/*
   * Asynchronous RAID-6 recovery calculations ASYNC_TX API.
   * Copyright(c) 2009 Intel Corporation
   *
   * based on raid6recov.c:
   *   Copyright 2002 H. Peter Anvin
   *
   * 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., 51
   * Franklin St - Fifth Floor, Boston, MA 02110-1301 USA.
   *
   */
  #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>
  
  static struct dma_async_tx_descriptor *
  async_sum_product(struct page *dest, struct page **srcs, unsigned char *coef,
  		  size_t len, struct async_submit_ctl *submit)
  {
  	struct dma_chan *chan = async_tx_find_channel(submit, DMA_PQ,
  						      &dest, 1, srcs, 2, len);
  	struct dma_device *dma = chan ? chan->device : NULL;
  	const u8 *amul, *bmul;
  	u8 ax, bx;
  	u8 *a, *b, *c;
  
  	if (dma) {
  		dma_addr_t dma_dest[2];
  		dma_addr_t dma_src[2];
  		struct device *dev = dma->dev;
  		struct dma_async_tx_descriptor *tx;
  		enum dma_ctrl_flags dma_flags = DMA_PREP_PQ_DISABLE_P;

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

  		dma_dest[1] = dma_map_page(dev, dest, 0, len, DMA_BIDIRECTIONAL);
  		dma_src[0] = dma_map_page(dev, srcs[0], 0, len, DMA_TO_DEVICE);
  		dma_src[1] = dma_map_page(dev, srcs[1], 0, len, DMA_TO_DEVICE);
  		tx = dma->device_prep_dma_pq(chan, dma_dest, dma_src, 2, coef,
  					     len, dma_flags);
  		if (tx) {
  			async_tx_submit(chan, tx, submit);
  			return tx;
  		}

  
  		/* could not get a descriptor, unmap and fall through to
  		 * the synchronous path
  		 */
  		dma_unmap_page(dev, dma_dest[1], len, DMA_BIDIRECTIONAL);
  		dma_unmap_page(dev, dma_src[0], len, DMA_TO_DEVICE);
  		dma_unmap_page(dev, dma_src[1], len, DMA_TO_DEVICE);

  	}
  
  	/* run the operation synchronously */
  	async_tx_quiesce(&submit->depend_tx);
  	amul = raid6_gfmul[coef[0]];
  	bmul = raid6_gfmul[coef[1]];
  	a = page_address(srcs[0]);
  	b = page_address(srcs[1]);
  	c = page_address(dest);
  
  	while (len--) {
  		ax    = amul[*a++];
  		bx    = bmul[*b++];
  		*c++ = ax ^ bx;
  	}
  
  	return NULL;
  }
  
  static struct dma_async_tx_descriptor *
  async_mult(struct page *dest, struct page *src, u8 coef, size_t len,
  	   struct async_submit_ctl *submit)
  {
  	struct dma_chan *chan = async_tx_find_channel(submit, DMA_PQ,
  						      &dest, 1, &src, 1, len);
  	struct dma_device *dma = chan ? chan->device : NULL;
  	const u8 *qmul; /* Q multiplier table */
  	u8 *d, *s;
  
  	if (dma) {
  		dma_addr_t dma_dest[2];
  		dma_addr_t dma_src[1];
  		struct device *dev = dma->dev;
  		struct dma_async_tx_descriptor *tx;
  		enum dma_ctrl_flags dma_flags = DMA_PREP_PQ_DISABLE_P;

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

  		dma_dest[1] = dma_map_page(dev, dest, 0, len, DMA_BIDIRECTIONAL);
  		dma_src[0] = dma_map_page(dev, src, 0, len, DMA_TO_DEVICE);
  		tx = dma->device_prep_dma_pq(chan, dma_dest, dma_src, 1, &coef,
  					     len, dma_flags);
  		if (tx) {
  			async_tx_submit(chan, tx, submit);
  			return tx;
  		}

  
  		/* could not get a descriptor, unmap and fall through to
  		 * the synchronous path
  		 */
  		dma_unmap_page(dev, dma_dest[1], len, DMA_BIDIRECTIONAL);
  		dma_unmap_page(dev, dma_src[0], len, DMA_TO_DEVICE);

  	}
  
  	/* no channel available, or failed to allocate a descriptor, so
  	 * perform the operation synchronously
  	 */
  	async_tx_quiesce(&submit->depend_tx);
  	qmul  = raid6_gfmul[coef];
  	d = page_address(dest);
  	s = page_address(src);
  
  	while (len--)
  		*d++ = qmul[*s++];
  
  	return NULL;
  }
  
  static struct dma_async_tx_descriptor *

  __2data_recov_4(int disks, size_t bytes, int faila, int failb,
  		struct page **blocks, struct async_submit_ctl *submit)

  {
  	struct dma_async_tx_descriptor *tx = NULL;
  	struct page *p, *q, *a, *b;
  	struct page *srcs[2];
  	unsigned char coef[2];
  	enum async_tx_flags flags = submit->flags;
  	dma_async_tx_callback cb_fn = submit->cb_fn;
  	void *cb_param = submit->cb_param;
  	void *scribble = submit->scribble;

  	p = blocks[disks-2];
  	q = blocks[disks-1];

  
  	a = blocks[faila];
  	b = blocks[failb];
  
  	/* in the 4 disk case P + Pxy == P and Q + Qxy == Q */
  	/* Dx = A*(P+Pxy) + B*(Q+Qxy) */
  	srcs[0] = p;
  	srcs[1] = q;
  	coef[0] = raid6_gfexi[failb-faila];
  	coef[1] = raid6_gfinv[raid6_gfexp[faila]^raid6_gfexp[failb]];

  	init_async_submit(submit, ASYNC_TX_FENCE, tx, NULL, NULL, scribble);

  	tx = async_sum_product(b, srcs, coef, bytes, submit);
  
  	/* Dy = P+Pxy+Dx */
  	srcs[0] = p;
  	srcs[1] = b;
  	init_async_submit(submit, flags | ASYNC_TX_XOR_ZERO_DST, tx, cb_fn,
  			  cb_param, scribble);
  	tx = async_xor(a, srcs, 0, 2, bytes, submit);
  
  	return tx;
  
  }
  
  static struct dma_async_tx_descriptor *

  __2data_recov_5(int disks, size_t bytes, int faila, int failb,
  		struct page **blocks, struct async_submit_ctl *submit)

  {
  	struct dma_async_tx_descriptor *tx = NULL;
  	struct page *p, *q, *g, *dp, *dq;
  	struct page *srcs[2];
  	unsigned char coef[2];
  	enum async_tx_flags flags = submit->flags;
  	dma_async_tx_callback cb_fn = submit->cb_fn;
  	void *cb_param = submit->cb_param;
  	void *scribble = submit->scribble;

  	int good_srcs, good, i;

  	good_srcs = 0;
  	good = -1;
  	for (i = 0; i < disks-2; i++) {
  		if (blocks[i] == NULL)
  			continue;

  		if (i == faila || i == failb)
  			continue;

  		good = i;
  		good_srcs++;

  	}

  	BUG_ON(good_srcs > 1);

  	p = blocks[disks-2];
  	q = blocks[disks-1];

  	g = blocks[good];
  
  	/* Compute syndrome with zero for the missing data pages
  	 * Use the dead data pages as temporary storage for delta p and
  	 * delta q
  	 */
  	dp = blocks[faila];
  	dq = blocks[failb];

  	init_async_submit(submit, ASYNC_TX_FENCE, tx, NULL, NULL, scribble);

  	tx = async_memcpy(dp, g, 0, 0, bytes, submit);

  	init_async_submit(submit, ASYNC_TX_FENCE, tx, NULL, NULL, scribble);

  	tx = async_mult(dq, g, raid6_gfexp[good], bytes, submit);
  
  	/* compute P + Pxy */
  	srcs[0] = dp;
  	srcs[1] = p;

  	init_async_submit(submit, ASYNC_TX_FENCE|ASYNC_TX_XOR_DROP_DST, tx,
  			  NULL, NULL, scribble);

  	tx = async_xor(dp, srcs, 0, 2, bytes, submit);
  
  	/* compute Q + Qxy */
  	srcs[0] = dq;
  	srcs[1] = q;

  	init_async_submit(submit, ASYNC_TX_FENCE|ASYNC_TX_XOR_DROP_DST, tx,
  			  NULL, NULL, scribble);

  	tx = async_xor(dq, srcs, 0, 2, bytes, submit);
  
  	/* Dx = A*(P+Pxy) + B*(Q+Qxy) */
  	srcs[0] = dp;
  	srcs[1] = dq;
  	coef[0] = raid6_gfexi[failb-faila];
  	coef[1] = raid6_gfinv[raid6_gfexp[faila]^raid6_gfexp[failb]];

  	init_async_submit(submit, ASYNC_TX_FENCE, tx, NULL, NULL, scribble);

  	tx = async_sum_product(dq, srcs, coef, bytes, submit);
  
  	/* Dy = P+Pxy+Dx */
  	srcs[0] = dp;
  	srcs[1] = dq;
  	init_async_submit(submit, flags | ASYNC_TX_XOR_DROP_DST, tx, cb_fn,
  			  cb_param, scribble);
  	tx = async_xor(dp, srcs, 0, 2, bytes, submit);
  
  	return tx;
  }
  
  static struct dma_async_tx_descriptor *
  __2data_recov_n(int disks, size_t bytes, int faila, int failb,
  	      struct page **blocks, struct async_submit_ctl *submit)
  {
  	struct dma_async_tx_descriptor *tx = NULL;
  	struct page *p, *q, *dp, *dq;
  	struct page *srcs[2];
  	unsigned char coef[2];
  	enum async_tx_flags flags = submit->flags;
  	dma_async_tx_callback cb_fn = submit->cb_fn;
  	void *cb_param = submit->cb_param;
  	void *scribble = submit->scribble;
  
  	p = blocks[disks-2];
  	q = blocks[disks-1];
  
  	/* Compute syndrome with zero for the missing data pages
  	 * Use the dead data pages as temporary storage for
  	 * delta p and delta q
  	 */
  	dp = blocks[faila];

  	blocks[faila] = NULL;

  	blocks[disks-2] = dp;
  	dq = blocks[failb];

  	blocks[failb] = NULL;

  	blocks[disks-1] = dq;

  	init_async_submit(submit, ASYNC_TX_FENCE, tx, NULL, NULL, scribble);

  	tx = async_gen_syndrome(blocks, 0, disks, bytes, submit);
  
  	/* Restore pointer table */
  	blocks[faila]   = dp;
  	blocks[failb]   = dq;
  	blocks[disks-2] = p;
  	blocks[disks-1] = q;
  
  	/* compute P + Pxy */
  	srcs[0] = dp;
  	srcs[1] = p;

  	init_async_submit(submit, ASYNC_TX_FENCE|ASYNC_TX_XOR_DROP_DST, tx,
  			  NULL, NULL, scribble);

  	tx = async_xor(dp, srcs, 0, 2, bytes, submit);
  
  	/* compute Q + Qxy */
  	srcs[0] = dq;
  	srcs[1] = q;

  	init_async_submit(submit, ASYNC_TX_FENCE|ASYNC_TX_XOR_DROP_DST, tx,
  			  NULL, NULL, scribble);

  	tx = async_xor(dq, srcs, 0, 2, bytes, submit);
  
  	/* Dx = A*(P+Pxy) + B*(Q+Qxy) */
  	srcs[0] = dp;
  	srcs[1] = dq;
  	coef[0] = raid6_gfexi[failb-faila];
  	coef[1] = raid6_gfinv[raid6_gfexp[faila]^raid6_gfexp[failb]];

  	init_async_submit(submit, ASYNC_TX_FENCE, tx, NULL, NULL, scribble);

  	tx = async_sum_product(dq, srcs, coef, bytes, submit);
  
  	/* Dy = P+Pxy+Dx */
  	srcs[0] = dp;
  	srcs[1] = dq;
  	init_async_submit(submit, flags | ASYNC_TX_XOR_DROP_DST, tx, cb_fn,
  			  cb_param, scribble);
  	tx = async_xor(dp, srcs, 0, 2, bytes, submit);
  
  	return tx;
  }
  
  /**
   * async_raid6_2data_recov - asynchronously calculate two missing data blocks
   * @disks: number of disks in the RAID-6 array
   * @bytes: block size
   * @faila: first failed drive index
   * @failb: second failed drive index
   * @blocks: array of source pointers where the last two entries are p and q
   * @submit: submission/completion modifiers
   */
  struct dma_async_tx_descriptor *
  async_raid6_2data_recov(int disks, size_t bytes, int faila, int failb,
  			struct page **blocks, struct async_submit_ctl *submit)
  {

  	void *scribble = submit->scribble;

  	int non_zero_srcs, i;

  	BUG_ON(faila == failb);
  	if (failb < faila)
  		swap(faila, failb);
  
  	pr_debug("%s: disks: %d len: %zu
  ", __func__, disks, bytes);

  	/* if a dma resource is not available or a scribble buffer is not
  	 * available punt to the synchronous path.  In the 'dma not
  	 * available' case be sure to use the scribble buffer to
  	 * preserve the content of 'blocks' as the caller intended.

  	 */

  	if (!async_dma_find_channel(DMA_PQ) || !scribble) {
  		void **ptrs = scribble ? scribble : (void **) blocks;

  
  		async_tx_quiesce(&submit->depend_tx);
  		for (i = 0; i < disks; i++)

  			if (blocks[i] == NULL)

  				ptrs[i] = (void *) raid6_empty_zero_page;

  			else
  				ptrs[i] = page_address(blocks[i]);

  
  		raid6_2data_recov(disks, bytes, faila, failb, ptrs);
  
  		async_tx_sync_epilog(submit);
  
  		return NULL;
  	}

  	non_zero_srcs = 0;
  	for (i = 0; i < disks-2 && non_zero_srcs < 4; i++)
  		if (blocks[i])
  			non_zero_srcs++;
  	switch (non_zero_srcs) {
  	case 0:
  	case 1:
  		/* There must be at least 2 sources - the failed devices. */
  		BUG();
  
  	case 2:

  		/* dma devices do not uniformly understand a zero source pq
  		 * operation (in contrast to the synchronous case), so

  		 * explicitly handle the special case of a 4 disk array with
  		 * both data disks missing.

  		 */

  		return __2data_recov_4(disks, bytes, faila, failb, blocks, submit);
  	case 3:

  		/* dma devices do not uniformly understand a single
  		 * source pq operation (in contrast to the synchronous

  		 * case), so explicitly handle the special case of a 5 disk
  		 * array with 2 of 3 data disks missing.

  		 */

  		return __2data_recov_5(disks, bytes, faila, failb, blocks, submit);

  	default:
  		return __2data_recov_n(disks, bytes, faila, failb, blocks, submit);
  	}
  }
  EXPORT_SYMBOL_GPL(async_raid6_2data_recov);
  
  /**
   * async_raid6_datap_recov - asynchronously calculate a data and the 'p' block
   * @disks: number of disks in the RAID-6 array
   * @bytes: block size
   * @faila: failed drive index
   * @blocks: array of source pointers where the last two entries are p and q
   * @submit: submission/completion modifiers
   */
  struct dma_async_tx_descriptor *
  async_raid6_datap_recov(int disks, size_t bytes, int faila,
  			struct page **blocks, struct async_submit_ctl *submit)
  {
  	struct dma_async_tx_descriptor *tx = NULL;
  	struct page *p, *q, *dq;
  	u8 coef;
  	enum async_tx_flags flags = submit->flags;
  	dma_async_tx_callback cb_fn = submit->cb_fn;
  	void *cb_param = submit->cb_param;
  	void *scribble = submit->scribble;

  	int good_srcs, good, i;

  	struct page *srcs[2];
  
  	pr_debug("%s: disks: %d len: %zu
  ", __func__, disks, bytes);

  	/* if a dma resource is not available or a scribble buffer is not
  	 * available punt to the synchronous path.  In the 'dma not
  	 * available' case be sure to use the scribble buffer to
  	 * preserve the content of 'blocks' as the caller intended.

  	 */

  	if (!async_dma_find_channel(DMA_PQ) || !scribble) {
  		void **ptrs = scribble ? scribble : (void **) blocks;

  
  		async_tx_quiesce(&submit->depend_tx);
  		for (i = 0; i < disks; i++)

  			if (blocks[i] == NULL)
  				ptrs[i] = (void*)raid6_empty_zero_page;
  			else
  				ptrs[i] = page_address(blocks[i]);

  
  		raid6_datap_recov(disks, bytes, faila, ptrs);
  
  		async_tx_sync_epilog(submit);
  
  		return NULL;
  	}

  	good_srcs = 0;
  	good = -1;
  	for (i = 0; i < disks-2; i++) {
  		if (i == faila)
  			continue;
  		if (blocks[i]) {
  			good = i;
  			good_srcs++;
  			if (good_srcs > 1)
  				break;
  		}
  	}
  	BUG_ON(good_srcs == 0);

  	p = blocks[disks-2];
  	q = blocks[disks-1];
  
  	/* Compute syndrome with zero for the missing data page
  	 * Use the dead data page as temporary storage for delta q
  	 */
  	dq = blocks[faila];

  	blocks[faila] = NULL;

  	blocks[disks-1] = dq;

  	/* in the 4-disk case we only need to perform a single source
  	 * multiplication with the one good data block.

  	 */

  	if (good_srcs == 1) {

  		struct page *g = blocks[good];

  		init_async_submit(submit, ASYNC_TX_FENCE, tx, NULL, NULL,
  				  scribble);

  		tx = async_memcpy(p, g, 0, 0, bytes, submit);

  		init_async_submit(submit, ASYNC_TX_FENCE, tx, NULL, NULL,
  				  scribble);

  		tx = async_mult(dq, g, raid6_gfexp[good], bytes, submit);
  	} else {

  		init_async_submit(submit, ASYNC_TX_FENCE, tx, NULL, NULL,
  				  scribble);

  		tx = async_gen_syndrome(blocks, 0, disks, bytes, submit);
  	}
  
  	/* Restore pointer table */
  	blocks[faila]   = dq;
  	blocks[disks-1] = q;
  
  	/* calculate g^{-faila} */
  	coef = raid6_gfinv[raid6_gfexp[faila]];
  
  	srcs[0] = dq;
  	srcs[1] = q;

  	init_async_submit(submit, ASYNC_TX_FENCE|ASYNC_TX_XOR_DROP_DST, tx,
  			  NULL, NULL, scribble);

  	tx = async_xor(dq, srcs, 0, 2, bytes, submit);

  	init_async_submit(submit, ASYNC_TX_FENCE, tx, NULL, NULL, scribble);

  	tx = async_mult(dq, dq, coef, bytes, submit);
  
  	srcs[0] = p;
  	srcs[1] = dq;
  	init_async_submit(submit, flags | ASYNC_TX_XOR_DROP_DST, tx, cb_fn,
  			  cb_param, scribble);
  	tx = async_xor(p, srcs, 0, 2, bytes, submit);
  
  	return tx;
  }
  EXPORT_SYMBOL_GPL(async_raid6_datap_recov);
  
  MODULE_AUTHOR("Dan Williams <dan.j.williams@intel.com>");
  MODULE_DESCRIPTION("asynchronous RAID-6 recovery api");
  MODULE_LICENSE("GPL");