/*
   * xor offload engine 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/kernel.h>
  #include <linux/interrupt.h>

  #include <linux/module.h>

  #include <linux/mm.h>
  #include <linux/dma-mapping.h>
  #include <linux/raid/xor.h>
  #include <linux/async_tx.h>

  /* do_async_xor - dma map the pages and perform the xor with an engine */
  static __async_inline struct dma_async_tx_descriptor *

  do_async_xor(struct dma_chan *chan, struct page *dest, struct page **src_list,

  	     unsigned int offset, int src_cnt, size_t len, dma_addr_t *dma_src,

  	     struct async_submit_ctl *submit)

  {

  	struct dma_device *dma = chan->device;

  	struct dma_async_tx_descriptor *tx = NULL;
  	int src_off = 0;

  	int i;

  	dma_async_tx_callback cb_fn_orig = submit->cb_fn;
  	void *cb_param_orig = submit->cb_param;
  	enum async_tx_flags flags_orig = submit->flags;

  	enum dma_ctrl_flags dma_flags;

  	int xor_src_cnt = 0;

  	dma_addr_t dma_dest;

  	/* map the dest bidrectional in case it is re-used as a source */
  	dma_dest = dma_map_page(dma->dev, dest, offset, len, DMA_BIDIRECTIONAL);
  	for (i = 0; i < src_cnt; i++) {
  		/* only map the dest once */

  		if (!src_list[i])
  			continue;

  		if (unlikely(src_list[i] == dest)) {

  			dma_src[xor_src_cnt++] = dma_dest;

  			continue;
  		}

  		dma_src[xor_src_cnt++] = dma_map_page(dma->dev, src_list[i], offset,
  						      len, DMA_TO_DEVICE);

  	}

  	src_cnt = xor_src_cnt;

  	while (src_cnt) {

  		submit->flags = flags_orig;

  		dma_flags = 0;

  		xor_src_cnt = min(src_cnt, (int)dma->max_xor);

  		/* if we are submitting additional xors, leave the chain open,
  		 * clear the callback parameters, and leave the destination
  		 * buffer mapped
  		 */
  		if (src_cnt > xor_src_cnt) {

  			submit->flags &= ~ASYNC_TX_ACK;

  			submit->flags |= ASYNC_TX_FENCE;

  			dma_flags = DMA_COMPL_SKIP_DEST_UNMAP;

  			submit->cb_fn = NULL;
  			submit->cb_param = NULL;

  		} else {

  			submit->cb_fn = cb_fn_orig;
  			submit->cb_param = cb_param_orig;

  		}

  		if (submit->cb_fn)

  			dma_flags |= DMA_PREP_INTERRUPT;

  		if (submit->flags & ASYNC_TX_FENCE)
  			dma_flags |= DMA_PREP_FENCE;

  		/* Since we have clobbered the src_list we are committed
  		 * to doing this asynchronously.  Drivers force forward progress
  		 * in case they can not provide a descriptor
  		 */
  		tx = dma->device_prep_dma_xor(chan, dma_dest, &dma_src[src_off],
  					      xor_src_cnt, len, dma_flags);

  		if (unlikely(!tx))

  			async_tx_quiesce(&submit->depend_tx);

  		/* spin wait for the preceding transactions to complete */

  		while (unlikely(!tx)) {
  			dma_async_issue_pending(chan);

  			tx = dma->device_prep_dma_xor(chan, dma_dest,
  						      &dma_src[src_off],
  						      xor_src_cnt, len,
  						      dma_flags);

  		}

  		async_tx_submit(chan, tx, submit);
  		submit->depend_tx = tx;

  
  		if (src_cnt > xor_src_cnt) {
  			/* drop completed sources */
  			src_cnt -= xor_src_cnt;
  			src_off += xor_src_cnt;
  
  			/* use the intermediate result a source */
  			dma_src[--src_off] = dma_dest;
  			src_cnt++;
  		} else
  			break;
  	}

  
  	return tx;

  }
  
  static void
  do_sync_xor(struct page *dest, struct page **src_list, unsigned int offset,

  	    int src_cnt, size_t len, struct async_submit_ctl *submit)

  {

  	int i;

  	int xor_src_cnt = 0;

  	int src_off = 0;
  	void *dest_buf;

  	void **srcs;

  	if (submit->scribble)
  		srcs = submit->scribble;
  	else
  		srcs = (void **) src_list;
  
  	/* convert to buffer pointers */

  	for (i = 0; i < src_cnt; i++)

  		if (src_list[i])
  			srcs[xor_src_cnt++] = page_address(src_list[i]) + offset;
  	src_cnt = xor_src_cnt;

  	/* set destination address */

  	dest_buf = page_address(dest) + offset;

  	if (submit->flags & ASYNC_TX_XOR_ZERO_DST)

  		memset(dest_buf, 0, len);

  	while (src_cnt > 0) {
  		/* process up to 'MAX_XOR_BLOCKS' sources */
  		xor_src_cnt = min(src_cnt, MAX_XOR_BLOCKS);
  		xor_blocks(xor_src_cnt, len, dest_buf, &srcs[src_off]);
  
  		/* drop completed sources */
  		src_cnt -= xor_src_cnt;
  		src_off += xor_src_cnt;
  	}

  	async_tx_sync_epilog(submit);

  }
  
  /**
   * async_xor - attempt to xor a set of blocks with a dma engine.

   * @dest: destination page

   * @src_list: array of source pages
   * @offset: common src/dst offset to start transaction

   * @src_cnt: number of source pages
   * @len: length in bytes

   * @submit: submission / completion modifiers
   *
   * honored flags: ASYNC_TX_ACK, ASYNC_TX_XOR_ZERO_DST, ASYNC_TX_XOR_DROP_DST
   *
   * xor_blocks always uses the dest as a source so the
   * ASYNC_TX_XOR_ZERO_DST flag must be set to not include dest data in
   * the calculation.  The assumption with dma eninges is that they only
   * use the destination buffer as a source when it is explicity specified
   * in the source list.
   *
   * src_list note: if the dest is also a source it must be at index zero.
   * The contents of this array will be overwritten if a scribble region
   * is not specified.

   */
  struct dma_async_tx_descriptor *
  async_xor(struct page *dest, struct page **src_list, unsigned int offset,

  	  int src_cnt, size_t len, struct async_submit_ctl *submit)

  {

  	struct dma_chan *chan = async_tx_find_channel(submit, DMA_XOR,

  						      &dest, 1, src_list,
  						      src_cnt, len);

  	dma_addr_t *dma_src = NULL;

  	BUG_ON(src_cnt <= 1);

  	if (submit->scribble)
  		dma_src = submit->scribble;
  	else if (sizeof(dma_addr_t) <= sizeof(struct page *))
  		dma_src = (dma_addr_t *) src_list;

  	if (dma_src && chan && is_dma_xor_aligned(chan->device, offset, 0, len)) {

  		/* run the xor asynchronously */
  		pr_debug("%s (async): len: %zu
  ", __func__, len);

  		return do_async_xor(chan, dest, src_list, offset, src_cnt, len,

  				    dma_src, submit);

  	} else {
  		/* run the xor synchronously */
  		pr_debug("%s (sync): len: %zu
  ", __func__, len);

  		WARN_ONCE(chan, "%s: no space for dma address conversion
  ",
  			  __func__);

  		/* in the sync case the dest is an implied source
  		 * (assumes the dest is the first source)

  		 */

  		if (submit->flags & ASYNC_TX_XOR_DROP_DST) {

  			src_cnt--;
  			src_list++;
  		}

  		/* wait for any prerequisite operations */

  		async_tx_quiesce(&submit->depend_tx);

  		do_sync_xor(dest, src_list, offset, src_cnt, len, submit);

  		return NULL;

  	}

  }
  EXPORT_SYMBOL_GPL(async_xor);
  
  static int page_is_zero(struct page *p, unsigned int offset, size_t len)
  {
  	char *a = page_address(p) + offset;
  	return ((*(u32 *) a) == 0 &&
  		memcmp(a, a + 4, len - 4) == 0);
  }

  static inline struct dma_chan *
  xor_val_chan(struct async_submit_ctl *submit, struct page *dest,
  		 struct page **src_list, int src_cnt, size_t len)
  {
  	#ifdef CONFIG_ASYNC_TX_DISABLE_XOR_VAL_DMA
  	return NULL;
  	#endif
  	return async_tx_find_channel(submit, DMA_XOR_VAL, &dest, 1, src_list,
  				     src_cnt, len);
  }

  /**

   * async_xor_val - attempt a xor parity check with a dma engine.

   * @dest: destination page used if the xor is performed synchronously

   * @src_list: array of source pages

   * @offset: offset in pages to start transaction
   * @src_cnt: number of source pages
   * @len: length in bytes
   * @result: 0 if sum == 0 else non-zero

   * @submit: submission / completion modifiers
   *
   * honored flags: ASYNC_TX_ACK
   *
   * src_list note: if the dest is also a source it must be at index zero.
   * The contents of this array will be overwritten if a scribble region
   * is not specified.

   */
  struct dma_async_tx_descriptor *

  async_xor_val(struct page *dest, struct page **src_list, unsigned int offset,

  	      int src_cnt, size_t len, enum sum_check_flags *result,

  	      struct async_submit_ctl *submit)

  {

  	struct dma_chan *chan = xor_val_chan(submit, dest, src_list, src_cnt, len);

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

  	struct dma_async_tx_descriptor *tx = NULL;

  	dma_addr_t *dma_src = NULL;

  
  	BUG_ON(src_cnt <= 1);

  	if (submit->scribble)
  		dma_src = submit->scribble;
  	else if (sizeof(dma_addr_t) <= sizeof(struct page *))
  		dma_src = (dma_addr_t *) src_list;

  	if (dma_src && device && src_cnt <= device->max_xor &&
  	    is_dma_xor_aligned(device, offset, 0, len)) {

  		unsigned long dma_prep_flags = 0;

  		int i;

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

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

  		for (i = 0; i < src_cnt; i++)
  			dma_src[i] = dma_map_page(device->dev, src_list[i],
  						  offset, len, DMA_TO_DEVICE);

  		tx = device->device_prep_dma_xor_val(chan, dma_src, src_cnt,
  						     len, result,
  						     dma_prep_flags);

  		if (unlikely(!tx)) {

  			async_tx_quiesce(&submit->depend_tx);

  			while (!tx) {

  				dma_async_issue_pending(chan);

  				tx = device->device_prep_dma_xor_val(chan,

  					dma_src, src_cnt, len, result,

  					dma_prep_flags);

  			}

  		}

  		async_tx_submit(chan, tx, submit);

  	} else {

  		enum async_tx_flags flags_orig = submit->flags;

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

  		WARN_ONCE(device && src_cnt <= device->max_xor,
  			  "%s: no space for dma address conversion
  ",
  			  __func__);

  		submit->flags |= ASYNC_TX_XOR_DROP_DST;
  		submit->flags &= ~ASYNC_TX_ACK;

  		tx = async_xor(dest, src_list, offset, src_cnt, len, submit);

  		async_tx_quiesce(&tx);

  		*result = !page_is_zero(dest, offset, len) << SUM_CHECK_P;

  		async_tx_sync_epilog(submit);
  		submit->flags = flags_orig;

  	}
  
  	return tx;
  }

  EXPORT_SYMBOL_GPL(async_xor_val);

  MODULE_AUTHOR("Intel Corporation");
  MODULE_DESCRIPTION("asynchronous xor/xor-zero-sum api");
  MODULE_LICENSE("GPL");