path: root/sys/powerpc/powerpc/busdma_machdep.c

/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * 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.
 */

/*
 * From amd64/busdma_machdep.c, r204214
 */

#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/cpufunc.h>
#include <machine/md_var.h>

#include "iommu_if.h"

#define MAX_BPAGES MIN(8192, physmem/40)

struct bounce_page;
struct bounce_zone;

struct bus_dma_tag {
	bus_size_t	  alignment;
	bus_addr_t	  boundary;
	bus_addr_t	  lowaddr;
	bus_addr_t	  highaddr;
	bus_size_t	  maxsize;
	bus_size_t	  maxsegsz;
	u_int		  nsegments;
	int		  flags;
	int		  map_count;
	bus_dma_lock_t	 *lockfunc;
	void		 *lockfuncarg;
	struct bounce_zone *bounce_zone;
	device_t	  iommu;
	void		 *iommu_cookie;
};

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

struct bus_dmamap {
	STAILQ_HEAD(, bounce_page) bpages;
	int		       pagesneeded;
	int		       pagesreserved;
	bus_dma_tag_t	       dmat;
	struct memdesc	       mem;
	bus_dma_segment_t     *segments;
	int		       nsegs;
	bus_dmamap_callback_t *callback;
	void		      *callback_arg;
	__sbintime_t	       queued_time;
	STAILQ_ENTRY(bus_dmamap) links;
	int		       contigalloc;
};

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

#define	dmat_alignment(dmat)	((dmat)->alignment)
#define	dmat_flags(dmat)	((dmat)->flags)
#define	dmat_highaddr(dmat)	((dmat)->highaddr)
#define	dmat_lowaddr(dmat)	((dmat)->lowaddr)
#define	dmat_lockfunc(dmat)	((dmat)->lockfunc)
#define	dmat_lockfuncarg(dmat)	((dmat)->lockfuncarg)

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

/*
 * Returns true if the address falls within the tag's exclusion window, or
 * fails to meet its alignment requirements.
 */
static __inline bool
must_bounce(bus_dma_tag_t dmat, bus_addr_t paddr)
{

	if (dmat->iommu == NULL && paddr > dmat->lowaddr &&
	    paddr <= dmat->highaddr)
		return (true);
	if (!vm_addr_align_ok(paddr, dmat->alignment))
		return (true);

	return (false);
}

#define BUS_DMA_COULD_BOUNCE	BUS_DMA_BUS3
#define BUS_DMA_MIN_ALLOC_COMP	BUS_DMA_BUS4
/*
 * 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)
{
	bus_dma_tag_t newtag;
	int error = 0;

	/* Basic sanity checking */
	if (boundary != 0 && boundary < maxsegsz)
		maxsegsz = boundary;

	if (maxsegsz == 0) {
		return (EINVAL);
	}

	/* Filters are no longer supported. */
	if (filter != NULL || filterarg != NULL)
		return (EINVAL);

	/* Return a NULL tag on failure */
	*dmat = NULL;

	newtag = (bus_dma_tag_t)malloc(sizeof(*newtag), 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, error);
		return (ENOMEM);
	}

	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->maxsize = maxsize;
	newtag->nsegments = nsegments;
	newtag->maxsegsz = maxsegsz;
	newtag->flags = flags;
	newtag->map_count = 0;
	if (lockfunc != NULL) {
		newtag->lockfunc = lockfunc;
		newtag->lockfuncarg = lockfuncarg;
	} else {
		newtag->lockfunc = _busdma_dflt_lock;
		newtag->lockfuncarg = 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);

		newtag->iommu = parent->iommu;
		newtag->iommu_cookie = parent->iommu_cookie;
	}

	if (newtag->lowaddr < ptoa((vm_paddr_t)Maxmem) && newtag->iommu == NULL)
		newtag->flags |= BUS_DMA_COULD_BOUNCE;

	if (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;

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

void
bus_dma_template_clone(bus_dma_template_t *t, bus_dma_tag_t dmat)
{

	if (t == NULL || dmat == NULL)
		return;

	t->alignment = dmat->alignment;
	t->boundary = dmat->boundary;
	t->lowaddr = dmat->lowaddr;
	t->highaddr = dmat->highaddr;
	t->maxsize = dmat->maxsize;
	t->nsegments = dmat->nsegments;
	t->maxsegsize = dmat->maxsegsz;
	t->flags = dmat->flags;
	t->lockfunc = dmat->lockfunc;
	t->lockfuncarg = dmat->lockfuncarg;
}

int
bus_dma_tag_set_domain(bus_dma_tag_t dmat, int domain)
{

	return (0);
}

int
bus_dma_tag_destroy(bus_dma_tag_t dmat)
{
	int error = 0;

	if (dmat != NULL) {
		if (dmat->map_count != 0) {
			error = EBUSY;
			goto out;
		}

		free(dmat, M_DEVBUF);
	}
out:
	CTR3(KTR_BUSDMA, "%s tag %p error %d", __func__, dmat, error);
	return (error);
}

/*
 * Allocate a handle for mapping from kva/uva/physical
 * address space into bus device space.
 */
int
bus_dmamap_create(bus_dma_tag_t dmat, int flags, bus_dmamap_t *mapp)
{
	int error;

	error = 0;

	*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);
	}

	/*
	 * 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;

		/* 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++;
	}

	(*mapp)->nsegs = 0;
	(*mapp)->segments = (bus_dma_segment_t *)malloc(
	    sizeof(bus_dma_segment_t) * dmat->nsegments, M_DEVBUF,
	    M_NOWAIT);
	if ((*mapp)->segments == NULL) {
		CTR3(KTR_BUSDMA, "%s: tag %p error %d",
		    __func__, dmat, ENOMEM);
		return (ENOMEM);
	}

	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);
}

/*
 * Destroy a handle for mapping from kva/uva/physical
 * address space into bus device space.
 */
int
bus_dmamap_destroy(bus_dma_tag_t dmat, bus_dmamap_t map)
{
	if (dmat->flags & BUS_DMA_COULD_BOUNCE) {
		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->segments, M_DEVBUF);
	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.
 */
int
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;

	bus_dmamap_create(dmat, flags, mapp);

	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 {
		/*
		 * XXX Use Contigmalloc until it is merged into this facility
		 *     and handles multi-seg allocations.  Nobody is doing
		 *     multi-seg allocations yet though.
		 * XXX Certain AGP hardware does.
		 */
		*vaddr = kmem_alloc_contig(dmat->maxsize, mflags, 0ul,
		    dmat->lowaddr, dmat->alignment ? dmat->alignment : 1ul,
		    dmat->boundary, attr);
		(*mapp)->contigalloc = 1;
	}
	if (*vaddr == NULL) {
		CTR4(KTR_BUSDMA, "%s: tag %p tag flags 0x%x error %d",
		    __func__, dmat, dmat->flags, ENOMEM);
		return (ENOMEM);
	} else if (!vm_addr_align_ok(vtophys(*vaddr), dmat->alignment)) {
		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);
}

/*
 * Free a piece of memory and it's allociated dmamap, that was allocated
 * via bus_dmamem_alloc.  Make the same choice for free/contigfree.
 */
void
bus_dmamem_free(bus_dma_tag_t dmat, void *vaddr, bus_dmamap_t map)
{

	if (!map->contigalloc)
		free(vaddr, M_DEVBUF);
	else
		kmem_free(vaddr, dmat->maxsize);
	bus_dmamap_destroy(dmat, map);
	CTR3(KTR_BUSDMA, "%s: tag %p flags 0x%x", __func__, dmat, dmat->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->pagesneeded == 0) {
		CTR4(KTR_BUSDMA, "lowaddr= %d Maxmem= %d, boundary= %d, "
		    "alignment= %d", dmat->lowaddr, ptoa((vm_paddr_t)Maxmem),
		    dmat->boundary, dmat->alignment);
		CTR2(KTR_BUSDMA, "map= %p, pagesneeded= %d", map, map->pagesneeded);
		/*
		 * Count the number of bounce pages
		 * needed in order to complete this transfer
		 */
		curaddr = buf;
		while (buflen != 0) {
			sgsize = MIN(buflen, dmat->maxsegsz);
			if (must_bounce(dmat, curaddr)) {
				sgsize = MIN(sgsize,
				    PAGE_SIZE - (curaddr & PAGE_MASK));
				map->pagesneeded++;
			}
			curaddr += sgsize;
			buflen -= sgsize;
		}
		CTR1(KTR_BUSDMA, "pagesneeded= %d\n", map->pagesneeded);
	}
}

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

	if (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);
		CTR2(KTR_BUSDMA, "map= %p, pagesneeded= %d", map, map->pagesneeded);
		/*
		 * Count the number of bounce pages
		 * needed in order to complete this transfer
		 */
		vaddr = (vm_offset_t)buf;
		vendaddr = (vm_offset_t)buf + buflen;

		while (vaddr < vendaddr) {
			bus_size_t sg_len;

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

/*
 * 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)
{
	int seg;

	/*
	 * Make sure we don't cross any boundaries.
	 */
	if (!vm_addr_bound_ok(curaddr, sgsize, dmat->boundary))
		sgsize = roundup2(curaddr, dmat->boundary) - 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 &&
		    vm_addr_bound_ok(segs[seg].ds_addr,
		    segs[seg].ds_len + sgsize, dmat->boundary))
			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);
}

/*
 * Utility function to load a physical buffer.  segp contains
 * 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_addr_t curaddr;
	bus_size_t sgsize;
	int error;

	if (segs == NULL)
		segs = map->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);
		}
	}

	while (buflen > 0) {
		curaddr = buf;
		sgsize = MIN(buflen, dmat->maxsegsz);
		if (map->pagesneeded != 0 && must_bounce(dmat, curaddr)) {
			sgsize = MIN(sgsize, PAGE_SIZE - (curaddr & PAGE_MASK));
			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? */
}

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));
}

/*
 * Utility function to load a linear buffer.  segp contains
 * the starting segment on entrance, 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_size_t sgsize;
	bus_addr_t curaddr;
	vm_offset_t kvaddr, vaddr;
	int error;

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

	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);
			kvaddr = vaddr;
		} else {
			curaddr = pmap_extract(pmap, vaddr);
			kvaddr = 0;
		}

		/*
		 * Compute the segment size, and adjust counts.
		 */
		max_sgsize = MIN(buflen, dmat->maxsegsz);
		sgsize = PAGE_SIZE - (curaddr & PAGE_MASK);
		if (map->pagesneeded != 0 && must_bounce(dmat, curaddr)) {
			sgsize = roundup2(sgsize, dmat->alignment);
			sgsize = MIN(sgsize, max_sgsize);
			curaddr = add_bounce_page(dmat, map, kvaddr, 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? */
}

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

	if (dmat->flags & BUS_DMA_COULD_BOUNCE) {
		map->dmat = dmat;
		map->mem = *mem;
		map->callback = callback;
		map->callback_arg = 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)
{

	map->nsegs = nsegs;
	if (segs != NULL)
		memcpy(map->segments, segs, map->nsegs*sizeof(segs[0]));
	if (dmat->iommu != NULL)
		IOMMU_MAP(dmat->iommu, map->segments, &map->nsegs,
		    dmat->lowaddr, dmat->highaddr, dmat->alignment,
		    dmat->boundary, dmat->iommu_cookie);

	if (segs != NULL)
		memcpy(segs, map->segments, map->nsegs*sizeof(segs[0]));
	else
		segs = map->segments;

	return (segs);
}

/*
 * Release the mapping held by map.
 */
void
bus_dmamap_unload(bus_dma_tag_t dmat, bus_dmamap_t map)
{
	if (dmat->iommu) {
		IOMMU_UNMAP(dmat->iommu, map->segments, map->nsegs, dmat->iommu_cookie);
		map->nsegs = 0;
	}

	free_bounce_pages(dmat, map);
}

void
bus_dmamap_sync(bus_dma_tag_t dmat, bus_dmamap_t map, bus_dmasync_op_t op)
{
	struct bounce_page *bpage;
	vm_offset_t datavaddr, tempvaddr;

	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) {
				tempvaddr = 0;
				datavaddr = bpage->datavaddr;
				if (datavaddr == 0) {
					tempvaddr = pmap_quick_enter_page(
					    bpage->datapage);
					datavaddr = tempvaddr |
					    bpage->dataoffs;
				}

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

				if (tempvaddr != 0)
					pmap_quick_remove_page(tempvaddr);
				bpage = STAILQ_NEXT(bpage, links);
			}
			dmat->bounce_zone->total_bounced++;
		}

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

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

				if (tempvaddr != 0)
					pmap_quick_remove_page(tempvaddr);
				bpage = STAILQ_NEXT(bpage, links);
			}
			dmat->bounce_zone->total_bounced++;
		}
	}

	powerpc_sync();
}

int
bus_dma_tag_set_iommu(bus_dma_tag_t tag, device_t iommu, void *cookie)
{
	tag->iommu = iommu;
	tag->iommu_cookie = cookie;

	return (0);
}