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/*
* 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>
*
* 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);

/**
* __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_ERROR)
panic("%s: DMA_ERROR waiting for depend_tx\n",
__func__);
tx->tx_submit(tx);
}
}


/**
* 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_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");
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