                         * reference a particular iova and hence no conflict.
                         */
                        return iova;
                }

                if (pfn < iova->pfn_lo)
                        node = node->rb_left;
                else if (pfn > iova->pfn_lo)
                        node = node->rb_right;
        }

        spin_unlock_irqrestore(&iovad->iova_rbtree_lock, flags);
        return NULL;
}

/**
 * __free_iova - frees the given iova
 * @iovad: iova domain in question.
 * @iova: iova in question.
 * Frees the given iova belonging to the giving domain
 */
void
__free_iova(struct iova_domain *iovad, struct iova *iova)
{
        unsigned long flags;

        spin_lock_irqsave(&iovad->iova_rbtree_lock, flags);
        __cached_rbnode_delete_update(iovad, iova);
        rb_erase(&iova->node, &iovad->rbroot);
        spin_unlock_irqrestore(&iovad->iova_rbtree_lock, flags);
        free_iova_mem(iova);
}

/**
 * free_iova - finds and frees the iova for a given pfn
 * @iovad: - iova domain in question.
 * @pfn: - pfn that is allocated previously
 * This functions finds an iova for a given pfn and then
 * frees the iova from that domain.
 */
void
free_iova(struct iova_domain *iovad, unsigned long pfn)
{
        struct iova *iova = find_iova(iovad, pfn);
        if (iova)
                __free_iova(iovad, iova);

}

/**
 * put_iova_domain - destroys the iova doamin
 * @iovad: - iova domain in question.
 * All the iova's in that domain are destroyed.
 */
void put_iova_domain(struct iova_domain *iovad)
{
        struct rb_node *node;
        unsigned long flags;

        spin_lock_irqsave(&iovad->iova_rbtree_lock, flags);
        node = rb_first(&iovad->rbroot);
        while (node) {
                struct iova *iova = container_of(node, struct iova, node);
                rb_erase(node, &iovad->rbroot);
                free_iova_mem(iova);
                node = rb_first(&iovad->rbroot);
        }
        spin_unlock_irqrestore(&iovad->iova_rbtree_lock, flags);
}

static int
__is_range_overlap(struct rb_node *node,
        unsigned long pfn_lo, unsigned long pfn_hi)
{
        struct iova *iova = container_of(node, struct iova, node);

        if ((pfn_lo <= iova->pfn_hi) && (pfn_hi >= iova->pfn_lo))
                return 1;
        return 0;
}

static struct iova *
__insert_new_range(struct iova_domain *iovad,
        unsigned long pfn_lo, unsigned long pfn_hi)
{
        struct iova *iova;

        iova = alloc_iova_mem();
        if (!iova)
                return iova;

        iova->pfn_hi = pfn_hi;
        iova->pfn_lo = pfn_lo;
        iova_insert_rbtree(&iovad->rbroot, iova);
        return iova;
}

static void
__adjust_overlap_range(struct iova *iova,
        unsigned long *pfn_lo, unsigned long *pfn_hi)
{
        if (*pfn_lo < iova->pfn_lo)
                iova->pfn_lo = *pfn_lo;
        if (*pfn_hi > iova->pfn_hi)
                *pfn_lo = iova->pfn_hi + 1;
}

/**
 * reserve_iova - reserves an iova in the given range
 * @iovad: - iova domain pointer
 * @pfn_lo: - lower page frame address
 * @pfn_hi:- higher pfn adderss
 * This function allocates reserves the address range from pfn_lo to pfn_hi so
 * that this address is not dished out as part of alloc_iova.
 */
struct iova *
reserve_iova(struct iova_domain *iovad,
        unsigned long pfn_lo, unsigned long pfn_hi)
{
        struct rb_node *node;
        unsigned long flags;
        struct iova *iova;
        unsigned int overlap = 0;

        spin_lock_irqsave(&iovad->iova_rbtree_lock, flags);
        for (node = rb_first(&iovad->rbroot); node; node = rb_next(node)) {
                if (__is_range_overlap(node, pfn_lo, pfn_hi)) {
                        iova = container_of(node, struct iova, node);
                        __adjust_overlap_range(iova, &pfn_lo, &pfn_hi);
                        if ((pfn_lo >= iova->pfn_lo) &&
                                (pfn_hi <= iova->pfn_hi))
                                goto finish;
                        overlap = 1;

                } else if (overlap)
                                break;
        }

        /* We are here either becasue this is the first reserver node
         * or need to insert remaining non overlap addr range
         */
        iova = __insert_new_range(iovad, pfn_lo, pfn_hi);
finish:

        spin_unlock_irqrestore(&iovad->iova_rbtree_lock, flags);
        return iova;
}

/**
 * copy_reserved_iova - copies the reserved between domains
 * @from: - source doamin from where to copy
 * @to: - destination domin where to copy
 * This function copies reserved iova's from one doamin to
 * other.
 */
void
copy_reserved_iova(struct iova_domain *from, struct iova_domain *to)
{
        unsigned long flags;
        struct rb_node *node;

        spin_lock_irqsave(&from->iova_rbtree_lock, flags);
        for (node = rb_first(&from->rbroot); node; node = rb_next(node)) {
                struct iova *iova = container_of(node, struct iova, node);
                struct iova *new_iova;
                new_iova = reserve_iova(to, iova->pfn_lo, iova->pfn_hi);
                if (!new_iova)
                        printk(KERN_ERR "Reserve iova range %lx@%lx failed\n",
                                iova->pfn_lo, iova->pfn_lo);
        }
        spin_unlock_irqrestore(&from->iova_rbtree_lock, flags);
}