xref: /netbsd-src/sys/arch/hp300/dev/dma.c (revision b8c616269f5ebf18ab2e35cb8099d683130a177c)
1 /*	$NetBSD: dma.c,v 1.28 2002/12/22 00:17:15 gmcgarry Exp $	*/
2 
3 /*-
4  * Copyright (c) 1996, 1997 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.
9  *
10  * Redistribution and use in source and binary forms, with or without
11  * modification, are permitted provided that the following conditions
12  * are met:
13  * 1. Redistributions of source code must retain the above copyright
14  *    notice, this list of conditions and the following disclaimer.
15  * 2. Redistributions in binary form must reproduce the above copyright
16  *    notice, this list of conditions and the following disclaimer in the
17  *    documentation and/or other materials provided with the distribution.
18  * 3. All advertising materials mentioning features or use of this software
19  *    must display the following acknowledgement:
20  *	This product includes software developed by the NetBSD
21  *	Foundation, Inc. and its contributors.
22  * 4. Neither the name of The NetBSD Foundation nor the names of its
23  *    contributors may be used to endorse or promote products derived
24  *    from this software without specific prior written permission.
25  *
26  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
27  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
28  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
29  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
30  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
31  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
32  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
33  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
34  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
35  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
36  * POSSIBILITY OF SUCH DAMAGE.
37  */
38 
39 /*
40  * Copyright (c) 1982, 1990, 1993
41  *	The Regents of the University of California.  All rights reserved.
42  *
43  * Redistribution and use in source and binary forms, with or without
44  * modification, are permitted provided that the following conditions
45  * are met:
46  * 1. Redistributions of source code must retain the above copyright
47  *    notice, this list of conditions and the following disclaimer.
48  * 2. Redistributions in binary form must reproduce the above copyright
49  *    notice, this list of conditions and the following disclaimer in the
50  *    documentation and/or other materials provided with the distribution.
51  * 3. All advertising materials mentioning features or use of this software
52  *    must display the following acknowledgement:
53  *	This product includes software developed by the University of
54  *	California, Berkeley and its contributors.
55  * 4. Neither the name of the University nor the names of its contributors
56  *    may be used to endorse or promote products derived from this software
57  *    without specific prior written permission.
58  *
59  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
60  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
61  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
62  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
63  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
64  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
65  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
66  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
67  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
68  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
69  * SUCH DAMAGE.
70  *
71  *	@(#)dma.c	8.1 (Berkeley) 6/10/93
72  */
73 
74 /*
75  * DMA driver
76  */
77 
78 #include <sys/cdefs.h>
79 __KERNEL_RCSID(0, "$NetBSD: dma.c,v 1.28 2002/12/22 00:17:15 gmcgarry Exp $");
80 
81 #include <machine/hp300spu.h>	/* XXX param.h includes cpu.h */
82 
83 #include <sys/param.h>
84 #include <sys/systm.h>
85 #include <sys/callout.h>
86 #include <sys/device.h>
87 #include <sys/kernel.h>
88 #include <sys/proc.h>
89 
90 #include <machine/bus.h>
91 
92 #include <m68k/cacheops.h>
93 
94 #include <hp300/dev/intiovar.h>
95 #include <hp300/dev/dmareg.h>
96 #include <hp300/dev/dmavar.h>
97 
98 /*
99  * The largest single request will be MAXPHYS bytes which will require
100  * at most MAXPHYS/NBPG+1 chain elements to describe, i.e. if none of
101  * the buffer pages are physically contiguous (MAXPHYS/NBPG) and the
102  * buffer is not page aligned (+1).
103  */
104 #define	DMAMAXIO	(MAXPHYS/NBPG+1)
105 
106 struct dma_chain {
107 	int	dc_count;
108 	char	*dc_addr;
109 };
110 
111 struct dma_channel {
112 	struct	dmaqueue *dm_job;		/* current job */
113 	struct	dmadevice *dm_hwaddr;		/* registers if DMA_C */
114 	struct	dmaBdevice *dm_Bhwaddr;		/* registers if not DMA_C */
115 	char	dm_flags;			/* misc. flags */
116 	u_short	dm_cmd;				/* DMA controller command */
117 	int	dm_cur;				/* current segment */
118 	int	dm_last;			/* last segment */
119 	struct	dma_chain dm_chain[DMAMAXIO];	/* all segments */
120 };
121 
122 struct dma_softc {
123 	struct  device sc_dev;
124 	bus_space_tag_t sc_bst;
125 	bus_space_handle_t sc_bsh;
126 
127 	struct	dmareg *sc_dmareg;		/* pointer to our hardware */
128 	struct	dma_channel sc_chan[NDMACHAN];	/* 2 channels */
129 	TAILQ_HEAD(, dmaqueue) sc_queue;	/* job queue */
130 	struct	callout sc_debug_ch;
131 	char	sc_type;			/* A, B, or C */
132 	int	sc_ipl;				/* our interrupt level */
133 	void	*sc_ih;				/* interrupt cookie */
134 };
135 
136 /* types */
137 #define	DMA_B	0
138 #define DMA_C	1
139 
140 /* flags */
141 #define DMAF_PCFLUSH	0x01
142 #define DMAF_VCFLUSH	0x02
143 #define DMAF_NOINTR	0x04
144 
145 int	dmamatch(struct device *, struct cfdata *, void *);
146 void	dmaattach(struct device *, struct device *, void *);
147 
148 CFATTACH_DECL(dma, sizeof(struct dma_softc),
149     dmamatch, dmaattach, NULL, NULL);
150 
151 int	dmaintr __P((void *));
152 
153 #ifdef DEBUG
154 int	dmadebug = 0;
155 #define DDB_WORD	0x01	/* same as DMAGO_WORD */
156 #define DDB_LWORD	0x02	/* same as DMAGO_LWORD */
157 #define	DDB_FOLLOW	0x04
158 #define DDB_IO		0x08
159 
160 void	dmatimeout __P((void *));
161 int	dmatimo[NDMACHAN];
162 
163 long	dmahits[NDMACHAN];
164 long	dmamisses[NDMACHAN];
165 long	dmabyte[NDMACHAN];
166 long	dmaword[NDMACHAN];
167 long	dmalword[NDMACHAN];
168 #endif
169 
170 static struct dma_softc *dma_softc;
171 
172 int
173 dmamatch(parent, match, aux)
174 	struct device *parent;
175 	struct cfdata *match;
176 	void *aux;
177 {
178 	struct intio_attach_args *ia = aux;
179 	static int dmafound = 0;                /* can only have one */
180 
181 	if (strcmp("dma", ia->ia_modname) != 0 || dmafound)
182 		return (0);
183 
184 	dmafound = 1;
185 	return (1);
186 }
187 
188 
189 
190 void
191 dmaattach(parent, self, aux)
192 	struct device *parent, *self;
193 	void *aux;
194 {
195 	struct dma_softc *sc = (struct dma_softc *)self;
196 	struct intio_attach_args *ia = aux;
197 	struct dma_channel *dc;
198 	struct dmareg *dma;
199 	int i;
200 	char rev;
201 
202 	/* There's just one. */
203 	dma_softc = sc;
204 
205 	sc->sc_bst = ia->ia_bst;
206 	if (bus_space_map(sc->sc_bst, ia->ia_iobase, INTIO_DEVSIZE, 0,
207 	     &sc->sc_bsh)) {
208 		printf("%s: can't map registers\n", sc->sc_dev.dv_xname);
209 		return;
210 	}
211 
212 	dma = (struct dmareg *)bus_space_vaddr(sc->sc_bst, sc->sc_bsh);
213 	sc->sc_dmareg = dma;
214 
215 	/*
216 	 * Determine the DMA type.  A DMA_A or DMA_B will fail the
217 	 * following probe.
218 	 *
219 	 * XXX Don't know how to easily differentiate the A and B cards,
220 	 * so we just hope nobody has an A card (A cards will work if
221 	 * splbio works out to ipl 3).
222 	 */
223 	if (badbaddr((char *)&dma->dma_id[2])) {
224 		rev = 'B';
225 #if !defined(HP320)
226 		panic("dmainit: DMA card requires hp320 support");
227 #endif
228 	} else
229 		rev = dma->dma_id[2];
230 
231 	sc->sc_type = (rev == 'B') ? DMA_B : DMA_C;
232 
233 	TAILQ_INIT(&sc->sc_queue);
234 	callout_init(&sc->sc_debug_ch);
235 
236 	for (i = 0; i < NDMACHAN; i++) {
237 		dc = &sc->sc_chan[i];
238 		dc->dm_job = NULL;
239 		switch (i) {
240 		case 0:
241 			dc->dm_hwaddr = &dma->dma_chan0;
242 			dc->dm_Bhwaddr = &dma->dma_Bchan0;
243 			break;
244 
245 		case 1:
246 			dc->dm_hwaddr = &dma->dma_chan1;
247 			dc->dm_Bhwaddr = &dma->dma_Bchan1;
248 			break;
249 
250 		default:
251 			panic("dmainit: more than 2 channels?");
252 			/* NOTREACHED */
253 		}
254 	}
255 
256 #ifdef DEBUG
257 	/* make sure timeout is really not needed */
258 	callout_reset(&sc->sc_debug_ch, 30 * hz, dmatimeout, sc);
259 #endif
260 
261 	printf(": 98620%c, 2 channels, %d-bit DMA\n",
262 	    rev, (rev == 'B') ? 16 : 32);
263 
264 	/*
265 	 * Defer hooking up our interrupt until the first
266 	 * DMA-using controller has hooked up theirs.
267 	 */
268 	sc->sc_ih = NULL;
269 }
270 
271 /*
272  * Compute the ipl and (re)establish the interrupt handler
273  * for the DMA controller.
274  */
275 void
276 dmacomputeipl()
277 {
278 	struct dma_softc *sc = dma_softc;
279 
280 	if (sc->sc_ih != NULL)
281 		intr_disestablish(sc->sc_ih);
282 
283 	/*
284 	 * Our interrupt level must be as high as the highest
285 	 * device using DMA (i.e. splbio).
286 	 */
287 	sc->sc_ipl = PSLTOIPL(hp300_ipls[HP300_IPL_BIO]);
288 	sc->sc_ih = intr_establish(dmaintr, sc, sc->sc_ipl, IPL_BIO);
289 }
290 
291 int
292 dmareq(dq)
293 	struct dmaqueue *dq;
294 {
295 	struct dma_softc *sc = dma_softc;
296 	int i, chan, s;
297 
298 #if 1
299 	s = splhigh();	/* XXXthorpej */
300 #else
301 	s = splbio();
302 #endif
303 
304 	chan = dq->dq_chan;
305 	for (i = NDMACHAN - 1; i >= 0; i--) {
306 		/*
307 		 * Can we use this channel?
308 		 */
309 		if ((chan & (1 << i)) == 0)
310 			continue;
311 
312 		/*
313 		 * We can use it; is it busy?
314 		 */
315 		if (sc->sc_chan[i].dm_job != NULL)
316 			continue;
317 
318 		/*
319 		 * Not busy; give the caller this channel.
320 		 */
321 		sc->sc_chan[i].dm_job = dq;
322 		dq->dq_chan = i;
323 		splx(s);
324 		return (1);
325 	}
326 
327 	/*
328 	 * Couldn't get a channel now; put this in the queue.
329 	 */
330 	TAILQ_INSERT_TAIL(&sc->sc_queue, dq, dq_list);
331 	splx(s);
332 	return (0);
333 }
334 
335 void
336 dmafree(dq)
337 	struct dmaqueue *dq;
338 {
339 	int unit = dq->dq_chan;
340 	struct dma_softc *sc = dma_softc;
341 	struct dma_channel *dc = &sc->sc_chan[unit];
342 	struct dmaqueue *dn;
343 	int chan, s;
344 
345 #if 1
346 	s = splhigh();	/* XXXthorpej */
347 #else
348 	s = splbio();
349 #endif
350 
351 #ifdef DEBUG
352 	dmatimo[unit] = 0;
353 #endif
354 
355 	DMA_CLEAR(dc);
356 
357 #if defined(CACHE_HAVE_PAC) || defined(M68040)
358 	/*
359 	 * XXX we may not always go thru the flush code in dmastop()
360 	 */
361 	if (dc->dm_flags & DMAF_PCFLUSH) {
362 		PCIA();
363 		dc->dm_flags &= ~DMAF_PCFLUSH;
364 	}
365 #endif
366 
367 #if defined(CACHE_HAVE_VAC)
368 	if (dc->dm_flags & DMAF_VCFLUSH) {
369 		/*
370 		 * 320/350s have VACs that may also need flushing.
371 		 * In our case we only flush the supervisor side
372 		 * because we know that if we are DMAing to user
373 		 * space, the physical pages will also be mapped
374 		 * in kernel space (via vmapbuf) and hence cache-
375 		 * inhibited by the pmap module due to the multiple
376 		 * mapping.
377 		 */
378 		DCIS();
379 		dc->dm_flags &= ~DMAF_VCFLUSH;
380 	}
381 #endif
382 
383 	/*
384 	 * Channel is now free.  Look for another job to run on this
385 	 * channel.
386 	 */
387 	dc->dm_job = NULL;
388 	chan = 1 << unit;
389 	for (dn = sc->sc_queue.tqh_first; dn != NULL;
390 	    dn = dn->dq_list.tqe_next) {
391 		if (dn->dq_chan & chan) {
392 			/* Found one... */
393 			TAILQ_REMOVE(&sc->sc_queue, dn, dq_list);
394 			dc->dm_job = dn;
395 			dn->dq_chan = dq->dq_chan;
396 			splx(s);
397 
398 			/* Start the initiator. */
399 			(*dn->dq_start)(dn->dq_softc);
400 			return;
401 		}
402 	}
403 	splx(s);
404 }
405 
406 void
407 dmago(unit, addr, count, flags)
408 	int unit;
409 	char *addr;
410 	int count;
411 	int flags;
412 {
413 	struct dma_softc *sc = dma_softc;
414 	struct dma_channel *dc = &sc->sc_chan[unit];
415 	char *dmaend = NULL;
416 	int seg, tcount;
417 
418 	if (count > MAXPHYS)
419 		panic("dmago: count > MAXPHYS");
420 
421 #if defined(HP320)
422 	if (sc->sc_type == DMA_B && (flags & DMAGO_LWORD))
423 		panic("dmago: no can do 32-bit DMA");
424 #endif
425 
426 #ifdef DEBUG
427 	if (dmadebug & DDB_FOLLOW)
428 		printf("dmago(%d, %p, %x, %x)\n",
429 		       unit, addr, count, flags);
430 	if (flags & DMAGO_LWORD)
431 		dmalword[unit]++;
432 	else if (flags & DMAGO_WORD)
433 		dmaword[unit]++;
434 	else
435 		dmabyte[unit]++;
436 #endif
437 	/*
438 	 * Build the DMA chain
439 	 */
440 	for (seg = 0; count > 0; seg++) {
441 		dc->dm_chain[seg].dc_addr = (char *) kvtop(addr);
442 #if defined(M68040)
443 		/*
444 		 * Push back dirty cache lines
445 		 */
446 		if (mmutype == MMU_68040)
447 			DCFP((paddr_t)dc->dm_chain[seg].dc_addr);
448 #endif
449 		if (count < (tcount = NBPG - ((int)addr & PGOFSET)))
450 			tcount = count;
451 		dc->dm_chain[seg].dc_count = tcount;
452 		addr += tcount;
453 		count -= tcount;
454 		if (flags & DMAGO_LWORD)
455 			tcount >>= 2;
456 		else if (flags & DMAGO_WORD)
457 			tcount >>= 1;
458 
459 		/*
460 		 * Try to compact the DMA transfer if the pages are adjacent.
461 		 * Note: this will never happen on the first iteration.
462 		 */
463 		if (dc->dm_chain[seg].dc_addr == dmaend
464 #if defined(HP320)
465 		    /* only 16-bit count on 98620B */
466 		    && (sc->sc_type != DMA_B ||
467 			dc->dm_chain[seg - 1].dc_count + tcount <= 65536)
468 #endif
469 		) {
470 #ifdef DEBUG
471 			dmahits[unit]++;
472 #endif
473 			dmaend += dc->dm_chain[seg].dc_count;
474 			dc->dm_chain[--seg].dc_count += tcount;
475 		} else {
476 #ifdef DEBUG
477 			dmamisses[unit]++;
478 #endif
479 			dmaend = dc->dm_chain[seg].dc_addr +
480 			    dc->dm_chain[seg].dc_count;
481 			dc->dm_chain[seg].dc_count = tcount;
482 		}
483 	}
484 	dc->dm_cur = 0;
485 	dc->dm_last = --seg;
486 	dc->dm_flags = 0;
487 	/*
488 	 * Set up the command word based on flags
489 	 */
490 	dc->dm_cmd = DMA_ENAB | DMA_IPL(sc->sc_ipl) | DMA_START;
491 	if ((flags & DMAGO_READ) == 0)
492 		dc->dm_cmd |= DMA_WRT;
493 	if (flags & DMAGO_LWORD)
494 		dc->dm_cmd |= DMA_LWORD;
495 	else if (flags & DMAGO_WORD)
496 		dc->dm_cmd |= DMA_WORD;
497 	if (flags & DMAGO_PRI)
498 		dc->dm_cmd |= DMA_PRI;
499 
500 #if defined(M68040)
501 	/*
502 	 * On the 68040 we need to flush (push) the data cache before a
503 	 * DMA (already done above) and flush again after DMA completes.
504 	 * In theory we should only need to flush prior to a write DMA
505 	 * and purge after a read DMA but if the entire page is not
506 	 * involved in the DMA we might purge some valid data.
507 	 */
508 	if (mmutype == MMU_68040 && (flags & DMAGO_READ))
509 		dc->dm_flags |= DMAF_PCFLUSH;
510 #endif
511 
512 #if defined(CACHE_HAVE_PAC)
513 	/*
514 	 * Remember if we need to flush external physical cache when
515 	 * DMA is done.  We only do this if we are reading (writing memory).
516 	 */
517 	if (ectype == EC_PHYS && (flags & DMAGO_READ))
518 		dc->dm_flags |= DMAF_PCFLUSH;
519 #endif
520 
521 #if defined(CACHE_HAVE_VAC)
522 	if (ectype == EC_VIRT && (flags & DMAGO_READ))
523 		dc->dm_flags |= DMAF_VCFLUSH;
524 #endif
525 
526 	/*
527 	 * Remember if we can skip the dma completion interrupt on
528 	 * the last segment in the chain.
529 	 */
530 	if (flags & DMAGO_NOINT) {
531 		if (dc->dm_cur == dc->dm_last)
532 			dc->dm_cmd &= ~DMA_ENAB;
533 		else
534 			dc->dm_flags |= DMAF_NOINTR;
535 	}
536 #ifdef DEBUG
537 	if (dmadebug & DDB_IO) {
538 		if (((dmadebug&DDB_WORD) && (dc->dm_cmd&DMA_WORD)) ||
539 		    ((dmadebug&DDB_LWORD) && (dc->dm_cmd&DMA_LWORD))) {
540 			printf("dmago: cmd %x, flags %x\n",
541 			       dc->dm_cmd, dc->dm_flags);
542 			for (seg = 0; seg <= dc->dm_last; seg++)
543 				printf("  %d: %d@%p\n", seg,
544 				    dc->dm_chain[seg].dc_count,
545 				    dc->dm_chain[seg].dc_addr);
546 		}
547 	}
548 	dmatimo[unit] = 1;
549 #endif
550 	DMA_ARM(sc, dc);
551 }
552 
553 void
554 dmastop(unit)
555 	int unit;
556 {
557 	struct dma_softc *sc = dma_softc;
558 	struct dma_channel *dc = &sc->sc_chan[unit];
559 
560 #ifdef DEBUG
561 	if (dmadebug & DDB_FOLLOW)
562 		printf("dmastop(%d)\n", unit);
563 	dmatimo[unit] = 0;
564 #endif
565 	DMA_CLEAR(dc);
566 
567 #if defined(CACHE_HAVE_PAC) || defined(M68040)
568 	if (dc->dm_flags & DMAF_PCFLUSH) {
569 		PCIA();
570 		dc->dm_flags &= ~DMAF_PCFLUSH;
571 	}
572 #endif
573 
574 #if defined(CACHE_HAVE_VAC)
575 	if (dc->dm_flags & DMAF_VCFLUSH) {
576 		/*
577 		 * 320/350s have VACs that may also need flushing.
578 		 * In our case we only flush the supervisor side
579 		 * because we know that if we are DMAing to user
580 		 * space, the physical pages will also be mapped
581 		 * in kernel space (via vmapbuf) and hence cache-
582 		 * inhibited by the pmap module due to the multiple
583 		 * mapping.
584 		 */
585 		DCIS();
586 		dc->dm_flags &= ~DMAF_VCFLUSH;
587 	}
588 #endif
589 
590 	/*
591 	 * We may get this interrupt after a device service routine
592 	 * has freed the dma channel.  So, ignore the intr if there's
593 	 * nothing on the queue.
594 	 */
595 	if (dc->dm_job != NULL)
596 		(*dc->dm_job->dq_done)(dc->dm_job->dq_softc);
597 }
598 
599 int
600 dmaintr(arg)
601 	void *arg;
602 {
603 	struct dma_softc *sc = arg;
604 	struct dma_channel *dc;
605 	int i, stat;
606 	int found = 0;
607 
608 #ifdef DEBUG
609 	if (dmadebug & DDB_FOLLOW)
610 		printf("dmaintr\n");
611 #endif
612 	for (i = 0; i < NDMACHAN; i++) {
613 		dc = &sc->sc_chan[i];
614 		stat = DMA_STAT(dc);
615 		if ((stat & DMA_INTR) == 0)
616 			continue;
617 		found++;
618 #ifdef DEBUG
619 		if (dmadebug & DDB_IO) {
620 			if (((dmadebug&DDB_WORD) && (dc->dm_cmd&DMA_WORD)) ||
621 			    ((dmadebug&DDB_LWORD) && (dc->dm_cmd&DMA_LWORD)))
622 			  printf("dmaintr: flags %x unit %d stat %x next %d\n",
623 			   dc->dm_flags, i, stat, dc->dm_cur + 1);
624 		}
625 		if (stat & DMA_ARMED)
626 			printf("dma channel %d: intr when armed\n", i);
627 #endif
628 		/*
629 		 * Load the next segemnt, or finish up if we're done.
630 		 */
631 		dc->dm_cur++;
632 		if (dc->dm_cur <= dc->dm_last) {
633 #ifdef DEBUG
634 			dmatimo[i] = 1;
635 #endif
636 			/*
637 			 * If we're the last segment, disable the
638 			 * completion interrupt, if necessary.
639 			 */
640 			if (dc->dm_cur == dc->dm_last &&
641 			    (dc->dm_flags & DMAF_NOINTR))
642 				dc->dm_cmd &= ~DMA_ENAB;
643 			DMA_CLEAR(dc);
644 			DMA_ARM(sc, dc);
645 		} else
646 			dmastop(i);
647 	}
648 	return(found);
649 }
650 
651 #ifdef DEBUG
652 void
653 dmatimeout(arg)
654 	void *arg;
655 {
656 	int i, s;
657 	struct dma_softc *sc = arg;
658 
659 	for (i = 0; i < NDMACHAN; i++) {
660 		s = splbio();
661 		if (dmatimo[i]) {
662 			if (dmatimo[i] > 1)
663 				printf("dma channel %d timeout #%d\n",
664 				    i, dmatimo[i]-1);
665 			dmatimo[i]++;
666 		}
667 		splx(s);
668 	}
669 	callout_reset(&sc->sc_debug_ch, 30 * hz, dmatimeout, sc);
670 }
671 #endif
672