/*
 * 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 dmaengine_unmap_data *unmap,
             struct async_submit_ctl *submit)
{
        struct dma_device *dma = chan->device;
        struct dma_async_tx_descriptor *tx = NULL;
        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 = 0;
        int src_cnt = unmap->to_cnt;
        int xor_src_cnt;
        dma_addr_t dma_dest = unmap->addr[unmap->to_cnt];
        dma_addr_t *src_list = unmap->addr;

        while (src_cnt) {
                dma_addr_t tmp;

                submit->flags = flags_orig;
                xor_src_cnt = min(src_cnt, (int)dma->max_xor);
                /* if we are submitting additional xors, leave the chain open
                 * and clear the callback parameters
                 */
                if (src_cnt > xor_src_cnt) {
                        submit->flags &= ~ASYNC_TX_ACK;
                        submit->flags |= ASYNC_TX_FENCE;
                        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;

                /* Drivers force forward progress in case they can not provide a
                 * descriptor
                 */
                tmp = src_list[0];
                if (src_list > unmap->addr)
                        src_list[0] = dma_dest;
                tx = dma->device_prep_dma_xor(chan, dma_dest, src_list,
                                              xor_src_cnt, unmap->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,
                                                      src_list,
                                                      xor_src_cnt, unmap->len,
                                                      dma_flags);
                }
                src_list[0] = tmp;

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

                if (src_cnt > xor_src_cnt) {
                        /* drop completed sources */
                        src_cnt -= xor_src_cnt;
                        /* use the intermediate result a source */
                        src_cnt++;
                        src_list += xor_src_cnt - 1;
                } 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);
        struct dma_device *device = chan ? chan->device : NULL;
        struct dmaengine_unmap_data *unmap = NULL;

        BUG_ON(src_cnt <= 1);

        if (device)
                unmap = dmaengine_get_unmap_data(device->dev, src_cnt+1, GFP_NOWAIT);

        if (unmap && is_dma_xor_aligned(device, offset, 0, len)) {
                struct dma_async_tx_descriptor *tx;
                int i, j;

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

                unmap->len = len;
                for (i = 0, j = 0; i < src_cnt; i++) {
                        if (!src_list[i])
                                continue;
                        unmap->to_cnt++;
                        unmap->addr[j++] = dma_map_page(device->dev, src_list[i],
                                                        offset, len, DMA_TO_DEVICE);
                }

                /* map it bidirectional as it may be re-used as a source */
                unmap->addr[j] = dma_map_page(device->dev, dest, offset, len,
                                              DMA_BIDIRECTIONAL);
                unmap->bidi_cnt = 1;

                tx = do_async_xor(chan, unmap, submit);
                dmaengine_unmap_put(unmap);
                return tx;
        } else {
                dmaengine_unmap_put(unmap);
                /* run the xor synchronously */
                pr_debug("%s (sync): len: %zu\n", __func__, len);
                WARN_ONCE(chan, "%s: no space for dma address conversion\n",
                          __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)
{
        return !memchr_inv(page_address(p) + offset, 0, len);
}

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;
        struct dmaengine_unmap_data *unmap = NULL;

        BUG_ON(src_cnt <= 1);

        if (device)
                unmap = dmaengine_get_unmap_data(device->dev, src_cnt, GFP_NOWAIT);

        if (unmap && 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\n", __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++) {
                        unmap->addr[i] = dma_map_page(device->dev, src_list[i],
                                                      offset, len, DMA_TO_DEVICE);
                        unmap->to_cnt++;
                }
                unmap->len = len;

                tx = device->device_prep_dma_xor_val(chan, unmap->addr, 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,
                                        unmap->addr, src_cnt, len, result,
                                        dma_prep_flags);
                        }
                }
                dma_set_unmap(tx, unmap);
                async_tx_submit(chan, tx, submit);
        } else {
                enum async_tx_flags flags_orig = submit->flags;

                pr_debug("%s: (sync) len: %zu\n", __func__, len);
                WARN_ONCE(device && src_cnt <= device->max_xor,
                          "%s: no space for dma address conversion\n",
                          __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;
        }
        dmaengine_unmap_put(unmap);

        return tx;
}
EXPORT_SYMBOL_GPL(async_xor_val);

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