async_tx.c

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/*
 * core routines for the asynchronous memory transfer/transform api
 *
 * Copyright © 2006, Intel Corporation.
 *
 *  Dan Williams <[email protected]>
 *
 *  with architecture considerations by:
 *  Neil Brown <[email protected]>
 *  Jeff Garzik <[email protected]>
 *
 * 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/module.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();
}

module_init(async_tx_init);
module_exit(async_tx_exit);

struct dma_chan *
__async_tx_find_channel(struct async_submit_ctl *submit,
            enum dma_transaction_type tx_type)
{
    struct dma_async_tx_descriptor *depend_tx = submit->depend_tx;

    /* 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);
#endif


static void
async_tx_channel_switch(struct dma_async_tx_descriptor *depend_tx,
            struct dma_async_tx_descriptor *tx)
{
    struct dma_chan *chan = depend_tx->chan;
    struct dma_device *device = chan->device;
    struct dma_async_tx_descriptor *intr_tx = (void *) ~0;

    /* first check to see if we can still append to depend_tx */
    txd_lock(depend_tx);
    if (txd_parent(depend_tx) && depend_tx->chan == tx->chan) {
        txd_chain(depend_tx, tx);
        intr_tx = NULL;
    }
    txd_unlock(depend_tx);

    /* attached dependency, flush the parent channel */
    if (!intr_tx) {
        device->device_issue_pending(chan);
        return;
    }

    /* 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;
        /* safe to chain outside the lock since we know we are
         * not submitted yet
         */
        txd_chain(intr_tx, tx);

        /* check if we need to append */
        txd_lock(depend_tx);
        if (txd_parent(depend_tx)) {
            txd_chain(depend_tx, intr_tx);
            async_tx_ack(intr_tx);
            intr_tx = NULL;
        }
        txd_unlock(depend_tx);

        if (intr_tx) {
            txd_clear_parent(intr_tx);
            intr_tx->tx_submit(intr_tx);
            async_tx_ack(intr_tx);
        }
        device->device_issue_pending(chan);
    } 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);
    }
}


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,
        struct async_submit_ctl *submit)
{
    struct dma_async_tx_descriptor *depend_tx = submit->depend_tx;

    tx->callback = submit->cb_fn;
    tx->callback_param = submit->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) || txd_next(depend_tx) ||
               txd_parent(tx));

        /* the lock prevents async_tx_run_dependencies from missing
         * the setting of ->next when ->parent != NULL
         */
        txd_lock(depend_tx);
        if (txd_parent(depend_tx)) {
            /* 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) {
                txd_chain(depend_tx, 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;
        }
        txd_unlock(depend_tx);

        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:
            txd_clear_parent(tx);
            tx->tx_submit(tx);
            break;
        }
    } else {
        txd_clear_parent(tx);
        tx->tx_submit(tx);
    }

    if (submit->flags & ASYNC_TX_ACK)
        async_tx_ack(tx);

    if (depend_tx)
        async_tx_ack(depend_tx);
}
EXPORT_SYMBOL_GPL(async_tx_submit);

struct dma_async_tx_descriptor *
async_trigger_callback(struct async_submit_ctl *submit)
{
    struct dma_chan *chan;
    struct dma_device *device;
    struct dma_async_tx_descriptor *tx;
    struct dma_async_tx_descriptor *depend_tx = submit->depend_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, submit);
    } else {
        pr_debug("%s: (sync)\n", __func__);

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

        async_tx_sync_epilog(submit);
    }

    return tx;
}
EXPORT_SYMBOL_GPL(async_trigger_callback);

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