Add a virtual table for the busdma methods on x86, to allow different

busdma implementations to coexist.  Copy busdma_machdep.c to
busdma_bounce.c, which is still a single implementation of the busdma
interface on x86 for now.  The busdma_machdep.c only contains common
and dispatch code.

Tested by:	pho (as part of the larger patch)
Sponsored by:	The FreeBSD Foundation
MFC after:	1 month

6 files changed, 1333 insertions, 998 deletions

diff --git a/sys/conf/files.amd64 b/sys/conf/files.amd64
index 1914c48de9bf..e1d1857c85b5 100644
--- a/sys/conf/files.amd64
+++ b/sys/conf/files.amd64
@@ -541,6 +541,7 @@ x86/isa/nmi.c			standard
 x86/isa/orm.c			optional	isa
 x86/pci/pci_bus.c		optional	pci
 x86/pci/qpi.c			optional	pci
+x86/x86/busdma_bounce.c		standard
 x86/x86/busdma_machdep.c	standard
 x86/x86/dump_machdep.c		standard
 x86/x86/fdt_machdep.c		optional	fdt
diff --git a/sys/conf/files.i386 b/sys/conf/files.i386
index e2596590a04e..a869b3953c55 100644
--- a/sys/conf/files.i386
+++ b/sys/conf/files.i386
@@ -564,6 +564,7 @@ x86/isa/nmi.c			standard
 x86/isa/orm.c			optional isa
 x86/pci/pci_bus.c		optional pci
 x86/pci/qpi.c			optional pci
+x86/x86/busdma_bounce.c		standard
 x86/x86/busdma_machdep.c	standard
 x86/x86/dump_machdep.c		standard
 x86/x86/fdt_machdep.c		optional fdt
diff --git a/sys/conf/files.pc98 b/sys/conf/files.pc98
index a8e60b6f7290..fd3ad4a2617a 100644
--- a/sys/conf/files.pc98
+++ b/sys/conf/files.pc98
@@ -247,6 +247,7 @@ x86/isa/atpic.c			optional atpic
 x86/isa/clock.c			standard
 x86/isa/isa.c			optional isa
 x86/pci/pci_bus.c		optional pci
+x86/x86/busdma_bounce.c		standard
 x86/x86/busdma_machdep.c	standard
 x86/x86/dump_machdep.c		standard
 x86/x86/intr_machdep.c		standard
diff --git a/sys/x86/include/busdma_impl.h b/sys/x86/include/busdma_impl.h
new file mode 100644
index 000000000000..70c9a6f42f1d
--- /dev/null
+++ b/sys/x86/include/busdma_impl.h
@@ -0,0 +1,97 @@
+/*-
+ * Copyright (c) 2013 The FreeBSD Foundation
+ * All rights reserved.
+ *
+ * This software was developed by Konstantin Belousov <kib@FreeBSD.org>
+ * under sponsorship from 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.
+ * 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 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.
+ *
+ * $FreeBSD$
+ */
+
+#ifndef	__X86_BUSDMA_IMPL_H
+#define	__X86_BUSDMA_IMPL_H
+
+struct bus_dma_tag_common {
+	struct bus_dma_impl *impl;
+	struct bus_dma_tag_common *parent;
+	bus_size_t	  alignment;
+	bus_addr_t	  boundary;
+	bus_addr_t	  lowaddr;
+	bus_addr_t	  highaddr;
+	bus_dma_filter_t *filter;
+	void		 *filterarg;
+	bus_size_t	  maxsize;
+	u_int		  nsegments;
+	bus_size_t	  maxsegsz;
+	int		  flags;
+	bus_dma_lock_t	 *lockfunc;
+	void		 *lockfuncarg;
+	int		  ref_count;
+};
+
+struct bus_dma_impl {
+	int (*tag_create)(bus_dma_tag_t parent,
+	    bus_size_t alignment, bus_addr_t boundary, bus_addr_t lowaddr,
+	    bus_addr_t highaddr, bus_dma_filter_t *filter,
+	    void *filterarg, bus_size_t maxsize, int nsegments,
+	    bus_size_t maxsegsz, int flags, bus_dma_lock_t *lockfunc,
+	    void *lockfuncarg, bus_dma_tag_t *dmat);
+	int (*tag_destroy)(bus_dma_tag_t dmat);
+	int (*map_create)(bus_dma_tag_t dmat, int flags, bus_dmamap_t *mapp);
+	int (*map_destroy)(bus_dma_tag_t dmat, bus_dmamap_t map);
+	int (*mem_alloc)(bus_dma_tag_t dmat, void** vaddr, int flags,
+	    bus_dmamap_t *mapp);
+	void (*mem_free)(bus_dma_tag_t dmat, void *vaddr, bus_dmamap_t map);
+	int (*load_ma)(bus_dma_tag_t dmat, bus_dmamap_t map,
+	    struct vm_page **ma, bus_size_t tlen, int ma_offs, int flags,
+	    bus_dma_segment_t *segs, int *segp);
+	int (*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);
+	int (*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);
+	void (*map_waitok)(bus_dma_tag_t dmat, bus_dmamap_t map,
+	    struct memdesc *mem, bus_dmamap_callback_t *callback,
+	    void *callback_arg);
+	bus_dma_segment_t *(*map_complete)(bus_dma_tag_t dmat, bus_dmamap_t map,
+	    bus_dma_segment_t *segs, int nsegs, int error);
+	void (*map_unload)(bus_dma_tag_t dmat, bus_dmamap_t map);
+	void (*map_sync)(bus_dma_tag_t dmat, bus_dmamap_t map,
+	    bus_dmasync_op_t op);
+};
+
+void busdma_lock_mutex(void *arg, bus_dma_lock_op_t op);
+void bus_dma_dflt_lock(void *arg, bus_dma_lock_op_t op);
+int bus_dma_run_filter(struct bus_dma_tag_common *dmat, bus_addr_t paddr);
+int common_bus_dma_tag_create(struct bus_dma_tag_common *parent,
+    bus_size_t alignment,
+    bus_addr_t boundary, bus_addr_t lowaddr, bus_addr_t highaddr,
+    bus_dma_filter_t *filter, void *filterarg, bus_size_t maxsize,
+    int nsegments, bus_size_t maxsegsz, int flags, bus_dma_lock_t *lockfunc,
+    void *lockfuncarg, size_t sz, void **dmat);
+
+extern struct bus_dma_impl bus_dma_bounce_impl;
+
+#endif
diff --git a/sys/x86/x86/busdma_bounce.c b/sys/x86/x86/busdma_bounce.c
new file mode 100644
index 000000000000..a767bff7409a
--- /dev/null
+++ b/sys/x86/x86/busdma_bounce.c
@@ -0,0 +1,1080 @@
+/*-
+ * Copyright (c) 1997, 1998 Justin T. Gibbs.
+ * 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,
+ *    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/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+#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/specialreg.h>
+#include <x86/include/busdma_impl.h>
+
+#ifdef __i386__
+#define MAX_BPAGES 512
+#else
+#define MAX_BPAGES 8192
+#endif
+#define BUS_DMA_COULD_BOUNCE	BUS_DMA_BUS3
+#define BUS_DMA_MIN_ALLOC_COMP	BUS_DMA_BUS4
+
+struct bounce_zone;
+
+struct bus_dma_tag {
+	struct bus_dma_tag_common common;
+	int		  map_count;
+	bus_dma_segment_t *segments;
+	struct bounce_zone *bounce_zone;
+};
+
+struct bounce_page {
+	vm_offset_t	vaddr;		/* kva of bounce buffer */
+	bus_addr_t	busaddr;	/* Physical address */
+	vm_offset_t	datavaddr;	/* kva of client data */
+	bus_addr_t	dataaddr;	/* client physical address */
+	bus_size_t	datacount;	/* client data count */
+	STAILQ_ENTRY(bounce_page) links;
+};
+
+int busdma_swi_pending;
+
+struct bounce_zone {
+	STAILQ_ENTRY(bounce_zone) links;
+	STAILQ_HEAD(bp_list, bounce_page) bounce_page_list;
+	int		total_bpages;
+	int		free_bpages;
+	int		reserved_bpages;
+	int		active_bpages;
+	int		total_bounced;
+	int		total_deferred;
+	int		map_count;
+	bus_size_t	alignment;
+	bus_addr_t	lowaddr;
+	char		zoneid[8];
+	char		lowaddrid[20];
+	struct sysctl_ctx_list sysctl_tree;
+	struct sysctl_oid *sysctl_tree_top;
+};
+
+static struct mtx bounce_lock;
+static int total_bpages;
+static int busdma_zonecount;
+static STAILQ_HEAD(, bounce_zone) bounce_zone_list;
+
+static SYSCTL_NODE(_hw, OID_AUTO, busdma, CTLFLAG_RD, 0, "Busdma parameters");
+SYSCTL_INT(_hw_busdma, OID_AUTO, total_bpages, CTLFLAG_RD, &total_bpages, 0,
+	   "Total bounce pages");
+
+struct bus_dmamap {
+	struct bp_list	       bpages;
+	int		       pagesneeded;
+	int		       pagesreserved;
+	bus_dma_tag_t	       dmat;
+	struct memdesc	       mem;
+	bus_dmamap_callback_t *callback;
+	void		      *callback_arg;
+	STAILQ_ENTRY(bus_dmamap) links;
+};
+
+static STAILQ_HEAD(, bus_dmamap) bounce_map_waitinglist;
+static STAILQ_HEAD(, bus_dmamap) bounce_map_callbacklist;
+static struct bus_dmamap nobounce_dmamap, contig_dmamap;
+
+static void init_bounce_pages(void *dummy);
+static int alloc_bounce_zone(bus_dma_tag_t dmat);
+static int alloc_bounce_pages(bus_dma_tag_t dmat, u_int numpages);
+static int reserve_bounce_pages(bus_dma_tag_t dmat, bus_dmamap_t map,
+				int commit);
+static bus_addr_t add_bounce_page(bus_dma_tag_t dmat, bus_dmamap_t map,
+				  vm_offset_t vaddr, bus_addr_t addr,
+				  bus_size_t size);
+static void free_bounce_page(bus_dma_tag_t dmat, struct bounce_page *bpage);
+int run_filter(bus_dma_tag_t dmat, bus_addr_t paddr);
+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 int _bus_dmamap_reserve_pages(bus_dma_tag_t dmat, bus_dmamap_t map,
+				     int flags);
+
+#ifdef XEN
+#undef pmap_kextract
+#define pmap_kextract pmap_kextract_ma
+#endif
+
+/*
+ * 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_dma_filter_t *filter, void *filterarg, 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, filter, filterarg,
+	    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 (parent != NULL && ((newtag->common.filter != NULL) ||
+	    ((parent->common.flags & BUS_DMA_COULD_BOUNCE) != 0)))
+		newtag->common.flags |= BUS_DMA_COULD_BOUNCE;
+
+	if (newtag->common.lowaddr < ptoa((vm_paddr_t)Maxmem) ||
+	    newtag->common.alignment > 1)
+		newtag->common.flags |= BUS_DMA_COULD_BOUNCE;
+
+	if (((newtag->common.flags & BUS_DMA_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(maxsize) - bz->total_bpages;
+
+			/* Add pages to our bounce pool */
+			if (alloc_bounce_pages(newtag, pages) < pages)
+				error = ENOMEM;
+		}
+		/* Performed initial allocation */
+		newtag->common.flags |= BUS_DMA_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)
+{
+	bus_dma_tag_t dmat_copy, parent;
+	int error;
+
+	error = 0;
+	dmat_copy = dmat;
+
+	if (dmat != NULL) {
+		if (dmat->map_count != 0) {
+			error = EBUSY;
+			goto out;
+		}
+		while (dmat != NULL) {
+			parent = (bus_dma_tag_t)dmat->common.parent;
+			atomic_subtract_int(&dmat->common.ref_count, 1);
+			if (dmat->common.ref_count == 0) {
+				if (dmat->segments != NULL)
+					free(dmat->segments, M_DEVBUF);
+				free(dmat, M_DEVBUF);
+				/*
+				 * Last reference count, so
+				 * release our reference
+				 * count on our parent.
+				 */
+				dmat = parent;
+			} else
+				dmat = NULL;
+		}
+	}
+out:
+	CTR3(KTR_BUSDMA, "%s tag %p error %d", __func__, dmat_copy, error);
+	return (error);
+}
+
+/*
+ * 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);
+		}
+	}
+
+	/*
+	 * 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->common.flags & BUS_DMA_COULD_BOUNCE) {
+		/* Must bounce */
+		if (dmat->bounce_zone == NULL) {
+			if ((error = alloc_bounce_zone(dmat)) != 0)
+				return (error);
+		}
+		bz = dmat->bounce_zone;
+
+		*mapp = (bus_dmamap_t)malloc(sizeof(**mapp), M_DEVBUF,
+		    M_NOWAIT | M_ZERO);
+		if (*mapp == NULL) {
+			CTR3(KTR_BUSDMA, "%s: tag %p error %d",
+			    __func__, dmat, ENOMEM);
+			return (ENOMEM);
+		}
+
+		/* Initialize the new map */
+		STAILQ_INIT(&((*mapp)->bpages));
+
+		/*
+		 * 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->common.flags & BUS_DMA_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->common.flags & BUS_DMA_MIN_ALLOC_COMP)
+			    == 0) {
+				if (error == 0) {
+					dmat->common.flags |=
+					    BUS_DMA_MIN_ALLOC_COMP;
+				}
+			} else
+				error = 0;
+		}
+		bz->map_count++;
+	} else {
+		*mapp = NULL;
+	}
+	if (error == 0)
+		dmat->map_count++;
+	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)
+{
+
+	if (map != NULL && map != &nobounce_dmamap && map != &contig_dmamap) {
+		if (STAILQ_FIRST(&map->bpages) != NULL) {
+			CTR3(KTR_BUSDMA, "%s: tag %p error %d",
+			    __func__, dmat, EBUSY);
+			return (EBUSY);
+		}
+		if (dmat->bounce_zone)
+			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)
+{
+	vm_memattr_t attr;
+	int mflags;
+
+	if (flags & BUS_DMA_NOWAIT)
+		mflags = M_NOWAIT;
+	else
+		mflags = M_WAITOK;
+
+	/* If we succeed, no mapping/bouncing will be required */
+	*mapp = NULL;
+
+	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
+		attr = VM_MEMATTR_DEFAULT;
+
+	/* 
+	 * XXX:
+	 * (dmat->alignment < dmat->maxsize) is just a quick hack; the exact
+	 * alignment guarantees of malloc need to be nailed down, and the
+	 * code below should be rewritten to take that into account.
+	 *
+	 * In the meantime, we'll 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 >= btoc(dmat->common.maxsize) &&
+	    dmat->common.alignment <= PAGE_SIZE &&
+	    (dmat->common.boundary == 0 ||
+	    dmat->common.boundary >= dmat->common.lowaddr)) {
+		/* Page-based multi-segment allocations allowed */
+		*vaddr = (void *)kmem_alloc_attr(kernel_arena,
+		    dmat->common.maxsize, mflags, 0ul, dmat->common.lowaddr,
+		    attr);
+		*mapp = &contig_dmamap;
+	} else {
+		*vaddr = (void *)kmem_alloc_contig(kernel_arena,
+		    dmat->common.maxsize, mflags, 0ul, dmat->common.lowaddr,
+		    dmat->common.alignment != 0 ? dmat->common.alignment : 1ul,
+		    dmat->common.boundary, attr);
+		*mapp = &contig_dmamap;
+	}
+	if (*vaddr == NULL) {
+		CTR4(KTR_BUSDMA, "%s: tag %p tag flags 0x%x error %d",
+		    __func__, dmat, dmat->common.flags, ENOMEM);
+		return (ENOMEM);
+	} else if (vtophys(*vaddr) & (dmat->common.alignment - 1)) {
+		printf("bus_dmamem_alloc failed to align memory properly.\n");
+	}
+	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.  Make the same choice for free/contigfree.
+ */
+static void
+bounce_bus_dmamem_free(bus_dma_tag_t dmat, void *vaddr, bus_dmamap_t map)
+{
+	/*
+	 * dmamem does not need to be bounced, so the map should be
+	 * NULL if malloc() was used and contig_dmamap if
+	 * kmem_alloc_contig() was used.
+	 */
+	if (!(map == NULL || map == &contig_dmamap))
+		panic("bus_dmamem_free: Invalid map freed\n");
+	if (map == NULL)
+		free(vaddr, M_DEVBUF);
+	else
+		kmem_free(kernel_arena, (vm_offset_t)vaddr,
+		    dmat->common.maxsize);
+	CTR3(KTR_BUSDMA, "%s: tag %p flags 0x%x", __func__, dmat,
+	    dmat->common.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 != &nobounce_dmamap && map->pagesneeded == 0)) {
+		/*
+		 * Count the number of bounce pages
+		 * needed in order to complete this transfer
+		 */
+		curaddr = buf;
+		while (buflen != 0) {
+			sgsize = MIN(buflen, dmat->common.maxsegsz);
+			if (bus_dma_run_filter(&dmat->common, curaddr)) {
+				sgsize = MIN(sgsize, PAGE_SIZE);
+				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 != &nobounce_dmamap && 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);
+		CTR3(KTR_BUSDMA, "map= %p, nobouncemap= %p, pagesneeded= %d",
+		    map, &nobounce_dmamap, 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 = PAGE_SIZE - ((vm_offset_t)vaddr & PAGE_MASK);
+			if (pmap == kernel_pmap)
+				paddr = pmap_kextract(vaddr);
+			else
+				paddr = pmap_extract(pmap, vaddr);
+			if (bus_dma_run_filter(&dmat->common, paddr) != 0) {
+				sg_len = roundup2(sg_len,
+				    dmat->common.alignment);
+				map->pagesneeded++;
+			}
+			vaddr += sg_len;
+		}
+		CTR1(KTR_BUSDMA, "pagesneeded= %d\n", map->pagesneeded);
+	}
+}
+
+static int
+_bus_dmamap_reserve_pages(bus_dma_tag_t dmat, bus_dmamap_t map, int flags)
+{
+
+	/* Reserve Necessary Bounce Pages */
+	mtx_lock(&bounce_lock);
+	if (flags & BUS_DMA_NOWAIT) {
+		if (reserve_bounce_pages(dmat, map, 0) != 0) {
+			mtx_unlock(&bounce_lock);
+			return (ENOMEM);
+		}
+	} else {
+		if (reserve_bounce_pages(dmat, map, 1) != 0) {
+			/* Queue us for resources */
+			STAILQ_INSERT_TAIL(&bounce_map_waitinglist, map, links);
+			mtx_unlock(&bounce_lock);
+			return (EINPROGRESS);
+		}
+	}
+	mtx_unlock(&bounce_lock);
+
+	return (0);
+}
+
+/*
+ * Add a single contiguous physical range to the segment list.
+ */
+static int
+_bus_dmamap_addseg(bus_dma_tag_t dmat, bus_dmamap_t map, bus_addr_t curaddr,
+    bus_size_t sgsize, bus_dma_segment_t *segs, int *segp)
+{
+	bus_addr_t baddr, bmask;
+	int seg;
+
+	/*
+	 * Make sure we don't cross any boundaries.
+	 */
+	bmask = ~(dmat->common.boundary - 1);
+	if (dmat->common.boundary > 0) {
+		baddr = (curaddr + dmat->common.boundary) & bmask;
+		if (sgsize > (baddr - curaddr))
+			sgsize = (baddr - curaddr);
+	}
+
+	/*
+	 * Insert chunk into a segment, coalescing with
+	 * previous segment if possible.
+	 */
+	seg = *segp;
+	if (seg == -1) {
+		seg = 0;
+		segs[seg].ds_addr = curaddr;
+		segs[seg].ds_len = sgsize;
+	} else {
+		if (curaddr == segs[seg].ds_addr + segs[seg].ds_len &&
+		    (segs[seg].ds_len + sgsize) <= dmat->common.maxsegsz &&
+		    (dmat->common.boundary == 0 ||
+		     (segs[seg].ds_addr & bmask) == (curaddr & bmask)))
+			segs[seg].ds_len += sgsize;
+		else {
+			if (++seg >= dmat->common.nsegments)
+				return (0);
+			segs[seg].ds_addr = curaddr;
+			segs[seg].ds_len = sgsize;
+		}
+	}
+	*segp = seg;
+	return (sgsize);
+}
+
+/*
+ * 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)
+{
+	bus_size_t sgsize;
+	bus_addr_t curaddr;
+	int error;
+
+	if (map == NULL || map == &contig_dmamap)
+		map = &nobounce_dmamap;
+
+	if (segs == NULL)
+		segs = dmat->segments;
+
+	if ((dmat->common.flags & BUS_DMA_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);
+		}
+	}
+
+	while (buflen > 0) {
+		curaddr = buf;
+		sgsize = MIN(buflen, dmat->common.maxsegsz);
+		if (((dmat->common.flags & BUS_DMA_COULD_BOUNCE) != 0) &&
+		    map->pagesneeded != 0 &&
+		    bus_dma_run_filter(&dmat->common, curaddr)) {
+			sgsize = MIN(sgsize, PAGE_SIZE);
+			curaddr = add_bounce_page(dmat, map, 0, curaddr,
+			    sgsize);
+		}
+		sgsize = _bus_dmamap_addseg(dmat, map, curaddr, sgsize, segs,
+		    segp);
+		if (sgsize == 0)
+			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)
+{
+	bus_size_t sgsize, max_sgsize;
+	bus_addr_t curaddr;
+	vm_offset_t vaddr;
+	int error;
+
+	if (map == NULL || map == &contig_dmamap)
+		map = &nobounce_dmamap;
+
+	if (segs == NULL)
+		segs = dmat->segments;
+
+	if ((dmat->common.flags & BUS_DMA_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);
+		}
+	}
+
+	vaddr = (vm_offset_t)buf;
+	while (buflen > 0) {
+		/*
+		 * Get the physical address for this segment.
+		 */
+		if (pmap == kernel_pmap)
+			curaddr = pmap_kextract(vaddr);
+		else
+			curaddr = pmap_extract(pmap, vaddr);
+
+		/*
+		 * Compute the segment size, and adjust counts.
+		 */
+		max_sgsize = MIN(buflen, dmat->common.maxsegsz);
+		sgsize = PAGE_SIZE - ((vm_offset_t)curaddr & PAGE_MASK);
+		if (((dmat->common.flags & BUS_DMA_COULD_BOUNCE) != 0) &&
+		    map->pagesneeded != 0 &&
+		    bus_dma_run_filter(&dmat->common, curaddr)) {
+			sgsize = roundup2(sgsize, dmat->common.alignment);
+			sgsize = MIN(sgsize, max_sgsize);
+			curaddr = add_bounce_page(dmat, map, vaddr, curaddr,
+			    sgsize);
+		} else {
+			sgsize = MIN(sgsize, max_sgsize);
+		}
+		sgsize = _bus_dmamap_addseg(dmat, map, curaddr, sgsize, segs,
+		    segp);
+		if (sgsize == 0)
+			break;
+		vaddr += sgsize;
+		buflen -= sgsize;
+	}
+
+	/*
+	 * 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 == NULL)
+		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)
+{
+	struct bounce_page *bpage;
+
+	while ((bpage = STAILQ_FIRST(&map->bpages)) != NULL) {
+		STAILQ_REMOVE_HEAD(&map->bpages, links);
+		free_bounce_page(dmat, bpage);
+	}
+}
+
+static void
+bounce_bus_dmamap_sync(bus_dma_tag_t dmat, bus_dmamap_t map,
+    bus_dmasync_op_t op)
+{
+	struct bounce_page *bpage;
+
+	if ((bpage = STAILQ_FIRST(&map->bpages)) != NULL) {
+		/*
+		 * Handle data bouncing.  We might also
+		 * want to add support for invalidating
+		 * the caches on broken hardware
+		 */
+		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) {
+				if (bpage->datavaddr != 0) {
+					bcopy((void *)bpage->datavaddr,
+					    (void *)bpage->vaddr,
+					    bpage->datacount);
+				} else {
+					physcopyout(bpage->dataaddr,
+					    (void *)bpage->vaddr,
+					    bpage->datacount);
+				}
+				bpage = STAILQ_NEXT(bpage, links);
+			}
+			dmat->bounce_zone->total_bounced++;
+		}
+
+		if ((op & BUS_DMASYNC_POSTREAD) != 0) {
+			while (bpage != NULL) {
+				if (bpage->datavaddr != 0) {
+					bcopy((void *)bpage->vaddr,
+					    (void *)bpage->datavaddr,
+					    bpage->datacount);
+				} else {
+					physcopyin((void *)bpage->vaddr,
+					    bpage->dataaddr,
+					    bpage->datacount);
+				}
+				bpage = STAILQ_NEXT(bpage, links);
+			}
+			dmat->bounce_zone->total_bounced++;
+		}
+	}
+}
+
+static void
+init_bounce_pages(void *dummy __unused)
+{
+
+	total_bpages = 0;
+	STAILQ_INIT(&bounce_zone_list);
+	STAILQ_INIT(&bounce_map_waitinglist);
+	STAILQ_INIT(&bounce_map_callbacklist);
+	mtx_init(&bounce_lock, "bounce pages lock", NULL, MTX_DEF);
+}
+SYSINIT(bpages, SI_SUB_LOCK, SI_ORDER_ANY, init_bounce_pages, NULL);
+
+static struct sysctl_ctx_list *
+busdma_sysctl_tree(struct bounce_zone *bz)
+{
+	return (&bz->sysctl_tree);
+}
+
+static struct sysctl_oid *
+busdma_sysctl_tree_top(struct bounce_zone *bz)
+{
+	return (bz->sysctl_tree_top);
+}
+
+#if defined(__amd64__) || defined(PAE)
+#define	SYSCTL_ADD_BUS_SIZE_T	SYSCTL_ADD_UQUAD
+#else
+#define	SYSCTL_ADD_BUS_SIZE_T(ctx, parent, nbr, name, flag, ptr, desc)	\
+	SYSCTL_ADD_UINT(ctx, parent, nbr, name, flag, ptr, 0, desc)
+#endif
+
+static int
+alloc_bounce_zone(bus_dma_tag_t dmat)
+{
+	struct bounce_zone *bz;
+
+	/* Check to see if we already have a suitable zone */
+	STAILQ_FOREACH(bz, &bounce_zone_list, links) {
+		if ((dmat->common.alignment <= bz->alignment) &&
+		    (dmat->common.lowaddr >= bz->lowaddr)) {
+			dmat->bounce_zone = bz;
+			return (0);
+		}
+	}
+
+	if ((bz = (struct bounce_zone *)malloc(sizeof(*bz), M_DEVBUF,
+	    M_NOWAIT | M_ZERO)) == NULL)
+		return (ENOMEM);
+
+	STAILQ_INIT(&bz->bounce_page_list);
+	bz->free_bpages = 0;
+	bz->reserved_bpages = 0;
+	bz->active_bpages = 0;
+	bz->lowaddr = dmat->common.lowaddr;
+	bz->alignment = MAX(dmat->common.alignment, PAGE_SIZE);
+	bz->map_count = 0;
+	snprintf(bz->zoneid, 8, "zone%d", busdma_zonecount);
+	busdma_zonecount++;
+	snprintf(bz->lowaddrid, 18, "%#jx", (uintmax_t)bz->lowaddr);
+	STAILQ_INSERT_TAIL(&bounce_zone_list, bz, links);
+	dmat->bounce_zone = bz;
+
+	sysctl_ctx_init(&bz->sysctl_tree);
+	bz->sysctl_tree_top = SYSCTL_ADD_NODE(&bz->sysctl_tree,
+	    SYSCTL_STATIC_CHILDREN(_hw_busdma), OID_AUTO, bz->zoneid,
+	    CTLFLAG_RD, 0, "");
+	if (bz->sysctl_tree_top == NULL) {
+		sysctl_ctx_free(&bz->sysctl_tree);
+		return (0);	/* XXX error code? */
+	}
+
+	SYSCTL_ADD_INT(busdma_sysctl_tree(bz),
+	    SYSCTL_CHILDREN(busdma_sysctl_tree_top(bz)), OID_AUTO,
+	    "total_bpages", CTLFLAG_RD, &bz->total_bpages, 0,
+	    "Total bounce pages");
+	SYSCTL_ADD_INT(busdma_sysctl_tree(bz),
+	    SYSCTL_CHILDREN(busdma_sysctl_tree_top(bz)), OID_AUTO,
+	    "free_bpages", CTLFLAG_RD, &bz->free_bpages, 0,
+	    "Free bounce pages");
+	SYSCTL_ADD_INT(busdma_sysctl_tree(bz),
+	    SYSCTL_CHILDREN(busdma_sysctl_tree_top(bz)), OID_AUTO,
+	    "reserved_bpages", CTLFLAG_RD, &bz->reserved_bpages, 0,
+	    "Reserved bounce pages");
+	SYSCTL_ADD_INT(busdma_sysctl_tree(bz),
+	    SYSCTL_CHILDREN(busdma_sysctl_tree_top(bz)), OID_AUTO,
+	    "active_bpages", CTLFLAG_RD, &bz->active_bpages, 0,
+	    "Active bounce pages");
+	SYSCTL_ADD_INT(busdma_sysctl_tree(bz),
+	    SYSCTL_CHILDREN(busdma_sysctl_tree_top(bz)), OID_AUTO,
+	    "total_bounced", CTLFLAG_RD, &bz->total_bounced, 0,
+	    "Total bounce requests");
+	SYSCTL_ADD_INT(busdma_sysctl_tree(bz),
+	    SYSCTL_CHILDREN(busdma_sysctl_tree_top(bz)), OID_AUTO,
+	    "total_deferred", CTLFLAG_RD, &bz->total_deferred, 0,
+	    "Total bounce requests that were deferred");
+	SYSCTL_ADD_STRING(busdma_sysctl_tree(bz),
+	    SYSCTL_CHILDREN(busdma_sysctl_tree_top(bz)), OID_AUTO,
+	    "lowaddr", CTLFLAG_RD, bz->lowaddrid, 0, "");
+	SYSCTL_ADD_BUS_SIZE_T(busdma_sysctl_tree(bz),
+	    SYSCTL_CHILDREN(busdma_sysctl_tree_top(bz)), OID_AUTO,
+	    "alignment", CTLFLAG_RD, &bz->alignment, "");
+
+	return (0);
+}
+
+static int
+alloc_bounce_pages(bus_dma_tag_t dmat, u_int numpages)
+{
+	struct bounce_zone *bz;
+	int count;
+
+	bz = dmat->bounce_zone;
+	count = 0;
+	while (numpages > 0) {
+		struct bounce_page *bpage;
+
+		bpage = (struct bounce_page *)malloc(sizeof(*bpage), M_DEVBUF,
+						     M_NOWAIT | M_ZERO);
+
+		if (bpage == NULL)
+			break;
+		bpage->vaddr = (vm_offset_t)contigmalloc(PAGE_SIZE, M_DEVBUF,
+							 M_NOWAIT, 0ul,
+							 bz->lowaddr,
+							 PAGE_SIZE,
+							 0);
+		if (bpage->vaddr == 0) {
+			free(bpage, M_DEVBUF);
+			break;
+		}
+		bpage->busaddr = pmap_kextract(bpage->vaddr);
+		mtx_lock(&bounce_lock);
+		STAILQ_INSERT_TAIL(&bz->bounce_page_list, bpage, links);
+		total_bpages++;
+		bz->total_bpages++;
+		bz->free_bpages++;
+		mtx_unlock(&bounce_lock);
+		count++;
+		numpages--;
+	}
+	return (count);
+}
+
+static int
+reserve_bounce_pages(bus_dma_tag_t dmat, bus_dmamap_t map, int commit)
+{
+	struct bounce_zone *bz;
+	int pages;
+
+	mtx_assert(&bounce_lock, MA_OWNED);
+	bz = dmat->bounce_zone;
+	pages = MIN(bz->free_bpages, map->pagesneeded - map->pagesreserved);
+	if (commit == 0 && map->pagesneeded > (map->pagesreserved + pages))
+		return (map->pagesneeded - (map->pagesreserved + pages));
+	bz->free_bpages -= pages;
+	bz->reserved_bpages += pages;
+	map->pagesreserved += pages;
+	pages = map->pagesneeded - map->pagesreserved;
+
+	return (pages);
+}
+
+static bus_addr_t
+add_bounce_page(bus_dma_tag_t dmat, bus_dmamap_t map, vm_offset_t vaddr,
+		bus_addr_t addr, bus_size_t size)
+{
+	struct bounce_zone *bz;
+	struct bounce_page *bpage;
+
+	KASSERT(dmat->bounce_zone != NULL, ("no bounce zone in dma tag"));
+	KASSERT(map != NULL && map != &nobounce_dmamap && map != &contig_dmamap,
+	    ("add_bounce_page: bad map %p", map));
+
+	bz = dmat->bounce_zone;
+	if (map->pagesneeded == 0)
+		panic("add_bounce_page: map doesn't need any pages");
+	map->pagesneeded--;
+
+	if (map->pagesreserved == 0)
+		panic("add_bounce_page: map doesn't need any pages");
+	map->pagesreserved--;
+
+	mtx_lock(&bounce_lock);
+	bpage = STAILQ_FIRST(&bz->bounce_page_list);
+	if (bpage == NULL)
+		panic("add_bounce_page: free page list is empty");
+
+	STAILQ_REMOVE_HEAD(&bz->bounce_page_list, links);
+	bz->reserved_bpages--;
+	bz->active_bpages++;
+	mtx_unlock(&bounce_lock);
+
+	if (dmat->common.flags & BUS_DMA_KEEP_PG_OFFSET) {
+		/* Page offset needs to be preserved. */
+		bpage->vaddr |= vaddr & PAGE_MASK;
+		bpage->busaddr |= vaddr & PAGE_MASK;
+	}
+	bpage->datavaddr = vaddr;
+	bpage->dataaddr = addr;
+	bpage->datacount = size;
+	STAILQ_INSERT_TAIL(&(map->bpages), bpage, links);
+	return (bpage->busaddr);
+}
+
+static void
+free_bounce_page(bus_dma_tag_t dmat, struct bounce_page *bpage)
+{
+	struct bus_dmamap *map;
+	struct bounce_zone *bz;
+
+	bz = dmat->bounce_zone;
+	bpage->datavaddr = 0;
+	bpage->datacount = 0;
+	if (dmat->common.flags & BUS_DMA_KEEP_PG_OFFSET) {
+		/*
+		 * Reset the bounce page to start at offset 0.  Other uses
+		 * of this bounce page may need to store a full page of
+		 * data and/or assume it starts on a page boundary.
+		 */
+		bpage->vaddr &= ~PAGE_MASK;
+		bpage->busaddr &= ~PAGE_MASK;
+	}
+
+	mtx_lock(&bounce_lock);
+	STAILQ_INSERT_HEAD(&bz->bounce_page_list, bpage, links);
+	bz->free_bpages++;
+	bz->active_bpages--;
+	if ((map = STAILQ_FIRST(&bounce_map_waitinglist)) != NULL) {
+		if (reserve_bounce_pages(map->dmat, map, 1) == 0) {
+			STAILQ_REMOVE_HEAD(&bounce_map_waitinglist, links);
+			STAILQ_INSERT_TAIL(&bounce_map_callbacklist,
+			    map, links);
+			busdma_swi_pending = 1;
+			bz->total_deferred++;
+			swi_sched(vm_ih, 0);
+		}
+	}
+	mtx_unlock(&bounce_lock);
+}
+
+void
+busdma_swi(void)
+{
+	bus_dma_tag_t dmat;
+	struct bus_dmamap *map;
+
+	mtx_lock(&bounce_lock);
+	while ((map = STAILQ_FIRST(&bounce_map_callbacklist)) != NULL) {
+		STAILQ_REMOVE_HEAD(&bounce_map_callbacklist, links);
+		mtx_unlock(&bounce_lock);
+		dmat = map->dmat;
+		(dmat->common.lockfunc)(dmat->common.lockfuncarg, BUS_DMA_LOCK);
+		bus_dmamap_load_mem(map->dmat, map, &map->mem,
+		    map->callback, map->callback_arg, BUS_DMA_WAITOK);
+		(dmat->common.lockfunc)(dmat->common.lockfuncarg,
+		    BUS_DMA_UNLOCK);
+		mtx_lock(&bounce_lock);
+	}
+	mtx_unlock(&bounce_lock);
+}
+
+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
+};
diff --git a/sys/x86/x86/busdma_machdep.c b/sys/x86/x86/busdma_machdep.c
index 722335421331..c96b26d579f2 100644
--- a/sys/x86/x86/busdma_machdep.c
+++ b/sys/x86/x86/busdma_machdep.c
@@ -1,7 +1,11 @@
 /*-
  * Copyright (c) 1997, 1998 Justin T. Gibbs.
+ * Copyright (c) 2013 The FreeBSD Foundation
  * All rights reserved.
  *
+ * This software was developed by Konstantin Belousov <kib@FreeBSD.org>
+ * under sponsorship from the FreeBSD Foundation.
+ *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
@@ -31,160 +35,17 @@ __FBSDID("$FreeBSD$");
 #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 <vm/pmap.h>
 #include <machine/bus.h>
-#include <machine/md_var.h>
-#include <machine/specialreg.h>
-
-#ifdef __i386__
-#define MAX_BPAGES 512
-#else
-#define MAX_BPAGES 8192
-#endif
-#define BUS_DMA_COULD_BOUNCE	BUS_DMA_BUS3
-#define BUS_DMA_MIN_ALLOC_COMP	BUS_DMA_BUS4
-
-struct bounce_zone;
-
-struct bus_dma_tag {
-	bus_dma_tag_t	  parent;
-	bus_size_t	  alignment;
-	bus_addr_t	  boundary;
-	bus_addr_t	  lowaddr;
-	bus_addr_t	  highaddr;
-	bus_dma_filter_t *filter;
-	void		 *filterarg;
-	bus_size_t	  maxsize;
-	u_int		  nsegments;
-	bus_size_t	  maxsegsz;
-	int		  flags;
-	int		  ref_count;
-	int		  map_count;
-	bus_dma_lock_t	 *lockfunc;
-	void		 *lockfuncarg;
-	bus_dma_segment_t *segments;
-	struct bounce_zone *bounce_zone;
-};
-
-struct bounce_page {
-	vm_offset_t	vaddr;		/* kva of bounce buffer */
-	bus_addr_t	busaddr;	/* Physical address */
-	vm_offset_t	datavaddr;	/* kva of client data */
-	bus_addr_t	dataaddr;	/* client physical address */
-	bus_size_t	datacount;	/* client data count */
-	STAILQ_ENTRY(bounce_page) links;
-};
-
-int busdma_swi_pending;
-
-struct bounce_zone {
-	STAILQ_ENTRY(bounce_zone) links;
-	STAILQ_HEAD(bp_list, bounce_page) bounce_page_list;
-	int		total_bpages;
-	int		free_bpages;
-	int		reserved_bpages;
-	int		active_bpages;
-	int		total_bounced;
-	int		total_deferred;
-	int		map_count;
-	bus_size_t	alignment;
-	bus_addr_t	lowaddr;
-	char		zoneid[8];
-	char		lowaddrid[20];
-	struct sysctl_ctx_list sysctl_tree;
-	struct sysctl_oid *sysctl_tree_top;
-};
-
-static struct mtx bounce_lock;
-static int total_bpages;
-static int busdma_zonecount;
-static STAILQ_HEAD(, bounce_zone) bounce_zone_list;
-
-static SYSCTL_NODE(_hw, OID_AUTO, busdma, CTLFLAG_RD, 0, "Busdma parameters");
-SYSCTL_INT(_hw_busdma, OID_AUTO, total_bpages, CTLFLAG_RD, &total_bpages, 0,
-	   "Total bounce pages");
-
-struct bus_dmamap {
-	struct bp_list	       bpages;
-	int		       pagesneeded;
-	int		       pagesreserved;
-	bus_dma_tag_t	       dmat;
-	struct memdesc	       mem;
-	bus_dmamap_callback_t *callback;
-	void		      *callback_arg;
-	STAILQ_ENTRY(bus_dmamap) links;
-};
-
-static STAILQ_HEAD(, bus_dmamap) bounce_map_waitinglist;
-static STAILQ_HEAD(, bus_dmamap) bounce_map_callbacklist;
-static struct bus_dmamap nobounce_dmamap, contig_dmamap;
-
-static void init_bounce_pages(void *dummy);
-static int alloc_bounce_zone(bus_dma_tag_t dmat);
-static int alloc_bounce_pages(bus_dma_tag_t dmat, u_int numpages);
-static int reserve_bounce_pages(bus_dma_tag_t dmat, bus_dmamap_t map,
-				int commit);
-static bus_addr_t add_bounce_page(bus_dma_tag_t dmat, bus_dmamap_t map,
-				  vm_offset_t vaddr, bus_addr_t addr,
-				  bus_size_t size);
-static void free_bounce_page(bus_dma_tag_t dmat, struct bounce_page *bpage);
-int run_filter(bus_dma_tag_t dmat, bus_addr_t paddr);
-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 int _bus_dmamap_reserve_pages(bus_dma_tag_t dmat, bus_dmamap_t map,
-				     int flags);
-
-#ifdef XEN
-#undef pmap_kextract
-#define pmap_kextract pmap_kextract_ma
-#endif
-
-/*
- * Return true if a match is made.
- *
- * To find a match walk the chain of bus_dma_tag_t's looking for 'paddr'.
- *
- * If paddr is within the bounds of the dma tag then call the filter callback
- * to check for a match, if there is no filter callback then assume a match.
- */
-int
-run_filter(bus_dma_tag_t dmat, bus_addr_t paddr)
-{
-	int retval;
-
-	retval = 0;
-
-	do {
-		if (((paddr > dmat->lowaddr && paddr <= dmat->highaddr)
-		 || ((paddr & (dmat->alignment - 1)) != 0))
-		 && (dmat->filter == NULL
-		  || (*dmat->filter)(dmat->filterarg, paddr) != 0))
-			retval = 1;
-
-		dmat = dmat->parent;		
-	} while (retval == 0 && dmat != NULL);
-	return (retval);
-}
+#include <x86/include/busdma_impl.h>
 
 /*
  * Convenience function for manipulating driver locks from busdma (during
@@ -216,169 +77,146 @@ busdma_lock_mutex(void *arg, bus_dma_lock_op_t op)
  * with the tag are meant to never be defered.
  * XXX Should have a way to identify which driver is responsible here.
  */
-static void
-dflt_lock(void *arg, bus_dma_lock_op_t op)
+void
+bus_dma_dflt_lock(void *arg, bus_dma_lock_op_t op)
 {
+
 	panic("driver error: busdma dflt_lock called");
 }
 
 /*
- * Allocate a device specific dma_tag.
+ * Return true if a match is made.
+ *
+ * To find a match walk the chain of bus_dma_tag_t's looking for 'paddr'.
+ *
+ * If paddr is within the bounds of the dma tag then call the filter callback
+ * to check for a match, if there is no filter callback then assume a match.
  */
 int
-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_dma_filter_t *filter,
-		   void *filterarg, 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_run_filter(struct bus_dma_tag_common *tc, bus_addr_t paddr)
 {
-	bus_dma_tag_t newtag;
-	int error = 0;
+	int retval;
 
+	retval = 0;
+	do {
+		if (((paddr > tc->lowaddr && paddr <= tc->highaddr) ||
+		    ((paddr & (tc->alignment - 1)) != 0)) &&
+		    (tc->filter == NULL ||
+		    (*tc->filter)(tc->filterarg, paddr) != 0))
+			retval = 1;
+
+		tc = tc->parent;		
+	} while (retval == 0 && tc != NULL);
+	return (retval);
+}
+
+int
+common_bus_dma_tag_create(struct bus_dma_tag_common *parent,
+    bus_size_t alignment, bus_addr_t boundary, bus_addr_t lowaddr,
+    bus_addr_t highaddr, bus_dma_filter_t *filter, void *filterarg,
+    bus_size_t maxsize, int nsegments, bus_size_t maxsegsz, int flags,
+    bus_dma_lock_t *lockfunc, void *lockfuncarg, size_t sz, void **dmat)
+{
+	void *newtag;
+	struct bus_dma_tag_common *common;
+
+	KASSERT(sz >= sizeof(struct bus_dma_tag_common), ("sz"));
 	/* Basic sanity checking */
 	if (boundary != 0 && boundary < maxsegsz)
 		maxsegsz = boundary;
-
-	if (maxsegsz == 0) {
+	if (maxsegsz == 0)
 		return (EINVAL);
-	}
-
 	/* Return a NULL tag on failure */
 	*dmat = NULL;
 
-	newtag = (bus_dma_tag_t)malloc(sizeof(*newtag), M_DEVBUF,
-	    M_ZERO | M_NOWAIT);
+	newtag = malloc(sz, M_DEVBUF, M_ZERO | M_NOWAIT);
 	if (newtag == NULL) {
 		CTR4(KTR_BUSDMA, "%s returned tag %p tag flags 0x%x error %d",
 		    __func__, newtag, 0, ENOMEM);
 		return (ENOMEM);
 	}
 
-	newtag->parent = parent;
-	newtag->alignment = alignment;
-	newtag->boundary = boundary;
-	newtag->lowaddr = trunc_page((vm_paddr_t)lowaddr) + (PAGE_SIZE - 1);
-	newtag->highaddr = trunc_page((vm_paddr_t)highaddr) + (PAGE_SIZE - 1);
-	newtag->filter = filter;
-	newtag->filterarg = filterarg;
-	newtag->maxsize = maxsize;
-	newtag->nsegments = nsegments;
-	newtag->maxsegsz = maxsegsz;
-	newtag->flags = flags;
-	newtag->ref_count = 1; /* Count ourself */
-	newtag->map_count = 0;
+	common = newtag;
+	common->impl = &bus_dma_bounce_impl;
+	common->parent = parent;
+	common->alignment = alignment;
+	common->boundary = boundary;
+	common->lowaddr = trunc_page((vm_paddr_t)lowaddr) + (PAGE_SIZE - 1);
+	common->highaddr = trunc_page((vm_paddr_t)highaddr) + (PAGE_SIZE - 1);
+	common->filter = filter;
+	common->filterarg = filterarg;
+	common->maxsize = maxsize;
+	common->nsegments = nsegments;
+	common->maxsegsz = maxsegsz;
+	common->flags = flags;
+	common->ref_count = 1; /* Count ourself */
 	if (lockfunc != NULL) {
-		newtag->lockfunc = lockfunc;
-		newtag->lockfuncarg = lockfuncarg;
+		common->lockfunc = lockfunc;
+		common->lockfuncarg = lockfuncarg;
 	} else {
-		newtag->lockfunc = dflt_lock;
-		newtag->lockfuncarg = NULL;
+		common->lockfunc = bus_dma_dflt_lock;
+		common->lockfuncarg = NULL;
 	}
-	newtag->segments = NULL;
 
 	/* Take into account any restrictions imposed by our parent tag */
 	if (parent != NULL) {
-		newtag->lowaddr = MIN(parent->lowaddr, newtag->lowaddr);
-		newtag->highaddr = MAX(parent->highaddr, newtag->highaddr);
-		if (newtag->boundary == 0)
-			newtag->boundary = parent->boundary;
-		else if (parent->boundary != 0)
-			newtag->boundary = MIN(parent->boundary,
-					       newtag->boundary);
-		if ((newtag->filter != NULL) ||
-		    ((parent->flags & BUS_DMA_COULD_BOUNCE) != 0))
-			newtag->flags |= BUS_DMA_COULD_BOUNCE;
-		if (newtag->filter == NULL) {
+		common->impl = parent->impl;
+		common->lowaddr = MIN(parent->lowaddr, common->lowaddr);
+		common->highaddr = MAX(parent->highaddr, common->highaddr);
+		if (common->boundary == 0)
+			common->boundary = parent->boundary;
+		else if (parent->boundary != 0) {
+			common->boundary = MIN(parent->boundary,
+			    common->boundary);
+		}
+		if (common->filter == NULL) {
 			/*
 			 * Short circuit looking at our parent directly
 			 * since we have encapsulated all of its information
 			 */
-			newtag->filter = parent->filter;
-			newtag->filterarg = parent->filterarg;
-			newtag->parent = parent->parent;
+			common->filter = parent->filter;
+			common->filterarg = parent->filterarg;
+			common->parent = parent->parent;
 		}
-		if (newtag->parent != NULL)
-			atomic_add_int(&parent->ref_count, 1);
+		atomic_add_int(&parent->ref_count, 1);
 	}
+	*dmat = common;
+	return (0);
+}
 
-	if (newtag->lowaddr < ptoa((vm_paddr_t)Maxmem)
-	 || newtag->alignment > 1)
-		newtag->flags |= BUS_DMA_COULD_BOUNCE;
-
-	if (((newtag->flags & BUS_DMA_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(maxsize) - bz->total_bpages;
+/*
+ * Allocate a device specific dma_tag.
+ */
+int
+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_dma_filter_t *filter, void *filterarg, bus_size_t maxsize,
+    int nsegments, bus_size_t maxsegsz, int flags, bus_dma_lock_t *lockfunc,
+    void *lockfuncarg, bus_dma_tag_t *dmat)
+{
+	struct bus_dma_tag_common *tc;
+	int error;
 
-			/* Add pages to our bounce pool */
-			if (alloc_bounce_pages(newtag, pages) < pages)
-				error = ENOMEM;
-		}
-		/* Performed initial allocation */
-		newtag->flags |= BUS_DMA_MIN_ALLOC_COMP;
-	}
-	
-	if (error != 0) {
-		free(newtag, M_DEVBUF);
+	if (parent == NULL) {
+		error = bus_dma_bounce_impl.tag_create(parent, alignment,
+		    boundary, lowaddr, highaddr, filter, filterarg, maxsize,
+		    nsegments, maxsegsz, flags, lockfunc, lockfuncarg, dmat);
 	} else {
-		*dmat = newtag;
+		tc = (struct bus_dma_tag_common *)parent;
+		error = tc->impl->tag_create(parent, alignment,
+		    boundary, lowaddr, highaddr, filter, filterarg, maxsize,
+		    nsegments, maxsegsz, flags, lockfunc, lockfuncarg, dmat);
 	}
-	CTR4(KTR_BUSDMA, "%s returned tag %p tag flags 0x%x error %d",
-	    __func__, newtag, (newtag != NULL ? newtag->flags : 0), error);
 	return (error);
 }
 
 int
 bus_dma_tag_destroy(bus_dma_tag_t dmat)
 {
-	bus_dma_tag_t dmat_copy;
-	int error;
-
-	error = 0;
-	dmat_copy = dmat;
+	struct bus_dma_tag_common *tc;
 
-	if (dmat != NULL) {
-
-		if (dmat->map_count != 0) {
-			error = EBUSY;
-			goto out;
-		}
-
-		while (dmat != NULL) {
-			bus_dma_tag_t parent;
-
-			parent = dmat->parent;
-			atomic_subtract_int(&dmat->ref_count, 1);
-			if (dmat->ref_count == 0) {
-				if (dmat->segments != NULL)
-					free(dmat->segments, M_DEVBUF);
-				free(dmat, M_DEVBUF);
-				/*
-				 * Last reference count, so
-				 * release our reference
-				 * count on our parent.
-				 */
-				dmat = parent;
-			} else
-				dmat = NULL;
-		}
-	}
-out:
-	CTR3(KTR_BUSDMA, "%s tag %p error %d", __func__, dmat_copy, error);
-	return (error);
+	tc = (struct bus_dma_tag_common *)dmat;
+	return (tc->impl->tag_destroy(dmat));
 }
 
 /*
@@ -388,83 +226,10 @@ out:
 int
 bus_dmamap_create(bus_dma_tag_t dmat, int flags, bus_dmamap_t *mapp)
 {
-	int error;
-
-	error = 0;
-
-	if (dmat->segments == NULL) {
-		dmat->segments = (bus_dma_segment_t *)malloc(
-		    sizeof(bus_dma_segment_t) * dmat->nsegments, M_DEVBUF,
-		    M_NOWAIT);
-		if (dmat->segments == 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->flags & BUS_DMA_COULD_BOUNCE) {
-
-		/* Must bounce */
-		struct bounce_zone *bz;
-		int maxpages;
-
-		if (dmat->bounce_zone == NULL) {
-			if ((error = alloc_bounce_zone(dmat)) != 0)
-				return (error);
-		}
-		bz = dmat->bounce_zone;
+	struct bus_dma_tag_common *tc;
 
-		*mapp = (bus_dmamap_t)malloc(sizeof(**mapp), M_DEVBUF,
-					     M_NOWAIT | M_ZERO);
-		if (*mapp == NULL) {
-			CTR3(KTR_BUSDMA, "%s: tag %p error %d",
-			    __func__, dmat, ENOMEM);
-			return (ENOMEM);
-		}
-
-		/* Initialize the new map */
-		STAILQ_INIT(&((*mapp)->bpages));
-
-		/*
-		 * Attempt to add pages to our pool on a per-instance
-		 * basis up to a sane limit.
-		 */
-		if (dmat->alignment > 1)
-			maxpages = MAX_BPAGES;
-		else
-			maxpages = MIN(MAX_BPAGES, Maxmem -atop(dmat->lowaddr));
-		if ((dmat->flags & BUS_DMA_MIN_ALLOC_COMP) == 0
-		 || (bz->map_count > 0 && bz->total_bpages < maxpages)) {
-			int pages;
-
-			pages = MAX(atop(dmat->maxsize), 1);
-			pages = MIN(maxpages - bz->total_bpages, pages);
-			pages = MAX(pages, 1);
-			if (alloc_bounce_pages(dmat, pages) < pages)
-				error = ENOMEM;
-
-			if ((dmat->flags & BUS_DMA_MIN_ALLOC_COMP) == 0) {
-				if (error == 0)
-					dmat->flags |= BUS_DMA_MIN_ALLOC_COMP;
-			} else {
-				error = 0;
-			}
-		}
-		bz->map_count++;
-	} else {
-		*mapp = NULL;
-	}
-	if (error == 0)
-		dmat->map_count++;
-	CTR4(KTR_BUSDMA, "%s: tag %p tag flags 0x%x error %d",
-	    __func__, dmat, dmat->flags, error);
-	return (error);
+	tc = (struct bus_dma_tag_common *)dmat;
+	return (tc->impl->map_create(dmat, flags, mapp));
 }
 
 /*
@@ -474,19 +239,10 @@ bus_dmamap_create(bus_dma_tag_t dmat, int flags, bus_dmamap_t *mapp)
 int
 bus_dmamap_destroy(bus_dma_tag_t dmat, bus_dmamap_t map)
 {
-	if (map != NULL && map != &nobounce_dmamap && map != &contig_dmamap) {
-		if (STAILQ_FIRST(&map->bpages) != NULL) {
-			CTR3(KTR_BUSDMA, "%s: tag %p error %d",
-			    __func__, dmat, EBUSY);
-			return (EBUSY);
-		}
-		if (dmat->bounce_zone)
-			dmat->bounce_zone->map_count--;
-		free(map, M_DEVBUF);
-	}
-	dmat->map_count--;
-	CTR2(KTR_BUSDMA, "%s: tag %p error 0", __func__, dmat);
-	return (0);
+	struct bus_dma_tag_common *tc;
+
+	tc = (struct bus_dma_tag_common *)dmat;
+	return (tc->impl->map_destroy(dmat, map));
 }
 
 
@@ -497,72 +253,12 @@ bus_dmamap_destroy(bus_dma_tag_t dmat, bus_dmamap_t map)
  */
 int
 bus_dmamem_alloc(bus_dma_tag_t dmat, void** vaddr, int flags,
-		 bus_dmamap_t *mapp)
+    bus_dmamap_t *mapp)
 {
-	vm_memattr_t attr;
-	int mflags;
-
-	if (flags & BUS_DMA_NOWAIT)
-		mflags = M_NOWAIT;
-	else
-		mflags = M_WAITOK;
+	struct bus_dma_tag_common *tc;
 
-	/* If we succeed, no mapping/bouncing will be required */
-	*mapp = NULL;
-
-	if (dmat->segments == NULL) {
-		dmat->segments = (bus_dma_segment_t *)malloc(
-		    sizeof(bus_dma_segment_t) * dmat->nsegments, M_DEVBUF,
-		    mflags);
-		if (dmat->segments == NULL) {
-			CTR4(KTR_BUSDMA, "%s: tag %p tag flags 0x%x error %d",
-			    __func__, dmat, dmat->flags, ENOMEM);
-			return (ENOMEM);
-		}
-	}
-	if (flags & BUS_DMA_ZERO)
-		mflags |= M_ZERO;
-	if (flags & BUS_DMA_NOCACHE)
-		attr = VM_MEMATTR_UNCACHEABLE;
-	else
-		attr = VM_MEMATTR_DEFAULT;
-
-	/* 
-	 * XXX:
-	 * (dmat->alignment < dmat->maxsize) is just a quick hack; the exact
-	 * alignment guarantees of malloc need to be nailed down, and the
-	 * code below should be rewritten to take that into account.
-	 *
-	 * In the meantime, we'll warn the user if malloc gets it wrong.
-	 */
-	if ((dmat->maxsize <= PAGE_SIZE) &&
-	   (dmat->alignment < dmat->maxsize) &&
-	    dmat->lowaddr >= ptoa((vm_paddr_t)Maxmem) &&
-	    attr == VM_MEMATTR_DEFAULT) {
-		*vaddr = malloc(dmat->maxsize, M_DEVBUF, mflags);
-	} else if (dmat->nsegments >= btoc(dmat->maxsize) &&
-	    dmat->alignment <= PAGE_SIZE &&
-	    (dmat->boundary == 0 || dmat->boundary >= dmat->lowaddr)) {
-		/* Page-based multi-segment allocations allowed */
-		*vaddr = (void *)kmem_alloc_attr(kernel_arena, dmat->maxsize,
-		    mflags, 0ul, dmat->lowaddr, attr);
-		*mapp = &contig_dmamap;
-	} else {
-		*vaddr = (void *)kmem_alloc_contig(kernel_arena, dmat->maxsize,
-		    mflags, 0ul, dmat->lowaddr, dmat->alignment ?
-		    dmat->alignment : 1ul, dmat->boundary, attr);
-		*mapp = &contig_dmamap;
-	}
-	if (*vaddr == NULL) {
-		CTR4(KTR_BUSDMA, "%s: tag %p tag flags 0x%x error %d",
-		    __func__, dmat, dmat->flags, ENOMEM);
-		return (ENOMEM);
-	} else if (vtophys(*vaddr) & (dmat->alignment - 1)) {
-		printf("bus_dmamem_alloc failed to align memory properly.\n");
-	}
-	CTR4(KTR_BUSDMA, "%s: tag %p tag flags 0x%x error %d",
-	    __func__, dmat, dmat->flags, 0);
-	return (0);
+	tc = (struct bus_dma_tag_common *)dmat;
+	return (tc->impl->mem_alloc(dmat, vaddr, flags, mapp));
 }
 
 /*
@@ -572,153 +268,10 @@ bus_dmamem_alloc(bus_dma_tag_t dmat, void** vaddr, int flags,
 void
 bus_dmamem_free(bus_dma_tag_t dmat, void *vaddr, bus_dmamap_t map)
 {
-	/*
-	 * dmamem does not need to be bounced, so the map should be
-	 * NULL if malloc() was used and contig_dmamap if
-	 * kmem_alloc_contig() was used.
-	 */
-	if (!(map == NULL || map == &contig_dmamap))
-		panic("bus_dmamem_free: Invalid map freed\n");
-	if (map == NULL)
-		free(vaddr, M_DEVBUF);
-	else
-		kmem_free(kernel_arena, (vm_offset_t)vaddr, dmat->maxsize);
-	CTR3(KTR_BUSDMA, "%s: tag %p flags 0x%x", __func__, dmat, dmat->flags);
-}
+	struct bus_dma_tag_common *tc;
 
-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 != &nobounce_dmamap && map->pagesneeded == 0)) {
-		/*
-		 * Count the number of bounce pages
-		 * needed in order to complete this transfer
-		 */
-		curaddr = buf;
-		while (buflen != 0) {
-			sgsize = MIN(buflen, dmat->maxsegsz);
-			if (run_filter(dmat, curaddr)) {
-				sgsize = MIN(sgsize, PAGE_SIZE);
-				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;
-
-	if ((map != &nobounce_dmamap && map->pagesneeded == 0)) {
-		CTR4(KTR_BUSDMA, "lowaddr= %d Maxmem= %d, boundary= %d, "
-		    "alignment= %d", dmat->lowaddr, ptoa((vm_paddr_t)Maxmem),
-		    dmat->boundary, dmat->alignment);
-		CTR3(KTR_BUSDMA, "map= %p, nobouncemap= %p, pagesneeded= %d",
-		    map, &nobounce_dmamap, 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) {
-			bus_size_t sg_len;
-
-			sg_len = PAGE_SIZE - ((vm_offset_t)vaddr & PAGE_MASK);
-			if (pmap == kernel_pmap)
-				paddr = pmap_kextract(vaddr);
-			else
-				paddr = pmap_extract(pmap, vaddr);
-			if (run_filter(dmat, paddr) != 0) {
-				sg_len = roundup2(sg_len, dmat->alignment);
-				map->pagesneeded++;
-			}
-			vaddr += sg_len;
-		}
-		CTR1(KTR_BUSDMA, "pagesneeded= %d\n", map->pagesneeded);
-	}
-}
-
-static int
-_bus_dmamap_reserve_pages(bus_dma_tag_t dmat, bus_dmamap_t map, int flags)
-{
-
-	/* Reserve Necessary Bounce Pages */
-	mtx_lock(&bounce_lock);
-	if (flags & BUS_DMA_NOWAIT) {
-		if (reserve_bounce_pages(dmat, map, 0) != 0) {
-			mtx_unlock(&bounce_lock);
-			return (ENOMEM);
-		}
-	} else {
-		if (reserve_bounce_pages(dmat, map, 1) != 0) {
-			/* Queue us for resources */
-			STAILQ_INSERT_TAIL(&bounce_map_waitinglist, map, links);
-			mtx_unlock(&bounce_lock);
-			return (EINPROGRESS);
-		}
-	}
-	mtx_unlock(&bounce_lock);
-
-	return (0);
-}
-
-/*
- * Add a single contiguous physical range to the segment list.
- */
-static int
-_bus_dmamap_addseg(bus_dma_tag_t dmat, bus_dmamap_t map, bus_addr_t curaddr,
-		   bus_size_t sgsize, bus_dma_segment_t *segs, int *segp)
-{
-	bus_addr_t baddr, bmask;
-	int seg;
-
-	/*
-	 * Make sure we don't cross any boundaries.
-	 */
-	bmask = ~(dmat->boundary - 1);
-	if (dmat->boundary > 0) {
-		baddr = (curaddr + dmat->boundary) & bmask;
-		if (sgsize > (baddr - curaddr))
-			sgsize = (baddr - curaddr);
-	}
-
-	/*
-	 * Insert chunk into a segment, coalescing with
-	 * previous segment if possible.
-	 */
-	seg = *segp;
-	if (seg == -1) {
-		seg = 0;
-		segs[seg].ds_addr = curaddr;
-		segs[seg].ds_len = sgsize;
-	} else {
-		if (curaddr == segs[seg].ds_addr + segs[seg].ds_len &&
-		    (segs[seg].ds_len + sgsize) <= dmat->maxsegsz &&
-		    (dmat->boundary == 0 ||
-		     (segs[seg].ds_addr & bmask) == (curaddr & bmask)))
-			segs[seg].ds_len += sgsize;
-		else {
-			if (++seg >= dmat->nsegments)
-				return (0);
-			segs[seg].ds_addr = curaddr;
-			segs[seg].ds_len = sgsize;
-		}
-	}
-	*segp = seg;
-	return (sgsize);
+	tc = (struct bus_dma_tag_common *)dmat;
+	tc->impl->mem_free(dmat, vaddr, map);
 }
 
 /*
@@ -726,53 +279,26 @@ _bus_dmamap_addseg(bus_dma_tag_t dmat, bus_dmamap_t map, bus_addr_t curaddr,
  * the starting segment on entrace, and the ending segment on exit.
  */
 int
-_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)
+_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)
 {
-	bus_size_t sgsize;
-	bus_addr_t curaddr;
-	int error;
-
-	if (map == NULL || map == &contig_dmamap)
-		map = &nobounce_dmamap;
+	struct bus_dma_tag_common *tc;
 
-	if (segs == NULL)
-		segs = dmat->segments;
-
-	if ((dmat->flags & BUS_DMA_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);
-		}
-	}
+	tc = (struct bus_dma_tag_common *)dmat;
+	return (tc->impl->load_phys(dmat, map, buf, buflen, flags, segs,
+	    segp));
+}
 
-	while (buflen > 0) {
-		curaddr = buf;
-		sgsize = MIN(buflen, dmat->maxsegsz);
-		if (((dmat->flags & BUS_DMA_COULD_BOUNCE) != 0) &&
-		    map->pagesneeded != 0 && run_filter(dmat, curaddr)) {
-			sgsize = MIN(sgsize, PAGE_SIZE);
-			curaddr = add_bounce_page(dmat, map, 0, curaddr,
-			    			  sgsize);
-		}
-		sgsize = _bus_dmamap_addseg(dmat, map, curaddr, sgsize, segs,
-		    segp);
-		if (sgsize == 0)
-			break;
-		buf += sgsize;
-		buflen -= sgsize;
-	}
+int
+_bus_dmamap_load_ma(bus_dma_tag_t dmat, bus_dmamap_t map, struct vm_page **ma,
+    bus_size_t tlen, int ma_offs, int flags, bus_dma_segment_t *segs,
+    int *segp)
+{
+	struct bus_dma_tag_common *tc;
 
-	/*
-	 * Did we fit?
-	 */
-	return (buflen != 0 ? EFBIG : 0); /* XXX better return value here? */
+	tc = (struct bus_dma_tag_common *)dmat;
+	return (tc->impl->load_ma(dmat, map, ma, tlen, ma_offs, flags,
+	    segs, segp));
 }
 
 /*
@@ -780,106 +306,35 @@ _bus_dmamap_load_phys(bus_dma_tag_t dmat,
  * the starting segment on entrace, and the ending segment on exit.
  */
 int
-_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)
+_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)
 {
-	bus_size_t sgsize;
-	bus_addr_t curaddr;
-	vm_offset_t vaddr;
-	int error;
-
-	if (map == NULL || map == &contig_dmamap)
-		map = &nobounce_dmamap;
-
-	if (segs == NULL)
-		segs = dmat->segments;
+	struct bus_dma_tag_common *tc;
 
-	if ((dmat->flags & BUS_DMA_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);
-		}
-	}
-
-	vaddr = (vm_offset_t)buf;
-
-	while (buflen > 0) {
-		bus_size_t max_sgsize;
-
-		/*
-		 * Get the physical address for this segment.
-		 */
-		if (pmap == kernel_pmap)
-			curaddr = pmap_kextract(vaddr);
-		else
-			curaddr = pmap_extract(pmap, vaddr);
-
-		/*
-		 * Compute the segment size, and adjust counts.
-		 */
-		max_sgsize = MIN(buflen, dmat->maxsegsz);
-		sgsize = PAGE_SIZE - ((vm_offset_t)curaddr & PAGE_MASK);
-		if (((dmat->flags & BUS_DMA_COULD_BOUNCE) != 0) &&
-		    map->pagesneeded != 0 && run_filter(dmat, curaddr)) {
-			sgsize = roundup2(sgsize, dmat->alignment);
-			sgsize = MIN(sgsize, max_sgsize);
-			curaddr = add_bounce_page(dmat, map, vaddr, curaddr,
-			    			  sgsize);
-		} else {
-			sgsize = MIN(sgsize, max_sgsize);
-		}
-		sgsize = _bus_dmamap_addseg(dmat, map, curaddr, sgsize, segs,
-					    segp);
-		if (sgsize == 0)
-			break;
-		vaddr += sgsize;
-		buflen -= sgsize;
-	}
-
-	/*
-	 * Did we fit?
-	 */
-	return (buflen != 0 ? EFBIG : 0); /* XXX better return value here? */
-}
-
-int
-_bus_dmamap_load_ma(bus_dma_tag_t dmat, bus_dmamap_t map,
-    struct vm_page **ma, bus_size_t tlen, int ma_offs, int flags,
-    bus_dma_segment_t *segs, int *segp)
-{
-
-	return (bus_dmamap_load_ma_triv(dmat, map, ma, tlen, ma_offs, flags,
-	    segs, segp));
+	tc = (struct bus_dma_tag_common *)dmat;
+	return (tc->impl->load_buffer(dmat, map, buf, buflen, pmap, flags, segs,
+	    segp));
 }
 
 void
 __bus_dmamap_waitok(bus_dma_tag_t dmat, bus_dmamap_t map,
-		    struct memdesc *mem, bus_dmamap_callback_t *callback,
-		    void *callback_arg)
+    struct memdesc *mem, bus_dmamap_callback_t *callback, void *callback_arg)
 {
-	if (map != NULL) {
-		map->mem = *mem;
-		map->dmat = dmat;
-		map->callback = callback;
-		map->callback_arg = callback_arg;
-	}
+	struct bus_dma_tag_common *tc;
+
+	tc = (struct bus_dma_tag_common *)dmat;
+	tc->impl->map_waitok(dmat, map, mem, callback, callback_arg);
 }
 
 bus_dma_segment_t *
 _bus_dmamap_complete(bus_dma_tag_t dmat, bus_dmamap_t map,
-		      bus_dma_segment_t *segs, int nsegs, int error)
+    bus_dma_segment_t *segs, int nsegs, int error)
 {
+	struct bus_dma_tag_common *tc;
 
-	if (segs == NULL)
-		segs = dmat->segments;
-	return (segs);
+	tc = (struct bus_dma_tag_common *)dmat;
+	return (tc->impl->map_complete(dmat, map, segs, nsegs, error));
 }
 
 /*
@@ -888,317 +343,17 @@ _bus_dmamap_complete(bus_dma_tag_t dmat, bus_dmamap_t map,
 void
 _bus_dmamap_unload(bus_dma_tag_t dmat, bus_dmamap_t map)
 {
-	struct bounce_page *bpage;
+	struct bus_dma_tag_common *tc;
 
-	while ((bpage = STAILQ_FIRST(&map->bpages)) != NULL) {
-		STAILQ_REMOVE_HEAD(&map->bpages, links);
-		free_bounce_page(dmat, bpage);
-	}
+	tc = (struct bus_dma_tag_common *)dmat;
+	tc->impl->map_unload(dmat, map);
 }
 
 void
 _bus_dmamap_sync(bus_dma_tag_t dmat, bus_dmamap_t map, bus_dmasync_op_t op)
 {
-	struct bounce_page *bpage;
+	struct bus_dma_tag_common *tc;
 
-	if ((bpage = STAILQ_FIRST(&map->bpages)) != NULL) {
-		/*
-		 * Handle data bouncing.  We might also
-		 * want to add support for invalidating
-		 * the caches on broken hardware
-		 */
-		CTR4(KTR_BUSDMA, "%s: tag %p tag flags 0x%x op 0x%x "
-		    "performing bounce", __func__, dmat, dmat->flags, op);
-
-		if (op & BUS_DMASYNC_PREWRITE) {
-			while (bpage != NULL) {
-				if (bpage->datavaddr != 0)
-					bcopy((void *)bpage->datavaddr,
-					      (void *)bpage->vaddr,
-					      bpage->datacount);
-				else
-					physcopyout(bpage->dataaddr,
-					      (void *)bpage->vaddr,
-					      bpage->datacount);
-				bpage = STAILQ_NEXT(bpage, links);
-			}
-			dmat->bounce_zone->total_bounced++;
-		}
-
-		if (op & BUS_DMASYNC_POSTREAD) {
-			while (bpage != NULL) {
-				if (bpage->datavaddr != 0)
-					bcopy((void *)bpage->vaddr,
-					      (void *)bpage->datavaddr,
-					      bpage->datacount);
-				else
-					physcopyin((void *)bpage->vaddr,
-					      bpage->dataaddr,
-					      bpage->datacount);
-				bpage = STAILQ_NEXT(bpage, links);
-			}
-			dmat->bounce_zone->total_bounced++;
-		}
-	}
-}
-
-static void
-init_bounce_pages(void *dummy __unused)
-{
-
-	total_bpages = 0;
-	STAILQ_INIT(&bounce_zone_list);
-	STAILQ_INIT(&bounce_map_waitinglist);
-	STAILQ_INIT(&bounce_map_callbacklist);
-	mtx_init(&bounce_lock, "bounce pages lock", NULL, MTX_DEF);
-}
-SYSINIT(bpages, SI_SUB_LOCK, SI_ORDER_ANY, init_bounce_pages, NULL);
-
-static struct sysctl_ctx_list *
-busdma_sysctl_tree(struct bounce_zone *bz)
-{
-	return (&bz->sysctl_tree);
-}
-
-static struct sysctl_oid *
-busdma_sysctl_tree_top(struct bounce_zone *bz)
-{
-	return (bz->sysctl_tree_top);
-}
-
-#if defined(__amd64__) || defined(PAE)
-#define	SYSCTL_ADD_BUS_SIZE_T	SYSCTL_ADD_UQUAD
-#else
-#define	SYSCTL_ADD_BUS_SIZE_T(ctx, parent, nbr, name, flag, ptr, desc)	\
-	SYSCTL_ADD_UINT(ctx, parent, nbr, name, flag, ptr, 0, desc)
-#endif
-
-static int
-alloc_bounce_zone(bus_dma_tag_t dmat)
-{
-	struct bounce_zone *bz;
-
-	/* Check to see if we already have a suitable zone */
-	STAILQ_FOREACH(bz, &bounce_zone_list, links) {
-		if ((dmat->alignment <= bz->alignment)
-		 && (dmat->lowaddr >= bz->lowaddr)) {
-			dmat->bounce_zone = bz;
-			return (0);
-		}
-	}
-
-	if ((bz = (struct bounce_zone *)malloc(sizeof(*bz), M_DEVBUF,
-	    M_NOWAIT | M_ZERO)) == NULL)
-		return (ENOMEM);
-
-	STAILQ_INIT(&bz->bounce_page_list);
-	bz->free_bpages = 0;
-	bz->reserved_bpages = 0;
-	bz->active_bpages = 0;
-	bz->lowaddr = dmat->lowaddr;
-	bz->alignment = MAX(dmat->alignment, PAGE_SIZE);
-	bz->map_count = 0;
-	snprintf(bz->zoneid, 8, "zone%d", busdma_zonecount);
-	busdma_zonecount++;
-	snprintf(bz->lowaddrid, 18, "%#jx", (uintmax_t)bz->lowaddr);
-	STAILQ_INSERT_TAIL(&bounce_zone_list, bz, links);
-	dmat->bounce_zone = bz;
-
-	sysctl_ctx_init(&bz->sysctl_tree);
-	bz->sysctl_tree_top = SYSCTL_ADD_NODE(&bz->sysctl_tree,
-	    SYSCTL_STATIC_CHILDREN(_hw_busdma), OID_AUTO, bz->zoneid,
-	    CTLFLAG_RD, 0, "");
-	if (bz->sysctl_tree_top == NULL) {
-		sysctl_ctx_free(&bz->sysctl_tree);
-		return (0);	/* XXX error code? */
-	}
-
-	SYSCTL_ADD_INT(busdma_sysctl_tree(bz),
-	    SYSCTL_CHILDREN(busdma_sysctl_tree_top(bz)), OID_AUTO,
-	    "total_bpages", CTLFLAG_RD, &bz->total_bpages, 0,
-	    "Total bounce pages");
-	SYSCTL_ADD_INT(busdma_sysctl_tree(bz),
-	    SYSCTL_CHILDREN(busdma_sysctl_tree_top(bz)), OID_AUTO,
-	    "free_bpages", CTLFLAG_RD, &bz->free_bpages, 0,
-	    "Free bounce pages");
-	SYSCTL_ADD_INT(busdma_sysctl_tree(bz),
-	    SYSCTL_CHILDREN(busdma_sysctl_tree_top(bz)), OID_AUTO,
-	    "reserved_bpages", CTLFLAG_RD, &bz->reserved_bpages, 0,
-	    "Reserved bounce pages");
-	SYSCTL_ADD_INT(busdma_sysctl_tree(bz),
-	    SYSCTL_CHILDREN(busdma_sysctl_tree_top(bz)), OID_AUTO,
-	    "active_bpages", CTLFLAG_RD, &bz->active_bpages, 0,
-	    "Active bounce pages");
-	SYSCTL_ADD_INT(busdma_sysctl_tree(bz),
-	    SYSCTL_CHILDREN(busdma_sysctl_tree_top(bz)), OID_AUTO,
-	    "total_bounced", CTLFLAG_RD, &bz->total_bounced, 0,
-	    "Total bounce requests");
-	SYSCTL_ADD_INT(busdma_sysctl_tree(bz),
-	    SYSCTL_CHILDREN(busdma_sysctl_tree_top(bz)), OID_AUTO,
-	    "total_deferred", CTLFLAG_RD, &bz->total_deferred, 0,
-	    "Total bounce requests that were deferred");
-	SYSCTL_ADD_STRING(busdma_sysctl_tree(bz),
-	    SYSCTL_CHILDREN(busdma_sysctl_tree_top(bz)), OID_AUTO,
-	    "lowaddr", CTLFLAG_RD, bz->lowaddrid, 0, "");
-	SYSCTL_ADD_BUS_SIZE_T(busdma_sysctl_tree(bz),
-	    SYSCTL_CHILDREN(busdma_sysctl_tree_top(bz)), OID_AUTO,
-	    "alignment", CTLFLAG_RD, &bz->alignment, "");
-
-	return (0);
-}
-
-static int
-alloc_bounce_pages(bus_dma_tag_t dmat, u_int numpages)
-{
-	struct bounce_zone *bz;
-	int count;
-
-	bz = dmat->bounce_zone;
-	count = 0;
-	while (numpages > 0) {
-		struct bounce_page *bpage;
-
-		bpage = (struct bounce_page *)malloc(sizeof(*bpage), M_DEVBUF,
-						     M_NOWAIT | M_ZERO);
-
-		if (bpage == NULL)
-			break;
-		bpage->vaddr = (vm_offset_t)contigmalloc(PAGE_SIZE, M_DEVBUF,
-							 M_NOWAIT, 0ul,
-							 bz->lowaddr,
-							 PAGE_SIZE,
-							 0);
-		if (bpage->vaddr == 0) {
-			free(bpage, M_DEVBUF);
-			break;
-		}
-		bpage->busaddr = pmap_kextract(bpage->vaddr);
-		mtx_lock(&bounce_lock);
-		STAILQ_INSERT_TAIL(&bz->bounce_page_list, bpage, links);
-		total_bpages++;
-		bz->total_bpages++;
-		bz->free_bpages++;
-		mtx_unlock(&bounce_lock);
-		count++;
-		numpages--;
-	}
-	return (count);
-}
-
-static int
-reserve_bounce_pages(bus_dma_tag_t dmat, bus_dmamap_t map, int commit)
-{
-	struct bounce_zone *bz;
-	int pages;
-
-	mtx_assert(&bounce_lock, MA_OWNED);
-	bz = dmat->bounce_zone;
-	pages = MIN(bz->free_bpages, map->pagesneeded - map->pagesreserved);
-	if (commit == 0 && map->pagesneeded > (map->pagesreserved + pages))
-		return (map->pagesneeded - (map->pagesreserved + pages));
-	bz->free_bpages -= pages;
-	bz->reserved_bpages += pages;
-	map->pagesreserved += pages;
-	pages = map->pagesneeded - map->pagesreserved;
-
-	return (pages);
-}
-
-static bus_addr_t
-add_bounce_page(bus_dma_tag_t dmat, bus_dmamap_t map, vm_offset_t vaddr,
-		bus_addr_t addr, bus_size_t size)
-{
-	struct bounce_zone *bz;
-	struct bounce_page *bpage;
-
-	KASSERT(dmat->bounce_zone != NULL, ("no bounce zone in dma tag"));
-	KASSERT(map != NULL && map != &nobounce_dmamap && map != &contig_dmamap,
-	    ("add_bounce_page: bad map %p", map));
-
-	bz = dmat->bounce_zone;
-	if (map->pagesneeded == 0)
-		panic("add_bounce_page: map doesn't need any pages");
-	map->pagesneeded--;
-
-	if (map->pagesreserved == 0)
-		panic("add_bounce_page: map doesn't need any pages");
-	map->pagesreserved--;
-
-	mtx_lock(&bounce_lock);
-	bpage = STAILQ_FIRST(&bz->bounce_page_list);
-	if (bpage == NULL)
-		panic("add_bounce_page: free page list is empty");
-
-	STAILQ_REMOVE_HEAD(&bz->bounce_page_list, links);
-	bz->reserved_bpages--;
-	bz->active_bpages++;
-	mtx_unlock(&bounce_lock);
-
-	if (dmat->flags & BUS_DMA_KEEP_PG_OFFSET) {
-		/* Page offset needs to be preserved. */
-		bpage->vaddr |= vaddr & PAGE_MASK;
-		bpage->busaddr |= vaddr & PAGE_MASK;
-	}
-	bpage->datavaddr = vaddr;
-	bpage->dataaddr = addr;
-	bpage->datacount = size;
-	STAILQ_INSERT_TAIL(&(map->bpages), bpage, links);
-	return (bpage->busaddr);
-}
-
-static void
-free_bounce_page(bus_dma_tag_t dmat, struct bounce_page *bpage)
-{
-	struct bus_dmamap *map;
-	struct bounce_zone *bz;
-
-	bz = dmat->bounce_zone;
-	bpage->datavaddr = 0;
-	bpage->datacount = 0;
-	if (dmat->flags & BUS_DMA_KEEP_PG_OFFSET) {
-		/*
-		 * Reset the bounce page to start at offset 0.  Other uses
-		 * of this bounce page may need to store a full page of
-		 * data and/or assume it starts on a page boundary.
-		 */
-		bpage->vaddr &= ~PAGE_MASK;
-		bpage->busaddr &= ~PAGE_MASK;
-	}
-
-	mtx_lock(&bounce_lock);
-	STAILQ_INSERT_HEAD(&bz->bounce_page_list, bpage, links);
-	bz->free_bpages++;
-	bz->active_bpages--;
-	if ((map = STAILQ_FIRST(&bounce_map_waitinglist)) != NULL) {
-		if (reserve_bounce_pages(map->dmat, map, 1) == 0) {
-			STAILQ_REMOVE_HEAD(&bounce_map_waitinglist, links);
-			STAILQ_INSERT_TAIL(&bounce_map_callbacklist,
-					   map, links);
-			busdma_swi_pending = 1;
-			bz->total_deferred++;
-			swi_sched(vm_ih, 0);
-		}
-	}
-	mtx_unlock(&bounce_lock);
-}
-
-void
-busdma_swi(void)
-{
-	bus_dma_tag_t dmat;
-	struct bus_dmamap *map;
-
-	mtx_lock(&bounce_lock);
-	while ((map = STAILQ_FIRST(&bounce_map_callbacklist)) != NULL) {
-		STAILQ_REMOVE_HEAD(&bounce_map_callbacklist, links);
-		mtx_unlock(&bounce_lock);
-		dmat = map->dmat;
-		(dmat->lockfunc)(dmat->lockfuncarg, BUS_DMA_LOCK);
-		bus_dmamap_load_mem(map->dmat, map, &map->mem,
-				map->callback, map->callback_arg,
-				BUS_DMA_WAITOK);
-		(dmat->lockfunc)(dmat->lockfuncarg, BUS_DMA_UNLOCK);
-		mtx_lock(&bounce_lock);
-	}
-	mtx_unlock(&bounce_lock);
+	tc = (struct bus_dma_tag_common *)dmat;
+	tc->impl->map_sync(dmat, map, op);
 }