/*	$NetBSD: bus_dma.c,v 1.4 2015/01/22 03:43:24 nonaka Exp $	*/

/*
 * Copyright (c) 2005 NONAKA Kimihiro <nonaka@netbsd.org>
 * All rights reserved.
 *
 * 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 AUTHOR ``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 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 1.4 2015/01/22 03:43:24 nonaka Exp $");

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/device.h>
#include <sys/malloc.h>
#include <sys/mbuf.h>
#define	_EVBSH3_BUS_DMA_PRIVATE
#include <sys/bus.h>

#include <uvm/uvm.h>

#include <sh3/cache.h>

#include <machine/autoconf.h>

#if defined(DEBUG) && defined(BUSDMA_DEBUG)
int busdma_debug = 0;
#define	DPRINTF(a)	if (busdma_debug) printf a
#else
#define	DPRINTF(a)
#endif

struct _bus_dma_tag evbsh3_bus_dma = {
	._cookie = NULL,

	._dmamap_create = _bus_dmamap_create,
	._dmamap_destroy = _bus_dmamap_destroy,
	._dmamap_load = _bus_dmamap_load,
	._dmamap_load_mbuf = _bus_dmamap_load_mbuf,
	._dmamap_load_uio = _bus_dmamap_load_uio,
	._dmamap_load_raw = _bus_dmamap_load_raw,
	._dmamap_unload = _bus_dmamap_unload,
	._dmamap_sync = _bus_dmamap_sync,

	._dmamem_alloc = _bus_dmamem_alloc,
	._dmamem_free = _bus_dmamem_free,
	._dmamem_map = _bus_dmamem_map,
	._dmamem_unmap = _bus_dmamem_unmap,
	._dmamem_mmap = _bus_dmamem_mmap,
};

/*
 * Create a DMA map.
 */
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)
{
	bus_dmamap_t map;
	void *mapstore;
	size_t mapsize;

	DPRINTF(("%s: t = %p, size = %ld, nsegments = %d, maxsegsz = %ld,"
		 " boundary = %ld, flags = %x\n",
		 __func__, t, size, nsegments, maxsegsz, boundary, flags));

	/*
	 * 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.  bus_dmamap_t includes one
	 * bus_dma_segment_t already, hence the (nsegments - 1).
	 *
	 * Note that we don't preserve WAITOK and NOWAIT flags.
	 * Preservation of ALLOCNOW notifies others that we've
	 * reserved these resources, and they are not to be freed.
	 */
	mapsize = sizeof(struct _bus_dmamap)
		+ (sizeof(bus_dma_segment_t) * (nsegments - 1));
	mapstore = malloc(mapsize, M_DMAMAP, M_ZERO
			  | ((flags & BUS_DMA_NOWAIT) ? M_NOWAIT : M_WAITOK));
	if (mapstore == NULL)
		return ENOMEM;

	DPRINTF(("%s: dmamp = %p\n", __func__, mapstore));

	map = (bus_dmamap_t)mapstore;
	map->_dm_size = size;
	map->_dm_segcnt = nsegments;
	map->_dm_maxsegsz = maxsegsz;
	map->_dm_boundary = boundary;
	map->_dm_flags = flags & ~(BUS_DMA_WAITOK | BUS_DMA_NOWAIT);

	map->dm_mapsize = 0;		/* no valid mappings */
	map->dm_nsegs = 0;

	*dmamp = map;
	return 0;
}

/*
 * Destroy a DMA map.
 */
void
_bus_dmamap_destroy(bus_dma_tag_t t, bus_dmamap_t map)
{

	DPRINTF(("%s: t = %p, map = %p\n", __func__, t, map));

	free(map, M_DMAMAP);
}

static inline int
_bus_dmamap_load_paddr(bus_dma_tag_t t, bus_dmamap_t map,
    paddr_t paddr, vaddr_t vaddr, int size, int *segp, paddr_t *lastaddrp,
    int first)
{
	bus_dma_segment_t * const segs = map->dm_segs;
	bus_addr_t bmask = ~(map->_dm_boundary - 1);
	bus_addr_t lastaddr;
	int nseg;
	int sgsize;

	nseg = *segp;
	lastaddr = *lastaddrp;

	DPRINTF(("%s: t = %p, map = %p, paddr = 0x%08lx,"
		 " vaddr = 0x%08lx, size = %d\n",
		 __func__, t, map, paddr, vaddr, size));
	DPRINTF(("%s: nseg = %d, bmask = 0x%08lx, lastaddr = 0x%08lx\n",
		 __func__, nseg, bmask, lastaddr));

	do {
		sgsize = size;

		/*
		 * Make sure we don't cross any boundaries.
		 */
		if (map->_dm_boundary > 0) {
			bus_addr_t baddr; /* next boundary address */

			baddr = (paddr + map->_dm_boundary) & bmask;
			if (sgsize > (baddr - paddr))
				sgsize = (baddr - paddr);
		}

		DPRINTF(("%s: sgsize = %d\n", __func__, sgsize));

		/*
		 * Insert chunk coalescing with previous segment if possible.
		 */
		if (first) {
			DPRINTF(("%s: first\n", __func__));
			first = 0;

			segs[nseg].ds_addr = SH3_PHYS_TO_P2SEG(paddr);
			segs[nseg].ds_len = sgsize;
			segs[nseg]._ds_vaddr = vaddr;
		}
		else if ((paddr == lastaddr)
			 && (segs[nseg].ds_len + sgsize <= map->_dm_maxsegsz)
			 && (map->_dm_boundary == 0 ||
			     (segs[nseg].ds_addr & bmask) == (paddr & bmask)))
		{
			DPRINTF(("%s: coalesce\n", __func__));

			segs[nseg].ds_len += sgsize;
		}
		else {
			DPRINTF(("%s: new\n", __func__));

			++nseg;
			if (nseg >= map->_dm_segcnt)
				break;

			segs[nseg].ds_addr = SH3_PHYS_TO_P2SEG(paddr);
			segs[nseg].ds_len = sgsize;
			segs[nseg]._ds_vaddr = vaddr;
		}

		paddr += sgsize;
		vaddr += sgsize;
		size -= sgsize;
		lastaddr = paddr;

		DPRINTF(("%s: lastaddr = 0x%08lx, paddr = 0x%08lx,"
			 " vaddr = 0x%08lx, size = %d\n",
			 __func__, lastaddr, paddr, vaddr, size));
	} while (size > 0);

	DPRINTF(("%s: nseg = %d\n", __func__, nseg));

	*segp = nseg;
	*lastaddrp = lastaddr;

	if (size != 0) {
		/*
		 * It didn't fit.  If there is a chained window, we
		 * will automatically fall back to it.
		 */
		return (EFBIG);		/* XXX better return value here? */
	}

	return (0);
}

static inline int
_bus_bus_dmamap_load_buffer(bus_dma_tag_t t, bus_dmamap_t map, void *buf,
    bus_size_t buflen, struct proc *p, int flags, int *segp)
{
	bus_size_t sgsize;
	bus_addr_t curaddr;
	bus_size_t len;
	paddr_t lastaddr;
	vaddr_t vaddr = (vaddr_t)buf;
	pmap_t pmap;
	int first;
	int error;

	DPRINTF(("%s: t = %p, map = %p, buf = %p, buflen = %ld,"
		 " p = %p, flags = %x\n",
		 __func__, t, map, buf, buflen, p, flags));

	if (p != NULL)
		pmap = p->p_vmspace->vm_map.pmap;
	else
		pmap = pmap_kernel();

	first = 1;
	lastaddr = 0;

	len = buflen;
	while (len > 0) {
		bool mapped;

		mapped = pmap_extract(pmap, vaddr, &curaddr);
		if (!mapped)
			return EFAULT;

		sgsize = PAGE_SIZE - (vaddr & PGOFSET);
		if (len < sgsize)
			sgsize = len;

		error = _bus_dmamap_load_paddr(t, map, curaddr, vaddr, sgsize,
					       segp, &lastaddr, first);
		if (error)
			return error;

		vaddr += sgsize;
		len -= sgsize;
		first = 0;
	}

	return 0;
}

/*
 * Load a 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)
{
	bus_addr_t addr = (bus_addr_t)buf;
	paddr_t lastaddr;
	int seg;
	int first;
	int error;

	DPRINTF(("%s: t = %p, map = %p, buf = %p, buflen = %ld,"
		 " p = %p, flags = %x\n",
		 __func__, t, map, buf, buflen, p, flags));

	/* make sure that on error condition we return "no valid mappings" */
	map->dm_mapsize = 0;
	map->dm_nsegs = 0;

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

	error = 0;
	seg = 0;

	if (SH3_P1SEG_BASE <= addr && addr + buflen <= SH3_P2SEG_END) {
		bus_addr_t curaddr;
		bus_size_t sgsize;
		bus_size_t len = buflen;

		DPRINTF(("%s: P[12]SEG (0x%08lx)\n", __func__, addr));

		first = 1;
		lastaddr = 0;

		while (len > 0) {
			curaddr = SH3_P1SEG_TO_PHYS(addr);

			sgsize = PAGE_SIZE - ((u_long)addr & PGOFSET);
			if (len < sgsize)
				sgsize = len;

			error = _bus_dmamap_load_paddr(t, map,
						       curaddr, addr, sgsize,
						       &seg, &lastaddr, first);
			if (error)
				break;

			addr += sgsize;
			len -= sgsize;
			first = 0;
		}
	}
	else {
		error = _bus_bus_dmamap_load_buffer(t, map, buf, buflen,
						    p, flags, &seg);
	}

	if (error)
		return (error);

	map->dm_nsegs = seg + 1;
	map->dm_mapsize = buflen;
	return 0;
}

/*
 * 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)
{
	struct mbuf *m;
	paddr_t lastaddr;
	int seg;
	int first;
	int error;

	DPRINTF(("%s: t = %p, map = %p, m0 = %p, flags = %x\n",
		 __func__, t, map, m0, flags));

	/* make sure that on error condition we return "no valid mappings" */
	map->dm_nsegs = 0;
	map->dm_mapsize = 0;

#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);

	seg = 0;
	first = 1;
	lastaddr = 0;

	for (m = m0; m != NULL; m = m->m_next) {
		paddr_t paddr;
		vaddr_t vaddr;
		int size;

		if (m->m_len == 0)
			continue;

		vaddr = (vaddr_t)m->m_data;
		size = m->m_len;

		if (SH3_P1SEG_BASE <= vaddr && vaddr < SH3_P3SEG_BASE) {
			paddr = (paddr_t)(PMAP_UNMAP_POOLPAGE(vaddr));
			error = _bus_dmamap_load_paddr(t, map,
						       paddr, vaddr, size,
						       &seg, &lastaddr, first);
			if (error)
				return error;
			first = 0;
		}
		else {
			/* XXX: stolen from load_buffer, need to refactor */
			while (size > 0) {
				bus_size_t sgsize;
				bool mapped;

				mapped = pmap_extract(pmap_kernel(), vaddr,
						      &paddr);
				if (!mapped)
					return EFAULT;

				sgsize = PAGE_SIZE - (vaddr & PGOFSET);
				if (size < sgsize)
					sgsize = size;

				error = _bus_dmamap_load_paddr(t, map,
						paddr, vaddr, sgsize,
						&seg, &lastaddr, first);
				if (error)
					return error;

				vaddr += sgsize;
				size -= sgsize;
				first = 0;
			}

		}
	}

	map->dm_nsegs = seg + 1;
	map->dm_mapsize = m0->m_pkthdr.len;
	return 0;
}

/*
 * 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)
{

	panic("_bus_dmamap_load_uio: not implemented");
}

/*
 * Like _bus_dmamap_load(), but for raw memory allocated with
 * bus_dmamem_alloc().
 */
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");
}

/*
 * Unload a DMA map.
 */
void
_bus_dmamap_unload(bus_dma_tag_t t, bus_dmamap_t map)
{

	DPRINTF(("%s: t = %p, map = %p\n", __func__, t, map));

	map->dm_nsegs = 0;
	map->dm_mapsize = 0;
}

/*
 * Synchronize a DMA map.
 */
void
_bus_dmamap_sync(bus_dma_tag_t t, bus_dmamap_t map, bus_addr_t offset,
    bus_size_t len, int ops)
{
	bus_size_t minlen;
	bus_addr_t addr, naddr;
	int i;

	DPRINTF(("%s: t = %p, map = %p, offset = %ld, len = %ld, ops = %x\n",
		 __func__, t, map, offset, len, ops));

#ifdef DIAGNOSTIC
	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");

	if (offset >= map->dm_mapsize)
		panic("_bus_dmamap_sync: bad offset");
	if ((offset + len) > map->dm_mapsize)
		panic("_bus_dmamap_sync: bad length");
#endif

	if (!sh_cache_enable_dcache) {
		/* Nothing to do */
		DPRINTF(("%s: disabled D-Cache\n", __func__));
		return;
	}

	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;
		naddr = addr + offset;

		if ((naddr >= SH3_P2SEG_BASE)
		 && (naddr + minlen <= SH3_P2SEG_END)) {
			DPRINTF(("%s: P2SEG (0x%08lx)\n", __func__, naddr));
			offset = 0;
			len -= minlen;
			continue;
		}

		DPRINTF(("%s: flushing segment %d "
			 "(0x%lx+%lx, 0x%lx+0x%lx) (remain = %ld)\n",
			 __func__, i,
			 addr, offset, addr, offset + minlen - 1, len));

		switch (ops) {
		case BUS_DMASYNC_PREREAD|BUS_DMASYNC_PREWRITE:
			if (SH_HAS_WRITEBACK_CACHE)
				sh_dcache_wbinv_range(naddr, minlen);
			else
				sh_dcache_inv_range(naddr, minlen);
			break;

		case BUS_DMASYNC_PREREAD:
			if (SH_HAS_WRITEBACK_CACHE &&
			    ((naddr | minlen) & (sh_cache_line_size - 1)) != 0)
				sh_dcache_wbinv_range(naddr, minlen);
			else
				sh_dcache_inv_range(naddr, minlen);
			break;

		case BUS_DMASYNC_PREWRITE:
			if (SH_HAS_WRITEBACK_CACHE)
				sh_dcache_wb_range(naddr, minlen);
			break;
		}
		offset = 0;
		len -= minlen;
	}
}

/*
 * Allocate memory safe for DMA.
 */
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)
{
	extern paddr_t avail_start, avail_end;	/* from pmap.c */
	struct pglist mlist;
	paddr_t curaddr, lastaddr;
	struct vm_page *m;
	int curseg, error;

	DPRINTF(("%s: t = %p, size = %ld, alignment = %ld, boundary = %ld,"
		 " segs = %p, nsegs = %d, rsegs = %p, flags = %x\n",
		 __func__, t, size, alignment, boundary,
		 segs, nsegs, rsegs, flags));
	DPRINTF(("%s: avail_start = 0x%08lx, avail_end = 0x%08lx\n",
		 __func__, avail_start, avail_end));

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

	/*
	 * Allocate the pages from the VM system.
	 */
	error = uvm_pglistalloc(size, avail_start, avail_end - PAGE_SIZE,
	    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 = segs[curseg].ds_addr = VM_PAGE_TO_PHYS(m);
	segs[curseg].ds_len = PAGE_SIZE;

	DPRINTF(("%s: m = %p, lastaddr = 0x%08lx\n", __func__, m, lastaddr));

	while ((m = TAILQ_NEXT(m, pageq.queue)) != NULL) {
		curaddr = VM_PAGE_TO_PHYS(m);
		DPRINTF(("%s: m = %p, curaddr = 0x%08lx, lastaddr = 0x%08lx\n",
			 __func__, m, curaddr, lastaddr));

		if (curaddr == (lastaddr + PAGE_SIZE)) {
			segs[curseg].ds_len += PAGE_SIZE;
		} else {
			DPRINTF(("%s: new segment\n", __func__));
			curseg++;
			segs[curseg].ds_addr = curaddr;
			segs[curseg].ds_len = PAGE_SIZE;
		}
		lastaddr = curaddr;
	}

	*rsegs = curseg + 1;

	DPRINTF(("%s: curseg = %d, *rsegs = %d\n", __func__, curseg, *rsegs));

	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;

	DPRINTF(("%s: t = %p, segs = %p, nsegs = %d\n",
		 __func__, t, segs, nsegs));

	/*
	 * Build a list of pages to free back to the VM system.
	 */
	TAILQ_INIT(&mlist);
	for (curseg = 0; curseg < nsegs; curseg++) {
		DPRINTF(("%s: segs[%d]: ds_addr = 0x%08lx, ds_len = %ld\n",
			 __func__, curseg,
			 segs[curseg].ds_addr, segs[curseg].ds_len));

		for (addr = segs[curseg].ds_addr;
		     addr < (segs[curseg].ds_addr + segs[curseg].ds_len);
		     addr += PAGE_SIZE)
		{
			m = PHYS_TO_VM_PAGE(addr);
			DPRINTF(("%s: m = %p\n", __func__, m));
			TAILQ_INSERT_TAIL(&mlist, m, pageq.queue);
		}
	}

	uvm_pglistfree(&mlist);
}


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, topva;
	bus_addr_t addr;
	int curseg;

	DPRINTF(("%s: t = %p, segs = %p, nsegs = %d, size = %d,"
		 " kvap = %p, flags = %x\n",
		 __func__, t, segs, nsegs, size, kvap, flags));

	/*
	 * If we're mapping only a single segment, use direct-mapped
	 * va, to avoid thrashing the TLB.
	 */
	if (nsegs == 1) {
		if (flags & BUS_DMA_COHERENT)
			*kvap = (void *)SH3_PHYS_TO_P2SEG(segs[0].ds_addr);
		else
			*kvap = (void *)SH3_PHYS_TO_P1SEG(segs[0].ds_addr);

		DPRINTF(("%s: addr = 0x%08lx, kva = %p\n",
			 __func__, segs[0].ds_addr, *kvap));
		return 0;
	}


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

	va = uvm_km_alloc(kernel_map, size, 0, UVM_KMF_VAONLY
			  | ((flags & BUS_DMA_NOWAIT) ? UVM_KMF_NOWAIT : 0));
	if (va == 0)
		return (ENOMEM);
	topva = va;

	for (curseg = 0; curseg < nsegs; curseg++) {
		DPRINTF(("%s: segs[%d]: ds_addr = 0x%08lx, ds_len = %ld\n",
			 __func__, curseg,
			 segs[curseg].ds_addr, segs[curseg].ds_len));

		for (addr = segs[curseg].ds_addr;
		     addr < segs[curseg].ds_addr + segs[curseg].ds_len;
		     addr += PAGE_SIZE, va += PAGE_SIZE, size -= PAGE_SIZE)
		{
			if (__predict_false(size == 0))
				panic("_bus_dmamem_map: size botch");

			pmap_kenter_pa(va, addr,
				       VM_PROT_READ | VM_PROT_WRITE, 0);
		}
	}

	pmap_update(pmap_kernel());
	*kvap = (void *)topva;
	return (0);
}

void
_bus_dmamem_unmap(bus_dma_tag_t t, void *kva, size_t size)
{
	vaddr_t vaddr = (vaddr_t)kva;

	DPRINTF(("%s: t = %p, kva = %p, size = %d\n",
		 __func__, t, kva, size));

#ifdef DIAGNOSTIC
	if (vaddr & PAGE_MASK)
		panic("_bus_dmamem_unmap");
#endif

	/* nothing to do if we mapped it via P1SEG or P2SEG */
	if (SH3_P1SEG_BASE <= vaddr && vaddr <= SH3_P2SEG_END)
		return;

	size = round_page(size);
	pmap_kremove(vaddr, size);
	pmap_update(pmap_kernel());
	uvm_km_free(kernel_map, vaddr, size, UVM_KMF_VAONLY);
}

paddr_t
_bus_dmamem_mmap(bus_dma_tag_t t, bus_dma_segment_t *segs, int nsegs,
    off_t off, int prot, int flags)
{

	/* Not implemented. */
	return (paddr_t)(-1);
}