xref: /netbsd-src/sys/arch/hp300/dev/dma.c (revision 8ac07aec990b9d2e483062509d0a9fa5b4f57cf2)
1 /*	$NetBSD: dma.c,v 1.39 2008/03/29 06:47:07 tsutsui 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 1.39 2008/03/29 06:47:07 tsutsui 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 	device_t 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 static int	dmamatch(device_t, cfdata_t, void *);
144 static void	dmaattach(device_t, device_t, void *);
145 
146 CFATTACH_DECL_NEW(dma, sizeof(struct dma_softc),
147     dmamatch, dmaattach, NULL, NULL);
148 
149 static int	dmaintr(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 static void	dmatimeout(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 static int
171 dmamatch(device_t parent, cfdata_t cf, void *aux)
172 {
173 	struct intio_attach_args *ia = aux;
174 	static int dmafound = 0;                /* can only have one */
175 
176 	if (strcmp("dma", ia->ia_modname) != 0 || dmafound)
177 		return 0;
178 
179 	dmafound = 1;
180 	return 1;
181 }
182 
183 static void
184 dmaattach(device_t parent, device_t self, void *aux)
185 {
186 	struct dma_softc *sc = device_private(self);
187 	struct intio_attach_args *ia = aux;
188 	struct dma_channel *dc;
189 	struct dmareg *dma;
190 	int i;
191 	char rev;
192 
193 	sc->sc_dev = self;
194 
195 	/* There's just one. */
196 	dma_softc = sc;
197 
198 	sc->sc_bst = ia->ia_bst;
199 	if (bus_space_map(sc->sc_bst, ia->ia_iobase, INTIO_DEVSIZE, 0,
200 	     &sc->sc_bsh)) {
201 		aprint_error(": can't map registers\n");
202 		return;
203 	}
204 
205 	dma = bus_space_vaddr(sc->sc_bst, sc->sc_bsh);
206 	sc->sc_dmareg = dma;
207 
208 	/*
209 	 * Determine the DMA type.  A DMA_A or DMA_B will fail the
210 	 * following probe.
211 	 *
212 	 * XXX Don't know how to easily differentiate the A and B cards,
213 	 * so we just hope nobody has an A card (A cards will work if
214 	 * splbio works out to ipl 3).
215 	 */
216 	if (hp300_bus_space_probe(sc->sc_bst, sc->sc_bsh, DMA_ID2, 1) == 0) {
217 		rev = 'B';
218 #if !defined(HP320)
219 		aprint_normal("\n");
220 		panic("%s: DMA card requires hp320 support", __func__);
221 #endif
222 	} else
223 		rev = dma->dma_id[2];
224 
225 	sc->sc_type = (rev == 'B') ? DMA_B : DMA_C;
226 
227 	TAILQ_INIT(&sc->sc_queue);
228 	callout_init(&sc->sc_debug_ch, 0);
229 
230 	for (i = 0; i < NDMACHAN; i++) {
231 		dc = &sc->sc_chan[i];
232 		dc->dm_job = NULL;
233 		switch (i) {
234 		case 0:
235 			dc->dm_hwaddr = &dma->dma_chan0;
236 			dc->dm_Bhwaddr = &dma->dma_Bchan0;
237 			break;
238 
239 		case 1:
240 			dc->dm_hwaddr = &dma->dma_chan1;
241 			dc->dm_Bhwaddr = &dma->dma_Bchan1;
242 			break;
243 
244 		default:
245 			aprint_normal("\n");
246 			panic("%s: more than 2 channels?", __func__);
247 			/* NOTREACHED */
248 		}
249 	}
250 
251 #ifdef DEBUG
252 	/* make sure timeout is really not needed */
253 	callout_reset(&sc->sc_debug_ch, 30 * hz, dmatimeout, sc);
254 #endif
255 
256 	aprint_normal(": 98620%c, 2 channels, %d-bit DMA\n",
257 	    rev, (rev == 'B') ? 16 : 32);
258 
259 	/*
260 	 * Defer hooking up our interrupt until the first
261 	 * DMA-using controller has hooked up theirs.
262 	 */
263 	sc->sc_ih = NULL;
264 }
265 
266 /*
267  * Compute the ipl and (re)establish the interrupt handler
268  * for the DMA controller.
269  */
270 void
271 dmacomputeipl(void)
272 {
273 	struct dma_softc *sc = dma_softc;
274 
275 	if (sc->sc_ih != NULL)
276 		intr_disestablish(sc->sc_ih);
277 
278 	/*
279 	 * Our interrupt level must be as high as the highest
280 	 * device using DMA (i.e. splbio).
281 	 */
282 	sc->sc_ipl = PSLTOIPL(hp300_ipl2psl[IPL_BIO]);
283 	sc->sc_ih = intr_establish(dmaintr, sc, sc->sc_ipl, IPL_BIO);
284 }
285 
286 int
287 dmareq(struct dmaqueue *dq)
288 {
289 	struct dma_softc *sc = dma_softc;
290 	int i, chan, s;
291 
292 #if 1
293 	s = splhigh();	/* XXXthorpej */
294 #else
295 	s = splbio();
296 #endif
297 
298 	chan = dq->dq_chan;
299 	for (i = NDMACHAN - 1; i >= 0; i--) {
300 		/*
301 		 * Can we use this channel?
302 		 */
303 		if ((chan & (1 << i)) == 0)
304 			continue;
305 
306 		/*
307 		 * We can use it; is it busy?
308 		 */
309 		if (sc->sc_chan[i].dm_job != NULL)
310 			continue;
311 
312 		/*
313 		 * Not busy; give the caller this channel.
314 		 */
315 		sc->sc_chan[i].dm_job = dq;
316 		dq->dq_chan = i;
317 		splx(s);
318 		return 1;
319 	}
320 
321 	/*
322 	 * Couldn't get a channel now; put this in the queue.
323 	 */
324 	TAILQ_INSERT_TAIL(&sc->sc_queue, dq, dq_list);
325 	splx(s);
326 	return 0;
327 }
328 
329 void
330 dmafree(struct dmaqueue *dq)
331 {
332 	int unit = dq->dq_chan;
333 	struct dma_softc *sc = dma_softc;
334 	struct dma_channel *dc = &sc->sc_chan[unit];
335 	struct dmaqueue *dn;
336 	int chan, s;
337 
338 #if 1
339 	s = splhigh();	/* XXXthorpej */
340 #else
341 	s = splbio();
342 #endif
343 
344 #ifdef DEBUG
345 	dmatimo[unit] = 0;
346 #endif
347 
348 	DMA_CLEAR(dc);
349 
350 #if defined(CACHE_HAVE_PAC) || defined(M68040)
351 	/*
352 	 * XXX we may not always go thru the flush code in dmastop()
353 	 */
354 	if (dc->dm_flags & DMAF_PCFLUSH) {
355 		PCIA();
356 		dc->dm_flags &= ~DMAF_PCFLUSH;
357 	}
358 #endif
359 
360 #if defined(CACHE_HAVE_VAC)
361 	if (dc->dm_flags & DMAF_VCFLUSH) {
362 		/*
363 		 * 320/350s have VACs that may also need flushing.
364 		 * In our case we only flush the supervisor side
365 		 * because we know that if we are DMAing to user
366 		 * space, the physical pages will also be mapped
367 		 * in kernel space (via vmapbuf) and hence cache-
368 		 * inhibited by the pmap module due to the multiple
369 		 * mapping.
370 		 */
371 		DCIS();
372 		dc->dm_flags &= ~DMAF_VCFLUSH;
373 	}
374 #endif
375 
376 	/*
377 	 * Channel is now free.  Look for another job to run on this
378 	 * channel.
379 	 */
380 	dc->dm_job = NULL;
381 	chan = 1 << unit;
382 	for (dn = TAILQ_FIRST(&sc->sc_queue); dn != NULL;
383 	    dn = TAILQ_NEXT(dn, dq_list)) {
384 		if (dn->dq_chan & chan) {
385 			/* Found one... */
386 			TAILQ_REMOVE(&sc->sc_queue, dn, dq_list);
387 			dc->dm_job = dn;
388 			dn->dq_chan = dq->dq_chan;
389 			splx(s);
390 
391 			/* Start the initiator. */
392 			(*dn->dq_start)(dn->dq_softc);
393 			return;
394 		}
395 	}
396 	splx(s);
397 }
398 
399 void
400 dmago(int unit, char *addr, int count, int flags)
401 {
402 	struct dma_softc *sc = dma_softc;
403 	struct dma_channel *dc = &sc->sc_chan[unit];
404 	char *dmaend = NULL;
405 	int seg, tcount;
406 
407 	if (count > MAXPHYS)
408 		panic("dmago: count > MAXPHYS");
409 
410 #if defined(HP320)
411 	if (sc->sc_type == DMA_B && (flags & DMAGO_LWORD))
412 		panic("dmago: no can do 32-bit DMA");
413 #endif
414 
415 #ifdef DEBUG
416 	if (dmadebug & DDB_FOLLOW)
417 		printf("dmago(%d, %p, %x, %x)\n",
418 		       unit, addr, count, flags);
419 	if (flags & DMAGO_LWORD)
420 		dmalword[unit]++;
421 	else if (flags & DMAGO_WORD)
422 		dmaword[unit]++;
423 	else
424 		dmabyte[unit]++;
425 #endif
426 	/*
427 	 * Build the DMA chain
428 	 */
429 	for (seg = 0; count > 0; seg++) {
430 		dc->dm_chain[seg].dc_addr = (char *) kvtop(addr);
431 #if defined(M68040)
432 		/*
433 		 * Push back dirty cache lines
434 		 */
435 		if (mmutype == MMU_68040)
436 			DCFP((paddr_t)dc->dm_chain[seg].dc_addr);
437 #endif
438 		if (count < (tcount = PAGE_SIZE - ((int)addr & PGOFSET)))
439 			tcount = count;
440 		dc->dm_chain[seg].dc_count = tcount;
441 		addr += tcount;
442 		count -= tcount;
443 		if (flags & DMAGO_LWORD)
444 			tcount >>= 2;
445 		else if (flags & DMAGO_WORD)
446 			tcount >>= 1;
447 
448 		/*
449 		 * Try to compact the DMA transfer if the pages are adjacent.
450 		 * Note: this will never happen on the first iteration.
451 		 */
452 		if (dc->dm_chain[seg].dc_addr == dmaend
453 #if defined(HP320)
454 		    /* only 16-bit count on 98620B */
455 		    && (sc->sc_type != DMA_B ||
456 			dc->dm_chain[seg - 1].dc_count + tcount <= 65536)
457 #endif
458 		) {
459 #ifdef DEBUG
460 			dmahits[unit]++;
461 #endif
462 			dmaend += dc->dm_chain[seg].dc_count;
463 			dc->dm_chain[--seg].dc_count += tcount;
464 		} else {
465 #ifdef DEBUG
466 			dmamisses[unit]++;
467 #endif
468 			dmaend = dc->dm_chain[seg].dc_addr +
469 			    dc->dm_chain[seg].dc_count;
470 			dc->dm_chain[seg].dc_count = tcount;
471 		}
472 	}
473 	dc->dm_cur = 0;
474 	dc->dm_last = --seg;
475 	dc->dm_flags = 0;
476 	/*
477 	 * Set up the command word based on flags
478 	 */
479 	dc->dm_cmd = DMA_ENAB | DMA_IPL(sc->sc_ipl) | DMA_START;
480 	if ((flags & DMAGO_READ) == 0)
481 		dc->dm_cmd |= DMA_WRT;
482 	if (flags & DMAGO_LWORD)
483 		dc->dm_cmd |= DMA_LWORD;
484 	else if (flags & DMAGO_WORD)
485 		dc->dm_cmd |= DMA_WORD;
486 	if (flags & DMAGO_PRI)
487 		dc->dm_cmd |= DMA_PRI;
488 
489 #if defined(M68040)
490 	/*
491 	 * On the 68040 we need to flush (push) the data cache before a
492 	 * DMA (already done above) and flush again after DMA completes.
493 	 * In theory we should only need to flush prior to a write DMA
494 	 * and purge after a read DMA but if the entire page is not
495 	 * involved in the DMA we might purge some valid data.
496 	 */
497 	if (mmutype == MMU_68040 && (flags & DMAGO_READ))
498 		dc->dm_flags |= DMAF_PCFLUSH;
499 #endif
500 
501 #if defined(CACHE_HAVE_PAC)
502 	/*
503 	 * Remember if we need to flush external physical cache when
504 	 * DMA is done.  We only do this if we are reading (writing memory).
505 	 */
506 	if (ectype == EC_PHYS && (flags & DMAGO_READ))
507 		dc->dm_flags |= DMAF_PCFLUSH;
508 #endif
509 
510 #if defined(CACHE_HAVE_VAC)
511 	if (ectype == EC_VIRT && (flags & DMAGO_READ))
512 		dc->dm_flags |= DMAF_VCFLUSH;
513 #endif
514 
515 	/*
516 	 * Remember if we can skip the dma completion interrupt on
517 	 * the last segment in the chain.
518 	 */
519 	if (flags & DMAGO_NOINT) {
520 		if (dc->dm_cur == dc->dm_last)
521 			dc->dm_cmd &= ~DMA_ENAB;
522 		else
523 			dc->dm_flags |= DMAF_NOINTR;
524 	}
525 #ifdef DEBUG
526 	if (dmadebug & DDB_IO) {
527 		if (((dmadebug&DDB_WORD) && (dc->dm_cmd&DMA_WORD)) ||
528 		    ((dmadebug&DDB_LWORD) && (dc->dm_cmd&DMA_LWORD))) {
529 			printf("dmago: cmd %x, flags %x\n",
530 			    dc->dm_cmd, dc->dm_flags);
531 			for (seg = 0; seg <= dc->dm_last; seg++)
532 				printf("  %d: %d@%p\n", seg,
533 				    dc->dm_chain[seg].dc_count,
534 				    dc->dm_chain[seg].dc_addr);
535 		}
536 	}
537 	dmatimo[unit] = 1;
538 #endif
539 	DMA_ARM(sc, dc);
540 }
541 
542 void
543 dmastop(int unit)
544 {
545 	struct dma_softc *sc = dma_softc;
546 	struct dma_channel *dc = &sc->sc_chan[unit];
547 
548 #ifdef DEBUG
549 	if (dmadebug & DDB_FOLLOW)
550 		printf("dmastop(%d)\n", unit);
551 	dmatimo[unit] = 0;
552 #endif
553 	DMA_CLEAR(dc);
554 
555 #if defined(CACHE_HAVE_PAC) || defined(M68040)
556 	if (dc->dm_flags & DMAF_PCFLUSH) {
557 		PCIA();
558 		dc->dm_flags &= ~DMAF_PCFLUSH;
559 	}
560 #endif
561 
562 #if defined(CACHE_HAVE_VAC)
563 	if (dc->dm_flags & DMAF_VCFLUSH) {
564 		/*
565 		 * 320/350s have VACs that may also need flushing.
566 		 * In our case we only flush the supervisor side
567 		 * because we know that if we are DMAing to user
568 		 * space, the physical pages will also be mapped
569 		 * in kernel space (via vmapbuf) and hence cache-
570 		 * inhibited by the pmap module due to the multiple
571 		 * mapping.
572 		 */
573 		DCIS();
574 		dc->dm_flags &= ~DMAF_VCFLUSH;
575 	}
576 #endif
577 
578 	/*
579 	 * We may get this interrupt after a device service routine
580 	 * has freed the dma channel.  So, ignore the intr if there's
581 	 * nothing on the queue.
582 	 */
583 	if (dc->dm_job != NULL)
584 		(*dc->dm_job->dq_done)(dc->dm_job->dq_softc);
585 }
586 
587 static int
588 dmaintr(void *arg)
589 {
590 	struct dma_softc *sc = arg;
591 	struct dma_channel *dc;
592 	int i, stat;
593 	int found = 0;
594 
595 #ifdef DEBUG
596 	if (dmadebug & DDB_FOLLOW)
597 		printf("dmaintr\n");
598 #endif
599 	for (i = 0; i < NDMACHAN; i++) {
600 		dc = &sc->sc_chan[i];
601 		stat = DMA_STAT(dc);
602 		if ((stat & DMA_INTR) == 0)
603 			continue;
604 		found++;
605 #ifdef DEBUG
606 		if (dmadebug & DDB_IO) {
607 			if (((dmadebug&DDB_WORD) && (dc->dm_cmd&DMA_WORD)) ||
608 			    ((dmadebug&DDB_LWORD) && (dc->dm_cmd&DMA_LWORD)))
609 			 	printf("dmaintr: flags %x unit %d stat %x "
610 				    "next %d\n",
611 				    dc->dm_flags, i, stat, dc->dm_cur + 1);
612 		}
613 		if (stat & DMA_ARMED)
614 			printf("dma channel %d: intr when armed\n", i);
615 #endif
616 		/*
617 		 * Load the next segemnt, or finish up if we're done.
618 		 */
619 		dc->dm_cur++;
620 		if (dc->dm_cur <= dc->dm_last) {
621 #ifdef DEBUG
622 			dmatimo[i] = 1;
623 #endif
624 			/*
625 			 * If we're the last segment, disable the
626 			 * completion interrupt, if necessary.
627 			 */
628 			if (dc->dm_cur == dc->dm_last &&
629 			    (dc->dm_flags & DMAF_NOINTR))
630 				dc->dm_cmd &= ~DMA_ENAB;
631 			DMA_CLEAR(dc);
632 			DMA_ARM(sc, dc);
633 		} else
634 			dmastop(i);
635 	}
636 	return found;
637 }
638 
639 #ifdef DEBUG
640 static void
641 dmatimeout(void *arg)
642 {
643 	int i, s;
644 	struct dma_softc *sc = arg;
645 
646 	for (i = 0; i < NDMACHAN; i++) {
647 		s = splbio();
648 		if (dmatimo[i]) {
649 			if (dmatimo[i] > 1)
650 				printf("dma channel %d timeout #%d\n",
651 				    i, dmatimo[i]-1);
652 			dmatimo[i]++;
653 		}
654 		splx(s);
655 	}
656 	callout_reset(&sc->sc_debug_ch, 30 * hz, dmatimeout, sc);
657 }
658 #endif
659