xref: /netbsd-src/sys/arch/hp300/dev/dma.c (revision 3816d47b2c42fcd6e549e3407f842a5b1a1d23ad)
1 /*	$NetBSD: dma.c,v 1.42 2008/06/22 16:29:36 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  *
19  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
20  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
21  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
22  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
23  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
24  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
25  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
26  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
27  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
28  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
29  * POSSIBILITY OF SUCH DAMAGE.
30  */
31 
32 /*
33  * Copyright (c) 1982, 1990, 1993
34  *	The Regents of the University of California.  All rights reserved.
35  *
36  * Redistribution and use in source and binary forms, with or without
37  * modification, are permitted provided that the following conditions
38  * are met:
39  * 1. Redistributions of source code must retain the above copyright
40  *    notice, this list of conditions and the following disclaimer.
41  * 2. Redistributions in binary form must reproduce the above copyright
42  *    notice, this list of conditions and the following disclaimer in the
43  *    documentation and/or other materials provided with the distribution.
44  * 3. Neither the name of the University nor the names of its contributors
45  *    may be used to endorse or promote products derived from this software
46  *    without specific prior written permission.
47  *
48  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
49  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
50  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
51  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
52  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
53  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
54  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
55  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
56  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
57  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
58  * SUCH DAMAGE.
59  *
60  *	@(#)dma.c	8.1 (Berkeley) 6/10/93
61  */
62 
63 /*
64  * DMA driver
65  */
66 
67 #include <sys/cdefs.h>
68 __KERNEL_RCSID(0, "$NetBSD: dma.c,v 1.42 2008/06/22 16:29:36 tsutsui Exp $");
69 
70 #include <machine/hp300spu.h>	/* XXX param.h includes cpu.h */
71 
72 #include <sys/param.h>
73 #include <sys/systm.h>
74 #include <sys/callout.h>
75 #include <sys/device.h>
76 #include <sys/kernel.h>
77 #include <sys/proc.h>
78 
79 #include <uvm/uvm_extern.h>
80 
81 #include <machine/bus.h>
82 
83 #include <m68k/cacheops.h>
84 
85 #include <hp300/dev/intiovar.h>
86 #include <hp300/dev/dmareg.h>
87 #include <hp300/dev/dmavar.h>
88 
89 /*
90  * The largest single request will be MAXPHYS bytes which will require
91  * at most MAXPHYS/PAGE_SIZE+1 chain elements to describe, i.e. if none of
92  * the buffer pages are physically contiguous (MAXPHYS/PAGE_SIZE) and the
93  * buffer is not page aligned (+1).
94  */
95 #define	DMAMAXIO	(MAXPHYS/PAGE_SIZE+1)
96 
97 struct dma_chain {
98 	int	dc_count;
99 	char	*dc_addr;
100 };
101 
102 struct dma_channel {
103 	struct	dmaqueue *dm_job;		/* current job */
104 	struct	dmadevice *dm_hwaddr;		/* registers if DMA_C */
105 	struct	dmaBdevice *dm_Bhwaddr;		/* registers if not DMA_C */
106 	char	dm_flags;			/* misc. flags */
107 	u_short	dm_cmd;				/* DMA controller command */
108 	int	dm_cur;				/* current segment */
109 	int	dm_last;			/* last segment */
110 	struct	dma_chain dm_chain[DMAMAXIO];	/* all segments */
111 };
112 
113 struct dma_softc {
114 	device_t sc_dev;
115 	bus_space_tag_t sc_bst;
116 	bus_space_handle_t sc_bsh;
117 
118 	struct	dmareg *sc_dmareg;		/* pointer to our hardware */
119 	struct	dma_channel sc_chan[NDMACHAN];	/* 2 channels */
120 	TAILQ_HEAD(, dmaqueue) sc_queue;	/* job queue */
121 	struct	callout sc_debug_ch;
122 	char	sc_type;			/* A, B, or C */
123 	int	sc_ipl;				/* our interrupt level */
124 	void	*sc_ih;				/* interrupt cookie */
125 };
126 
127 /* types */
128 #define	DMA_B	0
129 #define DMA_C	1
130 
131 /* flags */
132 #define DMAF_PCFLUSH	0x01
133 #define DMAF_VCFLUSH	0x02
134 #define DMAF_NOINTR	0x04
135 
136 static int	dmamatch(device_t, cfdata_t, void *);
137 static void	dmaattach(device_t, device_t, void *);
138 
139 CFATTACH_DECL_NEW(dma, sizeof(struct dma_softc),
140     dmamatch, dmaattach, NULL, NULL);
141 
142 static int	dmaintr(void *);
143 
144 #ifdef DEBUG
145 int	dmadebug = 0;
146 #define DDB_WORD	0x01	/* same as DMAGO_WORD */
147 #define DDB_LWORD	0x02	/* same as DMAGO_LWORD */
148 #define	DDB_FOLLOW	0x04
149 #define DDB_IO		0x08
150 
151 static void	dmatimeout(void *);
152 int	dmatimo[NDMACHAN];
153 
154 long	dmahits[NDMACHAN];
155 long	dmamisses[NDMACHAN];
156 long	dmabyte[NDMACHAN];
157 long	dmaword[NDMACHAN];
158 long	dmalword[NDMACHAN];
159 #endif
160 
161 static struct dma_softc *dma_softc;
162 
163 static int
164 dmamatch(device_t parent, cfdata_t cf, void *aux)
165 {
166 	struct intio_attach_args *ia = aux;
167 	static int dmafound = 0;                /* can only have one */
168 
169 	if (strcmp("dma", ia->ia_modname) != 0 || dmafound)
170 		return 0;
171 
172 	dmafound = 1;
173 	return 1;
174 }
175 
176 static void
177 dmaattach(device_t parent, device_t self, void *aux)
178 {
179 	struct dma_softc *sc = device_private(self);
180 	struct intio_attach_args *ia = aux;
181 	struct dma_channel *dc;
182 	struct dmareg *dma;
183 	int i;
184 	char rev;
185 
186 	sc->sc_dev = self;
187 
188 	/* There's just one. */
189 	dma_softc = sc;
190 
191 	sc->sc_bst = ia->ia_bst;
192 	if (bus_space_map(sc->sc_bst, ia->ia_iobase, INTIO_DEVSIZE, 0,
193 	     &sc->sc_bsh)) {
194 		aprint_error(": can't map registers\n");
195 		return;
196 	}
197 
198 	dma = bus_space_vaddr(sc->sc_bst, sc->sc_bsh);
199 	sc->sc_dmareg = dma;
200 
201 	/*
202 	 * Determine the DMA type.  A DMA_A or DMA_B will fail the
203 	 * following probe.
204 	 *
205 	 * XXX Don't know how to easily differentiate the A and B cards,
206 	 * so we just hope nobody has an A card (A cards will work if
207 	 * splbio works out to ipl 3).
208 	 */
209 	if (hp300_bus_space_probe(sc->sc_bst, sc->sc_bsh, DMA_ID2, 1) == 0) {
210 		rev = 'B';
211 #if !defined(HP320)
212 		aprint_normal("\n");
213 		panic("%s: DMA card requires hp320 support", __func__);
214 #endif
215 	} else
216 		rev = dma->dma_id[2];
217 
218 	sc->sc_type = (rev == 'B') ? DMA_B : DMA_C;
219 
220 	TAILQ_INIT(&sc->sc_queue);
221 	callout_init(&sc->sc_debug_ch, 0);
222 
223 	for (i = 0; i < NDMACHAN; i++) {
224 		dc = &sc->sc_chan[i];
225 		dc->dm_job = NULL;
226 		switch (i) {
227 		case 0:
228 			dc->dm_hwaddr = &dma->dma_chan0;
229 			dc->dm_Bhwaddr = &dma->dma_Bchan0;
230 			break;
231 
232 		case 1:
233 			dc->dm_hwaddr = &dma->dma_chan1;
234 			dc->dm_Bhwaddr = &dma->dma_Bchan1;
235 			break;
236 
237 		default:
238 			aprint_normal("\n");
239 			panic("%s: more than 2 channels?", __func__);
240 			/* NOTREACHED */
241 		}
242 	}
243 
244 #ifdef DEBUG
245 	/* make sure timeout is really not needed */
246 	callout_reset(&sc->sc_debug_ch, 30 * hz, dmatimeout, sc);
247 #endif
248 
249 	aprint_normal(": 98620%c, 2 channels, %d-bit DMA\n",
250 	    rev, (rev == 'B') ? 16 : 32);
251 
252 	/*
253 	 * Defer hooking up our interrupt until the first
254 	 * DMA-using controller has hooked up theirs.
255 	 */
256 	sc->sc_ih = NULL;
257 }
258 
259 /*
260  * Compute the ipl and (re)establish the interrupt handler
261  * for the DMA controller.
262  */
263 void
264 dmacomputeipl(void)
265 {
266 	struct dma_softc *sc = dma_softc;
267 
268 	if (sc->sc_ih != NULL)
269 		intr_disestablish(sc->sc_ih);
270 
271 	/*
272 	 * Our interrupt level must be as high as the highest
273 	 * device using DMA (i.e. splbio).
274 	 */
275 	sc->sc_ipl = PSLTOIPL(ipl2psl_table[IPL_VM]);
276 	sc->sc_ih = intr_establish(dmaintr, sc, sc->sc_ipl, IPL_VM);
277 }
278 
279 int
280 dmareq(struct dmaqueue *dq)
281 {
282 	struct dma_softc *sc = dma_softc;
283 	int i, chan, s;
284 
285 #if 1
286 	s = splhigh();	/* XXXthorpej */
287 #else
288 	s = splbio();
289 #endif
290 
291 	chan = dq->dq_chan;
292 	for (i = NDMACHAN - 1; i >= 0; i--) {
293 		/*
294 		 * Can we use this channel?
295 		 */
296 		if ((chan & (1 << i)) == 0)
297 			continue;
298 
299 		/*
300 		 * We can use it; is it busy?
301 		 */
302 		if (sc->sc_chan[i].dm_job != NULL)
303 			continue;
304 
305 		/*
306 		 * Not busy; give the caller this channel.
307 		 */
308 		sc->sc_chan[i].dm_job = dq;
309 		dq->dq_chan = i;
310 		splx(s);
311 		return 1;
312 	}
313 
314 	/*
315 	 * Couldn't get a channel now; put this in the queue.
316 	 */
317 	TAILQ_INSERT_TAIL(&sc->sc_queue, dq, dq_list);
318 	splx(s);
319 	return 0;
320 }
321 
322 void
323 dmafree(struct dmaqueue *dq)
324 {
325 	int unit = dq->dq_chan;
326 	struct dma_softc *sc = dma_softc;
327 	struct dma_channel *dc = &sc->sc_chan[unit];
328 	struct dmaqueue *dn;
329 	int chan, s;
330 
331 #if 1
332 	s = splhigh();	/* XXXthorpej */
333 #else
334 	s = splbio();
335 #endif
336 
337 #ifdef DEBUG
338 	dmatimo[unit] = 0;
339 #endif
340 
341 	DMA_CLEAR(dc);
342 
343 #if defined(CACHE_HAVE_PAC) || defined(M68040)
344 	/*
345 	 * XXX we may not always go thru the flush code in dmastop()
346 	 */
347 	if (dc->dm_flags & DMAF_PCFLUSH) {
348 		PCIA();
349 		dc->dm_flags &= ~DMAF_PCFLUSH;
350 	}
351 #endif
352 
353 #if defined(CACHE_HAVE_VAC)
354 	if (dc->dm_flags & DMAF_VCFLUSH) {
355 		/*
356 		 * 320/350s have VACs that may also need flushing.
357 		 * In our case we only flush the supervisor side
358 		 * because we know that if we are DMAing to user
359 		 * space, the physical pages will also be mapped
360 		 * in kernel space (via vmapbuf) and hence cache-
361 		 * inhibited by the pmap module due to the multiple
362 		 * mapping.
363 		 */
364 		DCIS();
365 		dc->dm_flags &= ~DMAF_VCFLUSH;
366 	}
367 #endif
368 
369 	/*
370 	 * Channel is now free.  Look for another job to run on this
371 	 * channel.
372 	 */
373 	dc->dm_job = NULL;
374 	chan = 1 << unit;
375 	for (dn = TAILQ_FIRST(&sc->sc_queue); dn != NULL;
376 	    dn = TAILQ_NEXT(dn, dq_list)) {
377 		if (dn->dq_chan & chan) {
378 			/* Found one... */
379 			TAILQ_REMOVE(&sc->sc_queue, dn, dq_list);
380 			dc->dm_job = dn;
381 			dn->dq_chan = dq->dq_chan;
382 			splx(s);
383 
384 			/* Start the initiator. */
385 			(*dn->dq_start)(dn->dq_softc);
386 			return;
387 		}
388 	}
389 	splx(s);
390 }
391 
392 void
393 dmago(int unit, char *addr, int count, int flags)
394 {
395 	struct dma_softc *sc = dma_softc;
396 	struct dma_channel *dc = &sc->sc_chan[unit];
397 	char *dmaend = NULL;
398 	int seg, tcount;
399 
400 	if (count > MAXPHYS)
401 		panic("dmago: count > MAXPHYS");
402 
403 #if defined(HP320)
404 	if (sc->sc_type == DMA_B && (flags & DMAGO_LWORD))
405 		panic("dmago: no can do 32-bit DMA");
406 #endif
407 
408 #ifdef DEBUG
409 	if (dmadebug & DDB_FOLLOW)
410 		printf("dmago(%d, %p, %x, %x)\n",
411 		       unit, addr, count, flags);
412 	if (flags & DMAGO_LWORD)
413 		dmalword[unit]++;
414 	else if (flags & DMAGO_WORD)
415 		dmaword[unit]++;
416 	else
417 		dmabyte[unit]++;
418 #endif
419 	/*
420 	 * Build the DMA chain
421 	 */
422 	for (seg = 0; count > 0; seg++) {
423 		dc->dm_chain[seg].dc_addr = (char *) kvtop(addr);
424 #if defined(M68040)
425 		/*
426 		 * Push back dirty cache lines
427 		 */
428 		if (mmutype == MMU_68040)
429 			DCFP((paddr_t)dc->dm_chain[seg].dc_addr);
430 #endif
431 		if (count < (tcount = PAGE_SIZE - ((int)addr & PGOFSET)))
432 			tcount = count;
433 		dc->dm_chain[seg].dc_count = tcount;
434 		addr += tcount;
435 		count -= tcount;
436 		if (flags & DMAGO_LWORD)
437 			tcount >>= 2;
438 		else if (flags & DMAGO_WORD)
439 			tcount >>= 1;
440 
441 		/*
442 		 * Try to compact the DMA transfer if the pages are adjacent.
443 		 * Note: this will never happen on the first iteration.
444 		 */
445 		if (dc->dm_chain[seg].dc_addr == dmaend
446 #if defined(HP320)
447 		    /* only 16-bit count on 98620B */
448 		    && (sc->sc_type != DMA_B ||
449 			dc->dm_chain[seg - 1].dc_count + tcount <= 65536)
450 #endif
451 		) {
452 #ifdef DEBUG
453 			dmahits[unit]++;
454 #endif
455 			dmaend += dc->dm_chain[seg].dc_count;
456 			dc->dm_chain[--seg].dc_count += tcount;
457 		} else {
458 #ifdef DEBUG
459 			dmamisses[unit]++;
460 #endif
461 			dmaend = dc->dm_chain[seg].dc_addr +
462 			    dc->dm_chain[seg].dc_count;
463 			dc->dm_chain[seg].dc_count = tcount;
464 		}
465 	}
466 	dc->dm_cur = 0;
467 	dc->dm_last = --seg;
468 	dc->dm_flags = 0;
469 	/*
470 	 * Set up the command word based on flags
471 	 */
472 	dc->dm_cmd = DMA_ENAB | DMA_IPL(sc->sc_ipl) | DMA_START;
473 	if ((flags & DMAGO_READ) == 0)
474 		dc->dm_cmd |= DMA_WRT;
475 	if (flags & DMAGO_LWORD)
476 		dc->dm_cmd |= DMA_LWORD;
477 	else if (flags & DMAGO_WORD)
478 		dc->dm_cmd |= DMA_WORD;
479 	if (flags & DMAGO_PRI)
480 		dc->dm_cmd |= DMA_PRI;
481 
482 #if defined(M68040)
483 	/*
484 	 * On the 68040 we need to flush (push) the data cache before a
485 	 * DMA (already done above) and flush again after DMA completes.
486 	 * In theory we should only need to flush prior to a write DMA
487 	 * and purge after a read DMA but if the entire page is not
488 	 * involved in the DMA we might purge some valid data.
489 	 */
490 	if (mmutype == MMU_68040 && (flags & DMAGO_READ))
491 		dc->dm_flags |= DMAF_PCFLUSH;
492 #endif
493 
494 #if defined(CACHE_HAVE_PAC)
495 	/*
496 	 * Remember if we need to flush external physical cache when
497 	 * DMA is done.  We only do this if we are reading (writing memory).
498 	 */
499 	if (ectype == EC_PHYS && (flags & DMAGO_READ))
500 		dc->dm_flags |= DMAF_PCFLUSH;
501 #endif
502 
503 #if defined(CACHE_HAVE_VAC)
504 	if (ectype == EC_VIRT && (flags & DMAGO_READ))
505 		dc->dm_flags |= DMAF_VCFLUSH;
506 #endif
507 
508 	/*
509 	 * Remember if we can skip the dma completion interrupt on
510 	 * the last segment in the chain.
511 	 */
512 	if (flags & DMAGO_NOINT) {
513 		if (dc->dm_cur == dc->dm_last)
514 			dc->dm_cmd &= ~DMA_ENAB;
515 		else
516 			dc->dm_flags |= DMAF_NOINTR;
517 	}
518 #ifdef DEBUG
519 	if (dmadebug & DDB_IO) {
520 		if (((dmadebug&DDB_WORD) && (dc->dm_cmd&DMA_WORD)) ||
521 		    ((dmadebug&DDB_LWORD) && (dc->dm_cmd&DMA_LWORD))) {
522 			printf("dmago: cmd %x, flags %x\n",
523 			    dc->dm_cmd, dc->dm_flags);
524 			for (seg = 0; seg <= dc->dm_last; seg++)
525 				printf("  %d: %d@%p\n", seg,
526 				    dc->dm_chain[seg].dc_count,
527 				    dc->dm_chain[seg].dc_addr);
528 		}
529 	}
530 	dmatimo[unit] = 1;
531 #endif
532 	DMA_ARM(sc, dc);
533 }
534 
535 void
536 dmastop(int unit)
537 {
538 	struct dma_softc *sc = dma_softc;
539 	struct dma_channel *dc = &sc->sc_chan[unit];
540 
541 #ifdef DEBUG
542 	if (dmadebug & DDB_FOLLOW)
543 		printf("dmastop(%d)\n", unit);
544 	dmatimo[unit] = 0;
545 #endif
546 	DMA_CLEAR(dc);
547 
548 #if defined(CACHE_HAVE_PAC) || defined(M68040)
549 	if (dc->dm_flags & DMAF_PCFLUSH) {
550 		PCIA();
551 		dc->dm_flags &= ~DMAF_PCFLUSH;
552 	}
553 #endif
554 
555 #if defined(CACHE_HAVE_VAC)
556 	if (dc->dm_flags & DMAF_VCFLUSH) {
557 		/*
558 		 * 320/350s have VACs that may also need flushing.
559 		 * In our case we only flush the supervisor side
560 		 * because we know that if we are DMAing to user
561 		 * space, the physical pages will also be mapped
562 		 * in kernel space (via vmapbuf) and hence cache-
563 		 * inhibited by the pmap module due to the multiple
564 		 * mapping.
565 		 */
566 		DCIS();
567 		dc->dm_flags &= ~DMAF_VCFLUSH;
568 	}
569 #endif
570 
571 	/*
572 	 * We may get this interrupt after a device service routine
573 	 * has freed the dma channel.  So, ignore the intr if there's
574 	 * nothing on the queue.
575 	 */
576 	if (dc->dm_job != NULL)
577 		(*dc->dm_job->dq_done)(dc->dm_job->dq_softc);
578 }
579 
580 static int
581 dmaintr(void *arg)
582 {
583 	struct dma_softc *sc = arg;
584 	struct dma_channel *dc;
585 	int i, stat;
586 	int found = 0;
587 
588 #ifdef DEBUG
589 	if (dmadebug & DDB_FOLLOW)
590 		printf("dmaintr\n");
591 #endif
592 	for (i = 0; i < NDMACHAN; i++) {
593 		dc = &sc->sc_chan[i];
594 		stat = DMA_STAT(dc);
595 		if ((stat & DMA_INTR) == 0)
596 			continue;
597 		found++;
598 #ifdef DEBUG
599 		if (dmadebug & DDB_IO) {
600 			if (((dmadebug&DDB_WORD) && (dc->dm_cmd&DMA_WORD)) ||
601 			    ((dmadebug&DDB_LWORD) && (dc->dm_cmd&DMA_LWORD)))
602 			 	printf("dmaintr: flags %x unit %d stat %x "
603 				    "next %d\n",
604 				    dc->dm_flags, i, stat, dc->dm_cur + 1);
605 		}
606 		if (stat & DMA_ARMED)
607 			printf("dma channel %d: intr when armed\n", i);
608 #endif
609 		/*
610 		 * Load the next segemnt, or finish up if we're done.
611 		 */
612 		dc->dm_cur++;
613 		if (dc->dm_cur <= dc->dm_last) {
614 #ifdef DEBUG
615 			dmatimo[i] = 1;
616 #endif
617 			/*
618 			 * If we're the last segment, disable the
619 			 * completion interrupt, if necessary.
620 			 */
621 			if (dc->dm_cur == dc->dm_last &&
622 			    (dc->dm_flags & DMAF_NOINTR))
623 				dc->dm_cmd &= ~DMA_ENAB;
624 			DMA_CLEAR(dc);
625 			DMA_ARM(sc, dc);
626 		} else
627 			dmastop(i);
628 	}
629 	return found;
630 }
631 
632 #ifdef DEBUG
633 static void
634 dmatimeout(void *arg)
635 {
636 	int i, s;
637 	struct dma_softc *sc = arg;
638 
639 	for (i = 0; i < NDMACHAN; i++) {
640 		s = splbio();
641 		if (dmatimo[i]) {
642 			if (dmatimo[i] > 1)
643 				printf("dma channel %d timeout #%d\n",
644 				    i, dmatimo[i]-1);
645 			dmatimo[i]++;
646 		}
647 		splx(s);
648 	}
649 	callout_reset(&sc->sc_debug_ch, 30 * hz, dmatimeout, sc);
650 }
651 #endif
652