xref: /netbsd-src/sys/dev/ic/siop_common.c (revision 481fca6e59249d8ffcf24fef7cfbe7b131bfb080)
1 /*	$NetBSD: siop_common.c,v 1.5 2000/06/28 17:13:04 mrg Exp $	*/
2 
3 /*
4  * Copyright (c) 2000 Manuel Bouyer.
5  *
6  * Redistribution and use in source and binary forms, with or without
7  * modification, are permitted provided that the following conditions
8  * are met:
9  * 1. Redistributions of source code must retain the above copyright
10  *    notice, this list of conditions and the following disclaimer.
11  * 2. Redistributions in binary form must reproduce the above copyright
12  *    notice, this list of conditions and the following disclaimer in the
13  *    documentation and/or other materials provided with the distribution.
14  * 3. All advertising materials mentioning features or use of this software
15  *    must display the following acknowledgement:
16  *	This product includes software developed by Manuel Bouyer
17  * 4. The name of the author may not be used to endorse or promote products
18  *    derived from this software without specific prior written permission.
19  *
20  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
21  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
22  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
23  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
24  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
25  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
26  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
27  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
28  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
29  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
30  *
31  */
32 
33 /* SYM53c7/8xx PCI-SCSI I/O Processors driver */
34 
35 #include <sys/param.h>
36 #include <sys/systm.h>
37 #include <sys/device.h>
38 #include <sys/malloc.h>
39 #include <sys/buf.h>
40 #include <sys/kernel.h>
41 #include <sys/scsiio.h>
42 
43 #include <machine/endian.h>
44 #include <machine/bus.h>
45 
46 #include <dev/scsipi/scsi_all.h>
47 #include <dev/scsipi/scsi_message.h>
48 #include <dev/scsipi/scsipi_all.h>
49 
50 #include <dev/scsipi/scsiconf.h>
51 
52 #include <dev/ic/siopreg.h>
53 #include <dev/ic/siopvar.h>
54 #include <dev/ic/siopvar_common.h>
55 
56 #undef DEBUG
57 #undef DEBUG_DR
58 
59 void
60 siop_common_reset(sc)
61 	struct siop_softc *sc;
62 {
63 	u_int32_t stest3;
64 
65 	/* reset the chip */
66 	bus_space_write_1(sc->sc_rt, sc->sc_rh, SIOP_ISTAT, ISTAT_SRST);
67 	delay(1000);
68 	bus_space_write_1(sc->sc_rt, sc->sc_rh, SIOP_ISTAT, 0);
69 
70 	/* init registers */
71 	bus_space_write_1(sc->sc_rt, sc->sc_rh, SIOP_SCNTL0,
72 	    SCNTL0_ARB_MASK | SCNTL0_EPC | SCNTL0_AAP);
73 	bus_space_write_1(sc->sc_rt, sc->sc_rh, SIOP_SCNTL1, 0);
74 	bus_space_write_1(sc->sc_rt, sc->sc_rh, SIOP_SCNTL3, sc->clock_div);
75 	bus_space_write_1(sc->sc_rt, sc->sc_rh, SIOP_SCXFER, 0);
76 	bus_space_write_1(sc->sc_rt, sc->sc_rh, SIOP_DIEN, 0xff);
77 	bus_space_write_1(sc->sc_rt, sc->sc_rh, SIOP_SIEN0,
78 	    0xff & ~(SIEN0_CMP | SIEN0_SEL | SIEN0_RSL));
79 	bus_space_write_1(sc->sc_rt, sc->sc_rh, SIOP_SIEN1,
80 	    0xff & ~(SIEN1_HTH | SIEN1_GEN));
81 	bus_space_write_1(sc->sc_rt, sc->sc_rh, SIOP_STEST2, 0);
82 	bus_space_write_1(sc->sc_rt, sc->sc_rh, SIOP_STEST3, STEST3_TE);
83 	bus_space_write_1(sc->sc_rt, sc->sc_rh, SIOP_STIME0,
84 	    (0xb << STIME0_SEL_SHIFT));
85 	bus_space_write_1(sc->sc_rt, sc->sc_rh, SIOP_SCID,
86 	    sc->sc_link.scsipi_scsi.adapter_target | SCID_RRE);
87 	bus_space_write_1(sc->sc_rt, sc->sc_rh, SIOP_RESPID0,
88 	    1 << sc->sc_link.scsipi_scsi.adapter_target);
89 	bus_space_write_1(sc->sc_rt, sc->sc_rh, SIOP_DCNTL,
90 	    (sc->features & SF_CHIP_PF) ? DCNTL_COM | DCNTL_PFEN : DCNTL_COM);
91 
92 	/* enable clock doubler or quadruler if appropriate */
93 	if (sc->features & (SF_CHIP_DBLR | SF_CHIP_QUAD)) {
94 		stest3 = bus_space_read_1(sc->sc_rt, sc->sc_rh, SIOP_STEST3);
95 		bus_space_write_1(sc->sc_rt, sc->sc_rh, SIOP_STEST1,
96 		    STEST1_DBLEN);
97 		if (sc->features & SF_CHIP_QUAD) {
98 			/* wait for PPL to lock */
99 			while ((bus_space_read_1(sc->sc_rt, sc->sc_rh,
100 			    SIOP_STEST4) & STEST4_LOCK) == 0)
101 				delay(10);
102 		} else {
103 			/* data sheet says 20us - more won't hurt */
104 			delay(100);
105 		}
106 		/* halt scsi clock, select doubler/quad, restart clock */
107 		bus_space_write_1(sc->sc_rt, sc->sc_rh, SIOP_STEST3,
108 		    stest3 | STEST3_HSC);
109 		bus_space_write_1(sc->sc_rt, sc->sc_rh, SIOP_STEST1,
110 		    STEST1_DBLEN | STEST1_DBLSEL);
111 		bus_space_write_1(sc->sc_rt, sc->sc_rh, SIOP_STEST3, stest3);
112 	} else {
113 		bus_space_write_1(sc->sc_rt, sc->sc_rh, SIOP_STEST1, 0);
114 	}
115 	if (sc->features & SF_CHIP_FIFO)
116 		bus_space_write_1(sc->sc_rt, sc->sc_rh, SIOP_CTEST5,
117 		    bus_space_read_1(sc->sc_rt, sc->sc_rh, SIOP_CTEST5) |
118 		    CTEST5_DFS);
119 
120 	sc->sc_reset(sc);
121 }
122 
123 int
124 siop_wdtr_neg(siop_cmd)
125 	struct siop_cmd *siop_cmd;
126 {
127 	struct siop_softc *sc = siop_cmd->siop_target->siop_sc;
128 	struct siop_target *siop_target = siop_cmd->siop_target;
129 	int target = siop_cmd->xs->sc_link->scsipi_scsi.target;
130 
131 	if (siop_target->status == TARST_WIDE_NEG) {
132 		/* we initiated wide negotiation */
133 		switch (siop_cmd->siop_table->msg_in[3]) {
134 		case MSG_EXT_WDTR_BUS_8_BIT:
135 			printf("%s: target %d using 8bit transfers\n",
136 			    sc->sc_dev.dv_xname, target);
137 			siop_target->flags &= ~SF_BUS_WIDE;
138 			sc->targets[target]->id &= ~(SCNTL3_EWS << 24);
139 			break;
140 		case MSG_EXT_WDTR_BUS_16_BIT:
141 			if (sc->features & SF_BUS_WIDE) {
142 				printf("%s: target %d using 16bit transfers\n",
143 				    sc->sc_dev.dv_xname, target);
144 				siop_target->flags |= TARF_WIDE;
145 				sc->targets[target]->id |= (SCNTL3_EWS << 24);
146 				break;
147 			}
148 		/* FALLTHROUH */
149 		default:
150 			/*
151  			 * hum, we got more than what we can handle, shoudn't
152 			 * happen. Reject, and stay async
153 			 */
154 			siop_target->flags &= ~TARF_WIDE;
155 			siop_target->status = TARST_OK;
156 			printf("%s: rejecting invalid wide negotiation from "
157 			    "target %d (%d)\n", sc->sc_dev.dv_xname, target,
158 			    siop_cmd->siop_table->msg_in[3]);
159 			siop_cmd->siop_table->t_msgout.count= htole32(1);
160 			siop_cmd->siop_table->t_msgout.addr =
161 			    htole32(siop_cmd->dsa);
162 			siop_cmd->siop_table->msg_out[0] = MSG_MESSAGE_REJECT;
163 			return SIOP_NEG_MSGOUT;
164 		}
165 		siop_cmd->siop_table->id =
166 		    htole32(sc->targets[target]->id);
167 		bus_space_write_1(sc->sc_rt, sc->sc_rh,
168 		    SIOP_SCNTL3,
169 		    (sc->targets[target]->id >> 24) & 0xff);
170 		/* we now need to do sync */
171 		siop_target->status = TARST_SYNC_NEG;
172 		siop_cmd->siop_table->msg_out[0] = MSG_EXTENDED;
173 		siop_cmd->siop_table->msg_out[1] = MSG_EXT_SDTR_LEN;
174 		siop_cmd->siop_table->msg_out[2] = MSG_EXT_SDTR;
175 		siop_cmd->siop_table->msg_out[3] = sc->minsync;
176 		siop_cmd->siop_table->msg_out[4] = sc->maxoff;
177 		siop_cmd->siop_table->t_msgout.count =
178 		    htole32(MSG_EXT_SDTR_LEN + 2);
179 		siop_cmd->siop_table->t_msgout.addr = htole32(siop_cmd->dsa);
180 		return SIOP_NEG_MSGOUT;
181 	} else {
182 		/* target initiated wide negotiation */
183 		if (siop_cmd->siop_table->msg_in[3] >= MSG_EXT_WDTR_BUS_16_BIT
184 		    && (sc->features & SF_BUS_WIDE)) {
185 			printf("%s: target %d using 16bit transfers\n",
186 			    sc->sc_dev.dv_xname, target);
187 			siop_target->flags |= TARF_WIDE;
188 			sc->targets[target]->id |= SCNTL3_EWS << 24;
189 			siop_cmd->siop_table->msg_out[3] =
190 			    MSG_EXT_WDTR_BUS_16_BIT;
191 		} else {
192 			printf("%s: target %d using 8bit transfers\n",
193 			    sc->sc_dev.dv_xname, target);
194 			siop_target->flags &= ~SF_BUS_WIDE;
195 			sc->targets[target]->id &= ~(SCNTL3_EWS << 24);
196 			siop_cmd->siop_table->msg_out[3] =
197 			    MSG_EXT_WDTR_BUS_8_BIT;
198 		}
199 		siop_cmd->siop_table->id =
200 		    htole32(sc->targets[target]->id);
201 		bus_space_write_1(sc->sc_rt, sc->sc_rh, SIOP_SCNTL3,
202 		    (sc->targets[target]->id >> 24) & 0xff);
203 		/*
204 		 * we did reset wide parameters, so fall back to async,
205 		 * but don't shedule a sync neg, target should initiate it
206 		 */
207 		siop_target->status = TARST_OK;
208 		siop_cmd->siop_table->msg_out[0] = MSG_EXTENDED;
209 		siop_cmd->siop_table->msg_out[1] = MSG_EXT_WDTR_LEN;
210 		siop_cmd->siop_table->msg_out[2] = MSG_EXT_WDTR;
211 		siop_cmd->siop_table->t_msgout.count=
212 		    htole32(MSG_EXT_WDTR_LEN + 2);
213 		siop_cmd->siop_table->t_msgout.addr = htole32(siop_cmd->dsa);
214 		return SIOP_NEG_MSGOUT;
215 	}
216 }
217 
218 int
219 siop_sdtr_neg(siop_cmd)
220 	struct siop_cmd *siop_cmd;
221 {
222 	struct siop_softc *sc = siop_cmd->siop_target->siop_sc;
223 	struct siop_target *siop_target = siop_cmd->siop_target;
224 	int target = siop_cmd->xs->sc_link->scsipi_scsi.target;
225 	int sync, offset, i;
226 	int send_msgout = 0;
227 
228 	sync = siop_cmd->siop_table->msg_in[3];
229 	offset = siop_cmd->siop_table->msg_in[4];
230 
231 	if (siop_target->status == TARST_SYNC_NEG) {
232 		/* we initiated sync negotiation */
233 		siop_target->status = TARST_OK;
234 #ifdef DEBUG
235 		printf("sdtr: sync %d offset %d\n", sync, offset);
236 #endif
237 		if (offset > sc->maxoff || sync < sc->minsync ||
238 			sync > sc->maxsync)
239 			goto reject;
240 		for (i = 0; i < sizeof(scf_period) / sizeof(scf_period[0]);
241 		    i++) {
242 			if (sc->clock_period != scf_period[i].clock)
243 				continue;
244 			if (scf_period[i].period == sync) {
245 				/* ok, found it. we now are sync. */
246 				printf("%s: target %d now synchronous at "
247 				    "%sMhz, offset %d\n", sc->sc_dev.dv_xname,
248 				    target, scf_period[i].rate, offset);
249 				sc->targets[target]->id &=
250 				    ~(SCNTL3_SCF_MASK << 24);
251 				sc->targets[target]->id |= scf_period[i].scf
252 				    << (24 + SCNTL3_SCF_SHIFT);
253 				if (sync < 25) /* Ultra */
254 					sc->targets[target]->id |=
255 					    SCNTL3_ULTRA << 24;
256 				else
257 					sc->targets[target]->id &=
258 					    ~(SCNTL3_ULTRA << 24);
259 				sc->targets[target]->id &=
260 				    ~(SCXFER_MO_MASK << 8);
261 				sc->targets[target]->id |=
262 				    (offset & SCXFER_MO_MASK) << 8;
263 				goto end;
264 			}
265 		}
266 		/*
267 		 * we didn't find it in our table, do async and send reject
268 		 * msg
269 		 */
270 reject:
271 		send_msgout = 1;
272 		siop_cmd->siop_table->t_msgout.count= htole32(1);
273 		siop_cmd->siop_table->msg_out[0] = MSG_MESSAGE_REJECT;
274 		printf("%s: target %d asynchronous\n", sc->sc_dev.dv_xname,
275 		    target);
276 		sc->targets[target]->id &= ~(SCNTL3_SCF_MASK << 24);
277 		sc->targets[target]->id &= ~(SCNTL3_ULTRA << 24);
278 		sc->targets[target]->id &= ~(SCXFER_MO_MASK << 8);
279 	} else { /* target initiated sync neg */
280 #ifdef DEBUG
281 		printf("sdtr (target): sync %d offset %d\n", sync, offset);
282 #endif
283 		if (offset == 0 || sync > sc->maxsync) { /* async */
284 			goto async;
285 		}
286 		if (offset > sc->maxoff)
287 			offset = sc->maxoff;
288 		if (sync < sc->minsync)
289 			sync = sc->minsync;
290 		/* look for sync period */
291 		for (i = 0; i < sizeof(scf_period) / sizeof(scf_period[0]);
292 		    i++) {
293 			if (sc->clock_period != scf_period[i].clock)
294 				continue;
295 			if (scf_period[i].period == sync) {
296 				/* ok, found it. we now are sync. */
297 				printf("%s: target %d now synchronous at "
298 				    "%sMhz, offset %d\n", sc->sc_dev.dv_xname,
299 				    target, scf_period[i].rate, offset);
300 				sc->targets[target]->id &=
301 				    ~(SCNTL3_SCF_MASK << 24);
302 				sc->targets[target]->id |= scf_period[i].scf
303 				    << (24 + SCNTL3_SCF_SHIFT);
304 				if (sync < 25) /* Ultra */
305 					sc->targets[target]->id |=
306 					    SCNTL3_ULTRA << 24;
307 				else
308 					sc->targets[target]->id &=
309 					    ~(SCNTL3_ULTRA << 24);
310 				sc->targets[target]->id &=
311 				    ~(SCXFER_MO_MASK << 8);
312 				sc->targets[target]->id |=
313 				    (offset & SCXFER_MO_MASK) << 8;
314 				siop_cmd->siop_table->msg_out[0] = MSG_EXTENDED;
315 				siop_cmd->siop_table->msg_out[1] =
316 				    MSG_EXT_SDTR_LEN;
317 				siop_cmd->siop_table->msg_out[2] = MSG_EXT_SDTR;
318 				siop_cmd->siop_table->msg_out[3] = sync;
319 				siop_cmd->siop_table->msg_out[4] = offset;
320 				siop_cmd->siop_table->t_msgout.count=
321 				    htole32(MSG_EXT_SDTR_LEN + 2);
322 				send_msgout = 1;
323 				goto end;
324 			}
325 		}
326 async:
327 		printf("%s: target %d asynchronous\n",
328 		    sc->sc_dev.dv_xname, target);
329 		sc->targets[target]->id &= ~(SCNTL3_SCF_MASK << 24);
330 		sc->targets[target]->id &= ~(SCNTL3_ULTRA << 24);
331 		sc->targets[target]->id &= ~(SCXFER_MO_MASK << 8);
332 		siop_cmd->siop_table->msg_out[0] = MSG_EXTENDED;
333 		siop_cmd->siop_table->msg_out[1] = MSG_EXT_SDTR_LEN;
334 		siop_cmd->siop_table->msg_out[2] = MSG_EXT_SDTR;
335 		siop_cmd->siop_table->msg_out[3] = 0;
336 		siop_cmd->siop_table->msg_out[4] = 0;
337 		siop_cmd->siop_table->t_msgout.count=
338 		    htole32(MSG_EXT_SDTR_LEN + 2);
339 		send_msgout = 1;
340 	}
341 end:
342 #ifdef DEBUG
343 	printf("id now 0x%x\n", sc->targets[target]->id);
344 #endif
345 	siop_cmd->siop_table->id = htole32(sc->targets[target]->id);
346 	bus_space_write_1(sc->sc_rt, sc->sc_rh, SIOP_SCNTL3,
347 	    (sc->targets[target]->id >> 24) & 0xff);
348 	bus_space_write_1(sc->sc_rt, sc->sc_rh, SIOP_SCXFER,
349 	    (sc->targets[target]->id >> 8) & 0xff);
350 	if (send_msgout) {
351 		siop_cmd->siop_table->t_msgout.addr = htole32(siop_cmd->dsa);
352 		return SIOP_NEG_MSGOUT;
353 	} else {
354 		return SIOP_NEG_ACK;
355 	}
356 }
357 
358 void
359 siop_minphys(bp)
360 	struct buf *bp;
361 {
362 	minphys(bp);
363 }
364 
365 int
366 siop_ioctl(link, cmd, arg, flag, p)
367 	struct scsipi_link *link;
368 	u_long cmd;
369 	caddr_t arg;
370 	int flag;
371 	struct proc *p;
372 {
373 	struct siop_softc *sc = link->adapter_softc;
374 	u_int8_t scntl1;
375 	int s;
376 
377 	switch (cmd) {
378 	case SCBUSIORESET:
379 		s = splbio();
380 		scntl1 = bus_space_read_1(sc->sc_rt, sc->sc_rh, SIOP_SCNTL1);
381 		bus_space_write_1(sc->sc_rt, sc->sc_rh, SIOP_SCNTL1,
382 		    scntl1 | SCNTL1_RST);
383 		/* minimum 25 us, more time won't hurt */
384 		delay(100);
385 		bus_space_write_1(sc->sc_rt, sc->sc_rh, SIOP_SCNTL1, scntl1);
386 		splx(s);
387 		return (0);
388 	default:
389 		return (ENOTTY);
390 	}
391 }
392 
393 void
394 siop_sdp(siop_cmd)
395 	struct siop_cmd *siop_cmd;
396 {
397 	/* save data pointer. Handle async only for now */
398 	int offset, dbc, sstat;
399 	struct siop_softc *sc = siop_cmd->siop_target->siop_sc;
400 	scr_table_t *table; /* table to patch */
401 
402 	if ((siop_cmd->xs->xs_control & (XS_CTL_DATA_OUT | XS_CTL_DATA_IN))
403 	    == 0)
404 	    return; /* no data pointers to save */
405 	offset = bus_space_read_1(sc->sc_rt, sc->sc_rh, SIOP_SCRATCHA + 1);
406 	if (offset >= SIOP_NSG) {
407 		printf("%s: bad offset in siop_sdp (%d)\n",
408 		    sc->sc_dev.dv_xname, offset);
409 		return;
410 	}
411 	table = &siop_cmd->siop_table->data[offset];
412 #ifdef DEBUG_DR
413 	printf("sdp: offset %d count=%d addr=0x%x ", offset,
414 	    table->count, table->addr);
415 #endif
416 	dbc = bus_space_read_4(sc->sc_rt, sc->sc_rh, SIOP_DBC) & 0x00ffffff;
417 	if (siop_cmd->xs->xs_control & XS_CTL_DATA_OUT) {
418 		/* need to account stale data in FIFO */
419 		int dfifo = bus_space_read_1(sc->sc_rt, sc->sc_rh, SIOP_DFIFO);
420 		if (sc->features & SF_CHIP_FIFO) {
421 			dfifo |= (bus_space_read_1(sc->sc_rt, sc->sc_rh,
422 			    SIOP_CTEST5) & CTEST5_BOMASK) << 8;
423 			dbc += (dfifo - (dbc & 0x3ff)) & 0x3ff;
424 		} else {
425 			dbc += (dfifo - (dbc & 0x7f)) & 0x7f;
426 		}
427 		sstat = bus_space_read_1(sc->sc_rt, sc->sc_rh, SIOP_SSTAT0);
428 		if (sstat & SSTAT0_OLF)
429 			dbc++;
430 		if (sstat & SSTAT0_ORF)
431 			dbc++;
432 		if (siop_cmd->siop_target->flags & TARF_WIDE) {
433 			sstat = bus_space_read_1(sc->sc_rt, sc->sc_rh,
434 			    SIOP_SSTAT2);
435 			if (sstat & SSTAT2_OLF1)
436 				dbc++;
437 			if (sstat & SSTAT2_ORF1)
438 				dbc++;
439 		}
440 		/* clear the FIFO */
441 		bus_space_write_1(sc->sc_rt, sc->sc_rh, SIOP_CTEST3,
442 		    bus_space_read_1(sc->sc_rt, sc->sc_rh, SIOP_CTEST3) |
443 		    CTEST3_CLF);
444 	}
445 	table->addr =
446 	    htole32(le32toh(table->addr) + le32toh(table->count) - dbc);
447 	table->count = htole32(dbc);
448 #ifdef DEBUG_DR
449 	printf("now count=%d addr=0x%x\n", table->count, table->addr);
450 #endif
451 }
452 
453 void
454 siop_clearfifo(sc)
455 	struct siop_softc *sc;
456 {
457 	int timeout = 0;
458 	int ctest3 = bus_space_read_1(sc->sc_rt, sc->sc_rh, SIOP_CTEST3);
459 
460 #ifdef DEBUG_INTR
461 	printf("DMA fifo not empty !\n");
462 #endif
463 	bus_space_write_1(sc->sc_rt, sc->sc_rh, SIOP_CTEST3,
464 	    ctest3 | CTEST3_CLF);
465 	while ((bus_space_read_1(sc->sc_rt, sc->sc_rh, SIOP_CTEST3) &
466 	    CTEST3_CLF) != 0) {
467 		delay(1);
468 		if (++timeout > 1000) {
469 			printf("clear fifo failed\n");
470 			bus_space_write_1(sc->sc_rt, sc->sc_rh, SIOP_CTEST3,
471 			    bus_space_read_1(sc->sc_rt, sc->sc_rh,
472 			    SIOP_CTEST3) & ~CTEST3_CLF);
473 			return;
474 		}
475 	}
476 }
477 
478 int
479 siop_modechange(sc)
480 	struct siop_softc *sc;
481 {
482 	int retry;
483 	int sist0, sist1, stest2, stest4;
484 	for (retry = 0; retry < 5; retry++) {
485 		/*
486 		 * datasheet says to wait 100ms and re-read SIST1,
487 		 * to check that DIFFSENSE is srable.
488 		 * We may delay() 5 times for  100ms at interrupt time;
489 		 * hopefully this will not happen often.
490 		 */
491 		delay(100000);
492 		sist0 = bus_space_read_1(sc->sc_rt, sc->sc_rh, SIOP_SIST0);
493 		sist1 = bus_space_read_1(sc->sc_rt, sc->sc_rh, SIOP_SIST1);
494 		if (sist1 & SIEN1_SBMC)
495 			continue; /* we got an irq again */
496 		stest4 = bus_space_read_1(sc->sc_rt, sc->sc_rh, SIOP_STEST4) &
497 		    STEST4_MODE_MASK;
498 		stest2 = bus_space_read_1(sc->sc_rt, sc->sc_rh, SIOP_STEST2);
499 		switch(stest4) {
500 		case STEST4_MODE_DIF:
501 			printf("%s: switching to differential mode\n",
502 			    sc->sc_dev.dv_xname);
503 			bus_space_write_1(sc->sc_rt, sc->sc_rh, SIOP_STEST2,
504 			    stest2 | STEST2_DIF);
505 			break;
506 		case STEST4_MODE_SE:
507 			printf("%s: switching to single-ended mode\n",
508 			    sc->sc_dev.dv_xname);
509 			bus_space_write_1(sc->sc_rt, sc->sc_rh, SIOP_STEST2,
510 			    stest2 & ~STEST2_DIF);
511 			break;
512 		case STEST4_MODE_LVD:
513 			printf("%s: switching to LVD mode\n",
514 			    sc->sc_dev.dv_xname);
515 			bus_space_write_1(sc->sc_rt, sc->sc_rh, SIOP_STEST2,
516 			    stest2 & ~STEST2_DIF);
517 			break;
518 		default:
519 			printf("%s: invalid SCSI mode 0x%x\n",
520 			    sc->sc_dev.dv_xname, stest4);
521 			return 0;
522 		}
523 		bus_space_write_1(sc->sc_rt, sc->sc_rh, SIOP_STEST0,
524 		    stest4 >> 2);
525 		return 1;
526 	}
527 	printf("%s: timeout waiting for DIFFSENSE to stabilise\n",
528 	    sc->sc_dev.dv_xname);
529 	return 0;
530 }
531