/*      $NetBSD: bus_dma.c,v 1.36 2022/07/26 20:08:54 andvar Exp $      */
/*      NetBSD: bus_dma.c,v 1.20 2000/01/10 03:24:36 simonb Exp         */

/*-
 * Copyright (c) 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.
 */

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: bus_dma.c,v 1.36 2022/07/26 20:08:54 andvar Exp $");

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

#include <uvm/uvm.h>

#include <mips/cache.h>

#define _ARC_BUS_DMA_PRIVATE
#include <sys/bus.h>

paddr_t kvtophys(vaddr_t);      /* XXX */

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

void
_bus_dma_tag_init(bus_dma_tag_t t)
{

        t->dma_offset = 0;

        t->_dmamap_create = _bus_dmamap_create;
        t->_dmamap_destroy = _bus_dmamap_destroy;
        t->_dmamap_load = _bus_dmamap_load;
        t->_dmamap_load_mbuf = _bus_dmamap_load_mbuf;
        t->_dmamap_load_uio = _bus_dmamap_load_uio;
        t->_dmamap_load_raw = _bus_dmamap_load_raw;
        t->_dmamap_unload = _bus_dmamap_unload;
        t->_dmamap_sync = _bus_dmamap_sync;
        t->_dmamem_alloc = _bus_dmamem_alloc;
        t->_dmamem_free = _bus_dmamem_free;
        t->_dmamem_map = _bus_dmamem_map;
        t->_dmamem_unmap = _bus_dmamem_unmap;
        t->_dmamem_mmap = _bus_dmamem_mmap;
}

static size_t
_bus_dmamap_mapsize(int const nsegments)
{
        KASSERT(nsegments > 0);
        return sizeof(struct arc_bus_dmamap) +
            (sizeof(bus_dma_segment_t) * (nsegments - 1));
}

/*
 * 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 arc_bus_dmamap *map;
        void *mapstore;

        /*
         * 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).
         */
        if ((mapstore = kmem_zalloc(_bus_dmamap_mapsize(nsegments),
            (flags & BUS_DMA_NOWAIT) ? KM_NOSLEEP : KM_SLEEP)) == NULL)
                return ENOMEM;

        map = (struct arc_bus_dmamap *)mapstore;
        map->_dm_size = size;
        map->_dm_segcnt = nsegments;
        map->_dm_maxmaxsegsz = maxsegsz;
        map->_dm_boundary = boundary;
        map->_dm_flags = flags & ~(BUS_DMA_WAITOK|BUS_DMA_NOWAIT);
        map->_dm_vmspace = NULL;
        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)
{

        kmem_free(map, _bus_dmamap_mapsize(map->_dm_segcnt));
}

/*
 * 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.
 */
static 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 baddr, bmask;
        paddr_t curaddr, lastaddr;
        vaddr_t vaddr = (vaddr_t)buf;
        int seg;

        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, &curaddr);
                else
                        curaddr = kvtophys(vaddr);

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

                /*
                 * 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 = curaddr + t->dma_offset;
                        map->dm_segs[seg].ds_len = sgsize;
                        map->dm_segs[seg]._ds_vaddr = vaddr;
                        map->dm_segs[seg]._ds_paddr = curaddr;
                        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_paddr & bmask) ==
                             (curaddr & bmask)))
                                map->dm_segs[seg].ds_len += sgsize;
                        else {
                                if (++seg >= map->_dm_segcnt)
                                        break;
                                map->dm_segs[seg].ds_addr =
                                    curaddr + t->dma_offset;
                                map->dm_segs[seg].ds_len = sgsize;
                                map->dm_segs[seg]._ds_vaddr = vaddr;
                                map->dm_segs[seg]._ds_paddr = curaddr;
                        }
                }

                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 direct-mapped DMA map with a linear
 * buffer.
 */
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;
        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;
                map->_dm_vmspace = vm;

                /*
                 * For linear buffers, we support marking the mapping
                 * as COHERENT.
                 *
                 * XXX Check TLB entries for cache-inhibit bits?
                 */
                if (buf >= (void *)MIPS_KSEG1_START &&
                    buf < (void *)MIPS_KSEG2_START)
                        map->_dm_flags |= ARC_DMAMAP_COHERENT;
        }
        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;
        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) {
                if (m->m_len == 0)
                        continue;
                error = _bus_dmamap_load_buffer(t, map, m->m_data, m->m_len,
                    vmspace_kernel(), flags, &lastaddr, &seg, first);
                first = 0;
        }
        if (error == 0) {
                map->dm_mapsize = m0->m_pkthdr.len;
                map->dm_nsegs = seg + 1;
                map->_dm_vmspace = vmspace_kernel();    /* always kernel */
        }
        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;
        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;
                map->_dm_vmspace = uio->uio_vmspace;
        }
        return error;
}

/*
 * Like _bus_dmamap_load(), but for raw memory.
 */
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)
{

        panic("_bus_dmamap_load_raw: not implemented");
}

/*
 * 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;
        map->_dm_flags &= ~ARC_DMAMAP_COHERENT;
}

/*
 * Common function for DMA map synchronization.  May be called by
 * chipset-specific DMA map synchronization functions.
 *
 * This version works with the virtually-indexed, write-back cache
 * found in the MIPS-3 CPUs available in ARC machines.
 */
void
_bus_dmamap_sync(bus_dma_tag_t t, bus_dmamap_t map, bus_addr_t offset,
    bus_size_t len, int ops)
{
        const struct mips_cache_info * const mci = &mips_cache_info;
        bus_size_t minlen;
        bus_addr_t addr, start, end, preboundary, firstboundary, lastboundary;
        int i, useindex;

        /*
         * Mixing PRE and POST operations is not allowed.
         */
        if ((ops & (BUS_DMASYNC_PREREAD|BUS_DMASYNC_PREWRITE)) != 0 &&
            (ops & (BUS_DMASYNC_POSTREAD|BUS_DMASYNC_POSTWRITE)) != 0)
                panic("_bus_dmamap_sync: mix PRE and POST");

#ifdef DIAGNOSTIC
        if (offset >= map->dm_mapsize)
                panic("_bus_dmamap_sync: bad offset %lu (map size is %lu)",
                      offset, map->dm_mapsize);
        if (len == 0 || (offset + len) > map->dm_mapsize)
                panic("_bus_dmamap_sync: bad length");
#endif

        /*
         * Since we're dealing with a virtually-indexed, write-back
         * cache, we need to do the following things:
         *
         *      PREREAD -- Invalidate D-cache.  Note we might have
         *      to also write-back here if we have to use an Index
         *      op, or if the buffer start/end is not cache-line aligned.
         *
         *      PREWRITE -- Write-back the D-cache.  If we have to use
         *      an Index op, we also have to invalidate.  Note that if
         *      we are doing PREREAD|PREWRITE, we can collapse everything
         *      into a single op.
         *
         *      POSTREAD -- Nothing.
         *
         *      POSTWRITE -- Nothing.
         */

        /*
         * Flush the write buffer.
         * XXX Is this always necessary?
         */
        wbflush();

        ops &= (BUS_DMASYNC_PREREAD|BUS_DMASYNC_PREWRITE);
        if (ops == 0)
                return;

        /*
         * If the mapping is of COHERENT DMA-safe memory, no cache
         * flush is necessary.
         */
        if (map->_dm_flags & ARC_DMAMAP_COHERENT)
                return;

        /*
         * If the mapping belongs to the kernel, or it belongs
         * to the currently-running process (XXX actually, vmspace),
         * then we can use Hit ops.  Otherwise, Index ops.
         *
         * This should be true the vast majority of the time.
         */
        if (__predict_true(VMSPACE_IS_KERNEL_P(map->_dm_vmspace) ||
            map->_dm_vmspace == curproc->p_vmspace))
                useindex = 0;
        else
                useindex = 1;

        for (i = 0; i < map->dm_nsegs && len != 0; i++) {
                /* Find the beginning segment. */
                if (offset >= map->dm_segs[i].ds_len) {
                        offset -= map->dm_segs[i].ds_len;
                        continue;
                }

                /*
                 * Now at the first segment to sync; nail
                 * each segment until we have exhausted the
                 * length.
                 */
                minlen = len < map->dm_segs[i].ds_len - offset ?
                    len : map->dm_segs[i].ds_len - offset;

                addr = map->dm_segs[i]._ds_vaddr;

#ifdef BUS_DMA_DEBUG
                printf("bus_dmamap_sync: flushing segment %d "
                    "(0x%lx..0x%lx) ...", i, addr + offset,
                    addr + offset + minlen - 1);
#endif

                /*
                 * If we are forced to use Index ops, it's always a
                 * Write-back,Invalidate, so just do one test.
                 */
                if (__predict_false(useindex)) {
                        mips_dcache_wbinv_range_index(addr + offset, minlen);
#ifdef BUS_DMA_DEBUG
                        printf("\n");
#endif
                        offset = 0;
                        len -= minlen;
                        continue;
                }

                start = addr + offset;
                switch (ops) {
                case BUS_DMASYNC_PREREAD|BUS_DMASYNC_PREWRITE:
                        mips_dcache_wbinv_range(start, minlen);
                        break;

                case BUS_DMASYNC_PREREAD:
                        end = start + minlen;
                        preboundary = start & ~mci->mci_dcache_align_mask;
                        firstboundary = (start + mci->mci_dcache_align_mask)
                            & ~mci->mci_dcache_align_mask;
                        lastboundary = end & ~mci->mci_dcache_align_mask;
                        if (preboundary < start && preboundary < lastboundary)
                                mips_dcache_wbinv_range(preboundary,
                                    mci->mci_dcache_align);
                        if (firstboundary < lastboundary)
                                mips_dcache_inv_range(firstboundary,
                                    lastboundary - firstboundary);
                        if (lastboundary < end)
                                mips_dcache_wbinv_range(lastboundary,
                                    mci->mci_dcache_align);
                        break;

                case BUS_DMASYNC_PREWRITE:
                        mips_dcache_wb_range(start, minlen);
                        break;
                }
#ifdef BUS_DMA_DEBUG
                printf("\n");
#endif
                offset = 0;
                len -= minlen;
        }
}

/*
 * 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)
{

        return _bus_dmamem_alloc_range(t, size, alignment, boundary,
            segs, nsegs, rsegs, flags, pmap_limits.avail_start,
            trunc_page(pmap_limits.avail_end));
}

/*
 * 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);

        high = pmap_limits.avail_end - 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 = TAILQ_FIRST(&mlist);
        curseg = 0;
        lastaddr = segs[curseg]._ds_paddr = VM_PAGE_TO_PHYS(m);
        segs[curseg].ds_addr = segs[curseg]._ds_paddr + t->dma_offset;
        segs[curseg].ds_len = PAGE_SIZE;
        m = TAILQ_NEXT(m, pageq.queue);

        for (; m != NULL; m = TAILQ_NEXT(m, pageq.queue)) {
                curaddr = VM_PAGE_TO_PHYS(m);
#ifdef DIAGNOSTIC
                if (curaddr < pmap_limits.avail_start || curaddr >= high) {
                        printf("uvm_pglistalloc returned non-sensical"
                            " address 0x%llx\n", (long long)curaddr);
                        panic("_bus_dmamem_alloc_range");
                }
#endif
                if (curaddr == (lastaddr + PAGE_SIZE))
                        segs[curseg].ds_len += PAGE_SIZE;
                else {
                        curseg++;
                        segs[curseg].ds_addr = curaddr + t->dma_offset;
                        segs[curseg].ds_len = PAGE_SIZE;
                        segs[curseg]._ds_paddr = curaddr;
                }
                lastaddr = curaddr;
        }

        *rsegs = curseg + 1;

        return 0;
}

/*
 * 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 = segs[curseg]._ds_paddr;
                    addr < (segs[curseg]._ds_paddr + segs[curseg].ds_len);
                    addr += PAGE_SIZE) {
                        m = PHYS_TO_VM_PAGE(addr);
                        TAILQ_INSERT_TAIL(&mlist, m, pageq.queue);
                }
        }

        uvm_pglistfree(&mlist);
}

/*
 * 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;

        /*
         * If we're only mapping 1 segment, use KSEG0 or KSEG1, to avoid
         * TLB thrashing.
         */
        if (nsegs == 1) {
                if (flags & BUS_DMA_COHERENT)
                        *kvap = (void *)MIPS_PHYS_TO_KSEG1(segs[0]._ds_paddr);
                else
                        *kvap = (void *)MIPS_PHYS_TO_KSEG0(segs[0]._ds_paddr);
                return 0;
        }

        size = round_page(size);

        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++) {
                segs[curseg]._ds_vaddr = va;
                for (addr = segs[curseg]._ds_paddr;
                    addr < (segs[curseg]._ds_paddr + segs[curseg].ds_len);
                    addr += PAGE_SIZE, va += PAGE_SIZE, size -= PAGE_SIZE) {
                        if (size == 0)
                                panic("_bus_dmamem_map: size botch");
                        pmap_enter(pmap_kernel(), va, addr,
                            VM_PROT_READ | VM_PROT_WRITE,
                            VM_PROT_READ | VM_PROT_WRITE | PMAP_WIRED);

                        /* XXX Do something about COHERENT here. */
                }
        }
        pmap_update(pmap_kernel());

        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)
{

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

        /*
         * Nothing to do if we mapped it with KSEG0 or KSEG1 (i.e.
         * not in KSEG2).
         */
        if (kva >= (void *)MIPS_KSEG0_START &&
            kva < (void *)MIPS_KSEG2_START)
                return;

        size = round_page(size);
        pmap_remove(pmap_kernel(), (vaddr_t)kva, (vaddr_t)kva + size);
        pmap_update(pmap_kernel());
        uvm_km_free(kernel_map, (vaddr_t)kva, 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 (segs[i]._ds_paddr & 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 mips_btop(segs[i]._ds_paddr + off);
        }

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