xref: /netbsd-src/sys/arch/hp300/dev/dma.c (revision 4b896b232495b7a9b8b94a1cf1e21873296d53b8)
1 /*	$NetBSD: dma.c,v 1.30 2003/08/07 16:27:27 agc 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. Neither the name of the University nor the names of its contributors
52  *    may be used to endorse or promote products derived from this software
53  *    without specific prior written permission.
54  *
55  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
56  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
57  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
58  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
59  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
60  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
61  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
62  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
63  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
64  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
65  * SUCH DAMAGE.
66  *
67  *	@(#)dma.c	8.1 (Berkeley) 6/10/93
68  */
69 
70 /*
71  * DMA driver
72  */
73 
74 #include <sys/cdefs.h>
75 __KERNEL_RCSID(0, "$NetBSD: dma.c,v 1.30 2003/08/07 16:27:27 agc Exp $");
76 
77 #include <machine/hp300spu.h>	/* XXX param.h includes cpu.h */
78 
79 #include <sys/param.h>
80 #include <sys/systm.h>
81 #include <sys/callout.h>
82 #include <sys/device.h>
83 #include <sys/kernel.h>
84 #include <sys/proc.h>
85 
86 #include <uvm/uvm_extern.h>
87 
88 #include <machine/bus.h>
89 
90 #include <m68k/cacheops.h>
91 
92 #include <hp300/dev/intiovar.h>
93 #include <hp300/dev/dmareg.h>
94 #include <hp300/dev/dmavar.h>
95 
96 /*
97  * The largest single request will be MAXPHYS bytes which will require
98  * at most MAXPHYS/PAGE_SIZE+1 chain elements to describe, i.e. if none of
99  * the buffer pages are physically contiguous (MAXPHYS/PAGE_SIZE) and the
100  * buffer is not page aligned (+1).
101  */
102 #define	DMAMAXIO	(MAXPHYS/PAGE_SIZE+1)
103 
104 struct dma_chain {
105 	int	dc_count;
106 	char	*dc_addr;
107 };
108 
109 struct dma_channel {
110 	struct	dmaqueue *dm_job;		/* current job */
111 	struct	dmadevice *dm_hwaddr;		/* registers if DMA_C */
112 	struct	dmaBdevice *dm_Bhwaddr;		/* registers if not DMA_C */
113 	char	dm_flags;			/* misc. flags */
114 	u_short	dm_cmd;				/* DMA controller command */
115 	int	dm_cur;				/* current segment */
116 	int	dm_last;			/* last segment */
117 	struct	dma_chain dm_chain[DMAMAXIO];	/* all segments */
118 };
119 
120 struct dma_softc {
121 	struct  device sc_dev;
122 	bus_space_tag_t sc_bst;
123 	bus_space_handle_t sc_bsh;
124 
125 	struct	dmareg *sc_dmareg;		/* pointer to our hardware */
126 	struct	dma_channel sc_chan[NDMACHAN];	/* 2 channels */
127 	TAILQ_HEAD(, dmaqueue) sc_queue;	/* job queue */
128 	struct	callout sc_debug_ch;
129 	char	sc_type;			/* A, B, or C */
130 	int	sc_ipl;				/* our interrupt level */
131 	void	*sc_ih;				/* interrupt cookie */
132 };
133 
134 /* types */
135 #define	DMA_B	0
136 #define DMA_C	1
137 
138 /* flags */
139 #define DMAF_PCFLUSH	0x01
140 #define DMAF_VCFLUSH	0x02
141 #define DMAF_NOINTR	0x04
142 
143 int	dmamatch(struct device *, struct cfdata *, void *);
144 void	dmaattach(struct device *, struct device *, void *);
145 
146 CFATTACH_DECL(dma, sizeof(struct dma_softc),
147     dmamatch, dmaattach, NULL, NULL);
148 
149 int	dmaintr __P((void *));
150 
151 #ifdef DEBUG
152 int	dmadebug = 0;
153 #define DDB_WORD	0x01	/* same as DMAGO_WORD */
154 #define DDB_LWORD	0x02	/* same as DMAGO_LWORD */
155 #define	DDB_FOLLOW	0x04
156 #define DDB_IO		0x08
157 
158 void	dmatimeout __P((void *));
159 int	dmatimo[NDMACHAN];
160 
161 long	dmahits[NDMACHAN];
162 long	dmamisses[NDMACHAN];
163 long	dmabyte[NDMACHAN];
164 long	dmaword[NDMACHAN];
165 long	dmalword[NDMACHAN];
166 #endif
167 
168 static struct dma_softc *dma_softc;
169 
170 int
171 dmamatch(parent, match, aux)
172 	struct device *parent;
173 	struct cfdata *match;
174 	void *aux;
175 {
176 	struct intio_attach_args *ia = aux;
177 	static int dmafound = 0;                /* can only have one */
178 
179 	if (strcmp("dma", ia->ia_modname) != 0 || dmafound)
180 		return (0);
181 
182 	dmafound = 1;
183 	return (1);
184 }
185 
186 
187 
188 void
189 dmaattach(parent, self, aux)
190 	struct device *parent, *self;
191 	void *aux;
192 {
193 	struct dma_softc *sc = (struct dma_softc *)self;
194 	struct intio_attach_args *ia = aux;
195 	struct dma_channel *dc;
196 	struct dmareg *dma;
197 	int i;
198 	char rev;
199 
200 	/* There's just one. */
201 	dma_softc = sc;
202 
203 	sc->sc_bst = ia->ia_bst;
204 	if (bus_space_map(sc->sc_bst, ia->ia_iobase, INTIO_DEVSIZE, 0,
205 	     &sc->sc_bsh)) {
206 		printf("%s: can't map registers\n", sc->sc_dev.dv_xname);
207 		return;
208 	}
209 
210 	dma = (struct dmareg *)bus_space_vaddr(sc->sc_bst, sc->sc_bsh);
211 	sc->sc_dmareg = dma;
212 
213 	/*
214 	 * Determine the DMA type.  A DMA_A or DMA_B will fail the
215 	 * following probe.
216 	 *
217 	 * XXX Don't know how to easily differentiate the A and B cards,
218 	 * so we just hope nobody has an A card (A cards will work if
219 	 * splbio works out to ipl 3).
220 	 */
221 	if (badbaddr((char *)&dma->dma_id[2])) {
222 		rev = 'B';
223 #if !defined(HP320)
224 		panic("dmainit: DMA card requires hp320 support");
225 #endif
226 	} else
227 		rev = dma->dma_id[2];
228 
229 	sc->sc_type = (rev == 'B') ? DMA_B : DMA_C;
230 
231 	TAILQ_INIT(&sc->sc_queue);
232 	callout_init(&sc->sc_debug_ch);
233 
234 	for (i = 0; i < NDMACHAN; i++) {
235 		dc = &sc->sc_chan[i];
236 		dc->dm_job = NULL;
237 		switch (i) {
238 		case 0:
239 			dc->dm_hwaddr = &dma->dma_chan0;
240 			dc->dm_Bhwaddr = &dma->dma_Bchan0;
241 			break;
242 
243 		case 1:
244 			dc->dm_hwaddr = &dma->dma_chan1;
245 			dc->dm_Bhwaddr = &dma->dma_Bchan1;
246 			break;
247 
248 		default:
249 			panic("dmainit: more than 2 channels?");
250 			/* NOTREACHED */
251 		}
252 	}
253 
254 #ifdef DEBUG
255 	/* make sure timeout is really not needed */
256 	callout_reset(&sc->sc_debug_ch, 30 * hz, dmatimeout, sc);
257 #endif
258 
259 	printf(": 98620%c, 2 channels, %d-bit DMA\n",
260 	    rev, (rev == 'B') ? 16 : 32);
261 
262 	/*
263 	 * Defer hooking up our interrupt until the first
264 	 * DMA-using controller has hooked up theirs.
265 	 */
266 	sc->sc_ih = NULL;
267 }
268 
269 /*
270  * Compute the ipl and (re)establish the interrupt handler
271  * for the DMA controller.
272  */
273 void
274 dmacomputeipl()
275 {
276 	struct dma_softc *sc = dma_softc;
277 
278 	if (sc->sc_ih != NULL)
279 		intr_disestablish(sc->sc_ih);
280 
281 	/*
282 	 * Our interrupt level must be as high as the highest
283 	 * device using DMA (i.e. splbio).
284 	 */
285 	sc->sc_ipl = PSLTOIPL(hp300_ipls[HP300_IPL_BIO]);
286 	sc->sc_ih = intr_establish(dmaintr, sc, sc->sc_ipl, IPL_BIO);
287 }
288 
289 int
290 dmareq(dq)
291 	struct dmaqueue *dq;
292 {
293 	struct dma_softc *sc = dma_softc;
294 	int i, chan, s;
295 
296 #if 1
297 	s = splhigh();	/* XXXthorpej */
298 #else
299 	s = splbio();
300 #endif
301 
302 	chan = dq->dq_chan;
303 	for (i = NDMACHAN - 1; i >= 0; i--) {
304 		/*
305 		 * Can we use this channel?
306 		 */
307 		if ((chan & (1 << i)) == 0)
308 			continue;
309 
310 		/*
311 		 * We can use it; is it busy?
312 		 */
313 		if (sc->sc_chan[i].dm_job != NULL)
314 			continue;
315 
316 		/*
317 		 * Not busy; give the caller this channel.
318 		 */
319 		sc->sc_chan[i].dm_job = dq;
320 		dq->dq_chan = i;
321 		splx(s);
322 		return (1);
323 	}
324 
325 	/*
326 	 * Couldn't get a channel now; put this in the queue.
327 	 */
328 	TAILQ_INSERT_TAIL(&sc->sc_queue, dq, dq_list);
329 	splx(s);
330 	return (0);
331 }
332 
333 void
334 dmafree(dq)
335 	struct dmaqueue *dq;
336 {
337 	int unit = dq->dq_chan;
338 	struct dma_softc *sc = dma_softc;
339 	struct dma_channel *dc = &sc->sc_chan[unit];
340 	struct dmaqueue *dn;
341 	int chan, s;
342 
343 #if 1
344 	s = splhigh();	/* XXXthorpej */
345 #else
346 	s = splbio();
347 #endif
348 
349 #ifdef DEBUG
350 	dmatimo[unit] = 0;
351 #endif
352 
353 	DMA_CLEAR(dc);
354 
355 #if defined(CACHE_HAVE_PAC) || defined(M68040)
356 	/*
357 	 * XXX we may not always go thru the flush code in dmastop()
358 	 */
359 	if (dc->dm_flags & DMAF_PCFLUSH) {
360 		PCIA();
361 		dc->dm_flags &= ~DMAF_PCFLUSH;
362 	}
363 #endif
364 
365 #if defined(CACHE_HAVE_VAC)
366 	if (dc->dm_flags & DMAF_VCFLUSH) {
367 		/*
368 		 * 320/350s have VACs that may also need flushing.
369 		 * In our case we only flush the supervisor side
370 		 * because we know that if we are DMAing to user
371 		 * space, the physical pages will also be mapped
372 		 * in kernel space (via vmapbuf) and hence cache-
373 		 * inhibited by the pmap module due to the multiple
374 		 * mapping.
375 		 */
376 		DCIS();
377 		dc->dm_flags &= ~DMAF_VCFLUSH;
378 	}
379 #endif
380 
381 	/*
382 	 * Channel is now free.  Look for another job to run on this
383 	 * channel.
384 	 */
385 	dc->dm_job = NULL;
386 	chan = 1 << unit;
387 	for (dn = sc->sc_queue.tqh_first; dn != NULL;
388 	    dn = dn->dq_list.tqe_next) {
389 		if (dn->dq_chan & chan) {
390 			/* Found one... */
391 			TAILQ_REMOVE(&sc->sc_queue, dn, dq_list);
392 			dc->dm_job = dn;
393 			dn->dq_chan = dq->dq_chan;
394 			splx(s);
395 
396 			/* Start the initiator. */
397 			(*dn->dq_start)(dn->dq_softc);
398 			return;
399 		}
400 	}
401 	splx(s);
402 }
403 
404 void
405 dmago(unit, addr, count, flags)
406 	int unit;
407 	char *addr;
408 	int count;
409 	int flags;
410 {
411 	struct dma_softc *sc = dma_softc;
412 	struct dma_channel *dc = &sc->sc_chan[unit];
413 	char *dmaend = NULL;
414 	int seg, tcount;
415 
416 	if (count > MAXPHYS)
417 		panic("dmago: count > MAXPHYS");
418 
419 #if defined(HP320)
420 	if (sc->sc_type == DMA_B && (flags & DMAGO_LWORD))
421 		panic("dmago: no can do 32-bit DMA");
422 #endif
423 
424 #ifdef DEBUG
425 	if (dmadebug & DDB_FOLLOW)
426 		printf("dmago(%d, %p, %x, %x)\n",
427 		       unit, addr, count, flags);
428 	if (flags & DMAGO_LWORD)
429 		dmalword[unit]++;
430 	else if (flags & DMAGO_WORD)
431 		dmaword[unit]++;
432 	else
433 		dmabyte[unit]++;
434 #endif
435 	/*
436 	 * Build the DMA chain
437 	 */
438 	for (seg = 0; count > 0; seg++) {
439 		dc->dm_chain[seg].dc_addr = (char *) kvtop(addr);
440 #if defined(M68040)
441 		/*
442 		 * Push back dirty cache lines
443 		 */
444 		if (mmutype == MMU_68040)
445 			DCFP((paddr_t)dc->dm_chain[seg].dc_addr);
446 #endif
447 		if (count < (tcount = PAGE_SIZE - ((int)addr & PGOFSET)))
448 			tcount = count;
449 		dc->dm_chain[seg].dc_count = tcount;
450 		addr += tcount;
451 		count -= tcount;
452 		if (flags & DMAGO_LWORD)
453 			tcount >>= 2;
454 		else if (flags & DMAGO_WORD)
455 			tcount >>= 1;
456 
457 		/*
458 		 * Try to compact the DMA transfer if the pages are adjacent.
459 		 * Note: this will never happen on the first iteration.
460 		 */
461 		if (dc->dm_chain[seg].dc_addr == dmaend
462 #if defined(HP320)
463 		    /* only 16-bit count on 98620B */
464 		    && (sc->sc_type != DMA_B ||
465 			dc->dm_chain[seg - 1].dc_count + tcount <= 65536)
466 #endif
467 		) {
468 #ifdef DEBUG
469 			dmahits[unit]++;
470 #endif
471 			dmaend += dc->dm_chain[seg].dc_count;
472 			dc->dm_chain[--seg].dc_count += tcount;
473 		} else {
474 #ifdef DEBUG
475 			dmamisses[unit]++;
476 #endif
477 			dmaend = dc->dm_chain[seg].dc_addr +
478 			    dc->dm_chain[seg].dc_count;
479 			dc->dm_chain[seg].dc_count = tcount;
480 		}
481 	}
482 	dc->dm_cur = 0;
483 	dc->dm_last = --seg;
484 	dc->dm_flags = 0;
485 	/*
486 	 * Set up the command word based on flags
487 	 */
488 	dc->dm_cmd = DMA_ENAB | DMA_IPL(sc->sc_ipl) | DMA_START;
489 	if ((flags & DMAGO_READ) == 0)
490 		dc->dm_cmd |= DMA_WRT;
491 	if (flags & DMAGO_LWORD)
492 		dc->dm_cmd |= DMA_LWORD;
493 	else if (flags & DMAGO_WORD)
494 		dc->dm_cmd |= DMA_WORD;
495 	if (flags & DMAGO_PRI)
496 		dc->dm_cmd |= DMA_PRI;
497 
498 #if defined(M68040)
499 	/*
500 	 * On the 68040 we need to flush (push) the data cache before a
501 	 * DMA (already done above) and flush again after DMA completes.
502 	 * In theory we should only need to flush prior to a write DMA
503 	 * and purge after a read DMA but if the entire page is not
504 	 * involved in the DMA we might purge some valid data.
505 	 */
506 	if (mmutype == MMU_68040 && (flags & DMAGO_READ))
507 		dc->dm_flags |= DMAF_PCFLUSH;
508 #endif
509 
510 #if defined(CACHE_HAVE_PAC)
511 	/*
512 	 * Remember if we need to flush external physical cache when
513 	 * DMA is done.  We only do this if we are reading (writing memory).
514 	 */
515 	if (ectype == EC_PHYS && (flags & DMAGO_READ))
516 		dc->dm_flags |= DMAF_PCFLUSH;
517 #endif
518 
519 #if defined(CACHE_HAVE_VAC)
520 	if (ectype == EC_VIRT && (flags & DMAGO_READ))
521 		dc->dm_flags |= DMAF_VCFLUSH;
522 #endif
523 
524 	/*
525 	 * Remember if we can skip the dma completion interrupt on
526 	 * the last segment in the chain.
527 	 */
528 	if (flags & DMAGO_NOINT) {
529 		if (dc->dm_cur == dc->dm_last)
530 			dc->dm_cmd &= ~DMA_ENAB;
531 		else
532 			dc->dm_flags |= DMAF_NOINTR;
533 	}
534 #ifdef DEBUG
535 	if (dmadebug & DDB_IO) {
536 		if (((dmadebug&DDB_WORD) && (dc->dm_cmd&DMA_WORD)) ||
537 		    ((dmadebug&DDB_LWORD) && (dc->dm_cmd&DMA_LWORD))) {
538 			printf("dmago: cmd %x, flags %x\n",
539 			       dc->dm_cmd, dc->dm_flags);
540 			for (seg = 0; seg <= dc->dm_last; seg++)
541 				printf("  %d: %d@%p\n", seg,
542 				    dc->dm_chain[seg].dc_count,
543 				    dc->dm_chain[seg].dc_addr);
544 		}
545 	}
546 	dmatimo[unit] = 1;
547 #endif
548 	DMA_ARM(sc, dc);
549 }
550 
551 void
552 dmastop(unit)
553 	int unit;
554 {
555 	struct dma_softc *sc = dma_softc;
556 	struct dma_channel *dc = &sc->sc_chan[unit];
557 
558 #ifdef DEBUG
559 	if (dmadebug & DDB_FOLLOW)
560 		printf("dmastop(%d)\n", unit);
561 	dmatimo[unit] = 0;
562 #endif
563 	DMA_CLEAR(dc);
564 
565 #if defined(CACHE_HAVE_PAC) || defined(M68040)
566 	if (dc->dm_flags & DMAF_PCFLUSH) {
567 		PCIA();
568 		dc->dm_flags &= ~DMAF_PCFLUSH;
569 	}
570 #endif
571 
572 #if defined(CACHE_HAVE_VAC)
573 	if (dc->dm_flags & DMAF_VCFLUSH) {
574 		/*
575 		 * 320/350s have VACs that may also need flushing.
576 		 * In our case we only flush the supervisor side
577 		 * because we know that if we are DMAing to user
578 		 * space, the physical pages will also be mapped
579 		 * in kernel space (via vmapbuf) and hence cache-
580 		 * inhibited by the pmap module due to the multiple
581 		 * mapping.
582 		 */
583 		DCIS();
584 		dc->dm_flags &= ~DMAF_VCFLUSH;
585 	}
586 #endif
587 
588 	/*
589 	 * We may get this interrupt after a device service routine
590 	 * has freed the dma channel.  So, ignore the intr if there's
591 	 * nothing on the queue.
592 	 */
593 	if (dc->dm_job != NULL)
594 		(*dc->dm_job->dq_done)(dc->dm_job->dq_softc);
595 }
596 
597 int
598 dmaintr(arg)
599 	void *arg;
600 {
601 	struct dma_softc *sc = arg;
602 	struct dma_channel *dc;
603 	int i, stat;
604 	int found = 0;
605 
606 #ifdef DEBUG
607 	if (dmadebug & DDB_FOLLOW)
608 		printf("dmaintr\n");
609 #endif
610 	for (i = 0; i < NDMACHAN; i++) {
611 		dc = &sc->sc_chan[i];
612 		stat = DMA_STAT(dc);
613 		if ((stat & DMA_INTR) == 0)
614 			continue;
615 		found++;
616 #ifdef DEBUG
617 		if (dmadebug & DDB_IO) {
618 			if (((dmadebug&DDB_WORD) && (dc->dm_cmd&DMA_WORD)) ||
619 			    ((dmadebug&DDB_LWORD) && (dc->dm_cmd&DMA_LWORD)))
620 			  printf("dmaintr: flags %x unit %d stat %x next %d\n",
621 			   dc->dm_flags, i, stat, dc->dm_cur + 1);
622 		}
623 		if (stat & DMA_ARMED)
624 			printf("dma channel %d: intr when armed\n", i);
625 #endif
626 		/*
627 		 * Load the next segemnt, or finish up if we're done.
628 		 */
629 		dc->dm_cur++;
630 		if (dc->dm_cur <= dc->dm_last) {
631 #ifdef DEBUG
632 			dmatimo[i] = 1;
633 #endif
634 			/*
635 			 * If we're the last segment, disable the
636 			 * completion interrupt, if necessary.
637 			 */
638 			if (dc->dm_cur == dc->dm_last &&
639 			    (dc->dm_flags & DMAF_NOINTR))
640 				dc->dm_cmd &= ~DMA_ENAB;
641 			DMA_CLEAR(dc);
642 			DMA_ARM(sc, dc);
643 		} else
644 			dmastop(i);
645 	}
646 	return(found);
647 }
648 
649 #ifdef DEBUG
650 void
651 dmatimeout(arg)
652 	void *arg;
653 {
654 	int i, s;
655 	struct dma_softc *sc = arg;
656 
657 	for (i = 0; i < NDMACHAN; i++) {
658 		s = splbio();
659 		if (dmatimo[i]) {
660 			if (dmatimo[i] > 1)
661 				printf("dma channel %d timeout #%d\n",
662 				    i, dmatimo[i]-1);
663 			dmatimo[i]++;
664 		}
665 		splx(s);
666 	}
667 	callout_reset(&sc->sc_debug_ch, 30 * hz, dmatimeout, sc);
668 }
669 #endif
670