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bus_dma.c revision 1.10
      1 /*	$NetBSD: bus_dma.c,v 1.10 2001/03/21 18:40:32 soren Exp $	*/
      2 
      3 /*-
      4  * Copyright (c) 1996, 1997, 1998 The NetBSD Foundation, Inc.
      5  * All rights reserved.
      6  *
      7  * This code is derived from software contributed to The NetBSD Foundation
      8  * by Jason R. Thorpe of the Numerical Aerospace Simulation Facility,
      9  * NASA Ames Research Center.
     10  *
     11  * Redistribution and use in source and binary forms, with or without
     12  * modification, are permitted provided that the following conditions
     13  * are met:
     14  * 1. Redistributions of source code must retain the above copyright
     15  *    notice, this list of conditions and the following disclaimer.
     16  * 2. Redistributions in binary form must reproduce the above copyright
     17  *    notice, this list of conditions and the following disclaimer in the
     18  *    documentation and/or other materials provided with the distribution.
     19  * 3. All advertising materials mentioning features or use of this software
     20  *    must display the following acknowledgement:
     21  *	This product includes software developed by the NetBSD
     22  *	Foundation, Inc. and its contributors.
     23  * 4. Neither the name of The NetBSD Foundation nor the names of its
     24  *    contributors may be used to endorse or promote products derived
     25  *    from this software without specific prior written permission.
     26  *
     27  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
     28  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
     29  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     30  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
     31  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
     32  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
     33  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
     34  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
     35  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
     36  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
     37  * POSSIBILITY OF SUCH DAMAGE.
     38  */
     39 /*
     40  * bus_dma routines for vax. File copied from arm32/bus_dma.c.
     41  * NetBSD: bus_dma.c,v 1.11 1998/09/21 22:53:35 thorpej Exp
     42  */
     43 
     44 #include <sys/param.h>
     45 #include <sys/systm.h>
     46 #include <sys/kernel.h>
     47 #include <sys/map.h>
     48 #include <sys/proc.h>
     49 #include <sys/buf.h>
     50 #include <sys/reboot.h>
     51 #include <sys/conf.h>
     52 #include <sys/file.h>
     53 #include <sys/malloc.h>
     54 #include <sys/mbuf.h>
     55 #include <sys/vnode.h>
     56 #include <sys/device.h>
     57 
     58 #include <uvm/uvm_extern.h>
     59 
     60 #define _VAX_BUS_DMA_PRIVATE
     61 #include <machine/bus.h>
     62 
     63 #include <machine/ka43.h>
     64 #include <machine/sid.h>
     65 
     66 extern	vaddr_t avail_start, avail_end, virtual_avail;
     67 
     68 int	_bus_dmamap_load_buffer __P((bus_dma_tag_t, bus_dmamap_t, void *,
     69 	    bus_size_t, struct proc *, int, vaddr_t *, int *, int));
     70 int	_bus_dma_inrange __P((bus_dma_segment_t *, int, bus_addr_t));
     71 int	_bus_dmamem_alloc_range __P((bus_dma_tag_t, bus_size_t, bus_size_t,
     72 	    bus_size_t, bus_dma_segment_t*, int, int *, int, vaddr_t, vaddr_t));
     73 /*
     74  * Common function for DMA map creation.  May be called by bus-specific
     75  * DMA map creation functions.
     76  */
     77 int
     78 _bus_dmamap_create(t, size, nsegments, maxsegsz, boundary, flags, dmamp)
     79 	bus_dma_tag_t t;
     80 	bus_size_t size;
     81 	int nsegments;
     82 	bus_size_t maxsegsz;
     83 	bus_size_t boundary;
     84 	int flags;
     85 	bus_dmamap_t *dmamp;
     86 {
     87 	struct vax_bus_dmamap *map;
     88 	void *mapstore;
     89 	size_t mapsize;
     90 
     91 #ifdef DEBUG_DMA
     92 	printf("dmamap_create: t=%p size=%lx nseg=%x msegsz=%lx boundary=%lx flags=%x\n",
     93 	    t, size, nsegments, maxsegsz, boundary, flags);
     94 #endif	/* DEBUG_DMA */
     95 
     96 	/*
     97 	 * Allocate and initialize the DMA map.  The end of the map
     98 	 * is a variable-sized array of segments, so we allocate enough
     99 	 * room for them in one shot.
    100 	 *
    101 	 * Note we don't preserve the WAITOK or NOWAIT flags.  Preservation
    102 	 * of ALLOCNOW notifies others that we've reserved these resources,
    103 	 * and they are not to be freed.
    104 	 *
    105 	 * The bus_dmamap_t includes one bus_dma_segment_t, hence
    106 	 * the (nsegments - 1).
    107 	 */
    108 	mapsize = sizeof(struct vax_bus_dmamap) +
    109 	    (sizeof(bus_dma_segment_t) * (nsegments - 1));
    110 	if ((mapstore = malloc(mapsize, M_DMAMAP,
    111 	    (flags & BUS_DMA_NOWAIT) ? M_NOWAIT : M_WAITOK)) == NULL)
    112 		return (ENOMEM);
    113 
    114 	bzero(mapstore, mapsize);
    115 	map = (struct vax_bus_dmamap *)mapstore;
    116 	map->_dm_size = size;
    117 	map->_dm_segcnt = nsegments;
    118 	map->_dm_maxsegsz = maxsegsz;
    119 	map->_dm_boundary = boundary;
    120 	map->_dm_flags = flags & ~(BUS_DMA_WAITOK|BUS_DMA_NOWAIT);
    121 	map->dm_mapsize = 0;		/* no valid mappings */
    122 	map->dm_nsegs = 0;
    123 
    124 	*dmamp = map;
    125 #ifdef DEBUG_DMA
    126 	printf("dmamap_create:map=%p\n", map);
    127 #endif	/* DEBUG_DMA */
    128 	return (0);
    129 }
    130 
    131 /*
    132  * Common function for DMA map destruction.  May be called by bus-specific
    133  * DMA map destruction functions.
    134  */
    135 void
    136 _bus_dmamap_destroy(t, map)
    137 	bus_dma_tag_t t;
    138 	bus_dmamap_t map;
    139 {
    140 
    141 #ifdef DEBUG_DMA
    142 	printf("dmamap_destroy: t=%p map=%p\n", t, map);
    143 #endif	/* DEBUG_DMA */
    144 #ifdef DIAGNOSTIC
    145 	if (map->dm_nsegs > 0)
    146 		printf("bus_dmamap_destroy() called for map with valid mappings\n");
    147 #endif	/* DIAGNOSTIC */
    148 	free(map, M_DEVBUF);
    149 }
    150 
    151 /*
    152  * Common function for loading a DMA map with a linear buffer.  May
    153  * be called by bus-specific DMA map load functions.
    154  */
    155 int
    156 _bus_dmamap_load(t, map, buf, buflen, p, flags)
    157 	bus_dma_tag_t t;
    158 	bus_dmamap_t map;
    159 	void *buf;
    160 	bus_size_t buflen;
    161 	struct proc *p;
    162 	int flags;
    163 {
    164 	vaddr_t lastaddr;
    165 	int seg, error;
    166 
    167 #ifdef DEBUG_DMA
    168 	printf("dmamap_load: t=%p map=%p buf=%p len=%lx p=%p f=%d\n",
    169 	    t, map, buf, buflen, p, flags);
    170 #endif	/* DEBUG_DMA */
    171 
    172 	/*
    173 	 * Make sure that on error condition we return "no valid mappings".
    174 	 */
    175 	map->dm_mapsize = 0;
    176 	map->dm_nsegs = 0;
    177 
    178 	if (buflen > map->_dm_size)
    179 		return (EINVAL);
    180 
    181 	seg = 0;
    182 	error = _bus_dmamap_load_buffer(t, map, buf, buflen, p, flags,
    183 	    &lastaddr, &seg, 1);
    184 	if (error == 0) {
    185 		map->dm_mapsize = buflen;
    186 		map->dm_nsegs = seg + 1;
    187 	}
    188 #ifdef DEBUG_DMA
    189 	printf("dmamap_load: error=%d\n", error);
    190 #endif	/* DEBUG_DMA */
    191 	return (error);
    192 }
    193 
    194 /*
    195  * Like _bus_dmamap_load(), but for mbufs.
    196  */
    197 int
    198 _bus_dmamap_load_mbuf(t, map, m0, flags)
    199 	bus_dma_tag_t t;
    200 	bus_dmamap_t map;
    201 	struct mbuf *m0;
    202 	int flags;
    203 {
    204 	vaddr_t lastaddr;
    205 	int seg, error, first;
    206 	struct mbuf *m;
    207 
    208 #ifdef DEBUG_DMA
    209 	printf("dmamap_load_mbuf: t=%p map=%p m0=%p f=%d\n",
    210 	    t, map, m0, flags);
    211 #endif	/* DEBUG_DMA */
    212 
    213 	/*
    214 	 * Make sure that on error condition we return "no valid mappings."
    215 	 */
    216 	map->dm_mapsize = 0;
    217 	map->dm_nsegs = 0;
    218 
    219 #ifdef DIAGNOSTIC
    220 	if ((m0->m_flags & M_PKTHDR) == 0)
    221 		panic("_bus_dmamap_load_mbuf: no packet header");
    222 #endif	/* DIAGNOSTIC */
    223 
    224 	if (m0->m_pkthdr.len > map->_dm_size)
    225 		return (EINVAL);
    226 
    227 	first = 1;
    228 	seg = 0;
    229 	error = 0;
    230 	for (m = m0; m != NULL && error == 0; m = m->m_next) {
    231 		error = _bus_dmamap_load_buffer(t, map, m->m_data, m->m_len,
    232 		    NULL, flags, &lastaddr, &seg, first);
    233 		first = 0;
    234 	}
    235 	if (error == 0) {
    236 		map->dm_mapsize = m0->m_pkthdr.len;
    237 		map->dm_nsegs = seg + 1;
    238 	}
    239 #ifdef DEBUG_DMA
    240 	printf("dmamap_load_mbuf: error=%d\n", error);
    241 #endif	/* DEBUG_DMA */
    242 	return (error);
    243 }
    244 
    245 /*
    246  * Like _bus_dmamap_load(), but for uios.
    247  */
    248 int
    249 _bus_dmamap_load_uio(t, map, uio, flags)
    250 	bus_dma_tag_t t;
    251 	bus_dmamap_t map;
    252 	struct uio *uio;
    253 	int flags;
    254 {
    255 	vaddr_t lastaddr;
    256 	int seg, i, error, first;
    257 	bus_size_t minlen, resid;
    258 	struct proc *p = NULL;
    259 	struct iovec *iov;
    260 	caddr_t addr;
    261 
    262 	/*
    263 	 * Make sure that on error condition we return "no valid mappings."
    264 	 */
    265 	map->dm_mapsize = 0;
    266 	map->dm_nsegs = 0;
    267 
    268 	resid = uio->uio_resid;
    269 	iov = uio->uio_iov;
    270 
    271 	if (uio->uio_segflg == UIO_USERSPACE) {
    272 		p = uio->uio_procp;
    273 #ifdef DIAGNOSTIC
    274 		if (p == NULL)
    275 			panic("_bus_dmamap_load_uio: USERSPACE but no proc");
    276 #endif
    277 	}
    278 
    279 	first = 1;
    280 	seg = 0;
    281 	error = 0;
    282 	for (i = 0; i < uio->uio_iovcnt && resid != 0 && error == 0; i++) {
    283 		/*
    284 		 * Now at the first iovec to load.  Load each iovec
    285 		 * until we have exhausted the residual count.
    286 		 */
    287 		minlen = resid < iov[i].iov_len ? resid : iov[i].iov_len;
    288 		addr = (caddr_t)iov[i].iov_base;
    289 
    290 		error = _bus_dmamap_load_buffer(t, map, addr, minlen,
    291 		    p, flags, &lastaddr, &seg, first);
    292 		first = 0;
    293 
    294 		resid -= minlen;
    295 	}
    296 	if (error == 0) {
    297 		map->dm_mapsize = uio->uio_resid;
    298 		map->dm_nsegs = seg + 1;
    299 	}
    300 	return (error);
    301 }
    302 
    303 /*
    304  * Like _bus_dmamap_load(), but for raw memory allocated with
    305  * bus_dmamem_alloc().
    306  */
    307 int
    308 _bus_dmamap_load_raw(t, map, segs, nsegs, size, flags)
    309 	bus_dma_tag_t t;
    310 	bus_dmamap_t map;
    311 	bus_dma_segment_t *segs;
    312 	int nsegs;
    313 	bus_size_t size;
    314 	int flags;
    315 {
    316 
    317 	panic("_bus_dmamap_load_raw: not implemented");
    318 }
    319 
    320 /*
    321  * Common function for unloading a DMA map.  May be called by
    322  * bus-specific DMA map unload functions.
    323  */
    324 void
    325 _bus_dmamap_unload(t, map)
    326 	bus_dma_tag_t t;
    327 	bus_dmamap_t map;
    328 {
    329 
    330 #ifdef DEBUG_DMA
    331 	printf("dmamap_unload: t=%p map=%p\n", t, map);
    332 #endif	/* DEBUG_DMA */
    333 
    334 	/*
    335 	 * No resources to free; just mark the mappings as
    336 	 * invalid.
    337 	 */
    338 	map->dm_mapsize = 0;
    339 	map->dm_nsegs = 0;
    340 }
    341 
    342 /*
    343  * Common function for DMA map synchronization.  May be called
    344  * by bus-specific DMA map synchronization functions.
    345  */
    346 void
    347 _bus_dmamap_sync(t, map, offset, len, ops)
    348 	bus_dma_tag_t t;
    349 	bus_dmamap_t map;
    350 	bus_addr_t offset;
    351 	bus_size_t len;
    352 	int ops;
    353 {
    354 #ifdef DEBUG_DMA
    355 	printf("dmamap_sync: t=%p map=%p offset=%lx len=%lx ops=%x\n",
    356 	    t, map, offset, len, ops);
    357 #endif	/* DEBUG_DMA */
    358 	/*
    359 	 * A vax only has snoop-cache, so this routine is a no-op.
    360 	 */
    361 	return;
    362 }
    363 
    364 /*
    365  * Common function for DMA-safe memory allocation.  May be called
    366  * by bus-specific DMA memory allocation functions.
    367  */
    368 
    369 int
    370 _bus_dmamem_alloc(t, size, alignment, boundary, segs, nsegs, rsegs, flags)
    371 	bus_dma_tag_t t;
    372 	bus_size_t size, alignment, boundary;
    373 	bus_dma_segment_t *segs;
    374 	int nsegs;
    375 	int *rsegs;
    376 	int flags;
    377 {
    378 	int error;
    379 
    380 	error =  (_bus_dmamem_alloc_range(t, size, alignment, boundary,
    381 	    segs, nsegs, rsegs, flags, round_page(avail_start),
    382 	    trunc_page(avail_end)));
    383 	return(error);
    384 }
    385 
    386 /*
    387  * Common function for freeing DMA-safe memory.  May be called by
    388  * bus-specific DMA memory free functions.
    389  */
    390 void
    391 _bus_dmamem_free(t, segs, nsegs)
    392 	bus_dma_tag_t t;
    393 	bus_dma_segment_t *segs;
    394 	int nsegs;
    395 {
    396 	vm_page_t m;
    397 	bus_addr_t addr;
    398 	struct pglist mlist;
    399 	int curseg;
    400 
    401 #ifdef DEBUG_DMA
    402 	printf("dmamem_free: t=%p segs=%p nsegs=%x\n", t, segs, nsegs);
    403 #endif	/* DEBUG_DMA */
    404 
    405 	/*
    406 	 * Build a list of pages to free back to the VM system.
    407 	 */
    408 	TAILQ_INIT(&mlist);
    409 	for (curseg = 0; curseg < nsegs; curseg++) {
    410 		for (addr = segs[curseg].ds_addr;
    411 		    addr < (segs[curseg].ds_addr + segs[curseg].ds_len);
    412 		    addr += PAGE_SIZE) {
    413 			m = PHYS_TO_VM_PAGE(addr);
    414 			TAILQ_INSERT_TAIL(&mlist, m, pageq);
    415 		}
    416 	}
    417 	uvm_pglistfree(&mlist);
    418 }
    419 
    420 /*
    421  * Common function for mapping DMA-safe memory.  May be called by
    422  * bus-specific DMA memory map functions.
    423  */
    424 int
    425 _bus_dmamem_map(t, segs, nsegs, size, kvap, flags)
    426 	bus_dma_tag_t t;
    427 	bus_dma_segment_t *segs;
    428 	int nsegs;
    429 	size_t size;
    430 	caddr_t *kvap;
    431 	int flags;
    432 {
    433 	vaddr_t va;
    434 	bus_addr_t addr;
    435 	int curseg;
    436 
    437 	/*
    438 	 * Special case (but common):
    439 	 * If there is only one physical segment then the already-mapped
    440 	 * virtual address is returned, since all physical memory is already
    441 	 * in the beginning of kernel virtual memory.
    442 	 */
    443 	if (nsegs == 1) {
    444 		*kvap = (caddr_t)(segs[0].ds_addr | KERNBASE);
    445 		/*
    446 		 * KA43 (3100/m76) must have its DMA-safe memory accessed
    447 		 * through DIAGMEM. Remap it here.
    448 		 */
    449 		if (vax_boardtype == VAX_BTYP_43) {
    450 			pmap_map((vaddr_t)*kvap, segs[0].ds_addr|KA43_DIAGMEM,
    451 			    (segs[0].ds_addr|KA43_DIAGMEM) + size,
    452 			    VM_PROT_READ|VM_PROT_WRITE);
    453 		}
    454 		return 0;
    455 	}
    456 	size = round_page(size);
    457 	va = uvm_km_valloc(kernel_map, size);
    458 
    459 	if (va == 0)
    460 		return (ENOMEM);
    461 
    462 	*kvap = (caddr_t)va;
    463 
    464 	for (curseg = 0; curseg < nsegs; curseg++) {
    465 		for (addr = segs[curseg].ds_addr;
    466 		    addr < (segs[curseg].ds_addr + segs[curseg].ds_len);
    467 		    addr += NBPG, va += NBPG, size -= NBPG) {
    468 			if (size == 0)
    469 				panic("_bus_dmamem_map: size botch");
    470 			if (vax_boardtype == VAX_BTYP_43)
    471 				addr |= KA43_DIAGMEM;
    472 			pmap_enter(pmap_kernel(), va, addr,
    473 			    VM_PROT_READ | VM_PROT_WRITE,
    474 			    VM_PROT_READ | VM_PROT_WRITE | PMAP_WIRED);
    475 		}
    476 	}
    477 	return (0);
    478 }
    479 
    480 /*
    481  * Common function for unmapping DMA-safe memory.  May be called by
    482  * bus-specific DMA memory unmapping functions.
    483  */
    484 void
    485 _bus_dmamem_unmap(t, kva, size)
    486 	bus_dma_tag_t t;
    487 	caddr_t kva;
    488 	size_t size;
    489 {
    490 
    491 #ifdef DEBUG_DMA
    492 	printf("dmamem_unmap: t=%p kva=%p size=%x\n", t, kva, size);
    493 #endif	/* DEBUG_DMA */
    494 #ifdef DIAGNOSTIC
    495 	if ((u_long)kva & PGOFSET)
    496 		panic("_bus_dmamem_unmap");
    497 #endif	/* DIAGNOSTIC */
    498 
    499 	/* Avoid free'ing if not mapped */
    500 	if (kva >= (caddr_t)virtual_avail)
    501 		uvm_km_free(kernel_map, (vaddr_t)kva, round_page(size));
    502 }
    503 
    504 /*
    505  * Common functin for mmap(2)'ing DMA-safe memory.  May be called by
    506  * bus-specific DMA mmap(2)'ing functions.
    507  */
    508 paddr_t
    509 _bus_dmamem_mmap(t, segs, nsegs, off, prot, flags)
    510 	bus_dma_tag_t t;
    511 	bus_dma_segment_t *segs;
    512 	int nsegs;
    513 	off_t off;
    514 	int prot, flags;
    515 {
    516 	int i;
    517 
    518 	for (i = 0; i < nsegs; i++) {
    519 #ifdef DIAGNOSTIC
    520 		if (off & PGOFSET)
    521 			panic("_bus_dmamem_mmap: offset unaligned");
    522 		if (segs[i].ds_addr & PGOFSET)
    523 			panic("_bus_dmamem_mmap: segment unaligned");
    524 		if (segs[i].ds_len & PGOFSET)
    525 			panic("_bus_dmamem_mmap: segment size not multiple"
    526 			    " of page size");
    527 #endif	/* DIAGNOSTIC */
    528 		if (off >= segs[i].ds_len) {
    529 			off -= segs[i].ds_len;
    530 			continue;
    531 		}
    532 
    533 		return (btop((u_long)segs[i].ds_addr + off));
    534 	}
    535 
    536 	/* Page not found. */
    537 	return (-1);
    538 }
    539 
    540 /**********************************************************************
    541  * DMA utility functions
    542  **********************************************************************/
    543 
    544 /*
    545  * Utility function to load a linear buffer.  lastaddrp holds state
    546  * between invocations (for multiple-buffer loads).  segp contains
    547  * the starting segment on entrace, and the ending segment on exit.
    548  * first indicates if this is the first invocation of this function.
    549  */
    550 int
    551 _bus_dmamap_load_buffer(t, map, buf, buflen, p, flags, lastaddrp, segp, first)
    552 	bus_dma_tag_t t;
    553 	bus_dmamap_t map;
    554 	void *buf;
    555 	bus_size_t buflen;
    556 	struct proc *p;
    557 	int flags;
    558 	vaddr_t *lastaddrp;
    559 	int *segp;
    560 	int first;
    561 {
    562 	bus_size_t sgsize;
    563 	bus_addr_t curaddr, lastaddr, baddr, bmask;
    564 	vaddr_t vaddr = (vaddr_t)buf;
    565 	int seg;
    566 	pmap_t pmap;
    567 
    568 #ifdef DEBUG_DMA
    569 	printf("_bus_dmamem_load_buffer(buf=%p, len=%lx, flags=%d, 1st=%d)\n",
    570 	    buf, buflen, flags, first);
    571 #endif	/* DEBUG_DMA */
    572 
    573 	if (p != NULL)
    574 		pmap = p->p_vmspace->vm_map.pmap;
    575 	else
    576 		pmap = pmap_kernel();
    577 
    578 	lastaddr = *lastaddrp;
    579 	bmask  = ~(map->_dm_boundary - 1);
    580 
    581 	for (seg = *segp; buflen > 0; ) {
    582 		/*
    583 		 * Get the physical address for this segment.
    584 		 */
    585 		(void) pmap_extract(pmap, (vaddr_t)vaddr, &curaddr);
    586 
    587 #if 0
    588 		/*
    589 		 * Make sure we're in an allowed DMA range.
    590 		 */
    591 		if (t->_ranges != NULL &&
    592 		    _bus_dma_inrange(t->_ranges, t->_nranges, curaddr) == 0)
    593 			return (EINVAL);
    594 #endif
    595 
    596 		/*
    597 		 * Compute the segment size, and adjust counts.
    598 		 */
    599 		sgsize = NBPG - ((u_long)vaddr & PGOFSET);
    600 		if (buflen < sgsize)
    601 			sgsize = buflen;
    602 
    603 		/*
    604 		 * Make sure we don't cross any boundaries.
    605 		 */
    606 		if (map->_dm_boundary > 0) {
    607 			baddr = (curaddr + map->_dm_boundary) & bmask;
    608 			if (sgsize > (baddr - curaddr))
    609 				sgsize = (baddr - curaddr);
    610 		}
    611 
    612 		/*
    613 		 * Insert chunk into a segment, coalescing with
    614 		 * previous segment if possible.
    615 		 */
    616 		if (first) {
    617 			map->dm_segs[seg].ds_addr = curaddr;
    618 			map->dm_segs[seg].ds_len = sgsize;
    619 			first = 0;
    620 		} else {
    621 			if (curaddr == lastaddr &&
    622 			    (map->dm_segs[seg].ds_len + sgsize) <=
    623 			     map->_dm_maxsegsz &&
    624 			    (map->_dm_boundary == 0 ||
    625 			     (map->dm_segs[seg].ds_addr & bmask) ==
    626 			     (curaddr & bmask)))
    627 				map->dm_segs[seg].ds_len += sgsize;
    628 			else {
    629 				if (++seg >= map->_dm_segcnt)
    630 					break;
    631 				map->dm_segs[seg].ds_addr = curaddr;
    632 				map->dm_segs[seg].ds_len = sgsize;
    633 			}
    634 		}
    635 
    636 		lastaddr = curaddr + sgsize;
    637 		vaddr += sgsize;
    638 		buflen -= sgsize;
    639 	}
    640 
    641 	*segp = seg;
    642 	*lastaddrp = lastaddr;
    643 
    644 	/*
    645 	 * Did we fit?
    646 	 */
    647 	if (buflen != 0)
    648 		return (EFBIG);		/* XXX better return value here? */
    649 	return (0);
    650 }
    651 
    652 /*
    653  * Check to see if the specified page is in an allowed DMA range.
    654  */
    655 int
    656 _bus_dma_inrange(ranges, nranges, curaddr)
    657 	bus_dma_segment_t *ranges;
    658 	int nranges;
    659 	bus_addr_t curaddr;
    660 {
    661 	bus_dma_segment_t *ds;
    662 	int i;
    663 
    664 	for (i = 0, ds = ranges; i < nranges; i++, ds++) {
    665 		if (curaddr >= ds->ds_addr &&
    666 		    round_page(curaddr) <= (ds->ds_addr + ds->ds_len))
    667 			return (1);
    668 	}
    669 
    670 	return (0);
    671 }
    672 
    673 /*
    674  * Allocate physical memory from the given physical address range.
    675  * Called by DMA-safe memory allocation methods.
    676  */
    677 int
    678 _bus_dmamem_alloc_range(t, size, alignment, boundary, segs, nsegs, rsegs,
    679     flags, low, high)
    680 	bus_dma_tag_t t;
    681 	bus_size_t size, alignment, boundary;
    682 	bus_dma_segment_t *segs;
    683 	int nsegs;
    684 	int *rsegs;
    685 	int flags;
    686 	vaddr_t low;
    687 	vaddr_t high;
    688 {
    689 	vaddr_t curaddr, lastaddr;
    690 	vm_page_t m;
    691 	struct pglist mlist;
    692 	int curseg, error;
    693 
    694 #ifdef DEBUG_DMA
    695 	printf("alloc_range: t=%p size=%lx align=%lx boundary=%lx segs=%p nsegs=%x rsegs=%p flags=%x lo=%lx hi=%lx\n",
    696 	    t, size, alignment, boundary, segs, nsegs, rsegs, flags, low, high);
    697 #endif	/* DEBUG_DMA */
    698 
    699 	/* Always round the size. */
    700 	size = round_page(size);
    701 
    702 	/*
    703 	 * Allocate pages from the VM system.
    704 	 */
    705 	TAILQ_INIT(&mlist);
    706 	error = uvm_pglistalloc(size, low, high, alignment, boundary,
    707 	    &mlist, nsegs, (flags & BUS_DMA_NOWAIT) == 0);
    708 	if (error)
    709 		return (error);
    710 
    711 	/*
    712 	 * Compute the location, size, and number of segments actually
    713 	 * returned by the VM code.
    714 	 */
    715 	m = mlist.tqh_first;
    716 	curseg = 0;
    717 	lastaddr = segs[curseg].ds_addr = VM_PAGE_TO_PHYS(m);
    718 	segs[curseg].ds_len = PAGE_SIZE;
    719 #ifdef DEBUG_DMA
    720 		printf("alloc: page %lx\n", lastaddr);
    721 #endif	/* DEBUG_DMA */
    722 	m = m->pageq.tqe_next;
    723 
    724 	for (; m != NULL; m = m->pageq.tqe_next) {
    725 		curaddr = VM_PAGE_TO_PHYS(m);
    726 #ifdef DIAGNOSTIC
    727 		if (curaddr < low || curaddr >= high) {
    728 			printf("uvm_pglistalloc returned non-sensical"
    729 			    " address 0x%lx\n", curaddr);
    730 			panic("_bus_dmamem_alloc_range");
    731 		}
    732 #endif	/* DIAGNOSTIC */
    733 #ifdef DEBUG_DMA
    734 		printf("alloc: page %lx\n", curaddr);
    735 #endif	/* DEBUG_DMA */
    736 		if (curaddr == (lastaddr + PAGE_SIZE))
    737 			segs[curseg].ds_len += PAGE_SIZE;
    738 		else {
    739 			curseg++;
    740 			segs[curseg].ds_addr = curaddr;
    741 			segs[curseg].ds_len = PAGE_SIZE;
    742 		}
    743 		lastaddr = curaddr;
    744 	}
    745 
    746 	*rsegs = curseg + 1;
    747 
    748 	return (0);
    749 }
    750 
    751 /*
    752  * "generic" DMA struct, nothing special.
    753  */
    754 struct vax_bus_dma_tag vax_bus_dma_tag = {
    755 	NULL,
    756 	0,
    757 	0,
    758 	0,
    759 	0,
    760 	0,
    761 	_bus_dmamap_create,
    762 	_bus_dmamap_destroy,
    763 	_bus_dmamap_load,
    764 	_bus_dmamap_load_mbuf,
    765 	_bus_dmamap_load_uio,
    766 	_bus_dmamap_load_raw,
    767 	_bus_dmamap_unload,
    768 	_bus_dmamap_sync,
    769 	_bus_dmamem_alloc,
    770 	_bus_dmamem_free,
    771 	_bus_dmamem_map,
    772 	_bus_dmamem_unmap,
    773 	_bus_dmamem_mmap,
    774 };
    775