/*
   * copy 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/highmem.h>

  #include <linux/module.h>

  #include <linux/mm.h>
  #include <linux/dma-mapping.h>
  #include <linux/async_tx.h>
  
  /**
   * async_memcpy - attempt to copy memory with a dma engine.
   * @dest: destination page
   * @src: src page

   * @dest_offset: offset into 'dest' to start transaction
   * @src_offset: offset into 'src' to start transaction

   * @len: length in bytes

   * @submit: submission / completion modifiers
   *
   * honored flags: ASYNC_TX_ACK

   */
  struct dma_async_tx_descriptor *
  async_memcpy(struct page *dest, struct page *src, unsigned int dest_offset,

  	     unsigned int src_offset, size_t len,
  	     struct async_submit_ctl *submit)

  {

  	struct dma_chan *chan = async_tx_find_channel(submit, DMA_MEMCPY,

  						      &dest, 1, &src, 1, len);

  	struct dma_device *device = chan ? chan->device : NULL;

  	struct dma_async_tx_descriptor *tx = NULL;

  	if (device && is_dma_copy_aligned(device, src_offset, dest_offset, len)) {

  		dma_addr_t dma_dest, dma_src;

  		unsigned long dma_prep_flags = 0;

  		if (submit->cb_fn)
  			dma_prep_flags |= DMA_PREP_INTERRUPT;
  		if (submit->flags & ASYNC_TX_FENCE)
  			dma_prep_flags |= DMA_PREP_FENCE;

  		dma_dest = dma_map_page(device->dev, dest, dest_offset, len,
  					DMA_FROM_DEVICE);

  		dma_src = dma_map_page(device->dev, src, src_offset, len,
  				       DMA_TO_DEVICE);

  		tx = device->device_prep_dma_memcpy(chan, dma_dest, dma_src,

  						    len, dma_prep_flags);

  	}

  	if (tx) {

  		pr_debug("%s: (async) len: %zu
  ", __func__, len);

  		async_tx_submit(chan, tx, submit);

  	} else {

  		void *dest_buf, *src_buf;

  		pr_debug("%s: (sync) len: %zu
  ", __func__, len);

  
  		/* wait for any prerequisite operations */

  		async_tx_quiesce(&submit->depend_tx);

  		dest_buf = kmap_atomic(dest, KM_USER0) + dest_offset;
  		src_buf = kmap_atomic(src, KM_USER1) + src_offset;

  
  		memcpy(dest_buf, src_buf, len);

  		kunmap_atomic(src_buf, KM_USER1);

  		kunmap_atomic(dest_buf, KM_USER0);

  		async_tx_sync_epilog(submit);

  	}
  
  	return tx;
  }
  EXPORT_SYMBOL_GPL(async_memcpy);

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