xref: /netbsd/sys/arch/vax/boot/boot/mfm.c (revision 6550d01e)
1 /*	$NetBSD: mfm.c,v 1.13 2009/10/26 19:16:58 cegger Exp $	*/
2 /*
3  * Copyright (c) 1996 Ludd, University of Lule}, Sweden.
4  * All rights reserved.
5  *
6  * This code is derived from software contributed to Ludd by
7  * Bertram Barth.
8  *
9  * Redistribution and use in source and binary forms, with or without
10  * modification, are permitted provided that the following conditions
11  * are met:
12  * 1. Redistributions of source code must retain the above copyright
13  *    notice, this list of conditions and the following disclaimer.
14  * 2. Redistributions in binary form must reproduce the above copyright
15  *    notice, this list of conditions and the following disclaimer in the
16  *    documentation and/or other materials provided with the distribution.
17  * 3. All advertising materials mentioning features or use of this software
18  *    must display the following acknowledgement:
19  *	This product includes software developed at Ludd, University of
20  *	Lule}, Sweden and its contributors.
21  * 4. The name of the author may not be used to endorse or promote products
22  *    derived from this software without specific prior written permission
23  *
24  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
25  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
26  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
27  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
28  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
29  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
30  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
31  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
32  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
33  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
34  */
35 
36 /*
37  * ToDo:
38  *
39  * - insert appropriate delays for diskette-drive where needed
40  * - allow more than one sector per diskette-read
41  * - check for and handle bad sectors
42  * - ???
43  */
44 
45 #include <sys/param.h>
46 #include <sys/reboot.h>
47 #include <sys/disklabel.h>
48 
49 #include <lib/libsa/stand.h>
50 #include <lib/libsa/ufs.h>
51 
52 #include <lib/libkern/libkern.h>
53 
54 #include "../include/pte.h"
55 #include "../include/sid.h"
56 #include "../include/mtpr.h"
57 #include "../include/reg.h"
58 #include "../include/rpb.h"
59 
60 #include "ka410.h"
61 #include "../vsa/hdc9224.h"
62 
63 #include "data.h"
64 #include "vaxstand.h"
65 
66 #define MAX_WAIT	(1000*1000)	/* # of loop-instructions in seconds */
67 
68 struct mfm_softc {
69 	int		part;
70 	int		unit;
71 };
72 
73 static struct disklabel mfmlabel;
74 static struct mfm_softc mfm_softc;
75 static char io_buf[DEV_BSIZE];
76 
77 /*
78  * These should probably be somewhere else, but ka410 is the only
79  * one with mfm disks anyway...
80  */
81 volatile unsigned char *ka410_intreq = (void*)0x2008000f;
82 volatile unsigned char *ka410_intclr = (void*)0x2008000f;
83 volatile unsigned char *ka410_intmsk = (void*)0x2008000c;
84 
85 static volatile struct hdc9224_DKCreg *dkc = (void *) 0x200c0000;
86 static volatile struct hdc9224_UDCreg sreg;	/* input */
87 static volatile struct hdc9224_UDCreg creg;	/* output */
88 
89 static void sreg_read(void);
90 static void creg_write(void);
91 static int mfm_rxprepare(void);
92 static int mfm_command(int cmd);
93 static int mfm_rxselect(int unit);
94 static int mfm_rdselect(int unit);
95 static int mfm_rxstrategy(void *f, int func, daddr_t dblk, size_t size, void *buf, size_t *rsize);
96 static int mfm_rdstrategy(void *f, int func, daddr_t dblk, size_t size, void *buf, size_t *rsize);
97 /*
98  * we have to wait 0.7 usec between two accesses to any of the
99  * dkc-registers, on a VS2000 with 1 MIPS, this is roughly one
100  * instruction. Thus the loop-overhead will be enough...
101  */
102 static void
103 sreg_read(void)
104 {
105 	int	i;
106 	char    *p;
107 
108 	dkc->dkc_cmd = 0x40;	/* set internal counter to zero */
109 	p = (void *) &sreg;
110 	for (i = 0; i < 10; i++)
111 		*p++ = dkc->dkc_reg;	/* dkc_reg auto-increments */
112 }
113 
114 static void
115 creg_write(void)
116 {
117 	int	i;
118 	char    *p;
119 
120 	dkc->dkc_cmd = 0x40;	/* set internal counter to zero */
121 	p = (void *) &creg;
122 	for (i = 0; i < 10; i++)
123 		dkc->dkc_reg = *p++;	/* dkc_reg auto-increments */
124 }
125 
126 /*
127  * floppies are handled in a quite strange way by this controller...
128  *
129  * before reading/writing a sector from/to floppy, we use the SEEK/READ_ID
130  * command to place the head at the desired location. Then we wait some
131  * time before issuing the real command in order to let the drive become
132  * ready...
133  */
134 int
135 mfm_rxprepare(void)
136 {
137 	int	error;
138 
139 	error = mfm_command(DKC_CMD_SEEKREADID | 0x04); /* step=1, verify=0 */
140 	if (error) {
141 		printf("error while stepping to position %d/%d/%x. Retry...\n",
142 		    creg.udc_dsect, creg.udc_dhead, creg.udc_dcyl);
143 		error = mfm_command(DKC_CMD_SEEKREADID | 0x04);
144 	}
145 	return error;
146 }
147 
148 int
149 mfm_rxselect(int unit)
150 {
151 	int	error;
152 
153 	/*
154 	 * bring "creg" in some known-to-work state and
155 	 * select the drive with the DRIVE SELECT command.
156 	 */
157 	creg.udc_dma7 = 0;
158 	creg.udc_dma15 = 0;
159 	creg.udc_dma23 = 0;
160 	creg.udc_dsect = 1;	/* sectors are numbered 1..15 !!! */
161 	creg.udc_dhead = 0;
162 	creg.udc_dcyl = 0;
163 	creg.udc_scnt = 0;
164 
165 	creg.udc_rtcnt = UDC_RC_RX33READ;
166 	creg.udc_mode = UDC_MD_RX33;
167 	creg.udc_term = UDC_TC_FDD;
168 
169 	/*
170 	 * this is ...
171 	 */
172 	error = mfm_command(DKC_CMD_DRSEL_RX33 | unit);
173 
174 	if ((error != 0) || ((sreg.udc_dstat & UDC_DS_READY) == 0)) {
175 		printf("\nfloppy-drive not ready (new floppy inserted?)\n\n");
176 
177 		creg.udc_rtcnt &= ~UDC_RC_INVRDY;	/* clear INVRDY-flag */
178 		error = mfm_command(DKC_CMD_DRSEL_RX33 | unit);
179 		if ((error != 0) || ((sreg.udc_dstat & UDC_DS_READY) == 0)) {
180 			printf("diskette not ready(1): %x/%x\n",
181 			       error, sreg.udc_dstat);
182 			printf("floppy-drive offline?\n");
183 			return (-1);
184 		}
185 		if (sreg.udc_dstat & UDC_DS_TRK00)
186 			error = mfm_command(DKC_CMD_STEPIN_FDD);
187 		else
188 			error = mfm_command(DKC_CMD_STEPOUT_FDD);
189 
190 		/*
191 		 * now ready should be 0, cause INVRDY is not set
192 		 * (retrying a command makes this fail...)
193 		 */
194 		if ((error != 0) || ((sreg.udc_dstat & UDC_DS_READY) == 1)) {
195 			printf("diskette not ready(2): %x/%x\n",
196 			       error, sreg.udc_dstat);
197 		}
198 		creg.udc_rtcnt |= UDC_RC_INVRDY;
199 		error = mfm_command(DKC_CMD_DRSEL_RX33 | unit);
200 
201 		if ((error != 0) || ((sreg.udc_dstat & UDC_DS_READY) == 0)) {
202 			printf("diskette not ready(3): %x/%x\n",
203 			       error, sreg.udc_dstat);
204 			printf("no floppy inserted or floppy-door open\n");
205 			return (-1);
206 		}
207 		printf("floppy-drive reselected.\n");
208 	}
209 	return (error);
210 }
211 
212 int
213 mfm_rdselect(int unit)
214 {
215 	int	error;
216 
217 	/*
218 	 * bring "creg" in some known-to-work state and
219 	 * select the drive with the DRIVE SELECT command.
220 	 */
221 	creg.udc_dma7 = 0;
222 	creg.udc_dma15 = 0;
223 	creg.udc_dma23 = 0;
224 	creg.udc_dsect = 0;	/* sectors are numbered 0..16 */
225 	creg.udc_dhead = 0;
226 	creg.udc_dcyl = 0;
227 	creg.udc_scnt = 0;
228 
229 	creg.udc_rtcnt = UDC_RC_HDD_READ;
230 	creg.udc_mode = UDC_MD_HDD;
231 	creg.udc_term = UDC_TC_HDD;
232 
233 	error = mfm_command(DKC_CMD_DRSEL_HDD | unit);
234 
235 	return (error);
236 }
237 
238 static int	mfm_retry = 0;
239 
240 int
241 mfm_command(int	cmd)
242 {
243 	int	termcode, ready, i;
244 
245 	creg_write();		/* write command-registers */
246 	*ka410_intclr = INTR_DC;
247 	dkc->dkc_cmd = cmd;	/* issue command */
248 	for (i = 0; i < MAX_WAIT; i++) {
249 		if (*ka410_intreq & INTR_DC)	/* wait for interrupt */
250 			break;
251 	}
252 	if ((*ka410_intreq & INTR_DC) == 0)
253 		printf("timeout in mfm_command...\n");
254 
255 	sreg_read();		/* read status-registers */
256 
257 	if (dkc->dkc_stat == (DKC_ST_DONE | DKC_TC_SUCCESS))
258 		return (0);
259 
260 	if (sreg.udc_cstat & UDC_CS_ECCERR) {
261 		printf(
262 "\nspurious(?) ECC/CRC error at s%d/t%d/c%d [s%d/t%d/c%d(%d)]\n",
263 		   sreg.udc_csect, sreg.udc_chead, sreg.udc_ccyl,
264 		   creg.udc_dsect, creg.udc_dhead, creg.udc_dcyl,creg.udc_scnt);
265 		if (sreg.udc_csect != creg.udc_dsect + creg.udc_scnt - 1) {
266 			printf("DMA: %x %x %x [%x]\n",
267 			    sreg.udc_dma23, sreg.udc_dma15,
268 			    sreg.udc_dma7, 512 * (sreg.udc_csect -
269 			    creg.udc_dsect));
270 			creg.udc_scnt = creg.udc_scnt -
271 			    (sreg.udc_csect - creg.udc_dsect) - 1;
272 			creg.udc_dsect = sreg.udc_csect + 1;
273 			creg.udc_dma23 = sreg.udc_dma23;
274 			creg.udc_dma15 = sreg.udc_dma15 + 2;
275 			creg.udc_dma7 = 0;
276 			printf("Retry starting from s%d/t%d/c%d (%d). ",
277 			    creg.udc_dsect, creg.udc_dhead, creg.udc_dcyl,
278 			    creg.udc_scnt);
279 		}
280 		goto retry;
281 	}
282 	termcode = (dkc->dkc_stat & DKC_ST_TERMCOD) >> 3;
283 	ready = sreg.udc_dstat & UDC_DS_READY;
284 
285 	printf("cmd:0x%x: termcode=0x%x, status=0x%x, cstat=0x%x, dstat=0x%x\n",
286 	       cmd, termcode, dkc->dkc_stat, sreg.udc_cstat, sreg.udc_dstat);
287 
288 	if (dkc->dkc_stat & DKC_ST_BADSECT)
289 		printf("bad sector found: s%d/t%d/c%d\n", creg.udc_dsect,
290 		       creg.udc_dhead, creg.udc_dcyl);
291 retry:
292 	if ((mfm_retry == 0) && (sreg.udc_cstat & UDC_CS_RETREQ)) {
293 		mfm_retry = 1;
294 		printf("Retrying... ");
295 		mfm_command(cmd);
296 		printf("Retry done.\n");
297 		mfm_retry = 0;
298 	}
299 	return ((dkc->dkc_stat & DKC_ST_TERMCOD) >> 3);
300 }
301 
302 /*
303  * on-disk geometry block
304  */
305 #define _aP	__attribute__ ((packed))	/* force byte-alignment */
306 
307 volatile struct mfm_xbn {
308 	char		mbz[10];/* 10 bytes of zero */
309 	long xbn_count	_aP;	/* number of XBNs */
310 	long dbn_count	_aP;	/* number of DBNs */
311 	long lbn_count	_aP;	/* number of LBNs (Logical-Block-Numbers) */
312 	long rbn_count	_aP;	/* number of RBNs (Replacement-Block-Numbers) */
313 	short		nspt;	/* number of sectors per track */
314 	short		ntracks;/* number of tracks */
315 	short		ncylinders;	/* number of cylinders */
316 	short		precomp;/* first cylinder for write precompensation */
317 	short		reduced;/* first cylinder for reduced write current */
318 	short		seek_rate;	/* seek rate or zero for buffered
319 					 * seeks */
320 	short		crc_eec;/* 0 if CRC is being used or 1 if ECC is
321 				 * being used */
322 	short		rct;	/* "replacement control table" (RCT) */
323 	short		rct_ncopies;	/* number of copies of the RCT */
324 	long media_id	_aP;	/* media identifier */
325 	short		interleave;	/* sector-to-sector interleave */
326 	short		headskew;	/* head-to-head skew */
327 	short		cylskew;/* cylinder-to-cylinder skew */
328 	short		gap0_size;	/* size of GAP 0 in the MFM format */
329 	short		gap1_size;	/* size of GAP 1 in the MFM format */
330 	short		gap2_size;	/* size of GAP 2 in the MFM format */
331 	short		gap3_size;	/* size of GAP 3 in the MFM format */
332 	short		sync_value;	/* sync value used to start a track
333 					 * when formatting */
334 	char		reserved[32];	/* reserved for use by the RQDX1/2/3
335 					 * formatter */
336 	short		serial_number;	/* serial number */
337 	char		fill[412];	/* Filler bytes to the end of the
338 					 * block */
339 	short		checksum;	/* checksum over the XBN */
340 } mfm_xbn;
341 
342 #ifdef verbose
343 display_xbn(struct mfm_xbn *p)
344 {
345 	printf("**DiskData**	XBNs: %d, DBNs: %d, LBNs: %d, RBNs: %d\n",
346 	    p->xbn_count, p->dbn_count, p->lbn_count, p->rbn_count);
347 	printf("sect/track: %d, tracks: %d, cyl: %d, precomp/reduced: %d/%d\n",
348 	    p->nspt, p->ntracks, p->ncylinders, p->precomp, p->reduced);
349 	printf("seek-rate: %d, crc/eec: %s, RCT: %d, RCT-copies: %d\n",
350 	    p->seek_rate, p->crc_eec ? "EEC" : "CRC", p->rct, p->rct_ncopies);
351 	printf("media-ID: 0x%x, interleave: %d, headskew: %d, cylskew: %d\n",
352 	    &p->media_id, p->interleave, p->headskew, p->cylskew);
353 	printf("gap0: %d, gap1: %d, gap2: %d, gap3: %d, sync-value: %d\n",
354 	    p->gap0_size, p->gap1_size, p->gap2_size, p->gap3_size,
355 	    p->sync_value);
356 	printf("serial: %d, checksum: %d, size: %d, reserved: %32c\n",
357 	    p->serial_number, p->checksum, sizeof(*p), p->reserved);
358 }
359 #endif
360 
361 int
362 mfmopen(struct open_file *f, int adapt, int ctlr, int unit, int part)
363 {
364 	char *msg;
365 	struct disklabel *lp = &mfmlabel;
366 	struct mfm_softc *msc = &mfm_softc;
367 	int err;
368 	size_t i;
369 
370 	memset(lp, 0, sizeof(struct disklabel));
371 	msc->unit = unit;
372 	msc->part = part;
373 
374 	err = mfmstrategy(msc, F_READ, LABELSECTOR, DEV_BSIZE, io_buf, &i);
375 	if (err) {
376 		printf("reading disklabel: %s\n", strerror(err));
377 		return 0;
378 	}
379 	msg = getdisklabel(io_buf + LABELOFFSET, lp);
380 	if (msg)
381 		printf("getdisklabel: %s\n", msg);
382 
383 	f->f_devdata = (void *) msc;
384 
385 	{
386 #ifdef verbose
387 		int		k;
388 		unsigned char  *ucp;
389 		struct mfm_xbn *xp;
390 #endif
391 
392 		/* mfmstrategy(msc, F_READ, -16, 8192, io_buf, &i); */
393 		mfmstrategy(msc, F_READ, -16, 512, io_buf, &i);
394 #ifdef verbose
395 		printf("dumping raw disk-block #0:\n");
396 		ucp = io_buf;
397 		for (k = 0; k < 128; k++) {
398 			if (ucp[k] < 0x10)
399 				printf("0");
400 			printf("%x ", ucp[k]);
401 			if (k % 8 == 7)
402 				printf("  ");
403 			if (k % 16 == 15)
404 				printf("\n");
405 		}
406 		printf("\n");
407 
408 		xp = (void *) io_buf;
409 		display_xbn(xp);
410 		printf("\n");
411 #endif
412 	}
413 
414 	if (unit == 2) {	/* floppy! */
415 		if (lp->d_ntracks != 2) {
416 #ifdef verbose
417 			printf("changing number of tracks from %d to %d.\n",
418 			       lp->d_ntracks, 2);
419 #endif
420 			lp->d_ntracks = 2;
421 		}
422 	} else {		/* hard-disk */
423 		unsigned short *usp = (void *) io_buf;
424 #ifdef verbose
425 		printf("label says: s/t/c = %d/%d/%d\n",
426 		       lp->d_nsectors, lp->d_ntracks, lp->d_ncylinders);
427 #endif
428 		if (lp->d_nsectors != usp[13]) {
429 #ifdef verbose
430 			printf("changing number of sectors from %d to %d.\n",
431 			       lp->d_nsectors, usp[13]);
432 #endif
433 			lp->d_nsectors = usp[13];
434 		}
435 		if (lp->d_ntracks != usp[14]) {
436 #ifdef verbose
437 			printf("changing number of heads/tracks from %d to %d.\n",
438 			       lp->d_ntracks, usp[14]);
439 #endif
440 			lp->d_ntracks = usp[14];
441 		}
442 		if (lp->d_ncylinders != usp[15]) {
443 #ifdef verbose
444 			printf("changing number of cylinders from %d to %d.\n",
445 			       lp->d_ncylinders, usp[15]);
446 #endif
447 			lp->d_ncylinders = usp[15];
448 		}
449 		lp->d_secpercyl = lp->d_nsectors * lp->d_ntracks;
450 	}
451 
452 	return (0);
453 }
454 
455 int
456 mfm_rxstrategy(void *f, int func, daddr_t dblk, size_t size, void *buf, size_t *rsize) {
457 	struct mfm_softc *msc = f;
458 	struct disklabel *lp;
459 	int	block, sect, head, cyl, scount, res;
460 	char *cbuf;
461 
462 	cbuf = (char*)buf;
463 
464 	lp = &mfmlabel;
465 	block = (dblk < 0 ? 0 : dblk + lp->d_partitions[msc->part].p_offset);
466 
467 	mfm_rxselect(msc->unit);
468 
469 	/*
470 	 * if label is empty, assume RX33
471 	 */
472 	if (lp->d_nsectors == 0)
473 		lp->d_nsectors = 15;
474 	if (lp->d_ntracks == 0)
475 		lp->d_ntracks = 2;
476 	if (lp->d_secpercyl == 0)
477 		lp->d_secpercyl = 30;
478 
479 	memset((void *) 0x200D0000, 0, size);
480 	scount = size / 512;
481 
482 	while (scount) {
483 		/*
484 		 * prepare drive/operation parameter
485 		 */
486 		cyl = block / lp->d_secpercyl;
487 		sect = block % lp->d_secpercyl;
488 		head = sect / lp->d_nsectors;
489 		sect = sect % lp->d_nsectors;
490 
491 		/*
492 		 * *rsize = 512;		one sector after the other
493 		 * ...
494 		 */
495 		*rsize = 512 * min(scount, lp->d_nsectors - sect);
496 
497 		/*
498 		 * now initialize the register values ...
499 		 */
500 		creg.udc_dma7 = 0;
501 		creg.udc_dma15 = 0;
502 		creg.udc_dma23 = 0;
503 
504 		creg.udc_dsect = sect + 1;	/* sectors are numbered 1..15
505 						 * !!! */
506 		head |= (cyl >> 4) & 0x70;
507 		creg.udc_dhead = head;
508 		creg.udc_dcyl = cyl;
509 
510 		creg.udc_scnt = *rsize / 512;
511 
512 		if (func == F_WRITE) {
513 			creg.udc_rtcnt = UDC_RC_RX33WRT;
514 			creg.udc_mode = UDC_MD_RX33;
515 			creg.udc_term = UDC_TC_FDD;
516 
517 			mfm_rxprepare();
518 			/* copy from buf */
519 			memcpy((void *) 0x200D0000, cbuf, *rsize);
520 			res = mfm_command(DKC_CMD_WRITE_RX33);
521 		} else {
522 			creg.udc_rtcnt = UDC_RC_RX33READ;
523 			creg.udc_mode = UDC_MD_RX33;
524 			creg.udc_term = UDC_TC_FDD;
525 
526 			mfm_rxprepare();
527 			/* clear disk buffer */
528 			memset((void *) 0x200D0000, 0, *rsize);
529 			res = mfm_command(DKC_CMD_READ_RX33);
530 			/* copy to buf */
531 			memcpy(cbuf, (void *) 0x200D0000, *rsize);
532 		}
533 
534 		scount -= *rsize / 512;
535 		block += *rsize / 512;
536 		cbuf += *rsize;
537 	}
538 
539 	*rsize = size;
540 	return 0;
541 }
542 
543 int
544 mfm_rdstrategy(void *f, int func, daddr_t dblk, size_t size, void *buf, size_t *rsize) {
545 	struct mfm_softc *msc = f;
546 	struct disklabel *lp;
547 	int	block, sect, head, cyl, scount, cmd, res;
548 	char *cbuf;
549 
550 	cbuf = (char *)buf;
551 
552 	lp = &mfmlabel;
553 	block = (dblk < 0 ? 0 : dblk + lp->d_partitions[msc->part].p_offset);
554 
555 	/*
556 	 * if label is empty, assume RD32 (XXX this must go away!!!)
557 	 */
558 	if (lp->d_nsectors == 0)
559 		lp->d_nsectors = 17;
560 	if (lp->d_ntracks == 0)
561 		lp->d_ntracks = 6;
562 	if (lp->d_secpercyl == 0)
563 		lp->d_secpercyl = 102;
564 
565 	mfm_rdselect(msc->unit);
566 
567 	memset((void *) 0x200D0000, 0, size);
568 	scount = size / 512;
569 
570 	while (scount) {
571 		/*
572 		 * prepare drive/operation parameter
573 		 */
574 		cyl = block / lp->d_secpercyl;
575 		sect = block % lp->d_secpercyl;
576 		head = sect / lp->d_nsectors;
577 		sect = sect % lp->d_nsectors;
578 
579 		if (dblk < 0) {
580 #ifdef verbose
581 			printf("using raw diskblock-data!\n");
582 			printf("block %d, dblk %d ==> cyl %d, head %d, sect %d\n",
583 			       block, dblk, cyl, sect, head);
584 #endif
585 		} else
586 			cyl += 1;	/* first cylinder is reserved for
587 					 * controller! */
588 
589 		*rsize = 512 * min(scount, lp->d_nsectors - sect);
590 		/*
591 		 * now re-initialize the register values ...
592 		 */
593 		creg.udc_dma7 = 0;
594 		creg.udc_dma15 = 0;
595 		creg.udc_dma23 = 0;
596 
597 		creg.udc_dsect = sect;
598 		head |= (cyl >> 4) & 0x70;
599 		creg.udc_dhead = head;
600 		creg.udc_dcyl = cyl;
601 
602 		creg.udc_scnt = *rsize / 512;
603 
604 		if (func == F_WRITE) {
605 			creg.udc_rtcnt = UDC_RC_HDD_WRT;
606 			creg.udc_mode = UDC_MD_HDD;
607 			creg.udc_term = UDC_TC_HDD;
608 			cmd = DKC_CMD_WRITE_HDD;
609 
610 			memcpy((void *) 0x200D0000, cbuf, *rsize);
611 			res = mfm_command(cmd);
612 		} else {
613 			creg.udc_rtcnt = UDC_RC_HDD_READ;
614 			creg.udc_mode = UDC_MD_HDD;
615 			creg.udc_term = UDC_TC_HDD;
616 			cmd = DKC_CMD_READ_HDD;
617 
618 			memset((void *) 0x200D0000, 0, *rsize);
619 			res = mfm_command(cmd);
620 			memcpy(cbuf, (void *) 0x200D0000, *rsize);
621 		}
622 
623 		scount -= *rsize / 512;
624 		block += *rsize / 512;
625 		cbuf += *rsize;
626 	}
627 
628 	/*
629 	 * unselect the drive ...
630 	 */
631 	mfm_command(DKC_CMD_DRDESELECT);
632 
633 	*rsize = size;
634 	return 0;
635 }
636 
637 int
638 mfmstrategy(void *f, int func, daddr_t dblk, size_t size, void *buf, size_t *rsize)
639 {
640 	struct mfm_softc *msc = f;
641 	int	res = -1;
642 
643 	switch (msc->unit) {
644 	case 0:
645 	case 1:
646 		res = mfm_rdstrategy(f, func, dblk, size, buf, rsize);
647 		break;
648 	case 2:
649 		res = mfm_rxstrategy(f, func, dblk, size, buf, rsize);
650 		break;
651 	default:
652 		printf("invalid unit %d in mfmstrategy()\n", msc->unit);
653 	}
654 	return (res);
655 }
656