/*
 * 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,
                      const unsigned char *scfs, int disks,
                      struct dmaengine_unmap_data *unmap,
                      enum dma_ctrl_flags dma_flags,
                      struct async_submit_ctl *submit)
{
        struct dma_async_tx_descriptor *tx = NULL;
        struct dma_device *dma = chan->device;
        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 short pq_src_cnt;
        dma_addr_t dma_dest[2];
        int src_off = 0;

        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;
                        submit->cb_fn = NULL;
                        submit->cb_param = NULL;
                } else {
                        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;

                /* Drivers force forward progress in case they can not provide
                 * a descriptor
                 */
                for (;;) {
                        dma_dest[0] = unmap->addr[disks - 2];
                        dma_dest[1] = unmap->addr[disks - 1];
                        tx = dma->device_prep_dma_pq(chan, dma_dest,
                                                     &unmap->addr[src_off],
                                                     pq_src_cnt,
                                                     &scfs[src_off], unmap->len,
                                                     dma_flags);
                        if (likely(tx))
                                break;
                        async_tx_quiesce(&submit->depend_tx);
                        dma_async_issue_pending(chan);
                }

                dma_set_unmap(tx, unmap);
                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;
        int start = -1, stop = disks - 3;

        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;
                        if (i < disks - 2) {
                                stop = i;
                                if (start == -1)
                                        start = i;
                        }
                }
        }
        if (submit->flags & ASYNC_TX_PQ_XOR_DST) {
                BUG_ON(!raid6_call.xor_syndrome);
                if (start >= 0)
                        raid6_call.xor_syndrome(disks, start, stop, len, srcs);
        } else
                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.
 */
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;
        struct dmaengine_unmap_data *unmap = NULL;

        BUG_ON(disks > 255 || !(P(blocks, disks) || Q(blocks, disks)));

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

        /* XORing P/Q is only implemented in software */
        if (unmap && !(submit->flags & ASYNC_TX_PQ_XOR_DST) &&
            (src_cnt <= dma_maxpq(device, 0) ||
             dma_maxpq(device, DMA_PREP_CONTINUE) > 0) &&
            is_dma_pq_aligned(device, offset, 0, len)) {
                struct dma_async_tx_descriptor *tx;
                enum dma_ctrl_flags dma_flags = 0;
                unsigned char coefs[src_cnt];
                int i, j;

                /* run the p+q asynchronously */
                pr_debug("%s: (async) disks: %d len: %zu\n",
                         __func__, disks, len);

                /* convert source addresses being careful to collapse 'empty'
                 * sources and update the coefficients accordingly
                 */
                unmap->len = len;
                for (i = 0, j = 0; i < src_cnt; i++) {
                        if (blocks[i] == NULL)
                                continue;
                        unmap->addr[j] = dma_map_page(device->dev, blocks[i], offset,
                                                      len, DMA_TO_DEVICE);
                        coefs[j] = raid6_gfexp[i];
                        unmap->to_cnt++;
                        j++;
                }

                /*
                 * DMAs use destinations as sources,
                 * so use BIDIRECTIONAL mapping
                 */
                unmap->bidi_cnt++;
                if (P(blocks, disks))
                        unmap->addr[j++] = dma_map_page(device->dev, P(blocks, disks),
                                                        offset, len, DMA_BIDIRECTIONAL);
                else {
                        unmap->addr[j++] = 0;
                        dma_flags |= DMA_PREP_PQ_DISABLE_P;
                }

                unmap->bidi_cnt++;
                if (Q(blocks, disks))
                        unmap->addr[j++] = dma_map_page(device->dev, Q(blocks, disks),
                                                       offset, len, DMA_BIDIRECTIONAL);
                else {
                        unmap->addr[j++] = 0;
                        dma_flags |= DMA_PREP_PQ_DISABLE_Q;
                }

                tx = do_async_gen_syndrome(chan, coefs, j, unmap, dma_flags, submit);
                dmaengine_unmap_put(unmap);
                return tx;
        }

        dmaengine_unmap_put(unmap);

        /* run the pq synchronously */
        pr_debug("%s: (sync) disks: %d len: %zu\n", __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;
        struct dmaengine_unmap_data *unmap = NULL;

        BUG_ON(disks < 4);

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

        if (unmap && disks <= dma_maxpq(device, 0) &&
            is_dma_pq_aligned(device, offset, 0, len)) {
                struct device *dev = device->dev;
                dma_addr_t pq[2];
                int i, j = 0, src_cnt = 0;

                pr_debug("%s: (async) disks: %d len: %zu\n",
                         __func__, disks, len);

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

                if (!P(blocks, disks)) {
                        pq[0] = 0;
                        dma_flags |= DMA_PREP_PQ_DISABLE_P;
                } else {
                        pq[0] = dma_map_page(dev, P(blocks, disks),
                                             offset, len,
                                             DMA_TO_DEVICE);
                        unmap->addr[j++] = pq[0];
                        unmap->to_cnt++;
                }
                if (!Q(blocks, disks)) {
                        pq[1] = 0;
                        dma_flags |= DMA_PREP_PQ_DISABLE_Q;
                } else {
                        pq[1] = dma_map_page(dev, Q(blocks, disks),
                                             offset, len,
                                             DMA_TO_DEVICE);
                        unmap->addr[j++] = pq[1];
                        unmap->to_cnt++;
                }

                if (submit->flags & ASYNC_TX_FENCE)
                        dma_flags |= DMA_PREP_FENCE;
                for (;;) {
                        tx = device->device_prep_dma_pq_val(chan, pq,
                                                            unmap->addr,
                                                            src_cnt,
                                                            coefs,
                                                            len, pqres,
                                                            dma_flags);
                        if (likely(tx))
                                break;
                        async_tx_quiesce(&submit->depend_tx);
                        dma_async_issue_pending(chan);
                }

                dma_set_unmap(tx, unmap);
                async_tx_submit(chan, tx, submit);
        } 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\n",
                         __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);
                tx = NULL;
        }
        dmaengine_unmap_put(unmap);

        return tx;
}
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\n", __func__);

        return -ENOMEM;
}

static void __exit async_pq_exit(void)
{
        __free_page(pq_scribble_page);
}

module_init(async_pq_init);
module_exit(async_pq_exit);

MODULE_DESCRIPTION("asynchronous raid6 syndrome generation/validation");
MODULE_LICENSE("GPL");