/*      $NetBSD: bus_dma.c,v 1.59 2026/06/22 12:34:20 rkujawa Exp $     */

/*-
 * Copyright (c) 1996, 1997, 1998 The NetBSD Foundation, Inc.
 * All rights reserved.
 *
 * This code is derived from software contributed to The NetBSD Foundation
 * by Jason R. Thorpe of the Numerical Aerospace Simulation Facility,
 * NASA Ames Research Center.
 *
 * 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.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. 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 FOUNDATION 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.
 */

#define _POWERPC_BUS_DMA_PRIVATE

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: bus_dma.c,v 1.59 2026/06/22 12:34:20 rkujawa Exp $");

#ifdef _KERNEL_OPT
#include "opt_ppcarch.h"
#endif

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/device.h>
#include <sys/kmem.h>
#include <sys/proc.h>
#include <sys/mbuf.h>
#include <sys/bus.h>
#include <sys/intr.h>

#include <uvm/uvm.h>
#include <uvm/uvm_physseg.h>

#if defined(PPC_BOOKE)
#define EIEIO   __asm volatile("mbar\t0" ::: "memory")
#define SYNC    __asm volatile("msync" ::: "memory")
#elif defined(PPC_IBM4XX) && !defined(PPC_IBM440)
/* eieio is implemented as sync */
#define EIEIO   __asm volatile("eieio" ::: "memory")
#define SYNC    /* nothing */
#else
#define EIEIO   __asm volatile("eieio" ::: "memory")
#define SYNC    __asm volatile("sync" ::: "memory")
#endif

int     _bus_dmamap_load_buffer (bus_dma_tag_t, bus_dmamap_t, void *,
            bus_size_t, struct vmspace *, int, paddr_t *, int *, int);

static inline void
dcbst(paddr_t pa, long len, int dcache_line_size)
{
        paddr_t epa;
        for (epa = pa + len; pa < epa; pa += dcache_line_size)
                __asm volatile("dcbst 0,%0" :: "r"(pa) : "memory");
}

static inline void
dcbi(paddr_t pa, long len, int dcache_line_size)
{
        paddr_t epa;
        for (epa = pa + len; pa < epa; pa += dcache_line_size)
                __asm volatile("dcbi 0,%0" :: "r"(pa) : "memory");
}

static inline void
dcbf(paddr_t pa, long len, int dcache_line_size)
{
        paddr_t epa;
        for (epa = pa + len; pa < epa; pa += dcache_line_size)
                __asm volatile("dcbf 0,%0" :: "r"(pa) : "memory");
}

/*
 * Common function for DMA map creation.  May be called by bus-specific
 * DMA map creation functions.
 */
int
_bus_dmamap_create(bus_dma_tag_t t, bus_size_t size, int nsegments, bus_size_t maxsegsz, bus_size_t boundary, int flags, bus_dmamap_t *dmamp)
{
        struct powerpc_bus_dmamap *map;
        void *mapstore;
        size_t mapsize;

        /*
         * Allocate and initialize the DMA map.  The end of the map
         * is a variable-sized array of segments, so we allocate enough
         * room for them in one shot.
         *
         * Note we don't preserve the WAITOK or NOWAIT flags.  Preservation
         * of ALLOCNOW notifies others that we've reserved these resources,
         * and they are not to be freed.
         *
         * The bus_dmamap_t includes one bus_dma_segment_t, hence
         * the (nsegments - 1).
         */
        mapsize = sizeof(*map) + sizeof(bus_dma_segment_t [nsegments - 1]);
        if ((mapstore = kmem_intr_alloc(mapsize,
            (flags & BUS_DMA_NOWAIT) ? KM_NOSLEEP : KM_SLEEP)) == NULL)
                return (ENOMEM);

        memset(mapstore, 0, mapsize);
        map = (struct powerpc_bus_dmamap *)mapstore;
        map->_dm_size = size;
        map->_dm_segcnt = nsegments;
        map->_dm_maxmaxsegsz = maxsegsz;
        map->_dm_boundary = boundary;
        map->_dm_bounce_thresh_min = t->_bounce_thresh_min;
        map->_dm_bounce_thresh_max = t->_bounce_thresh_max;
        map->_dm_flags = flags & ~(BUS_DMA_WAITOK|BUS_DMA_NOWAIT);
        map->dm_maxsegsz = maxsegsz;
        map->dm_mapsize = 0;            /* no valid mappings */
        map->dm_nsegs = 0;

        *dmamp = map;
        return (0);
}

/*
 * Common function for DMA map destruction.  May be called by bus-specific
 * DMA map destruction functions.
 */
void
_bus_dmamap_destroy(bus_dma_tag_t t, bus_dmamap_t map)
{

        size_t mapsize = sizeof(*map)
            + sizeof(bus_dma_segment_t [map->_dm_segcnt - 1]);
        kmem_intr_free(map, mapsize);
}

/*
 * Utility function to load a linear buffer.  lastaddrp holds state
 * between invocations (for multiple-buffer loads).  segp contains
 * the starting segment on entrance, and the ending segment on exit.
 * first indicates if this is the first invocation of this function.
 */
int
_bus_dmamap_load_buffer(bus_dma_tag_t t, bus_dmamap_t map, void *buf, bus_size_t buflen, struct vmspace *vm, int flags, paddr_t *lastaddrp, int *segp, int first)
{
        bus_size_t sgsize;
        bus_addr_t curaddr, lastaddr, baddr, bmask;
        vaddr_t vaddr = (vaddr_t)buf;
        int seg;

//      printf("%s(%p,%p,%p,%u,%p,%#x,%p,%p,%u)\n", __func__,
//          t, map, buf, buflen, vm, flags, lastaddrp, segp, first);

        lastaddr = *lastaddrp;
        bmask = ~(map->_dm_boundary - 1);

        for (seg = *segp; buflen > 0 ; ) {
                /*
                 * Get the physical address for this segment.
                 */
                if (!VMSPACE_IS_KERNEL_P(vm))
                        (void) pmap_extract(vm_map_pmap(&vm->vm_map),
                            vaddr, (void *)&curaddr);
                else
                        curaddr = vtophys(vaddr);

                /*
                 * If we're beyond the bounce threshold, notify
                 * the caller.
                 */
                if (map->_dm_bounce_thresh_min != 0 &&
                    curaddr < map->_dm_bounce_thresh_min)
                        return (EINVAL);
                if (map->_dm_bounce_thresh_max != 0 &&
                    curaddr >= map->_dm_bounce_thresh_max)
                        return (EINVAL);

                /*
                 * Compute the segment size, and adjust counts.
                 */
                sgsize = PAGE_SIZE - ((u_long)vaddr & PGOFSET);
                if (buflen < sgsize)
                        sgsize = buflen;
                sgsize = uimin(sgsize, map->dm_maxsegsz);

                /*
                 * Make sure we don't cross any boundaries.
                 */
                if (map->_dm_boundary > 0) {
                        baddr = (curaddr + map->_dm_boundary) & bmask;
                        if (sgsize > (baddr - curaddr))
                                sgsize = (baddr - curaddr);
                }

                /*
                 * Insert chunk into a segment, coalescing with
                 * the previous segment if possible.
                 */
                if (first) {
                        map->dm_segs[seg].ds_addr = PHYS_TO_BUS_MEM(t, curaddr);
                        map->dm_segs[seg].ds_len = sgsize;
                        first = 0;
                } else {
                        if (curaddr == lastaddr &&
                            (map->dm_segs[seg].ds_len + sgsize) <=
                             map->dm_maxsegsz &&
                            (map->_dm_boundary == 0 ||
                             (map->dm_segs[seg].ds_addr & bmask) ==
                             (PHYS_TO_BUS_MEM(t, curaddr) & bmask)))
                                map->dm_segs[seg].ds_len += sgsize;
                        else {
                                if (++seg >= map->_dm_segcnt)
                                        break;
                                map->dm_segs[seg].ds_addr =
                                        PHYS_TO_BUS_MEM(t, curaddr);
                                map->dm_segs[seg].ds_len = sgsize;
                        }
                }

                lastaddr = curaddr + sgsize;
                vaddr += sgsize;
                buflen -= sgsize;
        }

        *segp = seg;
        *lastaddrp = lastaddr;

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

        return (0);
}

/*
 * Common function for loading a DMA map with a linear buffer.  May
 * be called by bus-specific DMA map load functions.
 */
int
_bus_dmamap_load(bus_dma_tag_t t, bus_dmamap_t map, void *buf, bus_size_t buflen, struct proc *p, int flags)
{
        paddr_t lastaddr = 0;
        int seg, error;
        struct vmspace *vm;

        /*
         * Make sure that on error condition we return "no valid mappings".
         */
        map->dm_mapsize = 0;
        map->dm_nsegs = 0;
        KASSERT(map->dm_maxsegsz <= map->_dm_maxmaxsegsz);

        if (buflen > map->_dm_size)
                return (EINVAL);

        if (p != NULL) {
                vm = p->p_vmspace;
        } else {
                vm = vmspace_kernel();
        }

        seg = 0;
        error = _bus_dmamap_load_buffer(t, map, buf, buflen, vm, flags,
                &lastaddr, &seg, 1);
        if (error == 0) {
                map->dm_mapsize = buflen;
                map->dm_nsegs = seg + 1;
        }
        return (error);
}

/*
 * Like _bus_dmamap_load(), but for mbufs.
 */
int
_bus_dmamap_load_mbuf(bus_dma_tag_t t, bus_dmamap_t map, struct mbuf *m0, int flags)
{
        paddr_t lastaddr = 0;
        int seg, error, first;
        struct mbuf *m;

        /*
         * Make sure that on error condition we return "no valid mappings."
         */
        map->dm_mapsize = 0;
        map->dm_nsegs = 0;
        KASSERT(map->dm_maxsegsz <= map->_dm_maxmaxsegsz);

#ifdef DIAGNOSTIC
        if ((m0->m_flags & M_PKTHDR) == 0)
                panic("_bus_dmamap_load_mbuf: no packet header");
#endif

        if (m0->m_pkthdr.len > map->_dm_size)
                return (EINVAL);

        first = 1;
        seg = 0;
        error = 0;
        for (m = m0; m != NULL && error == 0; m = m->m_next, first = 0) {
                if (m->m_len == 0)
                        continue;
#ifdef POOL_VTOPHYS
                /* XXX Could be better about coalescing. */
                /* XXX Doesn't check boundaries. */
                switch (m->m_flags & (M_EXT|M_EXT_CLUSTER)) {
                case M_EXT|M_EXT_CLUSTER:
                        /* XXX KDASSERT */
                        KASSERT(m->m_ext.ext_paddr != M_PADDR_INVALID);
                        lastaddr = m->m_ext.ext_paddr +
                            (m->m_data - m->m_ext.ext_buf);
 have_addr:
                        /*
                         * If we're beyond the bounce threshold, notify
                         * the caller.
                         */
                        if (map->_dm_bounce_thresh_min != 0 &&
                            lastaddr < map->_dm_bounce_thresh_min) {
                                error = EINVAL;
                                continue;
                        }
                        if (map->_dm_bounce_thresh_max != 0 &&
                            lastaddr >= map->_dm_bounce_thresh_max) {
                                error = EINVAL;
                                continue;
                        }
                        if (first == 0 && ++seg >= map->_dm_segcnt) {
                                error = EFBIG;
                                continue;
                        }
                        map->dm_segs[seg].ds_addr =
                            PHYS_TO_BUS_MEM(t, lastaddr);
                        map->dm_segs[seg].ds_len = m->m_len;
                        lastaddr += m->m_len;
                        continue;

                case 0:
                        lastaddr = m->m_paddr + M_BUFOFFSET(m) +
                            (m->m_data - M_BUFADDR(m));
                        goto have_addr;

                default:
                        break;
                }
#endif
                error = _bus_dmamap_load_buffer(t, map, m->m_data,
                    m->m_len, vmspace_kernel(), flags, &lastaddr, &seg, first);
        }
        if (error == 0) {
                map->dm_mapsize = m0->m_pkthdr.len;
                map->dm_nsegs = seg + 1;
        }
        return (error);
}

/*
 * Like _bus_dmamap_load(), but for uios.
 */
int
_bus_dmamap_load_uio(bus_dma_tag_t t, bus_dmamap_t map, struct uio *uio, int flags)
{
        paddr_t lastaddr = 0;
        int seg, i, error, first;
        bus_size_t minlen, resid;
        struct iovec *iov;
        void *addr;

        /*
         * Make sure that on error condition we return "no valid mappings."
         */
        map->dm_mapsize = 0;
        map->dm_nsegs = 0;
        KASSERT(map->dm_maxsegsz <= map->_dm_maxmaxsegsz);

        resid = uio->uio_resid;
        iov = uio->uio_iov;

        first = 1;
        seg = 0;
        error = 0;
        for (i = 0; i < uio->uio_iovcnt && resid != 0 && error == 0; i++) {
                /*
                 * Now at the first iovec to load.  Load each iovec
                 * until we have exhausted the residual count.
                 */
                minlen = resid < iov[i].iov_len ? resid : iov[i].iov_len;
                addr = (void *)iov[i].iov_base;

                error = _bus_dmamap_load_buffer(t, map, addr, minlen,
                    uio->uio_vmspace, flags, &lastaddr, &seg, first);
                first = 0;

                resid -= minlen;
        }
        if (error == 0) {
                map->dm_mapsize = uio->uio_resid;
                map->dm_nsegs = seg + 1;
        }
        return (error);
}

/*
 * Like _bus_dmamap_load(), but for raw memory allocated with
 * bus_dmamem_alloc().
 *
 * XXX This is too much copypasta of _bus_dmamap_load_buffer.
 */
int
_bus_dmamap_load_raw(bus_dma_tag_t t, bus_dmamap_t map,
    bus_dma_segment_t *segs, int nsegs, bus_size_t size, int flags)
{
        bus_size_t sgsize, isgsize;
        bus_size_t busaddr, curaddr, lastaddr, baddr, bmask;
        int seg, iseg, first;
        bus_size_t size0 = size;

        if (size == 0)
                return 0;

        lastaddr = 0;
        bmask = ~(map->_dm_boundary - 1);

        first = 1;
        iseg = 0;
        busaddr = segs[iseg].ds_addr;
        isgsize = segs[iseg].ds_len;
        for (seg = 0; size > 0;) {
                /*
                 * Get the physical address for this segment.
                 */
                curaddr = BUS_MEM_TO_PHYS(t, busaddr);

                /*
                 * If we're beyond the bounce threshold, notify
                 * the caller.
                 */
                if (map->_dm_bounce_thresh_min != 0 &&
                    curaddr < map->_dm_bounce_thresh_min)
                        return EINVAL;
                if (map->_dm_bounce_thresh_max != 0 &&
                    curaddr >= map->_dm_bounce_thresh_max)
                        return EINVAL;

                /*
                 * Compute the segment size, and adjust counts.
                 */
                sgsize = PAGE_SIZE - ((u_long)curaddr & PGOFSET);
                sgsize = MIN(sgsize, isgsize);
                sgsize = MIN(sgsize, size);
                sgsize = MIN(sgsize, map->dm_maxsegsz);

                /*
                 * Make sure we don't cross any boundaries.
                 */
                if (map->_dm_boundary > 0) {
                        baddr = (curaddr + map->_dm_boundary) & bmask;
                        if (sgsize > (baddr - curaddr))
                                sgsize = (baddr - curaddr);
                }

                /*
                 * Insert chunk into a segment, coalescing with
                 * the previous segment if possible.
                 */
                if (first) {
                        map->dm_segs[seg].ds_addr =
                            PHYS_TO_BUS_MEM(t, curaddr);
                        map->dm_segs[seg].ds_len = sgsize;
                        first = 0;
                } else {
                        if (curaddr == lastaddr &&
                            (map->dm_segs[seg].ds_len + sgsize) <=
                             map->dm_maxsegsz &&
                            (map->_dm_boundary == 0 ||
                             (map->dm_segs[seg].ds_addr & bmask) ==
                             (PHYS_TO_BUS_MEM(t, curaddr) & bmask)))
                                map->dm_segs[seg].ds_len += sgsize;
                        else {
                                if (++seg >= map->_dm_segcnt)
                                        break;
                                map->dm_segs[seg].ds_addr =
                                        PHYS_TO_BUS_MEM(t, curaddr);
                                map->dm_segs[seg].ds_len = sgsize;
                        }
                }

                lastaddr = curaddr + sgsize;
                size -= sgsize;
                if ((isgsize -= sgsize) == 0) {
                        if (++iseg == nsegs) {
                                ++seg;
                                break;
                        }
                        KASSERT(iseg < nsegs);
                        busaddr = segs[iseg].ds_addr;
                        isgsize = segs[iseg].ds_len;
                }
        }

        if (size > 0) {
                map->dm_nsegs = 0;
                map->dm_mapsize = 0;
                return EFBIG;
        }

        map->dm_nsegs = seg;
        map->dm_mapsize = size0;

        return 0;
}

/*
 * Common function for unloading a DMA map.  May be called by
 * chipset-specific DMA map unload functions.
 */
void
_bus_dmamap_unload(bus_dma_tag_t t, bus_dmamap_t map)
{

        /*
         * No resources to free; just mark the mappings as
         * invalid.
         */
        map->dm_maxsegsz = map->_dm_maxmaxsegsz;
        map->dm_mapsize = 0;
        map->dm_nsegs = 0;
}

/*
 * Common function for DMA map synchronization.  May be called
 * by chipset-specific DMA map synchronization functions.
 */
void
_bus_dmamap_sync(bus_dma_tag_t t, bus_dmamap_t map, bus_addr_t offset, bus_size_t len, int ops)
{
        const int dcache_line_size = curcpu()->ci_ci.dcache_line_size;
        const bus_dma_segment_t *ds = map->dm_segs;

//      printf("%s(%p,%p,%#x,%u,%#x) from %p\n", __func__,
//          t, map, offset, len, ops, __builtin_return_address(0));

        if ((ops & (BUS_DMASYNC_PREREAD|BUS_DMASYNC_PREWRITE)) != 0 &&
            (ops & (BUS_DMASYNC_POSTREAD|BUS_DMASYNC_POSTWRITE)) != 0)
                panic("_bus_dmamap_sync: invalid ops %#x", ops);

#ifdef DIAGNOSTIC
        if (offset + len > map->dm_mapsize)
                panic("%s: ops %#x mapsize %u: bad offset (%u) and/or length (%u)", __func__, ops, map->dm_mapsize, offset, len);
#endif

        /*
         * Skip leading amount
         */
        while (offset >= ds->ds_len) {
                offset -= ds->ds_len;
                ds++;
        }
        EIEIO;
        for (; len > 0; ds++, offset = 0) {
                bus_size_t seglen = ds->ds_len - offset;
                bus_addr_t addr = BUS_MEM_TO_PHYS(t, ds->ds_addr) + offset;
                if (seglen > len)
                        seglen = len;
                len -= seglen;
                KASSERT(ds < &map->dm_segs[map->dm_nsegs]);
                /*
                 * Readjust things to start on cacheline boundarys
                 */
                offset = (addr & (dcache_line_size-1));
                seglen += offset;
                addr -= offset;
                /*
                 * Now do the appropriate thing.
                 */
                switch (ops) {
                case BUS_DMASYNC_PREWRITE:
                        /*
                         * Make sure cache contents are in memory for the DMA.
                         */
                        dcbst(addr, seglen, dcache_line_size);
                        break;
                case BUS_DMASYNC_PREREAD:
                        /*
                         * If the region to be invalidated doesn't fall on
                         * cacheline boundary, flush that cacheline so we
                         * preserve the leading content.
                         */
                        if (offset) {
                                dcbf(addr, 1, 1);
                                /*
                                 * If we are doing <= one cache line, stop now.
                                 */
                                if (seglen <= dcache_line_size)
                                        break;
                                /*
                                 * Advance one cache line since we've flushed
                                 * this one.
                                 */
                                addr += dcache_line_size;
                                seglen -= dcache_line_size;
                        }
                        /*
                         * If the byte after the region to be invalidated
                         * doesn't fall on cacheline boundary, flush that
                         * cacheline so we preserve the trailing content.
                         */
                        if (seglen & (dcache_line_size-1)) {
                                dcbf(addr + seglen, 1, 1);
                                if (seglen <= dcache_line_size)
                                        break;
                                /*
                                 * Truncate the length to a multiple of a
                                 * dcache line size.  No reason to flush
                                 * the last entry again.
                                 */
                                seglen &= ~(dcache_line_size - 1);
                        }
                        SYNC;                   /* is this needed? */
                        EIEIO;                  /* is this needed? */
                        /* FALLTHROUGH */
                case BUS_DMASYNC_POSTREAD|BUS_DMASYNC_POSTWRITE:
                case BUS_DMASYNC_POSTREAD:
                        /*
                         * The contents will have changed, make sure to remove
                         * them from the cache.  Note: some implementation
                         * implement dcbi identically to dcbf.  Thus if the
                         * cacheline has data, it will be written to memory.
                         * If the DMA is updating the same cacheline at the
                         * time, bad things can happen.
                         */
                        dcbi(addr, seglen, dcache_line_size);
                        break;
                case BUS_DMASYNC_POSTWRITE:
                        /*
                         * Do nothing.
                         */
                        break;
                case BUS_DMASYNC_PREREAD|BUS_DMASYNC_PREWRITE:
                        /*
                         * Force it to memory and remove from cache.
                         */
                        dcbf(addr, seglen, dcache_line_size);
                        break;
                }
        }
        __asm volatile("sync");
}

/*
 * Common function for DMA-safe memory allocation.  May be called
 * by bus-specific DMA memory allocation functions.
 */
int
_bus_dmamem_alloc(bus_dma_tag_t t, bus_size_t size, bus_size_t alignment, bus_size_t boundary, bus_dma_segment_t *segs, int nsegs, int *rsegs, int flags)
{
        paddr_t start = 0xffffffff, end = 0;
        uvm_physseg_t bank;

        for (bank = uvm_physseg_get_first();
             uvm_physseg_valid_p(bank);
             bank = uvm_physseg_get_next(bank)) {
                if (start > ptoa(uvm_physseg_get_avail_start(bank)))
                        start = ptoa(uvm_physseg_get_avail_start(bank));
                if (end < ptoa(uvm_physseg_get_avail_end(bank)))
                        end = ptoa(uvm_physseg_get_avail_end(bank));
        }

        return _bus_dmamem_alloc_range(t, size, alignment, boundary, segs,
            nsegs, rsegs, flags, start, end - PAGE_SIZE);
}

/*
 * Common function for freeing DMA-safe memory.  May be called by
 * bus-specific DMA memory free functions.
 */
void
_bus_dmamem_free(bus_dma_tag_t t, bus_dma_segment_t *segs, int nsegs)
{
        struct vm_page *m;
        bus_addr_t addr;
        struct pglist mlist;
        int curseg;

        /*
         * Build a list of pages to free back to the VM system.
         */
        TAILQ_INIT(&mlist);
        for (curseg = 0; curseg < nsegs; curseg++) {
                for (addr = BUS_MEM_TO_PHYS(t, segs[curseg].ds_addr);
                    addr < (BUS_MEM_TO_PHYS(t, segs[curseg].ds_addr)
                        + segs[curseg].ds_len);
                    addr += PAGE_SIZE) {
                        m = PHYS_TO_VM_PAGE(addr);
                        TAILQ_INSERT_TAIL(&mlist, m, pageq.queue);
                }
        }

        uvm_pglistfree(&mlist);
}

/*
 * Apparently, this code was written with the assumption that OEA PowerPC
 * have bus snooping, and that the DMA_MAP_COHERENT can be a no-op.
 *
 * The 4xx, (at least some) BookE and few OEA (Wii) cores have no DMA bus
 * snooping, so a coherent mapping has to be made cache-inhibited...
 *
 * Truth is, this needs a proper refactor (perhaps using tags like arm).
 */
#if defined(PPC_IBM4XX) /* || defined(PPC_BOOKE) */
#define PPC_DMAMEM_UNCACHED(flags)      \
        (((flags) & (BUS_DMA_DONTCACHE | BUS_DMA_COHERENT)) != 0)
#else
#define PPC_DMAMEM_UNCACHED(flags)      (((flags) & BUS_DMA_DONTCACHE) != 0)
#endif

/*
 * Common function for mapping DMA-safe memory.  May be called by
 * bus-specific DMA memory map functions.
 */
int
_bus_dmamem_map(bus_dma_tag_t t, bus_dma_segment_t *segs, int nsegs, size_t size, void **kvap, int flags)
{
        vaddr_t va;
        bus_addr_t addr;
        int curseg;
        const uvm_flag_t kmflags =
            (flags & BUS_DMA_NOWAIT) != 0 ? UVM_KMF_NOWAIT : 0;

        size = round_page(size);

#ifdef PMAP_MAP_POOLPAGE
        /*
         * If we are mapping a cacheable physically contiguous segment, treat
         * it as if we are mapping a poolpage and avoid consuming any KVAs.
         */
        if (nsegs == 1 && !PPC_DMAMEM_UNCACHED(flags)) {
                KASSERT(size == segs->ds_len);
                addr = BUS_MEM_TO_PHYS(t, segs->ds_addr);
                if (__predict_true(addr + size < PMAP_DIRECT_MAPPED_LEN)) {
                        *kvap = (void *)PMAP_MAP_POOLPAGE(addr);
                        return 0;
                }
        }
#endif

        va = uvm_km_alloc(kernel_map, size, 0, UVM_KMF_VAONLY | kmflags);

        if (va == 0)
                return (ENOMEM);

        *kvap = (void *)va;

        for (curseg = 0; curseg < nsegs; curseg++) {
                for (addr = BUS_MEM_TO_PHYS(t, segs[curseg].ds_addr);
                    addr < (BUS_MEM_TO_PHYS(t, segs[curseg].ds_addr)
                        + segs[curseg].ds_len);
                    addr += PAGE_SIZE, va += PAGE_SIZE, size -= PAGE_SIZE) {
                        if (size == 0)
                                panic("_bus_dmamem_map: size botch");
                        /*
                         * If we are mapping uncached, flush the page from
                         * cache before we map it.
                         */
                        if (PPC_DMAMEM_UNCACHED(flags))
                                dcbf(addr, PAGE_SIZE,
                                    curcpu()->ci_ci.dcache_line_size);
                        pmap_kenter_pa(va, addr,
                            VM_PROT_READ | VM_PROT_WRITE,
                            PMAP_WIRED |
                            (PPC_DMAMEM_UNCACHED(flags) ? PMAP_NOCACHE : 0));
                }
        }

        return (0);
}

/*
 * Common function for unmapping DMA-safe memory.  May be called by
 * bus-specific DMA memory unmapping functions.
 */
void
_bus_dmamem_unmap(bus_dma_tag_t t, void *kva, size_t size)
{
        vaddr_t va = (vaddr_t) kva;

#ifdef DIAGNOSTIC
        if (va & PGOFSET)
                panic("_bus_dmamem_unmap");
#endif

        if (va >= VM_MIN_KERNEL_ADDRESS && va < VM_MAX_KERNEL_ADDRESS) {
                size = round_page(size);
                pmap_kremove(va, size);
                uvm_km_free(kernel_map, va, size, UVM_KMF_VAONLY);
        }
}

/*
 * Common function for mmap(2)'ing DMA-safe memory.  May be called by
 * bus-specific DMA mmap(2)'ing functions.
 */
paddr_t
_bus_dmamem_mmap(bus_dma_tag_t t, bus_dma_segment_t *segs, int nsegs, off_t off, int prot, int flags)
{
        int i;

        for (i = 0; i < nsegs; i++) {
#ifdef DIAGNOSTIC
                if (off & PGOFSET)
                        panic("_bus_dmamem_mmap: offset unaligned");
                if (BUS_MEM_TO_PHYS(t, segs[i].ds_addr) & PGOFSET)
                        panic("_bus_dmamem_mmap: segment unaligned");
                if (segs[i].ds_len & PGOFSET)
                        panic("_bus_dmamem_mmap: segment size not multiple"
                            " of page size");
#endif
                if (off >= segs[i].ds_len) {
                        off -= segs[i].ds_len;
                        continue;
                }

                return (BUS_MEM_TO_PHYS(t, segs[i].ds_addr) + off);
        }

        /* Page not found. */
        return (-1);
}

/*
 * Allocate physical memory from the given physical address range.
 * Called by DMA-safe memory allocation methods.
 */
int
_bus_dmamem_alloc_range(
        bus_dma_tag_t t,
        bus_size_t size,
        bus_size_t alignment,
        bus_size_t boundary,
        bus_dma_segment_t *segs,
        int nsegs,
        int *rsegs,
        int flags,
        paddr_t low,
        paddr_t high)
{
        paddr_t curaddr, lastaddr;
        struct vm_page *m;
        struct pglist mlist;
        int curseg, error;

        /* Always round the size. */
        size = round_page(size);

        /*
         * Allocate pages from the VM system.
         */
        error = uvm_pglistalloc(size, low, high, alignment, boundary,
            &mlist, nsegs, (flags & BUS_DMA_NOWAIT) == 0);
        if (error)
                return (error);

        /*
         * Compute the location, size, and number of segments actually
         * returned by the VM code.
         */
        m = mlist.tqh_first;
        curseg = 0;
        lastaddr = VM_PAGE_TO_PHYS(m);
        segs[curseg].ds_addr = PHYS_TO_BUS_MEM(t, lastaddr);
        segs[curseg].ds_len = PAGE_SIZE;
        m = m->pageq.queue.tqe_next;

        for (; m != NULL; m = m->pageq.queue.tqe_next) {
                curaddr = VM_PAGE_TO_PHYS(m);
#ifdef DIAGNOSTIC
                if (curaddr < low || curaddr >= high) {
                        printf("vm_page_alloc_memory returned non-sensical"
                            " address 0x%lx\n", curaddr);
                        panic("_bus_dmamem_alloc_range");
                }
#endif
                if (curaddr == (lastaddr + PAGE_SIZE))
                        segs[curseg].ds_len += PAGE_SIZE;
                else {
                        curseg++;
                        segs[curseg].ds_addr = PHYS_TO_BUS_MEM(t, curaddr);
                        segs[curseg].ds_len = PAGE_SIZE;
                }
                lastaddr = curaddr;
        }

        *rsegs = curseg + 1;

        return (0);
}

/*
 * Generic form of PHYS_TO_BUS_MEM().
 */
bus_addr_t
_bus_dma_phys_to_bus_mem_generic(bus_dma_tag_t t, bus_addr_t addr)
{

        return (addr);
}

/*
 * Generic form of BUS_MEM_TO_PHYS().
 */
bus_addr_t
_bus_dma_bus_mem_to_phys_generic(bus_dma_tag_t t, bus_addr_t addr)
{

        return (addr);
}