// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Asynchronous RAID-6 recovery calculations ASYNC_TX API.
 * Copyright(c) 2009 Intel Corporation
 *
 * based on raid6recov.c:
 *   Copyright 2002 H. Peter Anvin
 */
#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/dmaengine.h>

static struct dma_async_tx_descriptor *
async_sum_product(struct page *dest, unsigned int d_off,
                struct page **srcs, unsigned int *src_offs, 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;
        struct dmaengine_unmap_data *unmap = NULL;
        const u8 *amul, *bmul;
        u8 ax, bx;
        u8 *a, *b, *c;

        if (dma)
                unmap = dmaengine_get_unmap_data(dma->dev, 3, GFP_NOWAIT);

        if (unmap) {
                struct device *dev = dma->dev;
                dma_addr_t pq[2];
                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;
                unmap->addr[0] = dma_map_page(dev, srcs[0], src_offs[0],
                                                len, DMA_TO_DEVICE);
                unmap->addr[1] = dma_map_page(dev, srcs[1], src_offs[1],
                                                len, DMA_TO_DEVICE);
                unmap->to_cnt = 2;

                unmap->addr[2] = dma_map_page(dev, dest, d_off,
                                                len, DMA_BIDIRECTIONAL);
                unmap->bidi_cnt = 1;
                /* engine only looks at Q, but expects it to follow P */
                pq[1] = unmap->addr[2];

                unmap->len = len;
                tx = dma->device_prep_dma_pq(chan, pq, unmap->addr, 2, coef,
                                             len, dma_flags);
                if (tx) {
                        dma_set_unmap(tx, unmap);
                        async_tx_submit(chan, tx, submit);
                        dmaengine_unmap_put(unmap);
                        return tx;
                }

                /* could not get a descriptor, unmap and fall through to
                 * the synchronous path
                 */
                dmaengine_unmap_put(unmap);
        }

        /* 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]) + src_offs[0];
        b = page_address(srcs[1]) + src_offs[1];
        c = page_address(dest) + d_off;

        while (len--) {
                ax    = amul[*a++];
                bx    = bmul[*b++];
                *c++ = ax ^ bx;
        }

        return NULL;
}

static struct dma_async_tx_descriptor *
async_mult(struct page *dest, unsigned int d_off, struct page *src,
                unsigned int s_off, 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;
        struct dmaengine_unmap_data *unmap = NULL;
        const u8 *qmul; /* Q multiplier table */
        u8 *d, *s;

        if (dma)
                unmap = dmaengine_get_unmap_data(dma->dev, 3, GFP_NOWAIT);

        if (unmap) {
                dma_addr_t dma_dest[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;
                unmap->addr[0] = dma_map_page(dev, src, s_off,
                                                len, DMA_TO_DEVICE);
                unmap->to_cnt++;
                unmap->addr[1] = dma_map_page(dev, dest, d_off,
                                                len, DMA_BIDIRECTIONAL);
                dma_dest[1] = unmap->addr[1];
                unmap->bidi_cnt++;
                unmap->len = len;

                /* this looks funny, but the engine looks for Q at
                 * dma_dest[1] and ignores dma_dest[0] as a dest
                 * due to DMA_PREP_PQ_DISABLE_P
                 */
                tx = dma->device_prep_dma_pq(chan, dma_dest, unmap->addr,
                                             1, &coef, len, dma_flags);

                if (tx) {
                        dma_set_unmap(tx, unmap);
                        dmaengine_unmap_put(unmap);
                        async_tx_submit(chan, tx, submit);
                        return tx;
                }

                /* could not get a descriptor, unmap and fall through to
                 * the synchronous path
                 */
                dmaengine_unmap_put(unmap);
        }

        /* 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) + d_off;
        s = page_address(src) + s_off;

        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, unsigned int *offs,
                struct async_submit_ctl *submit)
{
        struct dma_async_tx_descriptor *tx = NULL;
        struct page *p, *q, *a, *b;
        unsigned int p_off, q_off, a_off, b_off;
        struct page *srcs[2];
        unsigned int src_offs[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];
        p_off = offs[disks-2];
        q = blocks[disks-1];
        q_off = offs[disks-1];

        a = blocks[faila];
        a_off = offs[faila];
        b = blocks[failb];
        b_off = offs[failb];

        /* in the 4 disk case P + Pxy == P and Q + Qxy == Q */
        /* Dx = A*(P+Pxy) + B*(Q+Qxy) */
        srcs[0] = p;
        src_offs[0] = p_off;
        srcs[1] = q;
        src_offs[1] = q_off;
        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, b_off, srcs, src_offs, coef, bytes, submit);

        /* Dy = P+Pxy+Dx */
        srcs[0] = p;
        src_offs[0] = p_off;
        srcs[1] = b;
        src_offs[1] = b_off;
        init_async_submit(submit, flags | ASYNC_TX_XOR_ZERO_DST, tx, cb_fn,
                          cb_param, scribble);
        tx = async_xor_offs(a, a_off, srcs, src_offs, 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, unsigned int *offs,
                struct async_submit_ctl *submit)
{
        struct dma_async_tx_descriptor *tx = NULL;
        struct page *p, *q, *g, *dp, *dq;
        unsigned int p_off, q_off, g_off, dp_off, dq_off;
        struct page *srcs[2];
        unsigned int src_offs[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];
        p_off = offs[disks-2];
        q = blocks[disks-1];
        q_off = offs[disks-1];
        g = blocks[good];
        g_off = offs[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];
        dp_off = offs[faila];
        dq = blocks[failb];
        dq_off = offs[failb];

        init_async_submit(submit, ASYNC_TX_FENCE, tx, NULL, NULL, scribble);
        tx = async_memcpy(dp, g, dp_off, g_off, bytes, submit);
        init_async_submit(submit, ASYNC_TX_FENCE, tx, NULL, NULL, scribble);
        tx = async_mult(dq, dq_off, g, g_off,
                        raid6_gfexp[good], bytes, submit);

        /* compute P + Pxy */
        srcs[0] = dp;
        src_offs[0] = dp_off;
        srcs[1] = p;
        src_offs[1] = p_off;
        init_async_submit(submit, ASYNC_TX_FENCE|ASYNC_TX_XOR_DROP_DST, tx,
                          NULL, NULL, scribble);
        tx = async_xor_offs(dp, dp_off, srcs, src_offs, 2, bytes, submit);

        /* compute Q + Qxy */
        srcs[0] = dq;
        src_offs[0] = dq_off;
        srcs[1] = q;
        src_offs[1] = q_off;
        init_async_submit(submit, ASYNC_TX_FENCE|ASYNC_TX_XOR_DROP_DST, tx,
                          NULL, NULL, scribble);
        tx = async_xor_offs(dq, dq_off, srcs, src_offs, 2, bytes, submit);

        /* Dx = A*(P+Pxy) + B*(Q+Qxy) */
        srcs[0] = dp;
        src_offs[0] = dp_off;
        srcs[1] = dq;
        src_offs[1] = dq_off;
        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, dq_off, srcs, src_offs, coef, bytes, submit);

        /* Dy = P+Pxy+Dx */
        srcs[0] = dp;
        src_offs[0] = dp_off;
        srcs[1] = dq;
        src_offs[1] = dq_off;
        init_async_submit(submit, flags | ASYNC_TX_XOR_DROP_DST, tx, cb_fn,
                          cb_param, scribble);
        tx = async_xor_offs(dp, dp_off, srcs, src_offs, 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, unsigned int *offs,
                  struct async_submit_ctl *submit)
{
        struct dma_async_tx_descriptor *tx = NULL;
        struct page *p, *q, *dp, *dq;
        unsigned int p_off, q_off, dp_off, dq_off;
        struct page *srcs[2];
        unsigned int src_offs[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];
        p_off = offs[disks-2];
        q = blocks[disks-1];
        q_off = offs[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];
        dp_off = offs[faila];
        blocks[faila] = NULL;
        blocks[disks-2] = dp;
        offs[disks-2] = dp_off;
        dq = blocks[failb];
        dq_off = offs[failb];
        blocks[failb] = NULL;
        blocks[disks-1] = dq;
        offs[disks-1] = dq_off;

        init_async_submit(submit, ASYNC_TX_FENCE, tx, NULL, NULL, scribble);
        tx = async_gen_syndrome(blocks, offs, disks, bytes, submit);

        /* Restore pointer table */
        blocks[faila]   = dp;
        offs[faila] = dp_off;
        blocks[failb]   = dq;
        offs[failb] = dq_off;
        blocks[disks-2] = p;
        offs[disks-2] = p_off;
        blocks[disks-1] = q;
        offs[disks-1] = q_off;

        /* compute P + Pxy */
        srcs[0] = dp;
        src_offs[0] = dp_off;
        srcs[1] = p;
        src_offs[1] = p_off;
        init_async_submit(submit, ASYNC_TX_FENCE|ASYNC_TX_XOR_DROP_DST, tx,
                          NULL, NULL, scribble);
        tx = async_xor_offs(dp, dp_off, srcs, src_offs, 2, bytes, submit);

        /* compute Q + Qxy */
        srcs[0] = dq;
        src_offs[0] = dq_off;
        srcs[1] = q;
        src_offs[1] = q_off;
        init_async_submit(submit, ASYNC_TX_FENCE|ASYNC_TX_XOR_DROP_DST, tx,
                          NULL, NULL, scribble);
        tx = async_xor_offs(dq, dq_off, srcs, src_offs, 2, bytes, submit);

        /* Dx = A*(P+Pxy) + B*(Q+Qxy) */
        srcs[0] = dp;
        src_offs[0] = dp_off;
        srcs[1] = dq;
        src_offs[1] = dq_off;
        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, dq_off, srcs, src_offs, coef, bytes, submit);

        /* Dy = P+Pxy+Dx */
        srcs[0] = dp;
        src_offs[0] = dp_off;
        srcs[1] = dq;
        src_offs[1] = dq_off;
        init_async_submit(submit, flags | ASYNC_TX_XOR_DROP_DST, tx, cb_fn,
                          cb_param, scribble);
        tx = async_xor_offs(dp, dp_off, srcs, src_offs, 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
 * @offs: array of offset for pages in blocks
 * @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, unsigned int *offs,
                        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\n", __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] = raid6_get_zero_page();
                        else
                                ptrs[i] = page_address(blocks[i]) + offs[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, offs, 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, offs, submit);
        default:
                return __2data_recov_n(disks, bytes, faila, failb,
                                blocks, offs, 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
 * @offs: array of offset for pages in blocks
 * @submit: submission/completion modifiers
 */
struct dma_async_tx_descriptor *
async_raid6_datap_recov(int disks, size_t bytes, int faila,
                        struct page **blocks, unsigned int *offs,
                        struct async_submit_ctl *submit)
{
        struct dma_async_tx_descriptor *tx = NULL;
        struct page *p, *q, *dq;
        unsigned int p_off, q_off, dq_off;
        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];
        unsigned int src_offs[2];

        pr_debug("%s: disks: %d len: %zu\n", __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] = raid6_get_zero_page();
                        else
                                ptrs[i] = page_address(blocks[i]) + offs[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];
        p_off = offs[disks-2];
        q = blocks[disks-1];
        q_off = offs[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];
        dq_off = offs[faila];
        blocks[faila] = NULL;
        blocks[disks-1] = dq;
        offs[disks-1] = dq_off;

        /* 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];
                unsigned int g_off = offs[good];

                init_async_submit(submit, ASYNC_TX_FENCE, tx, NULL, NULL,
                                  scribble);
                tx = async_memcpy(p, g, p_off, g_off, bytes, submit);

                init_async_submit(submit, ASYNC_TX_FENCE, tx, NULL, NULL,
                                  scribble);
                tx = async_mult(dq, dq_off, g, g_off,
                                raid6_gfexp[good], bytes, submit);
        } else {
                init_async_submit(submit, ASYNC_TX_FENCE, tx, NULL, NULL,
                                  scribble);
                tx = async_gen_syndrome(blocks, offs, disks, bytes, submit);
        }

        /* Restore pointer table */
        blocks[faila]   = dq;
        offs[faila] = dq_off;
        blocks[disks-1] = q;
        offs[disks-1] = q_off;

        /* calculate g^{-faila} */
        coef = raid6_gfinv[raid6_gfexp[faila]];

        srcs[0] = dq;
        src_offs[0] = dq_off;
        srcs[1] = q;
        src_offs[1] = q_off;
        init_async_submit(submit, ASYNC_TX_FENCE|ASYNC_TX_XOR_DROP_DST, tx,
                          NULL, NULL, scribble);
        tx = async_xor_offs(dq, dq_off, srcs, src_offs, 2, bytes, submit);

        init_async_submit(submit, ASYNC_TX_FENCE, tx, NULL, NULL, scribble);
        tx = async_mult(dq, dq_off, dq, dq_off, coef, bytes, submit);

        srcs[0] = p;
        src_offs[0] = p_off;
        srcs[1] = dq;
        src_offs[1] = dq_off;
        init_async_submit(submit, flags | ASYNC_TX_XOR_DROP_DST, tx, cb_fn,
                          cb_param, scribble);
        tx = async_xor_offs(p, p_off, srcs, src_offs, 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");