// SPDX-License-Identifier: GPL-2.0-only
/*
 * core routines for the asynchronous memory transfer/transform api
 *
 * Copyright © 2006, Intel Corporation.
 *
 *      Dan Williams <dan.j.williams@intel.com>
 *
 *      with architecture considerations by:
 *      Neil Brown <neilb@suse.de>
 *      Jeff Garzik <jeff@garzik.org>
 */
#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);

/**
 * __async_tx_find_channel - find a channel to carry out the operation or let
 *      the transaction execute synchronously
 * @submit: transaction dependency and submission modifiers
 * @tx_type: transaction type
 */
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


/**
 * 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 = 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_COMPLETE)
                        panic("%s: DMA error waiting for depend_tx\n",
                              __func__);
                tx->tx_submit(tx);
        }
}


/**
 * enum submit_disposition - flags for routing an incoming operation
 * @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
 *
 * 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.
 */
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);

/**
 * async_trigger_callback - schedules the callback function to be run
 * @submit: submission and completion parameters
 *
 * honored flags: ASYNC_TX_ACK
 *
 * The callback is run after any dependent operations have completed.
 */
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);

/**
 * 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_COMPLETE)
                        panic("%s: DMA error waiting for transaction\n",
                              __func__);
                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");