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async_memset.c

/*
 * memory fill offload engine support
 *
 * 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/kernel.h>
#include <linux/interrupt.h>
#include <linux/mm.h>
#include <linux/dma-mapping.h>
#include <linux/async_tx.h>

/**
 * async_memset - attempt to fill memory with a dma engine.
 * @dest: destination page
 * @val: fill value
 * @offset: offset in pages to start transaction
 * @len: length in bytes
 * @flags: ASYNC_TX_ASSUME_COHERENT, ASYNC_TX_ACK, ASYNC_TX_DEP_ACK
 * @depend_tx: memset depends on the result of this transaction
 * @cb_fn: function to call when the memcpy completes
 * @cb_param: parameter to pass to the callback routine
 */
struct dma_async_tx_descriptor *
async_memset(struct page *dest, int val, unsigned int offset,
      size_t len, 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 = async_tx_find_channel(depend_tx, DMA_MEMSET);
      struct dma_device *device = chan ? chan->device : NULL;
      int int_en = cb_fn ? 1 : 0;
      struct dma_async_tx_descriptor *tx = device ?
            device->device_prep_dma_memset(chan, val, len,
                  int_en) : NULL;

      if (tx) { /* run the memset asynchronously */
            dma_addr_t dma_addr;
            enum dma_data_direction dir;

            pr_debug("%s: (async) len: %zu\n", __FUNCTION__, len);
            dir = (flags & ASYNC_TX_ASSUME_COHERENT) ?
                  DMA_NONE : DMA_FROM_DEVICE;

            dma_addr = dma_map_page(device->dev, dest, offset, len, dir);
            tx->tx_set_dest(dma_addr, tx, 0);

            async_tx_submit(chan, tx, flags, depend_tx, cb_fn, cb_param);
      } else { /* run the memset synchronously */
            void *dest_buf;
            pr_debug("%s: (sync) len: %zu\n", __FUNCTION__, len);

            dest_buf = (void *) (((char *) page_address(dest)) + offset);

            /* wait for any prerequisite operations */
            if (depend_tx) {
                  /* if ack is already set then we cannot be sure
                   * we are referring to the correct operation
                   */
                  BUG_ON(depend_tx->ack);
                  if (dma_wait_for_async_tx(depend_tx) == DMA_ERROR)
                        panic("%s: DMA_ERROR waiting for depend_tx\n",
                              __FUNCTION__);
            }

            memset(dest_buf, val, len);

            async_tx_sync_epilog(flags, depend_tx, cb_fn, cb_param);
      }

      return tx;
}
EXPORT_SYMBOL_GPL(async_memset);

static int __init async_memset_init(void)
{
      return 0;
}

static void __exit async_memset_exit(void)
{
      do { } while (0);
}

module_init(async_memset_init);
module_exit(async_memset_exit);

MODULE_AUTHOR("Intel Corporation");
MODULE_DESCRIPTION("asynchronous memset api");
MODULE_LICENSE("GPL");

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