arc/arc/bus_dma.c

/*	$NetBSD: bus_dma.c,v 1.12 2002/06/02 14:44:42 drochner Exp $	*/
/*	NetBSD: bus_dma.c,v 1.20 2000/01/10 03:24:36 simonb Exp 	*/

/*-
 * Copyright (c) 1997, 1998 The NetBSD Foundation, Inc.
 * All rights reserved.
 *
 * This code is derived from software contributed to The NetBSD Foundation
 * by Jason R. Thorpe of the Numerical Aerospace Simulation Facility,
 * NASA Ames Research Center.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *	This product includes software developed by the NetBSD
 *	Foundation, Inc. and its contributors.
 * 4. Neither the name of The NetBSD Foundation nor the names of its
 *    contributors may be used to endorse or promote products derived
 *    from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

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

#include <uvm/uvm_extern.h>

#include <mips/cache.h>

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

paddr_t	kvtophys __P((vaddr_t));	/* XXX */

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

extern paddr_t avail_start, avail_end;	/* from pmap.c */

void
_bus_dma_tag_init(t)
	bus_dma_tag_t t;
{
	t->dma_offset = 0;

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

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

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

	bzero(mapstore, mapsize);
	map = (struct arc_bus_dmamap *)mapstore;
	map->_dm_size = size;
	map->_dm_segcnt = nsegments;
	map->_dm_maxsegsz = maxsegsz;
	map->_dm_boundary = boundary;
	map->_dm_flags = flags & ~(BUS_DMA_WAITOK|BUS_DMA_NOWAIT);
	map->_dm_proc = NULL;
	map->dm_mapsize = 0;		/* no valid mappings */
	map->dm_nsegs = 0;

	*dmamp = map;
	return (0);
}

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

	free(map, M_DMAMAP);
}

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

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

	for (seg = *segp; buflen > 0 ; ) {
		/*
		 * Get the physical address for this segment.
		 */
		if (p != NULL) {
			(void) pmap_extract(p->p_vmspace->vm_map.pmap,
			    vaddr, &curaddr);
		} else
			curaddr = kvtophys(vaddr);

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

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

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

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

	*segp = seg;
	*lastaddrp = lastaddr;

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

	return (0);
}

/*
 * Common function for loading a direct-mapped DMA map with a linear
 * buffer.
 */
int
_bus_dmamap_load(t, map, buf, buflen, p, flags)
	bus_dma_tag_t t;
	bus_dmamap_t map;
	void *buf;
	bus_size_t buflen;
	struct proc *p;
	int flags;
{
	paddr_t lastaddr;
	int seg, error;

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

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

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

		/*
		 * For linear buffers, we support marking the mapping
		 * as COHERENT.
		 *
		 * XXX Check TLB entries for cache-inhibit bits?
		 */
		if (buf >= (void *)MIPS_KSEG1_START &&
		    buf < (void *)MIPS_KSEG2_START)
			map->_dm_flags |= ARC_DMAMAP_COHERENT;
	}
	return (error);
}

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

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

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

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

	first = 1;
	seg = 0;
	error = 0;
	for (m = m0; m != NULL && error == 0; m = m->m_next) {
		error = _bus_dmamap_load_buffer(t, map,
		    m->m_data, m->m_len, NULL, flags, &lastaddr, &seg, first);
		first = 0;
	}
	if (error == 0) {
		map->dm_mapsize = m0->m_pkthdr.len;
		map->dm_nsegs = seg + 1;
		map->_dm_proc = NULL;	/* always kernel */
	}
	return (error);
}

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

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

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

	if (uio->uio_segflg == UIO_USERSPACE) {
		p = uio->uio_procp;
#ifdef DIAGNOSTIC
		if (p == NULL)
			panic("_bus_dmamap_load_uio: USERSPACE but no proc");
#endif
	}

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

		error = _bus_dmamap_load_buffer(t, map, addr, minlen,
		    p, flags, &lastaddr, &seg, first);
		first = 0;

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

/*
 * Like _bus_dmamap_load(), but for raw memory.
 */
int
_bus_dmamap_load_raw(t, map, segs, nsegs, size, flags)
	bus_dma_tag_t t;
	bus_dmamap_t map;
	bus_dma_segment_t *segs;
	int nsegs;
	bus_size_t size;
	int flags;
{
	panic("_bus_dmamap_load_raw: not implemented");
}

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

	/*
	 * No resources to free; just mark the mappings as
	 * invalid.
	 */
	map->dm_mapsize = 0;
	map->dm_nsegs = 0;
	map->_dm_flags &= ~ARC_DMAMAP_COHERENT;
}

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

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

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

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

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

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

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

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

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

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

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

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

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

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

		case BUS_DMASYNC_PREREAD:
#if 1
			mips_dcache_wbinv_range(addr + offset, minlen);
#else
			mips_dcache_inv_range(addr + offset, minlen);
#endif
			break;

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

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

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

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

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

	high = avail_end - PAGE_SIZE;

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

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

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

	*rsegs = curseg + 1;

	return (0);
}

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

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

	uvm_pglistfree(&mlist);
}

/*
 * Common function for mapping DMA-safe memory.  May be called by
 * bus-specific DMA memory map functions.
 */
int
_bus_dmamem_map(t, segs, nsegs, size, kvap, flags)
	bus_dma_tag_t t;
	bus_dma_segment_t *segs;
	int nsegs;
	size_t size;
	caddr_t *kvap;
	int flags;
{
	vaddr_t va;
	bus_addr_t addr;
	int curseg;

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

	size = round_page(size);

	va = uvm_km_valloc(kernel_map, size);

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

	*kvap = (caddr_t)va;

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

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

	return (0);
}

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

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

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

	size = round_page(size);
	uvm_km_free(kernel_map, (vaddr_t)kva, size);
}

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

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

		return (mips_btop(segs[i]._ds_paddr + off));
	}

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