/*-
 * Copyright (c) 1997, 1998 Justin T. Gibbs.
 * Copyright (c) 2015-2016 The FreeBSD Foundation
 * All rights reserved.
 *
 * Portions of this software were developed by Andrew Turner
 * under sponsorship of the FreeBSD Foundation.
 *
 * Portions of this software were developed by Semihalf
 * under sponsorship of the FreeBSD Foundation.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions, and the following disclaimer,
 *    without modification, immediately at the beginning of the file.
 * 2. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE FOR
 * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/malloc.h>
#include <sys/bus.h>
#include <sys/interrupt.h>
#include <sys/kernel.h>
#include <sys/ktr.h>
#include <sys/lock.h>
#include <sys/proc.h>
#include <sys/memdesc.h>
#include <sys/mutex.h>
#include <sys/sysctl.h>
#include <sys/uio.h>

#include <vm/vm.h>
#include <vm/vm_extern.h>
#include <vm/vm_kern.h>
#include <vm/vm_page.h>
#include <vm/vm_map.h>

#include <machine/atomic.h>
#include <machine/bus.h>
#include <machine/md_var.h>
#include <machine/bus_dma_impl.h>

#define MAX_BPAGES 4096

enum {
        BF_COULD_BOUNCE         = 0x01,
        BF_MIN_ALLOC_COMP       = 0x02,
        BF_KMEM_ALLOC           = 0x04,
        BF_COHERENT             = 0x10,
};

struct bounce_page;
struct bounce_zone;

struct bus_dma_tag {
        struct bus_dma_tag_common common;
        int                     map_count;
        int                     bounce_flags;
        bus_dma_segment_t       *segments;
        struct bounce_zone      *bounce_zone;
};

static SYSCTL_NODE(_hw, OID_AUTO, busdma, CTLFLAG_RD | CTLFLAG_MPSAFE, 0,
    "Busdma parameters");

struct sync_list {
        char            *vaddr;         /* kva of client data */
        bus_addr_t      paddr;          /* physical address */
        vm_page_t       pages;          /* starting page of client data */
        bus_size_t      datacount;      /* client data count */
};

struct bus_dmamap {
        STAILQ_HEAD(, bounce_page) bpages;
        int                    pagesneeded;
        int                    pagesreserved;
        bus_dma_tag_t          dmat;
        struct memdesc         mem;
        bus_dmamap_callback_t *callback;
        void                  *callback_arg;
        __sbintime_t           queued_time;
        STAILQ_ENTRY(bus_dmamap) links;
        u_int                   flags;
#define DMAMAP_COULD_BOUNCE     (1 << 0)
#define DMAMAP_FROM_DMAMEM      (1 << 1)
        int                     sync_count;
        struct sync_list        slist[];
};

static void _bus_dmamap_count_pages(bus_dma_tag_t dmat, bus_dmamap_t map,
    pmap_t pmap, void *buf, bus_size_t buflen, int flags);
static void _bus_dmamap_count_phys(bus_dma_tag_t dmat, bus_dmamap_t map,
    vm_paddr_t buf, bus_size_t buflen, int flags);

static MALLOC_DEFINE(M_BUSDMA, "busdma", "busdma metadata");

#define dmat_alignment(dmat)    ((dmat)->common.alignment)
#define dmat_bounce_flags(dmat) ((dmat)->bounce_flags)
#define dmat_boundary(dmat)     ((dmat)->common.boundary)
#define dmat_flags(dmat)        ((dmat)->common.flags)
#define dmat_highaddr(dmat)     ((dmat)->common.highaddr)
#define dmat_lowaddr(dmat)      ((dmat)->common.lowaddr)
#define dmat_lockfunc(dmat)     ((dmat)->common.lockfunc)
#define dmat_lockfuncarg(dmat)  ((dmat)->common.lockfuncarg)
#define dmat_maxsegsz(dmat)     ((dmat)->common.maxsegsz)
#define dmat_nsegments(dmat)    ((dmat)->common.nsegments)

#include "../../kern/subr_busdma_bounce.c"

/*
 * Allocate a device specific dma_tag.
 */
static int
bounce_bus_dma_tag_create(bus_dma_tag_t parent, bus_size_t alignment,
    bus_addr_t boundary, bus_addr_t lowaddr, bus_addr_t highaddr,
    bus_size_t maxsize, int nsegments, bus_size_t maxsegsz, int flags,
    bus_dma_lock_t *lockfunc, void *lockfuncarg, bus_dma_tag_t *dmat)
{
        bus_dma_tag_t newtag;
        int error;

        *dmat = NULL;
        error = common_bus_dma_tag_create(parent != NULL ? &parent->common :
            NULL, alignment, boundary, lowaddr, highaddr, maxsize, nsegments,
            maxsegsz, flags, lockfunc, lockfuncarg,
            sizeof (struct bus_dma_tag), (void **)&newtag);
        if (error != 0)
                return (error);

        newtag->common.impl = &bus_dma_bounce_impl;
        newtag->map_count = 0;
        newtag->segments = NULL;

        if ((flags & BUS_DMA_COHERENT) != 0)
                newtag->bounce_flags |= BF_COHERENT;

        if (parent != NULL) {
                if ((parent->bounce_flags & BF_COULD_BOUNCE) != 0)
                        newtag->bounce_flags |= BF_COULD_BOUNCE;

                /* Copy some flags from the parent */
                newtag->bounce_flags |= parent->bounce_flags & BF_COHERENT;
        }

        if (newtag->common.lowaddr < ptoa((vm_paddr_t)Maxmem) ||
            newtag->common.alignment > 1)
                newtag->bounce_flags |= BF_COULD_BOUNCE;

        if (((newtag->bounce_flags & BF_COULD_BOUNCE) != 0) &&
            (flags & BUS_DMA_ALLOCNOW) != 0) {
                struct bounce_zone *bz;

                /* Must bounce */
                if ((error = alloc_bounce_zone(newtag)) != 0) {
                        free(newtag, M_DEVBUF);
                        return (error);
                }
                bz = newtag->bounce_zone;

                if (ptoa(bz->total_bpages) < maxsize) {
                        int pages;

                        pages = atop(round_page(maxsize)) - bz->total_bpages;

                        /* Add pages to our bounce pool */
                        if (alloc_bounce_pages(newtag, pages) < pages)
                                error = ENOMEM;
                }
                /* Performed initial allocation */
                newtag->bounce_flags |= BF_MIN_ALLOC_COMP;
        } else
                error = 0;

        if (error != 0)
                free(newtag, M_DEVBUF);
        else
                *dmat = newtag;
        CTR4(KTR_BUSDMA, "%s returned tag %p tag flags 0x%x error %d",
            __func__, newtag, (newtag != NULL ? newtag->common.flags : 0),
            error);
        return (error);
}

static int
bounce_bus_dma_tag_destroy(bus_dma_tag_t dmat)
{
        int error = 0;

        if (dmat != NULL) {
                if (dmat->map_count != 0) {
                        error = EBUSY;
                        goto out;
                }
                if (dmat->segments != NULL)
                        free(dmat->segments, M_DEVBUF);
                free(dmat, M_DEVBUF);
        }
out:
        CTR3(KTR_BUSDMA, "%s tag %p error %d", __func__, dmat, error);
        return (error);
}

static bus_dmamap_t
alloc_dmamap(bus_dma_tag_t dmat, int flags)
{
        u_long mapsize;
        bus_dmamap_t map;

        mapsize = sizeof(*map);
        mapsize += sizeof(struct sync_list) * dmat->common.nsegments;
        map = malloc(mapsize, M_DEVBUF, flags | M_ZERO);
        if (map == NULL)
                return (NULL);

        /* Initialize the new map */
        STAILQ_INIT(&map->bpages);

        return (map);
}

/*
 * Allocate a handle for mapping from kva/uva/physical
 * address space into bus device space.
 */
static int
bounce_bus_dmamap_create(bus_dma_tag_t dmat, int flags, bus_dmamap_t *mapp)
{
        struct bounce_zone *bz;
        int error, maxpages, pages;

        error = 0;

        if (dmat->segments == NULL) {
                dmat->segments = (bus_dma_segment_t *)malloc(
                    sizeof(bus_dma_segment_t) * dmat->common.nsegments,
                    M_DEVBUF, M_NOWAIT);
                if (dmat->segments == NULL) {
                        CTR3(KTR_BUSDMA, "%s: tag %p error %d",
                            __func__, dmat, ENOMEM);
                        return (ENOMEM);
                }
        }

        *mapp = alloc_dmamap(dmat, M_NOWAIT);
        if (*mapp == NULL) {
                CTR3(KTR_BUSDMA, "%s: tag %p error %d",
                    __func__, dmat, ENOMEM);
                return (ENOMEM);
        }

        /*
         * Bouncing might be required if the driver asks for an active
         * exclusion region, a data alignment that is stricter than 1, and/or
         * an active address boundary.
         */
        if (dmat->bounce_flags & BF_COULD_BOUNCE) {
                /* Must bounce */
                if (dmat->bounce_zone == NULL) {
                        if ((error = alloc_bounce_zone(dmat)) != 0) {
                                free(*mapp, M_DEVBUF);
                                return (error);
                        }
                }
                bz = dmat->bounce_zone;

                (*mapp)->flags = DMAMAP_COULD_BOUNCE;

                /*
                 * Attempt to add pages to our pool on a per-instance
                 * basis up to a sane limit.
                 */
                if (dmat->common.alignment > 1)
                        maxpages = MAX_BPAGES;
                else
                        maxpages = MIN(MAX_BPAGES, Maxmem -
                            atop(dmat->common.lowaddr));
                if ((dmat->bounce_flags & BF_MIN_ALLOC_COMP) == 0 ||
                    (bz->map_count > 0 && bz->total_bpages < maxpages)) {
                        pages = MAX(atop(dmat->common.maxsize), 1);
                        pages = MIN(maxpages - bz->total_bpages, pages);
                        pages = MAX(pages, 1);
                        if (alloc_bounce_pages(dmat, pages) < pages)
                                error = ENOMEM;
                        if ((dmat->bounce_flags & BF_MIN_ALLOC_COMP)
                            == 0) {
                                if (error == 0) {
                                        dmat->bounce_flags |=
                                            BF_MIN_ALLOC_COMP;
                                }
                        } else
                                error = 0;
                }
                bz->map_count++;
        }
        if (error == 0)
                dmat->map_count++;
        else
                free(*mapp, M_DEVBUF);
        CTR4(KTR_BUSDMA, "%s: tag %p tag flags 0x%x error %d",
            __func__, dmat, dmat->common.flags, error);
        return (error);
}

/*
 * Destroy a handle for mapping from kva/uva/physical
 * address space into bus device space.
 */
static int
bounce_bus_dmamap_destroy(bus_dma_tag_t dmat, bus_dmamap_t map)
{

        /* Check we are destroying the correct map type */
        if ((map->flags & DMAMAP_FROM_DMAMEM) != 0)
                panic("bounce_bus_dmamap_destroy: Invalid map freed\n");

        if (STAILQ_FIRST(&map->bpages) != NULL || map->sync_count != 0) {
                CTR3(KTR_BUSDMA, "%s: tag %p error %d", __func__, dmat, EBUSY);
                return (EBUSY);
        }
        if (dmat->bounce_zone) {
                KASSERT((map->flags & DMAMAP_COULD_BOUNCE) != 0,
                    ("%s: Bounce zone when cannot bounce", __func__));
                dmat->bounce_zone->map_count--;
        }
        free(map, M_DEVBUF);
        dmat->map_count--;
        CTR2(KTR_BUSDMA, "%s: tag %p error 0", __func__, dmat);
        return (0);
}

/*
 * Allocate a piece of memory that can be efficiently mapped into
 * bus device space based on the constraints lited in the dma tag.
 * A dmamap to for use with dmamap_load is also allocated.
 */
static int
bounce_bus_dmamem_alloc(bus_dma_tag_t dmat, void** vaddr, int flags,
    bus_dmamap_t *mapp)
{
        /*
         * XXX ARM64TODO:
         * This bus_dma implementation requires IO-Coherent architecutre.
         * If IO-Coherency is not guaranteed, the BUS_DMA_COHERENT flag has
         * to be implented using non-cacheable memory.
         */

        vm_memattr_t attr;
        int mflags;

        if (flags & BUS_DMA_NOWAIT)
                mflags = M_NOWAIT;
        else
                mflags = M_WAITOK;

        if (dmat->segments == NULL) {
                dmat->segments = (bus_dma_segment_t *)malloc(
                    sizeof(bus_dma_segment_t) * dmat->common.nsegments,
                    M_DEVBUF, mflags);
                if (dmat->segments == NULL) {
                        CTR4(KTR_BUSDMA, "%s: tag %p tag flags 0x%x error %d",
                            __func__, dmat, dmat->common.flags, ENOMEM);
                        return (ENOMEM);
                }
        }
        if (flags & BUS_DMA_ZERO)
                mflags |= M_ZERO;
        if (flags & BUS_DMA_NOCACHE)
                attr = VM_MEMATTR_UNCACHEABLE;
        else if ((flags & BUS_DMA_COHERENT) != 0 &&
            (dmat->bounce_flags & BF_COHERENT) == 0)
                /*
                 * If we have a non-coherent tag, and are trying to allocate
                 * a coherent block of memory it needs to be uncached.
                 */
                attr = VM_MEMATTR_UNCACHEABLE;
        else
                attr = VM_MEMATTR_DEFAULT;

        /*
         * Create the map, but don't set the could bounce flag as
         * this allocation should never bounce;
         */
        *mapp = alloc_dmamap(dmat, mflags);
        if (*mapp == NULL) {
                CTR4(KTR_BUSDMA, "%s: tag %p tag flags 0x%x error %d",
                    __func__, dmat, dmat->common.flags, ENOMEM);
                return (ENOMEM);
        }
        (*mapp)->flags = DMAMAP_FROM_DMAMEM;

        /*
         * Allocate the buffer from the malloc(9) allocator if...
         *  - It's small enough to fit into a single power of two sized bucket.
         *  - The alignment is less than or equal to the maximum size
         *  - The low address requirement is fulfilled.
         * else allocate non-contiguous pages if...
         *  - The page count that could get allocated doesn't exceed
         *    nsegments also when the maximum segment size is less
         *    than PAGE_SIZE.
         *  - The alignment constraint isn't larger than a page boundary.
         *  - There are no boundary-crossing constraints.
         * else allocate a block of contiguous pages because one or more of the
         * constraints is something that only the contig allocator can fulfill.
         *
         * NOTE: The (dmat->common.alignment <= dmat->maxsize) check
         * below is just a quick hack. The exact alignment guarantees
         * of malloc(9) need to be nailed down, and the code below
         * should be rewritten to take that into account.
         *
         * In the meantime warn the user if malloc gets it wrong.
         */
        if ((dmat->common.maxsize <= PAGE_SIZE) &&
           (dmat->common.alignment <= dmat->common.maxsize) &&
            dmat->common.lowaddr >= ptoa((vm_paddr_t)Maxmem) &&
            attr == VM_MEMATTR_DEFAULT) {
                *vaddr = malloc(dmat->common.maxsize, M_DEVBUF, mflags);
        } else if (dmat->common.nsegments >=
            howmany(dmat->common.maxsize, MIN(dmat->common.maxsegsz, PAGE_SIZE)) &&
            dmat->common.alignment <= PAGE_SIZE &&
            (dmat->common.boundary % PAGE_SIZE) == 0) {
                /* Page-based multi-segment allocations allowed */
                *vaddr = kmem_alloc_attr(dmat->common.maxsize, mflags,
                    0ul, dmat->common.lowaddr, attr);
                dmat->bounce_flags |= BF_KMEM_ALLOC;
        } else {
                *vaddr = kmem_alloc_contig(dmat->common.maxsize, mflags,
                    0ul, dmat->common.lowaddr, dmat->common.alignment != 0 ?
                    dmat->common.alignment : 1ul, dmat->common.boundary, attr);
                dmat->bounce_flags |= BF_KMEM_ALLOC;
        }
        if (*vaddr == NULL) {
                CTR4(KTR_BUSDMA, "%s: tag %p tag flags 0x%x error %d",
                    __func__, dmat, dmat->common.flags, ENOMEM);
                free(*mapp, M_DEVBUF);
                return (ENOMEM);
        } else if (!vm_addr_align_ok(vtophys(*vaddr), dmat->common.alignment)) {
                printf("bus_dmamem_alloc failed to align memory properly.\n");
        }
        dmat->map_count++;
        CTR4(KTR_BUSDMA, "%s: tag %p tag flags 0x%x error %d",
            __func__, dmat, dmat->common.flags, 0);
        return (0);
}

/*
 * Free a piece of memory and it's allociated dmamap, that was allocated
 * via bus_dmamem_alloc.
 */
static void
bounce_bus_dmamem_free(bus_dma_tag_t dmat, void *vaddr, bus_dmamap_t map)
{

        /*
         * Check the map came from bounce_bus_dmamem_alloc, so the map
         * should be NULL and the BF_KMEM_ALLOC flag cleared if malloc()
         * was used and set if kmem_alloc_contig() was used.
         */
        if ((map->flags & DMAMAP_FROM_DMAMEM) == 0)
                panic("bus_dmamem_free: Invalid map freed\n");
        if ((dmat->bounce_flags & BF_KMEM_ALLOC) == 0)
                free(vaddr, M_DEVBUF);
        else
                kmem_free(vaddr, dmat->common.maxsize);
        free(map, M_DEVBUF);
        dmat->map_count--;
        CTR3(KTR_BUSDMA, "%s: tag %p flags 0x%x", __func__, dmat,
            dmat->bounce_flags);
}

static void
_bus_dmamap_count_phys(bus_dma_tag_t dmat, bus_dmamap_t map, vm_paddr_t buf,
    bus_size_t buflen, int flags)
{
        bus_addr_t curaddr;
        bus_size_t sgsize;

        if ((map->flags & DMAMAP_COULD_BOUNCE) != 0 && map->pagesneeded == 0) {
                /*
                 * Count the number of bounce pages
                 * needed in order to complete this transfer
                 */
                curaddr = buf;
                while (buflen != 0) {
                        sgsize = buflen;
                        if (addr_needs_bounce(dmat, curaddr)) {
                                sgsize = MIN(sgsize,
                                    PAGE_SIZE - (curaddr & PAGE_MASK));
                                map->pagesneeded++;
                        }
                        curaddr += sgsize;
                        buflen -= sgsize;
                }
                CTR1(KTR_BUSDMA, "pagesneeded= %d\n", map->pagesneeded);
        }
}

static void
_bus_dmamap_count_pages(bus_dma_tag_t dmat, bus_dmamap_t map, pmap_t pmap,
    void *buf, bus_size_t buflen, int flags)
{
        vm_offset_t vaddr;
        vm_offset_t vendaddr;
        bus_addr_t paddr;
        bus_size_t sg_len;

        if ((map->flags & DMAMAP_COULD_BOUNCE) != 0 && map->pagesneeded == 0) {
                CTR4(KTR_BUSDMA, "lowaddr= %d Maxmem= %d, boundary= %d, "
                    "alignment= %d", dmat->common.lowaddr,
                    ptoa((vm_paddr_t)Maxmem),
                    dmat->common.boundary, dmat->common.alignment);
                CTR2(KTR_BUSDMA, "map= %p, pagesneeded= %d", map,
                    map->pagesneeded);
                /*
                 * Count the number of bounce pages
                 * needed in order to complete this transfer
                 */
                vaddr = (vm_offset_t)buf;
                vendaddr = (vm_offset_t)buf + buflen;

                while (vaddr < vendaddr) {
                        sg_len = MIN(vendaddr - vaddr,
                            PAGE_SIZE - ((vm_offset_t)vaddr & PAGE_MASK));
                        if (pmap == kernel_pmap)
                                paddr = pmap_kextract(vaddr);
                        else
                                paddr = pmap_extract(pmap, vaddr);
                        if (addr_needs_bounce(dmat, paddr)) {
                                sg_len = roundup2(sg_len,
                                    dmat->common.alignment);
                                map->pagesneeded++;
                        }
                        vaddr += sg_len;
                }
                CTR1(KTR_BUSDMA, "pagesneeded= %d\n", map->pagesneeded);
        }
}

/*
 * Utility function to load a physical buffer.  segp contains
 * the starting segment on entrace, and the ending segment on exit.
 */
static int
bounce_bus_dmamap_load_phys(bus_dma_tag_t dmat, bus_dmamap_t map,
    vm_paddr_t buf, bus_size_t buflen, int flags, bus_dma_segment_t *segs,
    int *segp)
{
        struct sync_list *sl;
        bus_size_t sgsize;
        bus_addr_t curaddr, sl_end;
        int error;

        if (segs == NULL)
                segs = dmat->segments;

        if ((dmat->bounce_flags & BF_COULD_BOUNCE) != 0) {
                _bus_dmamap_count_phys(dmat, map, buf, buflen, flags);
                if (map->pagesneeded != 0) {
                        error = _bus_dmamap_reserve_pages(dmat, map, flags);
                        if (error)
                                return (error);
                }
        }

        sl = map->slist + map->sync_count - 1;
        sl_end = 0;

        while (buflen > 0) {
                curaddr = buf;
                sgsize = buflen;
                if (((dmat->bounce_flags & BF_COULD_BOUNCE) != 0) &&
                    map->pagesneeded != 0 &&
                    addr_needs_bounce(dmat, curaddr)) {
                        sgsize = MIN(sgsize, PAGE_SIZE - (curaddr & PAGE_MASK));
                        curaddr = add_bounce_page(dmat, map, 0, curaddr,
                            sgsize);
                } else if ((dmat->bounce_flags & BF_COHERENT) == 0) {
                        if (map->sync_count > 0)
                                sl_end = sl->paddr + sl->datacount;

                        if (map->sync_count == 0 || curaddr != sl_end) {
                                if (++map->sync_count > dmat->common.nsegments)
                                        break;
                                sl++;
                                sl->vaddr = NULL;
                                sl->paddr = curaddr;
                                sl->datacount = sgsize;
                                sl->pages = PHYS_TO_VM_PAGE(curaddr);
                                KASSERT(sl->pages != NULL,
                                    ("%s: page at PA:0x%08lx is not in "
                                    "vm_page_array", __func__, curaddr));
                        } else
                                sl->datacount += sgsize;
                }
                if (!_bus_dmamap_addsegs(dmat, map, curaddr, sgsize, segs,
                    segp))
                        break;
                buf += sgsize;
                buflen -= sgsize;
        }

        /*
         * Did we fit?
         */
        return (buflen != 0 ? EFBIG : 0); /* XXX better return value here? */
}

/*
 * Utility function to load a linear buffer.  segp contains
 * the starting segment on entrace, and the ending segment on exit.
 */
static int
bounce_bus_dmamap_load_buffer(bus_dma_tag_t dmat, bus_dmamap_t map, void *buf,
    bus_size_t buflen, pmap_t pmap, int flags, bus_dma_segment_t *segs,
    int *segp)
{
        struct sync_list *sl;
        bus_size_t sgsize;
        bus_addr_t curaddr, sl_pend;
        char *kvaddr, *vaddr, *sl_vend;
        int error;

        if (segs == NULL)
                segs = dmat->segments;

        if ((dmat->bounce_flags & BF_COULD_BOUNCE) != 0) {
                _bus_dmamap_count_pages(dmat, map, pmap, buf, buflen, flags);
                if (map->pagesneeded != 0) {
                        error = _bus_dmamap_reserve_pages(dmat, map, flags);
                        if (error)
                                return (error);
                }
        }

        sl = map->slist + map->sync_count - 1;
        vaddr = buf;
        sl_pend = 0;
        sl_vend = NULL;

        while (buflen > 0) {
                /*
                 * Get the physical address for this segment.
                 */
                if (pmap == kernel_pmap) {
                        curaddr = pmap_kextract((vm_offset_t)vaddr);
                        kvaddr = vaddr;
                } else {
                        curaddr = pmap_extract(pmap, (vm_offset_t)vaddr);
                        kvaddr = NULL;
                }

                /*
                 * Compute the segment size, and adjust counts.
                 */
                sgsize = MIN(buflen, PAGE_SIZE - (curaddr & PAGE_MASK));
                if (((dmat->bounce_flags & BF_COULD_BOUNCE) != 0) &&
                    map->pagesneeded != 0 &&
                    addr_needs_bounce(dmat, curaddr)) {
                        sgsize = roundup2(sgsize, dmat->common.alignment);
                        sgsize = MIN(sgsize, buflen);
                        curaddr = add_bounce_page(dmat, map, kvaddr, curaddr,
                            sgsize);
                } else if ((dmat->bounce_flags & BF_COHERENT) == 0) {
                        if (map->sync_count > 0) {
                                sl_pend = sl->paddr + sl->datacount;
                                sl_vend = sl->vaddr + sl->datacount;
                        }

                        if (map->sync_count == 0 ||
                            (kvaddr != 0 && kvaddr != sl_vend) ||
                            (curaddr != sl_pend)) {
                                if (++map->sync_count > dmat->common.nsegments)
                                        goto cleanup;
                                sl++;
                                sl->vaddr = kvaddr;
                                sl->paddr = curaddr;
                                if (kvaddr != NULL) {
                                        sl->pages = NULL;
                                } else {
                                        sl->pages = PHYS_TO_VM_PAGE(curaddr);
                                        KASSERT(sl->pages != NULL,
                                            ("%s: page at PA:0x%08lx is not "
                                            "in vm_page_array", __func__,
                                            curaddr));
                                }
                                sl->datacount = sgsize;
                        } else
                                sl->datacount += sgsize;
                }
                if (!_bus_dmamap_addsegs(dmat, map, curaddr, sgsize, segs,
                    segp))
                        break;
                vaddr += sgsize;
                buflen -= MIN(sgsize, buflen); /* avoid underflow */
        }

cleanup:
        /*
         * Did we fit?
         */
        return (buflen != 0 ? EFBIG : 0); /* XXX better return value here? */
}

static void
bounce_bus_dmamap_waitok(bus_dma_tag_t dmat, bus_dmamap_t map,
    struct memdesc *mem, bus_dmamap_callback_t *callback, void *callback_arg)
{

        if ((map->flags & DMAMAP_COULD_BOUNCE) == 0)
                return;
        map->mem = *mem;
        map->dmat = dmat;
        map->callback = callback;
        map->callback_arg = callback_arg;
}

static bus_dma_segment_t *
bounce_bus_dmamap_complete(bus_dma_tag_t dmat, bus_dmamap_t map,
    bus_dma_segment_t *segs, int nsegs, int error)
{

        if (segs == NULL)
                segs = dmat->segments;
        return (segs);
}

/*
 * Release the mapping held by map.
 */
static void
bounce_bus_dmamap_unload(bus_dma_tag_t dmat, bus_dmamap_t map)
{
        free_bounce_pages(dmat, map);
        map->sync_count = 0;
}

static void
dma_preread_safe(char *va, size_t size)
{
        /*
         * Write back any partial cachelines immediately before and
         * after the DMA region.
         */
        if (!__is_aligned(va, dcache_line_size))
                cpu_dcache_wb_range(va, 1);
        if (!__is_aligned(va + size, dcache_line_size))
                cpu_dcache_wb_range(va + size, 1);

        cpu_dcache_inv_range(va, size);
}

static void
dma_dcache_sync(struct sync_list *sl, bus_dmasync_op_t op)
{
        uint32_t len, offset;
        vm_page_t m;
        vm_paddr_t pa;
        char *va, *tempva;
        bus_size_t size;

        offset = sl->paddr & PAGE_MASK;
        m = sl->pages;
        size = sl->datacount;
        pa = sl->paddr;

        for ( ; size != 0; size -= len, pa += len, offset = 0, ++m) {
                tempva = 0;
                if (sl->vaddr == NULL) {
                        len = min(PAGE_SIZE - offset, size);
                        tempva = pmap_quick_enter_page(m);
                        va = tempva + offset;
                        KASSERT(pa == (VM_PAGE_TO_PHYS(m) | offset),
                            ("unexpected vm_page_t phys: 0x%16lx != 0x%16lx",
                            VM_PAGE_TO_PHYS(m) | offset, pa));
                } else {
                        len = sl->datacount;
                        va = sl->vaddr;
                }

                switch (op) {
                case BUS_DMASYNC_PREWRITE:
                case BUS_DMASYNC_PREWRITE | BUS_DMASYNC_PREREAD:
                        cpu_dcache_wb_range(va, len);
                        break;
                case BUS_DMASYNC_PREREAD:
                        /*
                         * An mbuf may start in the middle of a cacheline. There
                         * will be no cpu writes to the beginning of that line
                         * (which contains the mbuf header) while dma is in
                         * progress.  Handle that case by doing a writeback of
                         * just the first cacheline before invalidating the
                         * overall buffer.  Any mbuf in a chain may have this
                         * misalignment.  Buffers which are not mbufs bounce if
                         * they are not aligned to a cacheline.
                         */
                        dma_preread_safe(va, len);
                        break;
                case BUS_DMASYNC_POSTREAD:
                case BUS_DMASYNC_POSTREAD | BUS_DMASYNC_POSTWRITE:
                        cpu_dcache_inv_range(va, len);
                        break;
                default:
                        panic("unsupported combination of sync operations: "
                              "0x%08x\n", op);
                }

                if (tempva != NULL)
                        pmap_quick_remove_page(tempva);
        }
}

static void
bounce_bus_dmamap_sync(bus_dma_tag_t dmat, bus_dmamap_t map,
    bus_dmasync_op_t op)
{
        struct bounce_page *bpage;
        struct sync_list *sl, *end;
        char *datavaddr, *tempvaddr;

        if (op == BUS_DMASYNC_POSTWRITE)
                return;

        if ((op & BUS_DMASYNC_POSTREAD) != 0) {
                /*
                 * Wait for any DMA operations to complete before the bcopy.
                 */
                fence();
        }

        if ((bpage = STAILQ_FIRST(&map->bpages)) != NULL) {
                CTR4(KTR_BUSDMA, "%s: tag %p tag flags 0x%x op 0x%x "
                    "performing bounce", __func__, dmat, dmat->common.flags,
                    op);

                if ((op & BUS_DMASYNC_PREWRITE) != 0) {
                        while (bpage != NULL) {
                                tempvaddr = NULL;
                                datavaddr = bpage->datavaddr;
                                if (datavaddr == NULL) {
                                        tempvaddr = pmap_quick_enter_page(
                                            bpage->datapage);
                                        datavaddr = tempvaddr + bpage->dataoffs;
                                }

                                bcopy(datavaddr, bpage->vaddr, bpage->datacount);
                                if (tempvaddr != NULL)
                                        pmap_quick_remove_page(tempvaddr);
                                if ((dmat->bounce_flags & BF_COHERENT) == 0)
                                        cpu_dcache_wb_range(bpage->vaddr,
                                            bpage->datacount);
                                bpage = STAILQ_NEXT(bpage, links);
                        }
                        dmat->bounce_zone->total_bounced++;
                } else if ((op & BUS_DMASYNC_PREREAD) != 0) {
                        while (bpage != NULL) {
                                if ((dmat->bounce_flags & BF_COHERENT) == 0)
                                        cpu_dcache_wbinv_range(bpage->vaddr,
                                            bpage->datacount);
                                bpage = STAILQ_NEXT(bpage, links);
                        }
                }

                if ((op & BUS_DMASYNC_POSTREAD) != 0) {
                        while (bpage != NULL) {
                                if ((dmat->bounce_flags & BF_COHERENT) == 0)
                                        cpu_dcache_inv_range(bpage->vaddr,
                                            bpage->datacount);
                                tempvaddr = NULL;
                                datavaddr = bpage->datavaddr;
                                if (datavaddr == NULL) {
                                        tempvaddr = pmap_quick_enter_page(
                                            bpage->datapage);
                                        datavaddr = tempvaddr + bpage->dataoffs;
                                }

                                bcopy(bpage->vaddr, datavaddr, bpage->datacount);

                                if (tempvaddr != NULL)
                                        pmap_quick_remove_page(tempvaddr);
                                bpage = STAILQ_NEXT(bpage, links);
                        }
                        dmat->bounce_zone->total_bounced++;
                }
        }

        /*
         * Cache maintenance for normal (non-COHERENT non-bounce) buffers.
         */
        if (map->sync_count != 0) {
                sl = &map->slist[0];
                end = &map->slist[map->sync_count];
                CTR3(KTR_BUSDMA, "%s: tag %p op 0x%x "
                    "performing sync", __func__, dmat, op);

                for ( ; sl != end; ++sl)
                        dma_dcache_sync(sl, op);
        }

        if ((op & (BUS_DMASYNC_PREREAD | BUS_DMASYNC_PREWRITE)) != 0) {
                /*
                 * Wait for the bcopy to complete before any DMA operations.
                 */
                fence();
        }
}

struct bus_dma_impl bus_dma_bounce_impl = {
        .tag_create = bounce_bus_dma_tag_create,
        .tag_destroy = bounce_bus_dma_tag_destroy,
        .map_create = bounce_bus_dmamap_create,
        .map_destroy = bounce_bus_dmamap_destroy,
        .mem_alloc = bounce_bus_dmamem_alloc,
        .mem_free = bounce_bus_dmamem_free,
        .load_phys = bounce_bus_dmamap_load_phys,
        .load_buffer = bounce_bus_dmamap_load_buffer,
        .load_ma = bus_dmamap_load_ma_triv,
        .map_waitok = bounce_bus_dmamap_waitok,
        .map_complete = bounce_bus_dmamap_complete,
        .map_unload = bounce_bus_dmamap_unload,
        .map_sync = bounce_bus_dmamap_sync
};