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async_xor.c

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

static void
do_async_xor(struct dma_async_tx_descriptor *tx, struct dma_device *device,
      struct dma_chan *chan, struct page *dest, struct page **src_list,
      unsigned int offset, unsigned int src_cnt, size_t len,
      enum async_tx_flags flags, struct dma_async_tx_descriptor *depend_tx,
      dma_async_tx_callback cb_fn, void *cb_param)
{
      dma_addr_t dma_addr;
      enum dma_data_direction dir;
      int i;

      pr_debug("%s: 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);

      dir = (flags & ASYNC_TX_ASSUME_COHERENT) ?
            DMA_NONE : DMA_TO_DEVICE;

      for (i = 0; i < src_cnt; i++) {
            dma_addr = dma_map_page(device->dev, src_list[i],
                  offset, len, dir);
            tx->tx_set_src(dma_addr, tx, i);
      }

      async_tx_submit(chan, tx, flags, depend_tx, cb_fn, cb_param);
}

static void
do_sync_xor(struct page *dest, struct page **src_list, unsigned int offset,
      unsigned int src_cnt, size_t len, enum async_tx_flags flags,
      struct dma_async_tx_descriptor *depend_tx,
      dma_async_tx_callback cb_fn, void *cb_param)
{
      void *_dest;
      int i;

      pr_debug("%s: len: %zu\n", __FUNCTION__, len);

      /* reuse the 'src_list' array to convert to buffer pointers */
      for (i = 0; i < src_cnt; i++)
            src_list[i] = (struct page *)
                  (page_address(src_list[i]) + offset);

      /* set destination address */
      _dest = page_address(dest) + offset;

      if (flags & ASYNC_TX_XOR_ZERO_DST)
            memset(_dest, 0, len);

      xor_blocks(src_cnt, len, _dest,
            (void **) src_list);

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

/**
 * async_xor - attempt to xor a set of blocks with a dma engine.
 *    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.
 * @dest: destination page
 * @src_list: array of source pages (if the dest is also a source it must be
 *    at index zero).  The contents of this array may be overwritten.
 * @offset: offset in pages to start transaction
 * @src_cnt: number of source pages
 * @len: length in bytes
 * @flags: ASYNC_TX_XOR_ZERO_DST, ASYNC_TX_XOR_DROP_DEST,
 *    ASYNC_TX_ASSUME_COHERENT, ASYNC_TX_ACK, ASYNC_TX_DEP_ACK
 * @depend_tx: xor depends on the result of this transaction.
 * @cb_fn: function to call when the xor completes
 * @cb_param: parameter to pass to the callback routine
 */
struct dma_async_tx_descriptor *
async_xor(struct page *dest, struct page **src_list, unsigned int offset,
      int src_cnt, 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_XOR);
      struct dma_device *device = chan ? chan->device : NULL;
      struct dma_async_tx_descriptor *tx = NULL;
      dma_async_tx_callback _cb_fn;
      void *_cb_param;
      unsigned long local_flags;
      int xor_src_cnt;
      int i = 0, src_off = 0, int_en;

      BUG_ON(src_cnt <= 1);

      while (src_cnt) {
            local_flags = flags;
            if (device) { /* run the xor asynchronously */
                  xor_src_cnt = min(src_cnt, device->max_xor);
                  /* if we are submitting additional xors
                   * only set the callback on the last transaction
                   */
                  if (src_cnt > xor_src_cnt) {
                        local_flags &= ~ASYNC_TX_ACK;
                        _cb_fn = NULL;
                        _cb_param = NULL;
                  } else {
                        _cb_fn = cb_fn;
                        _cb_param = cb_param;
                  }

                  int_en = _cb_fn ? 1 : 0;

                  tx = device->device_prep_dma_xor(
                        chan, xor_src_cnt, len, int_en);

                  if (tx) {
                        do_async_xor(tx, device, chan, dest,
                        &src_list[src_off], offset, xor_src_cnt, len,
                        local_flags, depend_tx, _cb_fn,
                        _cb_param);
                  } else /* fall through */
                        goto xor_sync;
            } else { /* run the xor synchronously */
xor_sync:
                  /* in the sync case the dest is an implied source
                   * (assumes the dest is at the src_off index)
                   */
                  if (flags & ASYNC_TX_XOR_DROP_DST) {
                        src_cnt--;
                        src_off++;
                  }

                  /* process up to 'MAX_XOR_BLOCKS' sources */
                  xor_src_cnt = min(src_cnt, MAX_XOR_BLOCKS);

                  /* if we are submitting additional xors
                   * only set the callback on the last transaction
                   */
                  if (src_cnt > xor_src_cnt) {
                        local_flags &= ~ASYNC_TX_ACK;
                        _cb_fn = NULL;
                        _cb_param = NULL;
                  } else {
                        _cb_fn = cb_fn;
                        _cb_param = cb_param;
                  }

                  /* 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__);
                  }

                  do_sync_xor(dest, &src_list[src_off], offset,
                        xor_src_cnt, len, local_flags, depend_tx,
                        _cb_fn, _cb_param);
            }

            /* the previous tx is hidden from the client,
             * so ack it
             */
            if (i && depend_tx)
                  async_tx_ack(depend_tx);

            depend_tx = tx;

            if (src_cnt > xor_src_cnt) {
                  /* drop completed sources */
                  src_cnt -= xor_src_cnt;
                  src_off += xor_src_cnt;

                  /* unconditionally preserve the destination */
                  flags &= ~ASYNC_TX_XOR_ZERO_DST;

                  /* use the intermediate result a source, but remember
                   * it's dropped, because it's implied, in the sync case
                   */
                  src_list[--src_off] = dest;
                  src_cnt++;
                  flags |= ASYNC_TX_XOR_DROP_DST;
            } else
                  src_cnt = 0;
            i++;
      }

      return tx;
}
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);
}

/**
 * async_xor_zero_sum - 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.  The dest page must be listed as a source
 *    at index zero.  The contents of this array may be overwritten.
 * @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
 * @flags: ASYNC_TX_ASSUME_COHERENT, ASYNC_TX_ACK, ASYNC_TX_DEP_ACK
 * @depend_tx: xor depends on the result of this transaction.
 * @cb_fn: function to call when the xor completes
 * @cb_param: parameter to pass to the callback routine
 */
struct dma_async_tx_descriptor *
async_xor_zero_sum(struct page *dest, struct page **src_list,
      unsigned int offset, int src_cnt, size_t len,
      u32 *result, 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_ZERO_SUM);
      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_zero_sum(chan, src_cnt, len, result,
                  int_en) : NULL;
      int i;

      BUG_ON(src_cnt <= 1);

      if (tx) {
            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_TO_DEVICE;

            for (i = 0; i < src_cnt; i++) {
                  dma_addr = dma_map_page(device->dev, src_list[i],
                        offset, len, dir);
                  tx->tx_set_src(dma_addr, tx, i);
            }

            async_tx_submit(chan, tx, flags, depend_tx, cb_fn, cb_param);
      } else {
            unsigned long xor_flags = flags;

            pr_debug("%s: (sync) len: %zu\n", __FUNCTION__, len);

            xor_flags |= ASYNC_TX_XOR_DROP_DST;
            xor_flags &= ~ASYNC_TX_ACK;

            tx = async_xor(dest, src_list, offset, src_cnt, len, xor_flags,
                  depend_tx, NULL, NULL);

            if (tx) {
                  if (dma_wait_for_async_tx(tx) == DMA_ERROR)
                        panic("%s: DMA_ERROR waiting for tx\n",
                              __FUNCTION__);
                  async_tx_ack(tx);
            }

            *result = page_is_zero(dest, offset, len) ? 0 : 1;

            tx = NULL;

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

      return tx;
}
EXPORT_SYMBOL_GPL(async_xor_zero_sum);

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

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

module_init(async_xor_init);
module_exit(async_xor_exit);

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

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