xref: /netbsd-src/sys/arch/powerpc/oea/cpu_subr.c (revision b8c616269f5ebf18ab2e35cb8099d683130a177c)
1 /*	$NetBSD: cpu_subr.c,v 1.1 2003/02/03 17:10:09 matt Exp $	*/
2 
3 /*-
4  * Copyright (c) 2001 Matt Thomas.
5  * Copyright (c) 2001 Tsubai Masanari.
6  * Copyright (c) 1998, 1999, 2001 Internet Research Institute, Inc.
7  * All rights reserved.
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 by
20  *	Internet Research Institute, Inc.
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
33  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
34  */
35 
36 #include "opt_ppcparam.h"
37 #include "opt_multiprocessor.h"
38 #include "opt_altivec.h"
39 #include "sysmon_envsys.h"
40 
41 #include <sys/param.h>
42 #include <sys/systm.h>
43 #include <sys/device.h>
44 
45 #include <uvm/uvm_extern.h>
46 
47 #include <powerpc/oea/hid.h>
48 #include <powerpc/oea/hid_601.h>
49 #include <powerpc/spr.h>
50 
51 #include <dev/sysmon/sysmonvar.h>
52 
53 static void cpu_config_l2cr(int);
54 static void cpu_print_speed(void);
55 #if NSYSMON_ENVSYS > 0
56 static void cpu_tau_setup(struct cpu_info *);
57 static int cpu_tau_gtredata __P((struct sysmon_envsys *,
58     struct envsys_tre_data *));
59 static int cpu_tau_streinfo __P((struct sysmon_envsys *,
60     struct envsys_basic_info *));
61 #endif
62 
63 int cpu;
64 int ncpus;
65 
66 #ifdef MULTIPROCESSOR
67 struct cpu_info cpu_info[CPU_MAXNUM];
68 #else
69 struct cpu_info cpu_info[1];
70 #endif
71 
72 int cpu_altivec;
73 char cpu_model[80];
74 
75 void
76 cpu_probe_cache(void)
77 {
78 	u_int assoc, pvr, vers;
79 
80 	pvr = mfpvr();
81 	vers = pvr >> 16;
82 
83 	switch (vers) {
84 #define	K	*1024
85 	case IBM750FX:
86 	case MPC601:
87 	case MPC750:
88 	case MPC7450:
89 	case MPC7455:
90 		curcpu()->ci_ci.dcache_size = 32 K;
91 		curcpu()->ci_ci.icache_size = 32 K;
92 		assoc = 8;
93 		break;
94 	case MPC603:
95 		curcpu()->ci_ci.dcache_size = 8 K;
96 		curcpu()->ci_ci.icache_size = 8 K;
97 		assoc = 2;
98 		break;
99 	case MPC603e:
100 	case MPC603ev:
101 	case MPC604:
102 	case MPC8240:
103 	case MPC8245:
104 		curcpu()->ci_ci.dcache_size = 16 K;
105 		curcpu()->ci_ci.icache_size = 16 K;
106 		assoc = 4;
107 		break;
108 	case MPC604ev:
109 		curcpu()->ci_ci.dcache_size = 32 K;
110 		curcpu()->ci_ci.icache_size = 32 K;
111 		assoc = 4;
112 		break;
113 	default:
114 		curcpu()->ci_ci.dcache_size = NBPG;
115 		curcpu()->ci_ci.icache_size = NBPG;
116 		assoc = 1;
117 #undef	K
118 	}
119 
120 	/* Presently common across all implementations. */
121 	curcpu()->ci_ci.dcache_line_size = CACHELINESIZE;
122 	curcpu()->ci_ci.icache_line_size = CACHELINESIZE;
123 
124 	/*
125 	 * Possibly recolor.
126 	 */
127 	uvm_page_recolor(atop(curcpu()->ci_ci.dcache_size / assoc));
128 }
129 
130 struct cpu_info *
131 cpu_attach_common(struct device *self, int id)
132 {
133 	struct cpu_info *ci;
134 	u_int pvr, vers;
135 
136 	ncpus++;
137 	ci = &cpu_info[id];
138 #ifndef MULTIPROCESSOR
139 	/*
140 	 * If this isn't the primary CPU, print an error message
141 	 * and just bail out.
142 	 */
143 	if (id != 0) {
144 		printf(": ID %d\n", id);
145 		printf("%s: processor off-line; multiprocessor support "
146 		    "not present in kernel\n", self->dv_xname);
147 		return (NULL);
148 	}
149 #endif
150 
151 	ci->ci_cpuid = id;
152 	ci->ci_intrdepth = -1;
153 	ci->ci_dev = self;
154 
155 	pvr = mfpvr();
156 	vers = (pvr >> 16) & 0xffff;
157 
158 	switch (id) {
159 	case 0:
160 		/* load my cpu_number to PIR */
161 		switch (vers) {
162 		case MPC601:
163 		case MPC604:
164 		case MPC604ev:
165 		case MPC7400:
166 		case MPC7410:
167 		case MPC7450:
168 		case MPC7455:
169 			mtspr(SPR_PIR, id);
170 		}
171 		cpu_setup(self, ci);
172 		break;
173 	default:
174 		if (id >= CPU_MAXNUM) {
175 			printf(": more than %d cpus?\n", CPU_MAXNUM);
176 			panic("cpuattach");
177 		}
178 #ifndef MULTIPROCESSOR
179 		printf(" not configured\n");
180 		return NULL;
181 #endif
182 	}
183 	return (ci);
184 }
185 
186 void
187 cpu_setup(self, ci)
188 	struct device *self;
189 	struct cpu_info *ci;
190 {
191 	u_int hid0, pvr, vers;
192 	char *bitmask, hidbuf[128];
193 	char model[80];
194 
195 	pvr = mfpvr();
196 	vers = (pvr >> 16) & 0xffff;
197 
198 	cpu_identify(model, sizeof(model));
199 	printf(": %s, ID %d%s\n", model,  cpu_number(),
200 	    cpu_number() == 0 ? " (primary)" : "");
201 
202 	hid0 = mfspr(SPR_HID0);
203 	cpu_probe_cache();
204 
205 	/*
206 	 * Configure power-saving mode.
207 	 */
208 	switch (vers) {
209 	case MPC603:
210 	case MPC603e:
211 	case MPC603ev:
212 	case MPC604ev:
213 	case MPC750:
214 	case IBM750FX:
215 	case MPC7400:
216 	case MPC7410:
217 	case MPC8240:
218 	case MPC8245:
219 		/* Select DOZE mode. */
220 		hid0 &= ~(HID0_DOZE | HID0_NAP | HID0_SLEEP);
221 		hid0 |= HID0_DOZE | HID0_DPM;
222 		powersave = 1;
223 		break;
224 
225 	case MPC7455:
226 	case MPC7450:
227 		/* Disable BTIC on 7450 Rev 2.0 or earlier */
228 		if ((pvr >> 16) == MPC7450 && (pvr & 0xFFFF) <= 0x0200)
229 			hid0 &= ~HID0_BTIC;
230 		/* Select NAP mode. */
231 		hid0 &= ~(HID0_DOZE | HID0_NAP | HID0_SLEEP);
232 		hid0 |= HID0_NAP | HID0_DPM;
233 		powersave = 0;		/* but don't use it */
234 		break;
235 
236 	default:
237 		/* No power-saving mode is available. */ ;
238 	}
239 
240 #ifdef NAPMODE
241 	switch (vers) {
242 	case IBM750FX:
243 	case MPC750:
244 	case MPC7400:
245 		/* Select NAP mode. */
246 		hid0 &= ~(HID0_DOZE | HID0_NAP | HID0_SLEEP);
247 		hid0 |= HID0_NAP;
248 		break;
249 	}
250 #endif
251 
252 	switch (vers) {
253 	case IBM750FX:
254 	case MPC750:
255 		hid0 &= ~HID0_DBP;		/* XXX correct? */
256 		hid0 |= HID0_EMCP | HID0_BTIC | HID0_SGE | HID0_BHT;
257 		break;
258 
259 	case MPC7400:
260 	case MPC7410:
261 		hid0 &= ~HID0_SPD;
262 		hid0 |= HID0_EMCP | HID0_BTIC | HID0_SGE | HID0_BHT;
263 		hid0 |= HID0_EIEC;
264 		break;
265 	}
266 
267 	mtspr(SPR_HID0, hid0);
268 
269 	switch (vers) {
270 	case MPC601:
271 		bitmask = HID0_601_BITMASK;
272 		break;
273 	case MPC7450:
274 	case MPC7455:
275 		bitmask = HID0_7450_BITMASK;
276 		break;
277 	default:
278 		bitmask = HID0_BITMASK;
279 		break;
280 	}
281 	bitmask_snprintf(hid0, bitmask, hidbuf, sizeof hidbuf);
282 	printf("%s: HID0 %s\n", self->dv_xname, hidbuf);
283 
284 	/*
285 	 * Display speed and cache configuration.
286 	 */
287 	if (vers == MPC750 || vers == MPC7400 || vers == IBM750FX ||
288 	    vers == MPC7410 || vers == MPC7450 || vers == MPC7455) {
289 		printf("%s", self->dv_xname);
290 		cpu_print_speed();
291 		printf("%s", self->dv_xname);
292 		cpu_config_l2cr(vers);
293 	}
294 
295 #if NSYSMON_ENVSYS > 0
296 	/*
297 	 * Attach MPC750 temperature sensor to the envsys subsystem.
298 	 * XXX the 74xx series also has this sensor, but it is not
299 	 * XXX supported by Motorola and may return values that are off by
300 	 * XXX 35-55 degrees C.
301 	 */
302 	if (vers == MPC750 || vers == IBM750FX)
303 		cpu_tau_setup(ci);
304 #endif
305 
306 	evcnt_attach_dynamic(&ci->ci_ev_clock, EVCNT_TYPE_INTR,
307 		NULL, self->dv_xname, "clock");
308 	evcnt_attach_dynamic(&ci->ci_ev_softclock, EVCNT_TYPE_INTR,
309 		NULL, self->dv_xname, "soft clock");
310 	evcnt_attach_dynamic(&ci->ci_ev_softnet, EVCNT_TYPE_INTR,
311 		NULL, self->dv_xname, "soft net");
312 	evcnt_attach_dynamic(&ci->ci_ev_softserial, EVCNT_TYPE_INTR,
313 		NULL, self->dv_xname, "soft serial");
314 	evcnt_attach_dynamic(&ci->ci_ev_traps, EVCNT_TYPE_TRAP,
315 		NULL, self->dv_xname, "traps");
316 	evcnt_attach_dynamic(&ci->ci_ev_kdsi, EVCNT_TYPE_TRAP,
317 		&ci->ci_ev_traps, self->dv_xname, "kernel DSI traps");
318 	evcnt_attach_dynamic(&ci->ci_ev_udsi, EVCNT_TYPE_TRAP,
319 		&ci->ci_ev_traps, self->dv_xname, "user DSI traps");
320 	evcnt_attach_dynamic(&ci->ci_ev_udsi_fatal, EVCNT_TYPE_TRAP,
321 		&ci->ci_ev_udsi, self->dv_xname, "user DSI failures");
322 	evcnt_attach_dynamic(&ci->ci_ev_isi, EVCNT_TYPE_TRAP,
323 		&ci->ci_ev_traps, self->dv_xname, "user ISI traps");
324 	evcnt_attach_dynamic(&ci->ci_ev_isi_fatal, EVCNT_TYPE_TRAP,
325 		&ci->ci_ev_isi, self->dv_xname, "user ISI failures");
326 	evcnt_attach_dynamic(&ci->ci_ev_scalls, EVCNT_TYPE_TRAP,
327 		&ci->ci_ev_traps, self->dv_xname, "system call traps");
328 	evcnt_attach_dynamic(&ci->ci_ev_pgm, EVCNT_TYPE_TRAP,
329 		&ci->ci_ev_traps, self->dv_xname, "PGM traps");
330 	evcnt_attach_dynamic(&ci->ci_ev_fpu, EVCNT_TYPE_TRAP,
331 		&ci->ci_ev_traps, self->dv_xname, "FPU unavailable traps");
332 	evcnt_attach_dynamic(&ci->ci_ev_fpusw, EVCNT_TYPE_TRAP,
333 		&ci->ci_ev_fpu, self->dv_xname, "FPU context switches");
334 	evcnt_attach_dynamic(&ci->ci_ev_ali, EVCNT_TYPE_TRAP,
335 		&ci->ci_ev_traps, self->dv_xname, "user alignment traps");
336 	evcnt_attach_dynamic(&ci->ci_ev_ali_fatal, EVCNT_TYPE_TRAP,
337 		&ci->ci_ev_ali, self->dv_xname, "user alignment traps");
338 	evcnt_attach_dynamic(&ci->ci_ev_umchk, EVCNT_TYPE_TRAP,
339 		&ci->ci_ev_umchk, self->dv_xname, "user MCHK failures");
340 	evcnt_attach_dynamic(&ci->ci_ev_vec, EVCNT_TYPE_TRAP,
341 		&ci->ci_ev_traps, self->dv_xname, "AltiVec unavailable");
342 #ifdef ALTIVEC
343 	if (cpu_altivec) {
344 		evcnt_attach_dynamic(&ci->ci_ev_vecsw, EVCNT_TYPE_TRAP,
345 		    &ci->ci_ev_vec, self->dv_xname, "AltiVec context switches");
346 	}
347 #endif
348 }
349 
350 struct cputab {
351 	const char name[8];
352 	uint16_t version;
353 	uint16_t revfmt;
354 };
355 #define	REVFMT_MAJMIN	1		/* %u.%u */
356 #define	REVFMT_HEX	2		/* 0x%04x */
357 #define	REVFMT_DEC	3		/* %u */
358 static const struct cputab models[] = {
359 	{ "601",	MPC601,		REVFMT_DEC },
360 	{ "602",	MPC602,		REVFMT_DEC },
361 	{ "603",	MPC603,		REVFMT_MAJMIN },
362 	{ "603e",	MPC603e,	REVFMT_MAJMIN },
363 	{ "603ev",	MPC603ev,	REVFMT_MAJMIN },
364 	{ "604",	MPC604,		REVFMT_MAJMIN },
365 	{ "604ev",	MPC604ev,	REVFMT_MAJMIN },
366 	{ "620",	MPC620,  	REVFMT_HEX },
367 	{ "750",	MPC750,		REVFMT_MAJMIN },
368 	{ "750FX",	IBM750FX,	REVFMT_MAJMIN },
369 	{ "7400",	MPC7400,	REVFMT_MAJMIN },
370 	{ "7410",	MPC7410,	REVFMT_MAJMIN },
371 	{ "7450",	MPC7450,	REVFMT_MAJMIN },
372 	{ "7455",	MPC7455,	REVFMT_MAJMIN },
373 	{ "8240",	MPC8240,	REVFMT_MAJMIN },
374 	{ "",		0,		REVFMT_HEX }
375 };
376 
377 void
378 cpu_identify(char *str, size_t len)
379 {
380 	u_int pvr, maj, min;
381 	uint16_t vers, rev, revfmt;
382 	const struct cputab *cp;
383 	const char *name;
384 	size_t n;
385 
386 	pvr = mfpvr();
387 	vers = pvr >> 16;
388 	rev = pvr;
389 	switch (vers) {
390 	case MPC7410:
391 		min = (pvr >> 0) & 0xff;
392 		maj = min <= 4 ? 1 : 2;
393 		break;
394 	default:
395 		maj = (pvr >>  8) & 0xf;
396 		min = (pvr >>  0) & 0xf;
397 	}
398 
399 	for (cp = models; cp->name[0] != '\0'; cp++) {
400 		if (cp->version == vers)
401 			break;
402 	}
403 
404 	if (str == NULL) {
405 		str = cpu_model;
406 		len = sizeof(cpu_model);
407 		cpu = vers;
408 	}
409 
410 	revfmt = cp->revfmt;
411 	name = cp->name;
412 	if (rev == MPC750 && pvr == 15) {
413 		name = "755";
414 		revfmt = REVFMT_HEX;
415 	}
416 
417 	if (cp->name[0] != '\0') {
418 		n = snprintf(str, len, "%s (Revision ", cp->name);
419 	} else {
420 		n = snprintf(str, len, "Version %#x (Revision ", vers);
421 	}
422 	if (len > n) {
423 		switch (revfmt) {
424 		case REVFMT_MAJMIN:
425 			snprintf(str + n, len - n, "%u.%u)", maj, min);
426 			break;
427 		case REVFMT_HEX:
428 			snprintf(str + n, len - n, "0x%04x)", rev);
429 			break;
430 		case REVFMT_DEC:
431 			snprintf(str + n, len - n, "%u)", rev);
432 			break;
433 		}
434 	}
435 }
436 
437 #ifdef L2CR_CONFIG
438 u_int l2cr_config = L2CR_CONFIG;
439 #else
440 u_int l2cr_config = 0;
441 #endif
442 
443 void
444 cpu_config_l2cr(int vers)
445 {
446 	u_int l2cr, x, msr;
447 
448 	l2cr = mfspr(SPR_L2CR);
449 
450 	/*
451 	 * For MP systems, the firmware may only configure the L2 cache
452 	 * on the first CPU.  In this case, assume that the other CPUs
453 	 * should use the same value for L2CR.
454 	 */
455 	if ((l2cr & L2CR_L2E) != 0 && l2cr_config == 0) {
456 		l2cr_config = l2cr;
457 	}
458 
459 	/*
460 	 * Configure L2 cache if not enabled.
461 	 */
462 	if ((l2cr & L2CR_L2E) == 0 && l2cr_config != 0) {
463 		l2cr = l2cr_config;
464 
465 		/* Disable interrupts and set the cache config bits. */
466 		msr = mfmsr();
467 		mtmsr(msr & ~PSL_EE);
468 #ifdef ALTIVEC
469 		if (cpu_altivec)
470 			__asm __volatile("dssall");
471 #endif
472 		__asm __volatile("sync");
473 		mtspr(SPR_L2CR, l2cr & ~L2CR_L2E);
474 		__asm __volatile("sync");
475 
476 		/* Wait for L2 clock to be stable (640 L2 clocks). */
477 		delay(100);
478 
479 		/* Invalidate all L2 contents. */
480 		mtspr(SPR_L2CR, l2cr | L2CR_L2I);
481 		do {
482 			x = mfspr(SPR_L2CR);
483 		} while (x & L2CR_L2IP);
484 
485 		/* Enable L2 cache. */
486 		l2cr |= L2CR_L2E;
487 		mtspr(SPR_L2CR, l2cr);
488 		mtmsr(msr);
489 	}
490 
491 	if (l2cr & L2CR_L2E) {
492 		if (vers == MPC7450 || vers == MPC7455) {
493 			u_int l3cr;
494 
495 			printf(": 256KB L2 cache");
496 
497 			l3cr = mfspr(SPR_L3CR);
498 			if (l3cr & L3CR_L3E)
499 				printf(", %cMB L3 backside cache",
500 				   l3cr & L3CR_L3SIZ ? '2' : '1');
501 			printf("\n");
502 			return;
503 		}
504 		if (vers == IBM750FX) {
505 			printf(": 512KB L2 cache\n");
506 			return;
507 		}
508 		switch (l2cr & L2CR_L2SIZ) {
509 		case L2SIZ_256K:
510 			printf(": 256KB");
511 			break;
512 		case L2SIZ_512K:
513 			printf(": 512KB");
514 			break;
515 		case L2SIZ_1M:
516 			printf(": 1MB");
517 			break;
518 		default:
519 			printf(": unknown size");
520 		}
521 		if (l2cr & L2CR_L2WT) {
522 			printf(" write-through");
523 		} else {
524 			printf(" write-back");
525 		}
526 		switch (l2cr & L2CR_L2RAM) {
527 		case L2RAM_FLOWTHRU_BURST:
528 			printf(" Flow-through synchronous burst SRAM");
529 			break;
530 		case L2RAM_PIPELINE_BURST:
531 			printf(" Pipelined synchronous burst SRAM");
532 			break;
533 		case L2RAM_PIPELINE_LATE:
534 			printf(" Pipelined synchronous late-write SRAM");
535 			break;
536 		default:
537 			printf(" unknown type");
538 		}
539 
540 		if (l2cr & L2CR_L2PE)
541 			printf(" with parity");
542 		printf(" backside cache");
543 	} else
544 		printf(": L2 cache not enabled");
545 
546 	printf("\n");
547 }
548 
549 void
550 cpu_print_speed(void)
551 {
552 	uint64_t cps;
553 
554 	mtspr(SPR_MMCR0, SPR_MMCR0_FC);
555 	mtspr(SPR_PMC1, 0);
556 	mtspr(SPR_MMCR0, SPR_MMCR0_PMC1SEL(PMCN_CYCLES));
557 	delay(100000);
558 	cps = (mfspr(SPR_PMC1) * 10) + 4999;
559 
560 	printf(": %lld.%02lld MHz\n", cps / 1000000, (cps / 10000) % 100);
561 }
562 
563 #if NSYSMON_ENVSYS > 0
564 const struct envsys_range cpu_tau_ranges[] = {
565 	{ 0, 0, ENVSYS_STEMP}
566 };
567 
568 struct envsys_basic_info cpu_tau_info[] = {
569 	{ 0, ENVSYS_STEMP, "CPU temp", 0, 0, ENVSYS_FVALID}
570 };
571 
572 void
573 cpu_tau_setup(struct cpu_info *ci)
574 {
575 	struct sysmon_envsys *sme;
576 	int error;
577 
578 	sme = &ci->ci_sysmon;
579 	sme->sme_nsensors = 1;
580 	sme->sme_envsys_version = 1000;
581 	sme->sme_ranges = cpu_tau_ranges;
582 	sme->sme_sensor_info = cpu_tau_info;
583 	sme->sme_sensor_data = &ci->ci_tau_info;
584 
585 	sme->sme_sensor_data->sensor = 0;
586 	sme->sme_sensor_data->warnflags = ENVSYS_WARN_OK;
587 	sme->sme_sensor_data->validflags = ENVSYS_FVALID|ENVSYS_FCURVALID;
588 	sme->sme_cookie = ci;
589 	sme->sme_gtredata = cpu_tau_gtredata;
590 	sme->sme_streinfo = cpu_tau_streinfo;
591 
592 	if ((error = sysmon_envsys_register(sme)) != 0)
593 		printf("%s: unable to register with sysmon (%d)\n",
594 		    ci->ci_dev->dv_xname, error);
595 }
596 
597 
598 /* Find the temperature of the CPU. */
599 int
600 cpu_tau_gtredata(sme, tred)
601 	 struct sysmon_envsys *sme;
602 	 struct envsys_tre_data *tred;
603 {
604 	struct cpu_info *ci;
605 	int i, threshold, count;
606 
607 	if (tred->sensor != 0) {
608 		tred->validflags = 0;
609 		return 0;
610 	}
611 
612 	threshold = 64; /* Half of the 7-bit sensor range */
613 	mtspr(SPR_THRM1, 0);
614 	mtspr(SPR_THRM2, 0);
615 	/* XXX This counter is supposed to be "at least 20 microseonds, in
616 	 * XXX units of clock cycles". Since we don't have convenient
617 	 * XXX access to the CPU speed, set it to a conservative value,
618 	 * XXX that is, assuming a fast (1GHz) G3 CPU (As of February 2002,
619 	 * XXX the fastest G3 processor is 700MHz) . The cost is that
620 	 * XXX measuring the temperature takes a bit longer.
621 	 */
622         mtspr(SPR_THRM3, SPR_THRM_TIMER(20000) | SPR_THRM_ENABLE);
623 
624 	/* Successive-approximation code adapted from Motorola
625 	 * application note AN1800/D, "Programming the Thermal Assist
626 	 * Unit in the MPC750 Microprocessor".
627 	 */
628 	for (i = 4; i >= 0 ; i--) {
629 		mtspr(SPR_THRM1,
630 		    SPR_THRM_THRESHOLD(threshold) | SPR_THRM_VALID);
631 		count = 0;
632 		while ((count < 100) &&
633 		    ((mfspr(SPR_THRM1) & SPR_THRM_TIV) == 0)) {
634 			count++;
635 			delay(1);
636 		}
637 		if (mfspr(SPR_THRM1) & SPR_THRM_TIN) {
638 			/* The interrupt bit was set, meaning the
639 			 * temperature was above the threshold
640 			 */
641 			threshold += 2 << i;
642 		} else {
643 			/* Temperature was below the threshold */
644 			threshold -= 2 << i;
645 		}
646 	}
647 	threshold += 2;
648 
649 	ci = (struct cpu_info *)sme->sme_cookie;
650 	/* Convert the temperature in degrees C to microkelvin */
651 	ci->ci_tau_info.cur.data_us = (threshold * 1000000) + 273150000;
652 
653 	*tred = ci->ci_tau_info;
654 
655 	return 0;
656 }
657 
658 int
659 cpu_tau_streinfo(sme, binfo)
660 	 struct sysmon_envsys *sme;
661 	 struct envsys_basic_info *binfo;
662 {
663 
664 	/* There is nothing to set here. */
665 	return (EINVAL);
666 }
667 #endif /* NSYSMON_ENVSYS > 0 */
668