/*
 * core routines for the asynchronous memory transfer/transform api
 *
 * Copyright \xC2\xA9 2006, Intel Corporation.
 *
 *      Dan Williams <dan.j.williams@intel.com>
 *
 *      with architecture considerations by:
 *      Neil Brown <neilb@suse.de>
 *      Jeff Garzik <jeff@garzik.org>
 *
 * 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.,
 * 51 Franklin St - Fifth Floor, Boston, MA 02110-1301 USA.
 *
 */
#include <linux/rculist.h>
#include <linux/kernel.h>
#include <linux/async_tx.h>

#ifdef CONFIG_DMA_ENGINE
static int __init async_tx_init(void)
{
        async_dmaengine_get();

        printk(KERN_INFO "async_tx: api initialized (async)\n");

        return 0;
}

static void __exit async_tx_exit(void)
{
        async_dmaengine_put();
}

/**
 * __async_tx_find_channel - find a channel to carry out the operation or let
 *      the transaction execute synchronously
 * @depend_tx: transaction dependency
 * @tx_type: transaction type
 */
struct dma_chan *
__async_tx_find_channel(struct dma_async_tx_descriptor *depend_tx,
        enum dma_transaction_type tx_type)
{
        /* see if we can keep the chain on one channel */
        if (depend_tx &&
            dma_has_cap(tx_type, depend_tx->chan->device->cap_mask))
                return depend_tx->chan;
        return async_dma_find_channel(tx_type);
}
EXPORT_SYMBOL_GPL(__async_tx_find_channel);
#else
static int __init async_tx_init(void)
{
        printk(KERN_INFO "async_tx: api initialized (sync-only)\n");
        return 0;
}

static void __exit async_tx_exit(void)
{
        do { } while (0);
}
#endif


/**
 * async_tx_channel_switch - queue an interrupt descriptor with a dependency
 *      pre-attached.
 * @depend_tx: the operation that must finish before the new operation runs
 * @tx: the new operation
 */
static void
async_tx_channel_switch(struct dma_async_tx_descriptor *depend_tx,
                        struct dma_async_tx_descriptor *tx)
{
        struct dma_chan *chan;
        struct dma_device *device;
        struct dma_async_tx_descriptor *intr_tx = (void *) ~0;

        /* first check to see if we can still append to depend_tx */
        spin_lock_bh(&depend_tx->lock);
        if (depend_tx->parent && depend_tx->chan == tx->chan) {
                tx->parent = depend_tx;
                depend_tx->next = tx;
                intr_tx = NULL;
        }
        spin_unlock_bh(&depend_tx->lock);

        if (!intr_tx)
                return;

        chan = depend_tx->chan;
        device = chan->device;

        /* see if we can schedule an interrupt
         * otherwise poll for completion
         */
        if (dma_has_cap(DMA_INTERRUPT, device->cap_mask))
                intr_tx = device->device_prep_dma_interrupt(chan, 0);
        else
                intr_tx = NULL;

        if (intr_tx) {
                intr_tx->callback = NULL;
                intr_tx->callback_param = NULL;
                tx->parent = intr_tx;
                /* safe to set ->next outside the lock since we know we are
                 * not submitted yet
                 */
                intr_tx->next = tx;

                /* check if we need to append */
                spin_lock_bh(&depend_tx->lock);
                if (depend_tx->parent) {
                        intr_tx->parent = depend_tx;
                        depend_tx->next = intr_tx;
                        async_tx_ack(intr_tx);
                        intr_tx = NULL;
                }
                spin_unlock_bh(&depend_tx->lock);

                if (intr_tx) {
                        intr_tx->parent = NULL;
                        intr_tx->tx_submit(intr_tx);
                        async_tx_ack(intr_tx);
                }
        } else {
                if (dma_wait_for_async_tx(depend_tx) == DMA_ERROR)
                        panic("%s: DMA_ERROR waiting for depend_tx\n",
                              __func__);
                tx->tx_submit(tx);
        }
}


/**
 * submit_disposition - while holding depend_tx->lock we must avoid submitting
 *      new operations to prevent a circular locking dependency with
 *      drivers that already hold a channel lock when calling
 *      async_tx_run_dependencies.
 * @ASYNC_TX_SUBMITTED: we were able to append the new operation under the lock
 * @ASYNC_TX_CHANNEL_SWITCH: when the lock is dropped schedule a channel switch
 * @ASYNC_TX_DIRECT_SUBMIT: when the lock is dropped submit directly
 */
enum submit_disposition {
        ASYNC_TX_SUBMITTED,
        ASYNC_TX_CHANNEL_SWITCH,
        ASYNC_TX_DIRECT_SUBMIT,
};

void
async_tx_submit(struct dma_chan *chan, struct dma_async_tx_descriptor *tx,
        enum async_tx_flags flags, struct dma_async_tx_descriptor *depend_tx,
        dma_async_tx_callback cb_fn, void *cb_param)
{
        tx->callback = cb_fn;
        tx->callback_param = cb_param;

        if (depend_tx) {
                enum submit_disposition s;

                /* sanity check the dependency chain:
                 * 1/ if ack is already set then we cannot be sure
                 * we are referring to the correct operation
                 * 2/ dependencies are 1:1 i.e. two transactions can
                 * not depend on the same parent
                 */
                BUG_ON(async_tx_test_ack(depend_tx) || depend_tx->next ||
                       tx->parent);

                /* the lock prevents async_tx_run_dependencies from missing
                 * the setting of ->next when ->parent != NULL
                 */
                spin_lock_bh(&depend_tx->lock);
                if (depend_tx->parent) {
                        /* we have a parent so we can not submit directly
                         * if we are staying on the same channel: append
                         * else: channel switch
                         */
                        if (depend_tx->chan == chan) {
                                tx->parent = depend_tx;
                                depend_tx->next = tx;
                                s = ASYNC_TX_SUBMITTED;
                        } else
                                s = ASYNC_TX_CHANNEL_SWITCH;
                } else {
                        /* we do not have a parent so we may be able to submit
                         * directly if we are staying on the same channel
                         */
                        if (depend_tx->chan == chan)
                                s = ASYNC_TX_DIRECT_SUBMIT;
                        else
                                s = ASYNC_TX_CHANNEL_SWITCH;
                }
                spin_unlock_bh(&depend_tx->lock);

                switch (s) {
                case ASYNC_TX_SUBMITTED:
                        break;
                case ASYNC_TX_CHANNEL_SWITCH:
                        async_tx_channel_switch(depend_tx, tx);
                        break;
                case ASYNC_TX_DIRECT_SUBMIT:
                        tx->parent = NULL;
                        tx->tx_submit(tx);
                        break;
                }
        } else {
                tx->parent = NULL;
                tx->tx_submit(tx);
        }

        if (flags & ASYNC_TX_ACK)
                async_tx_ack(tx);

        if (depend_tx && (flags & ASYNC_TX_DEP_ACK))
                async_tx_ack(depend_tx);
}
EXPORT_SYMBOL_GPL(async_tx_submit);

/**
 * async_trigger_callback - schedules the callback function to be run after
 * any dependent operations have been completed.
 * @flags: ASYNC_TX_ACK, ASYNC_TX_DEP_ACK
 * @depend_tx: 'callback' requires the completion of this transaction
 * @cb_fn: function to call after depend_tx completes
 * @cb_param: parameter to pass to the callback routine
 */
struct dma_async_tx_descriptor *
async_trigger_callback(enum async_tx_flags flags,
        struct dma_async_tx_descriptor *depend_tx,
        dma_async_tx_callback cb_fn, void *cb_param)
{
        struct dma_chan *chan;
        struct dma_device *device;
        struct dma_async_tx_descriptor *tx;

        if (depend_tx) {
                chan = depend_tx->chan;
                device = chan->device;

                /* see if we can schedule an interrupt
                 * otherwise poll for completion
                 */
                if (device && !dma_has_cap(DMA_INTERRUPT, device->cap_mask))
                        device = NULL;

                tx = device ? device->device_prep_dma_interrupt(chan, 0) : NULL;
        } else
                tx = NULL;

        if (tx) {
                pr_debug("%s: (async)\n", __func__);

                async_tx_submit(chan, tx, flags, depend_tx, cb_fn, cb_param);
        } else {
                pr_debug("%s: (sync)\n", __func__);

                /* wait for any prerequisite operations */
                async_tx_quiesce(&depend_tx);

                async_tx_sync_epilog(cb_fn, cb_param);
        }

        return tx;
}
EXPORT_SYMBOL_GPL(async_trigger_callback);

/**
 * async_tx_quiesce - ensure tx is complete and freeable upon return
 * @tx - transaction to quiesce
 */
void async_tx_quiesce(struct dma_async_tx_descriptor **tx)
{
        if (*tx) {
                /* if ack is already set then we cannot be sure
                 * we are referring to the correct operation
                 */
                BUG_ON(async_tx_test_ack(*tx));
                if (dma_wait_for_async_tx(*tx) == DMA_ERROR)
                        panic("DMA_ERROR waiting for transaction\n");
                async_tx_ack(*tx);
                *tx = NULL;
        }
}
EXPORT_SYMBOL_GPL(async_tx_quiesce);

module_init(async_tx_init);
module_exit(async_tx_exit);

MODULE_AUTHOR("Intel Corporation");
MODULE_DESCRIPTION("Asynchronous Bulk Memory Transactions API");
MODULE_LICENSE("GPL");