add sg_dma.c on i386, soon to be used.

2 files changed, 959 insertions, 1 deletions

diff --git a/sys/arch/i386/conf/files.i386 b/sys/arch/i386/conf/files.i386
index ad1befb9562..5cc161db001 100644
--- a/sys/arch/i386/conf/files.i386
+++ b/sys/arch/i386/conf/files.i386
@@ -1,4 +1,4 @@
-#	$OpenBSD: files.i386,v 1.192 2009/06/06 03:20:58 deraadt Exp $
+#	$OpenBSD: files.i386,v 1.193 2009/06/06 05:31:01 oga Exp $
 #
 # new style config file for i386 architecture
 #
@@ -13,6 +13,7 @@ major	{ccd = 16}
 file	arch/i386/i386/autoconf.c
 file	arch/i386/i386/bus_space.c
 file	arch/i386/i386/bus_dma.c
+file	arch/i386/i386/sg_dma.c		!small_kernel
 file	arch/i386/i386/conf.c
 file	arch/i386/i386/db_disasm.c	ddb
 file	arch/i386/i386/db_interface.c	ddb
diff --git a/sys/arch/i386/i386/sg_dma.c b/sys/arch/i386/i386/sg_dma.c
new file mode 100644
index 00000000000..a0d2f021e41
--- /dev/null
+++ b/sys/arch/i386/i386/sg_dma.c
@@ -0,0 +1,957 @@
+/*	$OpenBSD: sg_dma.c,v 1.1 2009/06/06 05:31:01 oga Exp $	*/
+/*
+ * Copyright (c) 2009 Owain G. Ainsworth <oga@openbsd.org>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+/*
+ * Copyright (c) 2003 Henric Jungheim
+ * Copyright (c) 2001, 2002 Eduardo Horvath
+ * Copyright (c) 1999, 2000 Matthew R. Green
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. 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 ``AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+/*
+ * Support for scatter/gather style dma through agp or an iommu.
+ */
+#include <sys/param.h>
+#include <sys/extent.h>
+#include <sys/malloc.h>
+#include <sys/systm.h>
+#include <sys/device.h>
+#include <sys/mbuf.h>
+#include <sys/mutex.h>
+
+#include <uvm/uvm_extern.h>
+
+#include <machine/bus.h>
+#include <machine/cpu.h>
+
+#ifndef MAX_DMA_SEGS
+#define MAX_DMA_SEGS	20
+#endif
+
+/* 
+ * per-map DVMA page table
+ */
+struct sg_page_entry {
+	SPLAY_ENTRY(sg_page_entry)	spe_node;
+	paddr_t				spe_pa;
+	bus_addr_t			spe_va;
+};
+
+/* this should be in the map's dm_cookie. */
+struct sg_page_map {
+	SPLAY_HEAD(sg_page_tree, sg_page_entry) spm_tree;
+	int			 spm_maxpage;	/* Size of allocated page map */
+	int			 spm_pagecnt;	/* Number of entries in use */
+	bus_addr_t		 spm_start;	/* dva when bound */
+	bus_size_t		 spm_size;	/* size of bound map */
+	struct sg_page_entry	 spm_map[1];
+};
+
+int		sg_dmamap_load_seg(bus_dma_tag_t, struct sg_cookie *,
+		    bus_dmamap_t, bus_dma_segment_t *, int, int, bus_size_t,
+		    bus_size_t);
+struct sg_page_map *sg_iomap_create(int);
+int		sg_dmamap_append_range(bus_dma_tag_t, bus_dmamap_t, paddr_t,
+		    bus_size_t, int, bus_size_t);
+int		sg_iomap_insert_page(struct sg_page_map *, paddr_t);
+bus_addr_t	sg_iomap_translate(struct sg_page_map *, paddr_t);
+void		sg_iomap_load_map(struct sg_cookie *, struct sg_page_map *,
+		    bus_addr_t, int);
+void		sg_iomap_unload_map(struct sg_cookie *, struct sg_page_map *);
+void		sg_iomap_destroy(struct sg_page_map *);
+void		sg_iomap_clear_pages(struct sg_page_map *);
+
+struct sg_cookie *
+sg_dmatag_init(char *name, void *hdl, bus_addr_t start, bus_size_t size,
+    void bind(void *, bus_addr_t, paddr_t, int),
+    void unbind(void *, bus_addr_t), void flush_tlb(void *))
+{
+	struct sg_cookie	*cookie;
+
+	cookie = malloc(sizeof(*cookie), M_DEVBUF, M_NOWAIT|M_ZERO);
+	if (cookie == NULL)
+		return (NULL);
+
+	cookie->sg_ex = extent_create(name, start, start + size - 1,
+	    M_DEVBUF, NULL, NULL, EX_NOWAIT | EX_NOCOALESCE);
+	if (cookie->sg_ex == NULL) {
+		free(cookie, M_DEVBUF);
+		return (NULL);
+	}
+
+	cookie->sg_hdl = hdl;
+	mtx_init(&cookie->sg_mtx, IPL_HIGH);
+	cookie->bind_page = bind;
+	cookie->unbind_page = unbind;
+	cookie->flush_tlb = flush_tlb;
+
+	return (cookie);
+}
+
+void
+sg_dmatag_destroy(struct sg_cookie *cookie)
+{
+	extent_destroy(cookie->sg_ex);
+	free(cookie, M_DEVBUF);
+}
+
+int
+sg_dmamap_create(bus_dma_tag_t t, bus_size_t size, int nsegments,
+    bus_size_t maxsegsz, bus_size_t boundary, int flags, bus_dmamap_t *dmamap)
+{
+	struct sg_page_map	*spm;
+	bus_dmamap_t		 map;
+	int			 ret;
+
+	if ((ret = _bus_dmamap_create(t, size, nsegments, maxsegsz, boundary,
+	    flags, &map)) != 0)
+		return (ret);
+
+	if ((spm = sg_iomap_create(atop(round_page(size)))) == NULL) {
+		_bus_dmamap_destroy(t, map);
+		return (ENOMEM);
+	}
+
+	map->_dm_cookie = spm;
+	*dmamap = map;
+
+	return (0);
+}
+
+void
+sg_dmamap_set_alignment(bus_dma_tag_t tag, bus_dmamap_t dmam,
+    u_long alignment)
+{
+	if (alignment < PAGE_SIZE)
+		return;
+
+	dmam->dm_segs[0]._ds_align = alignment;
+}
+
+void
+sg_dmamap_destroy(bus_dma_tag_t t, bus_dmamap_t map)
+{
+	/*
+	 * The specification (man page) requires a loaded
+	 * map to be unloaded before it is destroyed.
+	 */
+	if (map->dm_nsegs)
+		bus_dmamap_unload(t, map);
+
+        if (map->_dm_cookie)
+                sg_iomap_destroy(map->_dm_cookie);
+	map->_dm_cookie = NULL;
+	_bus_dmamap_destroy(t, map);
+}
+
+/*
+ * Load a contiguous kva buffer into a dmamap.  The physical pages are
+ * not assumed to be contiguous.  Two passes are made through the buffer
+ * and both call pmap_extract() for the same va->pa translations.  It
+ * is possible to run out of pa->dvma mappings; the code should be smart
+ * enough to resize the iomap (when the "flags" permit allocation).  It
+ * is trivial to compute the number of entries required (round the length
+ * up to the page size and then divide by the page size)...
+ */
+int
+sg_dmamap_load(bus_dma_tag_t t, bus_dmamap_t map, void *buf,
+    bus_size_t buflen, struct proc *p, int flags)
+{
+	int err = 0;
+	bus_size_t sgsize;
+	u_long dvmaddr, sgstart, sgend;
+	bus_size_t align, boundary;
+	struct sg_cookie *is = t->_cookie;
+	struct sg_page_map *spm = map->_dm_cookie;
+	pmap_t pmap;
+
+	if (map->dm_nsegs) {
+		/*
+		 * Is it still in use? _bus_dmamap_load should have taken care
+		 * of this.
+		 */
+#ifdef DIAGNOSTIC
+		panic("sg_dmamap_load: map still in use");
+#endif
+		bus_dmamap_unload(t, map);
+	}
+
+	/*
+	 * Make sure that on error condition we return "no valid mappings".
+	 */
+	map->dm_nsegs = 0;
+
+	if (buflen < 1 || buflen > map->_dm_size)
+		return (EINVAL);
+
+	/*
+	 * A boundary presented to bus_dmamem_alloc() takes precedence
+	 * over boundary in the map.
+	 */
+	if ((boundary = (map->dm_segs[0]._ds_boundary)) == 0)
+		boundary = map->_dm_boundary;
+	align = MAX(map->dm_segs[0]._ds_align, PAGE_SIZE);
+
+	pmap = p ? p->p_vmspace->vm_map.pmap : pmap = pmap_kernel();
+
+	/* Count up the total number of pages we need */
+	sg_iomap_clear_pages(spm);
+	{ /* Scope */
+		bus_addr_t a, aend;
+		bus_addr_t addr = (bus_addr_t)buf;
+		int seg_len = buflen;
+
+		aend = round_page(addr + seg_len);
+		for (a = trunc_page(addr); a < aend; a += PAGE_SIZE) {
+			paddr_t pa;
+
+			if (pmap_extract(pmap, a, &pa) == FALSE) {
+				printf("iomap pmap error addr 0x%llx\n", a);
+				sg_iomap_clear_pages(spm);
+				return (EFBIG);
+			}
+
+			err = sg_iomap_insert_page(spm, pa);
+			if (err) {
+				printf("iomap insert error: %d for "
+				    "va 0x%llx pa 0x%lx "
+				    "(buf %p len %lld/%llx)\n",
+				    err, a, pa, buf, buflen, buflen);
+				sg_iomap_clear_pages(spm);
+				return (EFBIG);
+			}
+		}
+	}
+	sgsize = spm->spm_pagecnt * PAGE_SIZE;
+
+	mtx_enter(&is->sg_mtx);
+	if (flags & BUS_DMA_24BIT) {
+		sgstart = MAX(is->sg_ex->ex_start, 0xff000000);
+		sgend = MIN(is->sg_ex->ex_end, 0xffffffff);
+	} else {
+		sgstart = is->sg_ex->ex_start;
+		sgend = is->sg_ex->ex_end;
+	}
+
+	/* 
+	 * If our segment size is larger than the boundary we need to 
+	 * split the transfer up into little pieces ourselves.
+	 */
+	err = extent_alloc_subregion(is->sg_ex, sgstart, sgend,
+	    sgsize, align, 0, (sgsize > boundary) ? 0 : boundary, 
+	    EX_NOWAIT | EX_BOUNDZERO, (u_long *)&dvmaddr);
+	mtx_leave(&is->sg_mtx);
+	if (err != 0)
+		return (err);
+
+	/* Set the active DVMA map */
+	spm->spm_start = dvmaddr;
+	spm->spm_size = sgsize;
+
+	map->dm_mapsize = buflen;
+
+	sg_iomap_load_map(is, spm, dvmaddr, flags);
+
+	{ /* Scope */
+		bus_addr_t a, aend;
+		bus_addr_t addr = (bus_addr_t)buf;
+		int seg_len = buflen;
+
+		aend = round_page(addr + seg_len);
+		for (a = trunc_page(addr); a < aend; a += PAGE_SIZE) {
+			bus_addr_t pgstart;
+			bus_addr_t pgend;
+			paddr_t pa;
+			int pglen;
+
+			/* Yuck... Redoing the same pmap_extract... */
+			if (pmap_extract(pmap, a, &pa) == FALSE) {
+				printf("iomap pmap error addr 0x%llx\n", a);
+				err = EFBIG;
+				break;
+			}
+
+			pgstart = pa | (MAX(a, addr) & PAGE_MASK);
+			pgend = pa | (MIN(a + PAGE_SIZE - 1,
+			    addr + seg_len - 1) & PAGE_MASK);
+			pglen = pgend - pgstart + 1;
+
+			if (pglen < 1)
+				continue;
+
+			err = sg_dmamap_append_range(t, map, pgstart,
+			    pglen, flags, boundary);
+			if (err == EFBIG)
+				break;
+			else if (err) {
+				printf("iomap load seg page: %d for "
+				    "va 0x%llx pa %lx (%llx - %llx) "
+				    "for %d/0x%x\n",
+				    err, a, pa, pgstart, pgend, pglen, pglen);
+				break;
+			}
+		}
+	}
+	if (err) {
+		sg_iomap_unload_map(is, spm);
+		sg_iomap_clear_pages(spm);
+		map->dm_mapsize = 0;
+		map->dm_nsegs = 0;
+		mtx_enter(&is->sg_mtx);
+		extent_free(is->sg_ex, dvmaddr, sgsize, EX_NOWAIT);
+		spm->spm_start = 0;
+		spm->spm_size = 0;
+		mtx_leave(&is->sg_mtx);
+	}
+
+	return (err);
+}
+
+/*
+ * Load an mbuf into our map. we convert it to some bus_dma_segment_ts then
+ * pass it to load_raw.
+ */
+int
+sg_dmamap_load_mbuf(bus_dma_tag_t t, bus_dmamap_t map, struct mbuf *mb,
+    int flags)
+{
+	/*
+	 * This code is adapted from sparc64, for very fragmented data
+	 * we may need to adapt the algorithm
+	 */
+	bus_dma_segment_t	segs[MAX_DMA_SEGS];
+	size_t			len;
+	int			i;
+
+	/*
+	 * Make sure that on error condition we return "no valid mappings".
+	 */
+	map->dm_mapsize = 0;
+	map->dm_nsegs = 0;
+
+	if (mb->m_pkthdr.len > map->_dm_size)
+		return (EINVAL);
+
+	i = 0;
+	len = 0;
+	while (mb) {
+		vaddr_t	vaddr = mtod(mb, vaddr_t);
+		long	buflen = (long)mb->m_len;
+
+		len += buflen;
+		while (buflen > 0 && i < MAX_DMA_SEGS) {
+			paddr_t	pa;
+			long incr;
+
+			incr = min(buflen, NBPG);
+
+			if (pmap_extract(pmap_kernel(), vaddr, &pa) == FALSE)
+				return EINVAL;
+
+			buflen -= incr;
+			vaddr += incr;
+
+			if (i > 0 && pa == (segs[i - 1].ds_addr +
+			    segs[i - 1].ds_len) && ((segs[i - 1].ds_len + incr)
+			    < map->_dm_maxsegsz)) {
+				/* contigious, great! */
+				segs[i - 1].ds_len += incr;
+				continue;
+			}
+			segs[i].ds_addr = pa;
+			segs[i].ds_len = incr;
+			segs[i]._ds_boundary = 0;
+			segs[i]._ds_align = 0;
+			i++;
+		}
+		mb = mb->m_next;
+		if (mb && i >= MAX_DMA_SEGS) {
+			/* our map, it is too big! */
+			return (EFBIG);
+		}
+	}
+
+	return (sg_dmamap_load_raw(t, map, segs, i, (bus_size_t)len, flags));
+}
+
+/*
+ * Load a uio into the map. Turn it into segments and call load_raw()
+ */
+int
+sg_dmamap_load_uio(bus_dma_tag_t t, bus_dmamap_t map, struct uio *uio,
+    int flags)
+{
+	/*
+	 * loading uios is kinda broken since we can't lock the pages.
+	 * and unlock them at unload. Perhaps page loaning is the answer.
+	 * 'till then we only accept kernel data
+	 */
+	bus_dma_segment_t	segs[MAX_DMA_SEGS];
+	size_t			len;
+	int			i, j;
+
+	/*
+	 * Make sure that on errror we return "no valid mappings".
+	 */
+	map->dm_mapsize = 0;
+	map->dm_nsegs = 0;
+
+	if (uio->uio_resid > map->_dm_size)
+		return (EINVAL);
+
+	if (uio->uio_segflg != UIO_SYSSPACE)
+		return (EOPNOTSUPP);
+
+	i = j = 0;
+	len = 0;
+	while (j < uio->uio_iovcnt) {
+		vaddr_t	vaddr = (vaddr_t)uio->uio_iov[j].iov_base;
+		long	buflen = (long)uio->uio_iov[j].iov_len;
+
+		len += buflen;
+		while (buflen > 0 && i < MAX_DMA_SEGS) {
+			paddr_t pa;
+			long incr;
+
+			incr = min(buflen, NBPG);
+			(void)pmap_extract(pmap_kernel(), vaddr, &pa);
+			buflen -= incr;
+			vaddr += incr;
+
+			if (i > 0 && pa == (segs[i - 1].ds_addr +
+			    segs[i -1].ds_len) && ((segs[i - 1].ds_len + incr)
+			    < map->_dm_maxsegsz)) {
+				/* contigious, yay! */
+				segs[i - 1].ds_len += incr;
+				continue;
+			}
+			segs[i].ds_addr = pa;
+			segs[i].ds_len = incr;
+			segs[i]._ds_boundary = 0;
+			segs[i]._ds_align = 0;
+			i++;
+		}
+		j++;
+		if ((uio->uio_iovcnt - j) && i >= MAX_DMA_SEGS) {
+			/* Our map, is it too big! */
+			return (EFBIG);
+		}
+
+	}
+
+	return (sg_dmamap_load_raw(t, map, segs, i, (bus_size_t)len, flags));
+}
+
+/*
+ * Load a dvmamap from an array of segs.  It calls sg_dmamap_append_range()
+ * or for part of the 2nd pass through the mapping.
+ */
+int
+sg_dmamap_load_raw(bus_dma_tag_t t, bus_dmamap_t map,
+    bus_dma_segment_t *segs, int nsegs, bus_size_t size, int flags)
+{
+	int i;
+	int left;
+	int err = 0;
+	bus_size_t sgsize;
+	bus_size_t boundary, align;
+	u_long dvmaddr, sgstart, sgend;
+	struct sg_cookie *is = t->_cookie;
+	struct sg_page_map *spm = map->_dm_cookie;
+
+	if (map->dm_nsegs) {
+		/* Already in use?? */
+#ifdef DIAGNOSTIC
+		panic("sg_dmamap_load_raw: map still in use");
+#endif
+		bus_dmamap_unload(t, map);
+	}
+
+	/*
+	 * A boundary presented to bus_dmamem_alloc() takes precedence
+	 * over boundary in the map.
+	 */
+	if ((boundary = segs[0]._ds_boundary) == 0)
+		boundary = map->_dm_boundary;
+
+	align = MAX(MAX(segs[0]._ds_align, map->dm_segs[0]._ds_align),
+	    PAGE_SIZE);
+
+	/*
+	 * Make sure that on error condition we return "no valid mappings".
+	 */
+	map->dm_nsegs = 0;
+
+	sg_iomap_clear_pages(spm);
+	/* Count up the total number of pages we need */
+	for (i = 0, left = size; left > 0 && i < nsegs; i++) {
+		bus_addr_t a, aend;
+		bus_size_t len = segs[i].ds_len;
+		bus_addr_t addr = segs[i].ds_addr;
+		int seg_len = MIN(left, len);
+
+		if (len < 1)
+			continue;
+
+		aend = round_page(addr + seg_len);
+		for (a = trunc_page(addr); a < aend; a += PAGE_SIZE) {
+
+			err = sg_iomap_insert_page(spm, a);
+			if (err) {
+				printf("iomap insert error: %d for "
+				    "pa 0x%llx\n", err, a);
+				sg_iomap_clear_pages(spm);
+				return (EFBIG);
+			}
+		}
+
+		left -= seg_len;
+	}
+	sgsize = spm->spm_pagecnt * PAGE_SIZE;
+
+	mtx_enter(&is->sg_mtx);
+	if (flags & BUS_DMA_24BIT) {
+		sgstart = MAX(is->sg_ex->ex_start, 0xff000000);
+		sgend = MIN(is->sg_ex->ex_end, 0xffffffff);
+	} else {
+		sgstart = is->sg_ex->ex_start;
+		sgend = is->sg_ex->ex_end;
+	}
+
+	/* 
+	 * If our segment size is larger than the boundary we need to 
+	 * split the transfer up into little pieces ourselves.
+	 */
+	err = extent_alloc_subregion(is->sg_ex, sgstart, sgend,
+	    sgsize, align, 0, (sgsize > boundary) ? 0 : boundary, 
+	    EX_NOWAIT | EX_BOUNDZERO, (u_long *)&dvmaddr);
+	mtx_leave(&is->sg_mtx);
+
+	if (err != 0)
+		return (err);
+
+	/* Set the active DVMA map */
+	spm->spm_start = dvmaddr;
+	spm->spm_size = sgsize;
+
+	map->dm_mapsize = size;
+
+	sg_iomap_load_map(is, spm, dvmaddr, flags);
+
+	err = sg_dmamap_load_seg(t, is, map, segs, nsegs, flags,
+	    size, boundary);
+
+	if (err) {
+		sg_iomap_unload_map(is, spm);
+		sg_iomap_clear_pages(spm);
+		map->dm_mapsize = 0;
+		map->dm_nsegs = 0;
+		mtx_enter(&is->sg_mtx);
+		extent_free(is->sg_ex, dvmaddr, sgsize, EX_NOWAIT);
+		spm->spm_start = 0;
+		spm->spm_size = 0;
+		mtx_leave(&is->sg_mtx);
+	}
+
+	return (err);
+}
+
+/*
+ * Insert a range of addresses into a loaded map respecting the specified
+ * boundary and alignment restrictions.  The range is specified by its 
+ * physical address and length.  The range cannot cross a page boundary.
+ * This code (along with most of the rest of the function in this file)
+ * assumes that the IOMMU page size is equal to PAGE_SIZE.
+ */
+int
+sg_dmamap_append_range(bus_dma_tag_t t, bus_dmamap_t map, paddr_t pa,
+    bus_size_t length, int flags, bus_size_t boundary)
+{
+	struct sg_page_map *spm = map->_dm_cookie;
+	bus_addr_t sgstart, sgend, bd_mask;
+	bus_dma_segment_t *seg = NULL;
+	int i = map->dm_nsegs;
+
+	sgstart = sg_iomap_translate(spm, pa);
+	sgend = sgstart + length - 1;
+
+#ifdef DIAGNOSTIC
+	if (sgstart == NULL || sgstart > sgend) {
+		printf("append range invalid mapping for %lx "
+		    "(0x%llx - 0x%llx)\n", pa, sgstart, sgend);
+		map->dm_nsegs = 0;
+		return (EINVAL);
+	}
+#endif
+
+#ifdef DEBUG
+	if (trunc_page(sgstart) != trunc_page(sgend)) {
+		printf("append range crossing page boundary! "
+		    "pa %lx length %lld/0x%llx sgstart %llx sgend %llx\n",
+		    pa, length, length, sgstart, sgend);
+	}
+#endif
+
+	/*
+	 * We will attempt to merge this range with the previous entry
+	 * (if there is one).
+	 */
+	if (i > 0) {
+		seg = &map->dm_segs[i - 1];
+		if (sgstart == seg->ds_addr + seg->ds_len) {
+			length += seg->ds_len;
+			sgstart = seg->ds_addr;
+			sgend = sgstart + length - 1;
+		} else
+			seg = NULL;
+	}
+
+	if (seg == NULL) {
+		seg = &map->dm_segs[i];
+		if (++i > map->_dm_segcnt) {
+			map->dm_nsegs = 0;
+			return (EFBIG);
+		}
+	}
+
+	/*
+	 * At this point, "i" is the index of the *next* bus_dma_segment_t
+	 * (the segment count, aka map->dm_nsegs) and "seg" points to the
+	 * *current* entry.  "length", "sgstart", and "sgend" reflect what
+	 * we intend to put in "*seg".  No assumptions should be made about
+	 * the contents of "*seg".  Only "boundary" issue can change this
+	 * and "boundary" is often zero, so explicitly test for that case
+	 * (the test is strictly an optimization).
+	 */ 
+	if (boundary != 0) {
+		bd_mask = ~(boundary - 1);
+
+		while ((sgstart & bd_mask) != (sgend & bd_mask)) {
+			/*
+			 * We are crossing a boundary so fill in the current
+			 * segment with as much as possible, then grab a new
+			 * one.
+			 */
+
+			seg->ds_addr = sgstart;
+			seg->ds_len = boundary - (sgstart & bd_mask);
+
+			sgstart += seg->ds_len; /* sgend stays the same */
+			length -= seg->ds_len;
+
+			seg = &map->dm_segs[i];
+			if (++i > map->_dm_segcnt) {
+				map->dm_nsegs = 0;
+				return (EFBIG);
+			}
+		}
+	}
+
+	seg->ds_addr = sgstart;
+	seg->ds_len = length;
+	map->dm_nsegs = i;
+
+	return (0);
+}
+
+/*
+ * Populate the iomap from a bus_dma_segment_t array.  See note for
+ * sg_dmamap_load() regarding page entry exhaustion of the iomap.
+ * This is less of a problem for load_seg, as the number of pages
+ * is usually similar to the number of segments (nsegs).
+ */
+int
+sg_dmamap_load_seg(bus_dma_tag_t t, struct sg_cookie *is,
+    bus_dmamap_t map, bus_dma_segment_t *segs, int nsegs, int flags,
+    bus_size_t size, bus_size_t boundary)
+{
+	int i;
+	int left;
+	int seg;
+
+	/*
+	 * Keep in mind that each segment could span
+	 * multiple pages and that these are not always
+	 * adjacent. The code is no longer adding dvma
+	 * aliases to the IOMMU.  The STC will not cross
+	 * page boundaries anyway and a IOMMU table walk
+	 * vs. what may be a streamed PCI DMA to a ring
+	 * descriptor is probably a wash.  It eases TLB
+	 * pressure and in the worst possible case, it is
+	 * only as bad a non-IOMMUed architecture.  More
+	 * importantly, the code is not quite as hairy.
+	 * (It's bad enough as it is.)
+	 */
+	left = size;
+	seg = 0;
+	for (i = 0; left > 0 && i < nsegs; i++) {
+		bus_addr_t a, aend;
+		bus_size_t len = segs[i].ds_len;
+		bus_addr_t addr = segs[i].ds_addr;
+		int seg_len = MIN(left, len);
+
+		if (len < 1)
+			continue;
+
+		aend = round_page(addr + seg_len);
+		for (a = trunc_page(addr); a < aend; a += PAGE_SIZE) {
+			bus_addr_t pgstart;
+			bus_addr_t pgend;
+			int pglen;
+			int err;
+
+			pgstart = MAX(a, addr);
+			pgend = MIN(a + PAGE_SIZE - 1, addr + seg_len - 1);
+			pglen = pgend - pgstart + 1;
+			
+			if (pglen < 1)
+				continue;
+
+			err = sg_dmamap_append_range(t, map, pgstart,
+			    pglen, flags, boundary);
+			if (err == EFBIG)
+				return (err);
+			if (err) {
+				printf("iomap load seg page: %d for "
+				    "pa 0x%llx (%llx - %llx for %d/%x\n",
+				    err, a, pgstart, pgend, pglen, pglen);
+				return (err);
+			}
+
+		}
+
+		left -= seg_len;
+	}
+	return (0);
+}
+
+/*
+ * Unload a dvmamap.
+ */
+void
+sg_dmamap_unload(bus_dma_tag_t t, bus_dmamap_t map)
+{
+	struct sg_cookie	*is = t->_cookie;
+	struct sg_page_map	*spm = map->_dm_cookie;
+	bus_addr_t		 dvmaddr = spm->spm_start;
+	bus_size_t		 sgsize = spm->spm_size;
+	int			 error;
+
+	/* Remove the IOMMU entries */
+	sg_iomap_unload_map(is, spm);
+
+	/* Clear the iomap */
+	sg_iomap_clear_pages(spm);
+
+	mtx_enter(&is->sg_mtx);
+	error = extent_free(is->sg_ex, dvmaddr, 
+		sgsize, EX_NOWAIT);
+	spm->spm_start = 0;
+	spm->spm_size = 0;
+	mtx_leave(&is->sg_mtx);
+	if (error != 0)
+		printf("warning: %qd of DVMA space lost\n", sgsize);
+	_bus_dmamap_unload(t, map);
+}
+
+/*
+ * Alloc dma safe memory, telling the backend that we're scatter gather
+ * to ease pressure on the vm.
+ *
+ * This assumes that we can map all physical memory. 
+ */
+int
+sg_dmamem_alloc(bus_dma_tag_t t, bus_size_t size,
+    bus_size_t alignment, bus_size_t boundary, bus_dma_segment_t *segs,
+    int nsegs, int *rsegs, int flags)
+{
+	return (_bus_dmamem_alloc_range(t, size, alignment, boundary,
+	    segs, nsegs, rsegs, flags | BUS_DMA_SG, 0, -1));
+}
+
+/*
+ * Create a new iomap.
+ */
+struct sg_page_map *
+sg_iomap_create(int n)
+{
+	struct sg_page_map	*spm;
+
+	/* Safety for heavily fragmented data, such as mbufs */
+	n += 4;
+	if (n < 16)
+		n = 16;
+
+	spm = malloc(sizeof(*spm) + (n - 1) * sizeof(spm->spm_map[0]),
+		M_DEVBUF, M_NOWAIT | M_ZERO);
+	if (spm == NULL)
+		return (NULL);
+
+	/* Initialize the map. */
+	spm->spm_maxpage = n;
+	SPLAY_INIT(&spm->spm_tree);
+
+	return (spm);
+}
+
+/*
+ * Destroy an iomap.
+ */
+void
+sg_iomap_destroy(struct sg_page_map *spm)
+{
+#ifdef DIAGNOSTIC
+	if (spm->spm_pagecnt > 0)
+		printf("sg_iomap_destroy: %d page entries in use\n",
+		    spm->spm_pagecnt);
+#endif
+
+	free(spm, M_DEVBUF);
+}
+
+/*
+ * Utility function used by splay tree to order page entries by pa.
+ */
+static inline int
+iomap_compare(struct sg_page_entry *a, struct sg_page_entry *b)
+{
+	return ((a->spe_pa > b->spe_pa) ? 1 :
+		(a->spe_pa < b->spe_pa) ? -1 : 0);
+}
+
+SPLAY_PROTOTYPE(sg_page_tree, sg_page_entry, spe_node, iomap_compare);
+
+SPLAY_GENERATE(sg_page_tree, sg_page_entry, spe_node, iomap_compare);
+
+/*
+ * Insert a pa entry in the iomap.
+ */
+int
+sg_iomap_insert_page(struct sg_page_map *spm, paddr_t pa)
+{
+	struct sg_page_entry *e;
+
+	if (spm->spm_pagecnt >= spm->spm_maxpage) {
+		struct sg_page_entry spe;
+
+		spe.spe_pa = pa;
+		if (SPLAY_FIND(sg_page_tree, &spm->spm_tree, &spe))
+			return (0);
+
+		return (ENOMEM);
+	}
+
+	e = &spm->spm_map[spm->spm_pagecnt];
+
+	e->spe_pa = pa;
+	e->spe_va = NULL;
+
+	e = SPLAY_INSERT(sg_page_tree, &spm->spm_tree, e);
+
+	/* Duplicates are okay, but only count them once. */
+	if (e)
+		return (0);
+
+	++spm->spm_pagecnt;
+
+	return (0);
+}
+
+/*
+ * Locate the iomap by filling in the pa->va mapping and inserting it
+ * into the IOMMU tables.
+ */
+void
+sg_iomap_load_map(struct sg_cookie *sc, struct sg_page_map *spm,
+    bus_addr_t vmaddr, int flags)
+{
+	struct sg_page_entry	*e;
+	int			 i;
+
+	for (i = 0, e = spm->spm_map; i < spm->spm_pagecnt; ++i, ++e) {
+		e->spe_va = vmaddr;
+		sc->bind_page(sc->sg_hdl, e->spe_va, e->spe_pa, flags);
+		vmaddr += PAGE_SIZE;
+	}
+	sc->flush_tlb(sc->sg_hdl);
+}
+
+/*
+ * Remove the iomap from the IOMMU.
+ */
+void
+sg_iomap_unload_map(struct sg_cookie *sc, struct sg_page_map *spm)
+{
+	struct sg_page_entry	*e;
+	int			 i;
+
+	for (i = 0, e = spm->spm_map; i < spm->spm_pagecnt; ++i, ++e)
+		sc->unbind_page(sc->sg_hdl, e->spe_va);
+	sc->flush_tlb(sc->sg_hdl);
+
+}
+
+/*
+ * Translate a physical address (pa) into a DVMA address.
+ */
+bus_addr_t
+sg_iomap_translate(struct sg_page_map *spm, paddr_t pa)
+{
+	struct sg_page_entry	*e, pe;
+	paddr_t			 offset = pa & PAGE_MASK;
+
+	pe.spe_pa = trunc_page(pa);
+
+	e = SPLAY_FIND(sg_page_tree, &spm->spm_tree, &pe);
+
+	if (e == NULL)
+		return (NULL);
+
+	return (e->spe_va | offset);
+}
+
+/*
+ * Clear the iomap table and tree.
+ */
+void
+sg_iomap_clear_pages(struct sg_page_map *spm)
+{
+	spm->spm_pagecnt = 0;
+	SPLAY_INIT(&spm->spm_tree);
+}