/*
   * Copyright(c) 2007 Yuri Tikhonov <yur@emcraft.com>
   * Copyright(c) 2009 Intel Corporation
   *
   * This program is free software; you can redistribute it and/or modify it
   * under the terms of the GNU General Public License as published by the Free
   * Software Foundation; either version 2 of the License, or (at your option)
   * any later version.
   *
   * This program is distributed in the hope that 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., 59
   * Temple Place - Suite 330, Boston, MA  02111-1307, USA.
   *
   * The full GNU General Public License is included in this distribution in the
   * file called COPYING.
   */
  #include <linux/kernel.h>
  #include <linux/interrupt.h>

  #include <linux/module.h>

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

  #include <linux/gfp.h>

  
  /**

   * pq_scribble_page - space to hold throwaway P or Q buffer for
   * synchronous gen_syndrome

   */

  static struct page *pq_scribble_page;

  /* the struct page *blocks[] parameter passed to async_gen_syndrome()
   * and async_syndrome_val() contains the 'P' destination address at
   * blocks[disks-2] and the 'Q' destination address at blocks[disks-1]
   *
   * note: these are macros as they are used as lvalues
   */
  #define P(b, d) (b[d-2])
  #define Q(b, d) (b[d-1])
  
  /**
   * do_async_gen_syndrome - asynchronously calculate P and/or Q
   */
  static __async_inline struct dma_async_tx_descriptor *
  do_async_gen_syndrome(struct dma_chan *chan, struct page **blocks,
  		      const unsigned char *scfs, unsigned int offset, int disks,
  		      size_t len, dma_addr_t *dma_src,
  		      struct async_submit_ctl *submit)
  {
  	struct dma_async_tx_descriptor *tx = NULL;
  	struct dma_device *dma = chan->device;
  	enum dma_ctrl_flags dma_flags = 0;
  	enum async_tx_flags flags_orig = submit->flags;
  	dma_async_tx_callback cb_fn_orig = submit->cb_fn;
  	dma_async_tx_callback cb_param_orig = submit->cb_param;
  	int src_cnt = disks - 2;
  	unsigned char coefs[src_cnt];
  	unsigned short pq_src_cnt;
  	dma_addr_t dma_dest[2];
  	int src_off = 0;
  	int idx;
  	int i;
  
  	/* DMAs use destinations as sources, so use BIDIRECTIONAL mapping */
  	if (P(blocks, disks))
  		dma_dest[0] = dma_map_page(dma->dev, P(blocks, disks), offset,
  					   len, DMA_BIDIRECTIONAL);
  	else
  		dma_flags |= DMA_PREP_PQ_DISABLE_P;
  	if (Q(blocks, disks))
  		dma_dest[1] = dma_map_page(dma->dev, Q(blocks, disks), offset,
  					   len, DMA_BIDIRECTIONAL);
  	else
  		dma_flags |= DMA_PREP_PQ_DISABLE_Q;
  
  	/* convert source addresses being careful to collapse 'empty'
  	 * sources and update the coefficients accordingly
  	 */
  	for (i = 0, idx = 0; i < src_cnt; i++) {

  		if (blocks[i] == NULL)

  			continue;
  		dma_src[idx] = dma_map_page(dma->dev, blocks[i], offset, len,
  					    DMA_TO_DEVICE);
  		coefs[idx] = scfs[i];
  		idx++;
  	}
  	src_cnt = idx;
  
  	while (src_cnt > 0) {
  		submit->flags = flags_orig;
  		pq_src_cnt = min(src_cnt, dma_maxpq(dma, dma_flags));
  		/* if we are submitting additional pqs, leave the chain open,
  		 * clear the callback parameters, and leave the destination
  		 * buffers mapped
  		 */
  		if (src_cnt > pq_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 {
  			dma_flags &= ~DMA_COMPL_SKIP_DEST_UNMAP;
  			submit->cb_fn = cb_fn_orig;
  			submit->cb_param = cb_param_orig;
  			if (cb_fn_orig)
  				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
  		 */
  		for (;;) {
  			tx = dma->device_prep_dma_pq(chan, dma_dest,
  						     &dma_src[src_off],
  						     pq_src_cnt,
  						     &coefs[src_off], len,
  						     dma_flags);
  			if (likely(tx))
  				break;
  			async_tx_quiesce(&submit->depend_tx);
  			dma_async_issue_pending(chan);
  		}
  
  		async_tx_submit(chan, tx, submit);
  		submit->depend_tx = tx;
  
  		/* drop completed sources */
  		src_cnt -= pq_src_cnt;
  		src_off += pq_src_cnt;
  
  		dma_flags |= DMA_PREP_CONTINUE;
  	}
  
  	return tx;
  }
  
  /**
   * do_sync_gen_syndrome - synchronously calculate a raid6 syndrome
   */
  static void
  do_sync_gen_syndrome(struct page **blocks, unsigned int offset, int disks,
  		     size_t len, struct async_submit_ctl *submit)
  {
  	void **srcs;
  	int i;
  
  	if (submit->scribble)
  		srcs = submit->scribble;
  	else
  		srcs = (void **) blocks;
  
  	for (i = 0; i < disks; i++) {

  		if (blocks[i] == NULL) {

  			BUG_ON(i > disks - 3); /* P or Q can't be zero */

  			srcs[i] = (void*)raid6_empty_zero_page;

  		} else
  			srcs[i] = page_address(blocks[i]) + offset;
  	}
  	raid6_call.gen_syndrome(disks, len, srcs);
  	async_tx_sync_epilog(submit);
  }
  
  /**
   * async_gen_syndrome - asynchronously calculate a raid6 syndrome
   * @blocks: source blocks from idx 0..disks-3, P @ disks-2 and Q @ disks-1
   * @offset: common offset into each block (src and dest) to start transaction
   * @disks: number of blocks (including missing P or Q, see below)
   * @len: length of operation in bytes
   * @submit: submission/completion modifiers
   *
   * General note: This routine assumes a field of GF(2^8) with a
   * primitive polynomial of 0x11d and a generator of {02}.
   *
   * 'disks' note: callers can optionally omit either P or Q (but not
   * both) from the calculation by setting blocks[disks-2] or
   * blocks[disks-1] to NULL.  When P or Q is omitted 'len' must be <=
   * PAGE_SIZE as a temporary buffer of this size is used in the
   * synchronous path.  'disks' always accounts for both destination

   * buffers.  If any source buffers (blocks[i] where i < disks - 2) are
   * set to NULL those buffers will be replaced with the raid6_zero_page
   * in the synchronous path and omitted in the hardware-asynchronous
   * path.

   *
   * 'blocks' note: if submit->scribble is NULL then the contents of

   * 'blocks' may be overwritten to perform address conversions
   * (dma_map_page() or page_address()).

   */
  struct dma_async_tx_descriptor *
  async_gen_syndrome(struct page **blocks, unsigned int offset, int disks,
  		   size_t len, struct async_submit_ctl *submit)
  {
  	int src_cnt = disks - 2;
  	struct dma_chan *chan = async_tx_find_channel(submit, DMA_PQ,
  						      &P(blocks, disks), 2,
  						      blocks, src_cnt, len);
  	struct dma_device *device = chan ? chan->device : NULL;
  	dma_addr_t *dma_src = NULL;
  
  	BUG_ON(disks > 255 || !(P(blocks, disks) || Q(blocks, disks)));
  
  	if (submit->scribble)
  		dma_src = submit->scribble;
  	else if (sizeof(dma_addr_t) <= sizeof(struct page *))
  		dma_src = (dma_addr_t *) blocks;
  
  	if (dma_src && device &&
  	    (src_cnt <= dma_maxpq(device, 0) ||

  	     dma_maxpq(device, DMA_PREP_CONTINUE) > 0) &&
  	    is_dma_pq_aligned(device, offset, 0, len)) {

  		/* run the p+q asynchronously */
  		pr_debug("%s: (async) disks: %d len: %zu
  ",
  			 __func__, disks, len);
  		return do_async_gen_syndrome(chan, blocks, raid6_gfexp, offset,
  					     disks, len, dma_src, submit);
  	}
  
  	/* run the pq synchronously */
  	pr_debug("%s: (sync) disks: %d len: %zu
  ", __func__, disks, len);
  
  	/* wait for any prerequisite operations */
  	async_tx_quiesce(&submit->depend_tx);
  
  	if (!P(blocks, disks)) {

  		P(blocks, disks) = pq_scribble_page;

  		BUG_ON(len + offset > PAGE_SIZE);
  	}
  	if (!Q(blocks, disks)) {

  		Q(blocks, disks) = pq_scribble_page;

  		BUG_ON(len + offset > PAGE_SIZE);
  	}
  	do_sync_gen_syndrome(blocks, offset, disks, len, submit);
  
  	return NULL;
  }
  EXPORT_SYMBOL_GPL(async_gen_syndrome);

  static inline struct dma_chan *
  pq_val_chan(struct async_submit_ctl *submit, struct page **blocks, int disks, size_t len)
  {
  	#ifdef CONFIG_ASYNC_TX_DISABLE_PQ_VAL_DMA
  	return NULL;
  	#endif
  	return async_tx_find_channel(submit, DMA_PQ_VAL, NULL, 0,  blocks,
  				     disks, len);
  }

  /**
   * async_syndrome_val - asynchronously validate a raid6 syndrome
   * @blocks: source blocks from idx 0..disks-3, P @ disks-2 and Q @ disks-1
   * @offset: common offset into each block (src and dest) to start transaction
   * @disks: number of blocks (including missing P or Q, see below)
   * @len: length of operation in bytes
   * @pqres: on val failure SUM_CHECK_P_RESULT and/or SUM_CHECK_Q_RESULT are set
   * @spare: temporary result buffer for the synchronous case
   * @submit: submission / completion modifiers
   *
   * The same notes from async_gen_syndrome apply to the 'blocks',
   * and 'disks' parameters of this routine.  The synchronous path
   * requires a temporary result buffer and submit->scribble to be
   * specified.
   */
  struct dma_async_tx_descriptor *
  async_syndrome_val(struct page **blocks, unsigned int offset, int disks,
  		   size_t len, enum sum_check_flags *pqres, struct page *spare,
  		   struct async_submit_ctl *submit)
  {

  	struct dma_chan *chan = pq_val_chan(submit, blocks, disks, len);

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

  	unsigned char coefs[disks-2];

  	enum dma_ctrl_flags dma_flags = submit->cb_fn ? DMA_PREP_INTERRUPT : 0;
  	dma_addr_t *dma_src = NULL;

  	int src_cnt = 0;

  
  	BUG_ON(disks < 4);
  
  	if (submit->scribble)
  		dma_src = submit->scribble;
  	else if (sizeof(dma_addr_t) <= sizeof(struct page *))
  		dma_src = (dma_addr_t *) blocks;

  	if (dma_src && device && disks <= dma_maxpq(device, 0) &&
  	    is_dma_pq_aligned(device, offset, 0, len)) {

  		struct device *dev = device->dev;
  		dma_addr_t *pq = &dma_src[disks-2];
  		int i;
  
  		pr_debug("%s: (async) disks: %d len: %zu
  ",
  			 __func__, disks, len);
  		if (!P(blocks, disks))
  			dma_flags |= DMA_PREP_PQ_DISABLE_P;

  		else

  			pq[0] = dma_map_page(dev, P(blocks, disks),

  					     offset, len,
  					     DMA_TO_DEVICE);

  		if (!Q(blocks, disks))
  			dma_flags |= DMA_PREP_PQ_DISABLE_Q;

  		else

  			pq[1] = dma_map_page(dev, Q(blocks, disks),

  					     offset, len,
  					     DMA_TO_DEVICE);

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

  		for (i = 0; i < disks-2; i++)
  			if (likely(blocks[i])) {
  				dma_src[src_cnt] = dma_map_page(dev, blocks[i],
  								offset, len,
  								DMA_TO_DEVICE);
  				coefs[src_cnt] = raid6_gfexp[i];
  				src_cnt++;
  			}

  
  		for (;;) {
  			tx = device->device_prep_dma_pq_val(chan, pq, dma_src,

  							    src_cnt,
  							    coefs,

  							    len, pqres,
  							    dma_flags);
  			if (likely(tx))
  				break;
  			async_tx_quiesce(&submit->depend_tx);
  			dma_async_issue_pending(chan);
  		}
  		async_tx_submit(chan, tx, submit);
  
  		return tx;
  	} else {
  		struct page *p_src = P(blocks, disks);
  		struct page *q_src = Q(blocks, disks);
  		enum async_tx_flags flags_orig = submit->flags;
  		dma_async_tx_callback cb_fn_orig = submit->cb_fn;
  		void *scribble = submit->scribble;
  		void *cb_param_orig = submit->cb_param;
  		void *p, *q, *s;
  
  		pr_debug("%s: (sync) disks: %d len: %zu
  ",
  			 __func__, disks, len);
  
  		/* caller must provide a temporary result buffer and
  		 * allow the input parameters to be preserved
  		 */
  		BUG_ON(!spare || !scribble);
  
  		/* wait for any prerequisite operations */
  		async_tx_quiesce(&submit->depend_tx);
  
  		/* recompute p and/or q into the temporary buffer and then
  		 * check to see the result matches the current value
  		 */
  		tx = NULL;
  		*pqres = 0;
  		if (p_src) {
  			init_async_submit(submit, ASYNC_TX_XOR_ZERO_DST, NULL,
  					  NULL, NULL, scribble);
  			tx = async_xor(spare, blocks, offset, disks-2, len, submit);
  			async_tx_quiesce(&tx);
  			p = page_address(p_src) + offset;
  			s = page_address(spare) + offset;
  			*pqres |= !!memcmp(p, s, len) << SUM_CHECK_P;
  		}
  
  		if (q_src) {
  			P(blocks, disks) = NULL;
  			Q(blocks, disks) = spare;
  			init_async_submit(submit, 0, NULL, NULL, NULL, scribble);
  			tx = async_gen_syndrome(blocks, offset, disks, len, submit);
  			async_tx_quiesce(&tx);
  			q = page_address(q_src) + offset;
  			s = page_address(spare) + offset;
  			*pqres |= !!memcmp(q, s, len) << SUM_CHECK_Q;
  		}
  
  		/* restore P, Q and submit */
  		P(blocks, disks) = p_src;
  		Q(blocks, disks) = q_src;
  
  		submit->cb_fn = cb_fn_orig;
  		submit->cb_param = cb_param_orig;
  		submit->flags = flags_orig;
  		async_tx_sync_epilog(submit);
  
  		return NULL;
  	}
  }
  EXPORT_SYMBOL_GPL(async_syndrome_val);
  
  static int __init async_pq_init(void)
  {

  	pq_scribble_page = alloc_page(GFP_KERNEL);

  	if (pq_scribble_page)

  		return 0;
  
  	pr_err("%s: failed to allocate required spare page
  ", __func__);
  
  	return -ENOMEM;
  }
  
  static void __exit async_pq_exit(void)
  {

  	put_page(pq_scribble_page);

  }
  
  module_init(async_pq_init);
  module_exit(async_pq_exit);
  
  MODULE_DESCRIPTION("asynchronous raid6 syndrome generation/validation");
  MODULE_LICENSE("GPL");