aboutsummaryrefslogtreecommitdiff
path: root/sys/kern/kern_cpu.c
blob: f9a541dcf8e76aaec14a62e050e1a26f00b6915b (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
/*-
 * Copyright (c) 2004-2005 Nate Lawson (SDG)
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");

#include <sys/param.h>
#include <sys/bus.h>
#include <sys/cpu.h>
#include <sys/eventhandler.h>
#include <sys/kernel.h>
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/module.h>
#include <sys/proc.h>
#include <sys/queue.h>
#include <sys/sched.h>
#include <sys/sysctl.h>
#include <sys/systm.h>
#include <sys/sbuf.h>
#include <sys/sx.h>
#include <sys/timetc.h>

#include "cpufreq_if.h"

/*
 * Common CPU frequency glue code.  Drivers for specific hardware can
 * attach this interface to allow users to get/set the CPU frequency.
 */

/*
 * Number of levels we can handle.  Levels are synthesized from settings
 * so for M settings and N drivers, there may be M*N levels.
 */
#define CF_MAX_LEVELS	64

struct cpufreq_softc {
	struct sx			lock;
	struct cf_level			curr_level;
	int				curr_priority;
	struct cf_level			saved_level;
	int				saved_priority;
	struct cf_level_lst		all_levels;
	int				all_count;
	int				max_mhz;
	device_t			dev;
	struct sysctl_ctx_list		sysctl_ctx;
};

struct cf_setting_array {
	struct cf_setting		sets[MAX_SETTINGS];
	int				count;
	TAILQ_ENTRY(cf_setting_array)	link;
};

TAILQ_HEAD(cf_setting_lst, cf_setting_array);

#define CF_MTX_INIT(x)		sx_init((x), "cpufreq lock")
#define CF_MTX_LOCK(x)		sx_xlock((x))
#define CF_MTX_UNLOCK(x)	sx_xunlock((x))
#define CF_MTX_ASSERT(x)	sx_assert((x), SX_XLOCKED)

#define CF_DEBUG(msg...)	do {		\
	if (cf_verbose)				\
		printf("cpufreq: " msg);	\
	} while (0)

static int	cpufreq_attach(device_t dev);
static int	cpufreq_detach(device_t dev);
static void	cpufreq_evaluate(void *arg);
static int	cf_set_method(device_t dev, const struct cf_level *level,
		    int priority);
static int	cf_get_method(device_t dev, struct cf_level *level);
static int	cf_levels_method(device_t dev, struct cf_level *levels,
		    int *count);
static int	cpufreq_insert_abs(struct cpufreq_softc *sc,
		    struct cf_setting *sets, int count);
static int	cpufreq_expand_set(struct cpufreq_softc *sc,
		    struct cf_setting_array *set_arr);
static struct cf_level *cpufreq_dup_set(struct cpufreq_softc *sc,
		    struct cf_level *dup, struct cf_setting *set);
static int	cpufreq_curr_sysctl(SYSCTL_HANDLER_ARGS);
static int	cpufreq_levels_sysctl(SYSCTL_HANDLER_ARGS);
static int	cpufreq_settings_sysctl(SYSCTL_HANDLER_ARGS);

static device_method_t cpufreq_methods[] = {
	DEVMETHOD(device_probe,		bus_generic_probe),
	DEVMETHOD(device_attach,	cpufreq_attach),
	DEVMETHOD(device_detach,	cpufreq_detach),

        DEVMETHOD(cpufreq_set,		cf_set_method),
        DEVMETHOD(cpufreq_get,		cf_get_method),
        DEVMETHOD(cpufreq_levels,	cf_levels_method),
	{0, 0}
};
static driver_t cpufreq_driver = {
	"cpufreq", cpufreq_methods, sizeof(struct cpufreq_softc)
};
static devclass_t cpufreq_dc;
DRIVER_MODULE(cpufreq, cpu, cpufreq_driver, cpufreq_dc, 0, 0);

static eventhandler_tag	cf_ev_tag;

static int		cf_lowest_freq;
static int		cf_verbose;
TUNABLE_INT("debug.cpufreq.lowest", &cf_lowest_freq);
TUNABLE_INT("debug.cpufreq.verbose", &cf_verbose);
SYSCTL_NODE(_debug, OID_AUTO, cpufreq, CTLFLAG_RD, NULL, "cpufreq debugging");
SYSCTL_INT(_debug_cpufreq, OID_AUTO, lowest, CTLFLAG_RW, &cf_lowest_freq, 1,
    "Don't provide levels below this frequency.");
SYSCTL_INT(_debug_cpufreq, OID_AUTO, verbose, CTLFLAG_RW, &cf_verbose, 1,
    "Print verbose debugging messages");

static int
cpufreq_attach(device_t dev)
{
	struct cpufreq_softc *sc;
	device_t parent;
	int numdevs;

	CF_DEBUG("initializing %s\n", device_get_nameunit(dev));
	sc = device_get_softc(dev);
	parent = device_get_parent(dev);
	sc->dev = dev;
	sysctl_ctx_init(&sc->sysctl_ctx);
	TAILQ_INIT(&sc->all_levels);
	CF_MTX_INIT(&sc->lock);
	sc->curr_level.total_set.freq = CPUFREQ_VAL_UNKNOWN;
	sc->saved_level.total_set.freq = CPUFREQ_VAL_UNKNOWN;
	sc->max_mhz = CPUFREQ_VAL_UNKNOWN;

	/*
	 * Only initialize one set of sysctls for all CPUs.  In the future,
	 * if multiple CPUs can have different settings, we can move these
	 * sysctls to be under every CPU instead of just the first one.
	 */
	numdevs = devclass_get_count(cpufreq_dc);
	if (numdevs > 1)
		return (0);

	CF_DEBUG("initializing one-time data for %s\n",
	    device_get_nameunit(dev));
	SYSCTL_ADD_PROC(&sc->sysctl_ctx,
	    SYSCTL_CHILDREN(device_get_sysctl_tree(parent)),
	    OID_AUTO, "freq", CTLTYPE_INT | CTLFLAG_RW, sc, 0,
	    cpufreq_curr_sysctl, "I", "Current CPU frequency");
	SYSCTL_ADD_PROC(&sc->sysctl_ctx,
	    SYSCTL_CHILDREN(device_get_sysctl_tree(parent)),
	    OID_AUTO, "freq_levels", CTLTYPE_STRING | CTLFLAG_RD, sc, 0,
	    cpufreq_levels_sysctl, "A", "CPU frequency levels");
	cf_ev_tag = EVENTHANDLER_REGISTER(cpufreq_changed, cpufreq_evaluate,
	    NULL, EVENTHANDLER_PRI_ANY);

	return (0);
}

static int
cpufreq_detach(device_t dev)
{
	struct cpufreq_softc *sc;
	int numdevs;

	CF_DEBUG("shutdown %s\n", device_get_nameunit(dev));
	sc = device_get_softc(dev);
	sysctl_ctx_free(&sc->sysctl_ctx);

	/* Only clean up these resources when the last device is detaching. */
	numdevs = devclass_get_count(cpufreq_dc);
	if (numdevs == 1) {
		CF_DEBUG("final shutdown for %s\n", device_get_nameunit(dev));
		EVENTHANDLER_DEREGISTER(cpufreq_changed, cf_ev_tag);
	}

	return (0);
}

static void
cpufreq_evaluate(void *arg)
{
	/* TODO: Re-evaluate when notified of changes to drivers. */
}

static int
cf_set_method(device_t dev, const struct cf_level *level, int priority)
{
	struct cpufreq_softc *sc;
	const struct cf_setting *set;
	struct pcpu *pc;
	int cpu_id, error, i;

	sc = device_get_softc(dev);
	error = 0;
	set = NULL;

	/*
	 * Check that the TSC isn't being used as a timecounter.
	 * If it is, then return EBUSY and refuse to change the
	 * clock speed.
	 */
	if (strcmp(timecounter->tc_name, "TSC") == 0)
		return (EBUSY);

	/*
	 * If the caller didn't specify a level and one is saved, prepare to
	 * restore the saved level.  If none has been saved, return an error.
	 * If they did specify one, but the requested level has a lower
	 * priority, don't allow the new level right now.
	 */
	CF_MTX_LOCK(&sc->lock);
	if (level == NULL) {
		if (sc->saved_level.total_set.freq != CPUFREQ_VAL_UNKNOWN) {
			level = &sc->saved_level;
			priority = sc->saved_priority;
			CF_DEBUG("restoring saved level, freq %d prio %d\n",
			    level->total_set.freq, priority);
		} else {
			CF_DEBUG("NULL level, no saved level\n");
			error = ENXIO;
			goto out;
		}
	} else if (priority < sc->curr_priority) {
		CF_DEBUG("ignoring, curr prio %d less than %d\n", priority,
		    sc->curr_priority);
		error = EPERM;
		goto out;
	}

	/* Reject levels that are below our specified threshold. */
	if (level->total_set.freq <= cf_lowest_freq) {
		CF_DEBUG("rejecting freq %d, less than %d limit\n",
		    level->total_set.freq, cf_lowest_freq);
		error = EINVAL;
		goto out;
	}

	/* If already at this level, just return. */
	if (CPUFREQ_CMP(sc->curr_level.total_set.freq, level->total_set.freq)) {
		CF_DEBUG("skipping freq %d, same as current level %d\n",
		    level->total_set.freq, sc->curr_level.total_set.freq);
		goto out;
	}

	/* First, set the absolute frequency via its driver. */
	set = &level->abs_set;
	if (set->dev) {
		if (!device_is_attached(set->dev)) {
			error = ENXIO;
			goto out;
		}

		/* Bind to the target CPU before switching, if necessary. */
		cpu_id = PCPU_GET(cpuid);
		pc = cpu_get_pcpu(set->dev);
		if (cpu_id != pc->pc_cpuid) {
			mtx_lock_spin(&sched_lock);
			sched_bind(curthread, pc->pc_cpuid);
			mtx_unlock_spin(&sched_lock);
		}
		CF_DEBUG("setting abs freq %d on %s (cpu %d)\n", set->freq,
		    device_get_nameunit(set->dev), PCPU_GET(cpuid));
		error = CPUFREQ_DRV_SET(set->dev, set);
		if (cpu_id != pc->pc_cpuid) {
			mtx_lock_spin(&sched_lock);
			sched_unbind(curthread);
			mtx_unlock_spin(&sched_lock);
		}
		if (error) {
			goto out;
		}
	}

	/* Next, set any/all relative frequencies via their drivers. */
	for (i = 0; i < level->rel_count; i++) {
		set = &level->rel_set[i];
		if (!device_is_attached(set->dev)) {
			error = ENXIO;
			goto out;
		}

		/* Bind to the target CPU before switching, if necessary. */
		cpu_id = PCPU_GET(cpuid);
		pc = cpu_get_pcpu(set->dev);
		if (cpu_id != pc->pc_cpuid) {
			mtx_lock_spin(&sched_lock);
			sched_bind(curthread, pc->pc_cpuid);
			mtx_unlock_spin(&sched_lock);
		}
		CF_DEBUG("setting rel freq %d on %s (cpu %d)\n", set->freq,
		    device_get_nameunit(set->dev), PCPU_GET(cpuid));
		error = CPUFREQ_DRV_SET(set->dev, set);
		if (cpu_id != pc->pc_cpuid) {
			mtx_lock_spin(&sched_lock);
			sched_unbind(curthread);
			mtx_unlock_spin(&sched_lock);
		}
		if (error) {
			/* XXX Back out any successful setting? */
			goto out;
		}
	}

	/* If we were restoring a saved state, reset it to "unused". */
	if (level == &sc->saved_level) {
		CF_DEBUG("resetting saved level\n");
		sc->saved_level.total_set.freq = CPUFREQ_VAL_UNKNOWN;
		sc->saved_priority = 0;
	}

	/*
	 * Before recording the current level, check if we're going to a
	 * higher priority and have not saved a level yet.  If so, save the
	 * previous level and priority.
	 */
	if (sc->curr_level.total_set.freq != CPUFREQ_VAL_UNKNOWN &&
	    sc->saved_level.total_set.freq == CPUFREQ_VAL_UNKNOWN &&
	    priority > sc->curr_priority) {
		CF_DEBUG("saving level, freq %d prio %d\n",
		    sc->curr_level.total_set.freq, sc->curr_priority);
		sc->saved_level = sc->curr_level;
		sc->saved_priority = sc->curr_priority;
	}
	sc->curr_level = *level;
	sc->curr_priority = priority;
	error = 0;

out:
	CF_MTX_UNLOCK(&sc->lock);
	if (error && set)
		device_printf(set->dev, "set freq failed, err %d\n", error);
	return (error);
}

static int
cf_get_method(device_t dev, struct cf_level *level)
{
	struct cpufreq_softc *sc;
	struct cf_level *levels;
	struct cf_setting *curr_set, set;
	struct pcpu *pc;
	device_t *devs;
	int count, error, i, numdevs;
	uint64_t rate;

	sc = device_get_softc(dev);
	error = 0;
	levels = NULL;

	/* If we already know the current frequency, we're done. */
	CF_MTX_LOCK(&sc->lock);
	curr_set = &sc->curr_level.total_set;
	if (curr_set->freq != CPUFREQ_VAL_UNKNOWN) {
		CF_DEBUG("get returning known freq %d\n", curr_set->freq);
		goto out;
	}
	CF_MTX_UNLOCK(&sc->lock);

	/*
	 * We need to figure out the current level.  Loop through every
	 * driver, getting the current setting.  Then, attempt to get a best
	 * match of settings against each level.
	 */
	count = CF_MAX_LEVELS;
	levels = malloc(count * sizeof(*levels), M_TEMP, M_NOWAIT);
	if (levels == NULL)
		return (ENOMEM);
	error = CPUFREQ_LEVELS(sc->dev, levels, &count);
	if (error) {
		if (error == E2BIG)
			printf("cpufreq: need to increase CF_MAX_LEVELS\n");
		free(levels, M_TEMP);
		return (error);
	}
	error = device_get_children(device_get_parent(dev), &devs, &numdevs);
	if (error) {
		free(levels, M_TEMP);
		return (error);
	}

	/*
	 * Reacquire the lock and search for the given level.
	 *
	 * XXX Note: this is not quite right since we really need to go
	 * through each level and compare both absolute and relative
	 * settings for each driver in the system before making a match.
	 * The estimation code below catches this case though.
	 */
	CF_MTX_LOCK(&sc->lock);
	for (i = 0; i < numdevs && curr_set->freq == CPUFREQ_VAL_UNKNOWN; i++) {
		if (!device_is_attached(devs[i]))
			continue;
		error = CPUFREQ_DRV_GET(devs[i], &set);
		if (error)
			continue;
		for (i = 0; i < count; i++) {
			if (CPUFREQ_CMP(set.freq, levels[i].total_set.freq)) {
				sc->curr_level = levels[i];
				break;
			}
		}
	}
	free(devs, M_TEMP);
	if (curr_set->freq != CPUFREQ_VAL_UNKNOWN) {
		CF_DEBUG("get matched freq %d from drivers\n", curr_set->freq);
		goto out;
	}

	/*
	 * We couldn't find an exact match, so attempt to estimate and then
	 * match against a level.
	 */
	pc = cpu_get_pcpu(dev);
	if (pc == NULL) {
		error = ENXIO;
		goto out;
	}
	cpu_est_clockrate(pc->pc_cpuid, &rate);
	rate /= 1000000;
	for (i = 0; i < count; i++) {
		if (CPUFREQ_CMP(rate, levels[i].total_set.freq)) {
			sc->curr_level = levels[i];
			CF_DEBUG("get estimated freq %d\n", curr_set->freq);
			break;
		}
	}

out:
	if (error == 0)
		*level = sc->curr_level;

	CF_MTX_UNLOCK(&sc->lock);
	if (levels)
		free(levels, M_TEMP);
	return (error);
}

static int
cf_levels_method(device_t dev, struct cf_level *levels, int *count)
{
	struct cf_setting_array *set_arr;
	struct cf_setting_lst rel_sets;
	struct cpufreq_softc *sc;
	struct cf_level *lev;
	struct cf_setting *sets;
	struct pcpu *pc;
	device_t *devs;
	int error, i, numdevs, set_count, type;
	uint64_t rate;

	if (levels == NULL || count == NULL)
		return (EINVAL);

	TAILQ_INIT(&rel_sets);
	sc = device_get_softc(dev);
	error = device_get_children(device_get_parent(dev), &devs, &numdevs);
	if (error)
		return (error);
	sets = malloc(MAX_SETTINGS * sizeof(*sets), M_TEMP, M_NOWAIT);
	if (sets == NULL) {
		free(devs, M_TEMP);
		return (ENOMEM);
	}

	/* Get settings from all cpufreq drivers. */
	CF_MTX_LOCK(&sc->lock);
	for (i = 0; i < numdevs; i++) {
		/* Skip devices that aren't ready. */
		if (!device_is_attached(devs[i]))
			continue;

		/*
		 * Get settings, skipping drivers that offer no settings or
		 * provide settings for informational purposes only.
		 */
		error = CPUFREQ_DRV_TYPE(devs[i], &type);
		if (error || (type & CPUFREQ_FLAG_INFO_ONLY)) {
			if (error == 0) {
				CF_DEBUG("skipping info-only driver %s\n",
				    device_get_nameunit(devs[i]));
			}
			continue;
		}
		set_count = MAX_SETTINGS;
		error = CPUFREQ_DRV_SETTINGS(devs[i], sets, &set_count);
		if (error || set_count == 0)
			continue;

		/* Add the settings to our absolute/relative lists. */
		switch (type & CPUFREQ_TYPE_MASK) {
		case CPUFREQ_TYPE_ABSOLUTE:
			error = cpufreq_insert_abs(sc, sets, set_count);
			break;
		case CPUFREQ_TYPE_RELATIVE:
			CF_DEBUG("adding %d relative settings\n", set_count);
			set_arr = malloc(sizeof(*set_arr), M_TEMP, M_NOWAIT);
			if (set_arr == NULL) {
				error = ENOMEM;
				goto out;
			}
			bcopy(sets, set_arr->sets, set_count * sizeof(*sets));
			set_arr->count = set_count;
			TAILQ_INSERT_TAIL(&rel_sets, set_arr, link);
			break;
		default:
			error = EINVAL;
		}
		if (error)
			goto out;
	}

	/*
	 * If there are no absolute levels, create a fake one at 100%.  We
	 * then cache the clockrate for later use as our base frequency.
	 *
	 * XXX This assumes that the first time through, if we only have
	 * relative drivers, the CPU is currently running at 100%.
	 */
	if (TAILQ_EMPTY(&sc->all_levels)) {
		if (sc->max_mhz == CPUFREQ_VAL_UNKNOWN) {
			pc = cpu_get_pcpu(dev);
			cpu_est_clockrate(pc->pc_cpuid, &rate);
			sc->max_mhz = rate / 1000000;
		}
		memset(&sets[0], CPUFREQ_VAL_UNKNOWN, sizeof(*sets));
		sets[0].freq = sc->max_mhz;
		sets[0].dev = NULL;
		error = cpufreq_insert_abs(sc, sets, 1);
		if (error)
			goto out;
	}

	/* Create a combined list of absolute + relative levels. */
	TAILQ_FOREACH(set_arr, &rel_sets, link)
		cpufreq_expand_set(sc, set_arr);

	/* If the caller doesn't have enough space, return the actual count. */
	if (sc->all_count > *count) {
		*count = sc->all_count;
		error = E2BIG;
		goto out;
	}

	/* Finally, output the list of levels. */
	i = 0;
	TAILQ_FOREACH(lev, &sc->all_levels, link) {
		/* Skip levels that have a frequency that is too low. */
		if (lev->total_set.freq <= cf_lowest_freq) {
			sc->all_count--;
			continue;
		}

		levels[i] = *lev;
		i++;
	}
	*count = sc->all_count;
	error = 0;

out:
	/* Clear all levels since we regenerate them each time. */
	while ((lev = TAILQ_FIRST(&sc->all_levels)) != NULL) {
		TAILQ_REMOVE(&sc->all_levels, lev, link);
		free(lev, M_TEMP);
	}
	sc->all_count = 0;

	CF_MTX_UNLOCK(&sc->lock);
	while ((set_arr = TAILQ_FIRST(&rel_sets)) != NULL) {
		TAILQ_REMOVE(&rel_sets, set_arr, link);
		free(set_arr, M_TEMP);
	}
	free(devs, M_TEMP);
	free(sets, M_TEMP);
	return (error);
}

/*
 * Create levels for an array of absolute settings and insert them in
 * sorted order in the specified list.
 */
static int
cpufreq_insert_abs(struct cpufreq_softc *sc, struct cf_setting *sets,
    int count)
{
	struct cf_level_lst *list;
	struct cf_level *level, *search;
	int i;

	CF_MTX_ASSERT(&sc->lock);

	list = &sc->all_levels;
	for (i = 0; i < count; i++) {
		level = malloc(sizeof(*level), M_TEMP, M_NOWAIT | M_ZERO);
		if (level == NULL)
			return (ENOMEM);
		level->abs_set = sets[i];
		level->total_set = sets[i];
		level->total_set.dev = NULL;
		sc->all_count++;

		if (TAILQ_EMPTY(list)) {
			CF_DEBUG("adding abs setting %d at head\n",
			    sets[i].freq);
			TAILQ_INSERT_HEAD(list, level, link);
			continue;
		}

		TAILQ_FOREACH_REVERSE(search, list, cf_level_lst, link) {
			if (sets[i].freq <= search->total_set.freq) {
				CF_DEBUG("adding abs setting %d after %d\n",
				    sets[i].freq, search->total_set.freq);
				TAILQ_INSERT_AFTER(list, search, level, link);
				break;
			}
		}
	}
	return (0);
}

/*
 * Expand a group of relative settings, creating derived levels from them.
 */
static int
cpufreq_expand_set(struct cpufreq_softc *sc, struct cf_setting_array *set_arr)
{
	struct cf_level *fill, *search;
	struct cf_setting *set;
	int i;

	CF_MTX_ASSERT(&sc->lock);

	TAILQ_FOREACH(search, &sc->all_levels, link) {
		/* Skip this level if we've already modified it. */
		for (i = 0; i < search->rel_count; i++) {
			if (search->rel_set[i].dev == set_arr->sets[0].dev)
				break;
		}
		if (i != search->rel_count) {
			CF_DEBUG("skipping modified level, freq %d (dev %s)\n",
			    search->total_set.freq,
			    device_get_nameunit(search->rel_set[i].dev));
			continue;
		}

		/* Add each setting to the level, duplicating if necessary. */
		for (i = 0; i < set_arr->count; i++) {
			set = &set_arr->sets[i];

			/*
			 * If this setting is less than 100%, split the level
			 * into two and add this setting to the new level.
			 */
			fill = search;
			if (set->freq < 10000)
				fill = cpufreq_dup_set(sc, search, set);

			/*
			 * The new level was a duplicate of an existing level
			 * so we freed it.  Go to the next setting.
			 */
			if (fill == NULL)
				continue;

			/* Add this setting to the existing or new level. */
			KASSERT(fill->rel_count < MAX_SETTINGS,
			    ("cpufreq: too many relative drivers (%d)",
			    MAX_SETTINGS));
			fill->rel_set[fill->rel_count] = *set;
			fill->rel_count++;
			CF_DEBUG(
			"expand set added rel setting %d%% to %d level\n",
			    set->freq / 100, fill->total_set.freq);
		}
	}

	return (0);
}

static struct cf_level *
cpufreq_dup_set(struct cpufreq_softc *sc, struct cf_level *dup,
    struct cf_setting *set)
{
	struct cf_level_lst *list;
	struct cf_level *fill, *itr;
	struct cf_setting *fill_set, *itr_set;
	int i;

	CF_MTX_ASSERT(&sc->lock);

	/*
	 * Create a new level, copy it from the old one, and update the
	 * total frequency and power by the percentage specified in the
	 * relative setting.
	 */
	fill = malloc(sizeof(*fill), M_TEMP, M_NOWAIT);
	if (fill == NULL)
		return (NULL);
	*fill = *dup;
	fill_set = &fill->total_set;
	fill_set->freq =
	    ((uint64_t)fill_set->freq * set->freq) / 10000;
	if (fill_set->power != CPUFREQ_VAL_UNKNOWN) {
		fill_set->power = ((uint64_t)fill_set->power * set->freq)
		    / 10000;
	}
	if (set->lat != CPUFREQ_VAL_UNKNOWN) {
		if (fill_set->lat != CPUFREQ_VAL_UNKNOWN)
			fill_set->lat += set->lat;
		else
			fill_set->lat = set->lat;
	}
	CF_DEBUG("dup set considering derived setting %d\n", fill_set->freq);

	/*
	 * If we copied an old level that we already modified (say, at 100%),
	 * we need to remove that setting before adding this one.  Since we
	 * process each setting array in order, we know any settings for this
	 * driver will be found at the end.
	 */
	for (i = fill->rel_count; i != 0; i--) {
		if (fill->rel_set[i - 1].dev != set->dev)
			break;
		CF_DEBUG("removed last relative driver: %s\n",
		    device_get_nameunit(set->dev));
		fill->rel_count--;
	}

	/*
	 * Insert the new level in sorted order.  If we find a duplicate,
	 * free the new level.  We can do this since any existing level will
	 * be guaranteed to have the same or less settings and thus consume
	 * less power.  For example, a level with one absolute setting of
	 * 800 Mhz uses less power than one composed of an absolute setting
	 * of 1600 Mhz and a relative setting at 50%.
	 */
	list = &sc->all_levels;
	if (TAILQ_EMPTY(list)) {
		CF_DEBUG("dup done, inserted %d at head\n", fill_set->freq);
		TAILQ_INSERT_HEAD(list, fill, link);
	} else {
		TAILQ_FOREACH_REVERSE(itr, list, cf_level_lst, link) {
			itr_set = &itr->total_set;
			if (CPUFREQ_CMP(fill_set->freq, itr_set->freq)) {
				CF_DEBUG(
			"dup done, freeing new level %d, matches %d\n",
				    fill_set->freq, itr_set->freq);
				free(fill, M_TEMP);
				fill = NULL;
				break;
			} else if (fill_set->freq < itr_set->freq) {
				CF_DEBUG(
			"dup done, inserting new level %d after %d\n",
				    fill_set->freq, itr_set->freq);
				TAILQ_INSERT_AFTER(list, itr, fill, link);
				sc->all_count++;
				break;
			}
		}
	}

	return (fill);
}

static int
cpufreq_curr_sysctl(SYSCTL_HANDLER_ARGS)
{
	struct cpufreq_softc *sc;
	struct cf_level *levels;
	int count, devcount, error, freq, i, n;
	device_t *devs;

	devs = NULL;
	sc = oidp->oid_arg1;
	levels = malloc(CF_MAX_LEVELS * sizeof(*levels), M_TEMP, M_NOWAIT);
	if (levels == NULL)
		return (ENOMEM);

	error = CPUFREQ_GET(sc->dev, &levels[0]);
	if (error)
		goto out;
	freq = levels[0].total_set.freq;
	error = sysctl_handle_int(oidp, &freq, 0, req);
	if (error != 0 || req->newptr == NULL)
		goto out;

	/*
	 * While we only call cpufreq_get() on one device (assuming all
	 * CPUs have equal levels), we call cpufreq_set() on all CPUs.
	 * This is needed for some MP systems.
	 */
	error = devclass_get_devices(cpufreq_dc, &devs, &devcount);
	if (error)
		goto out;
	for (n = 0; n < devcount; n++) {
		count = CF_MAX_LEVELS;
		error = CPUFREQ_LEVELS(devs[n], levels, &count);
		if (error) {
			if (error == E2BIG)
				printf(
			"cpufreq: need to increase CF_MAX_LEVELS\n");
			break;
		}
		for (i = 0; i < count; i++) {
			if (CPUFREQ_CMP(levels[i].total_set.freq, freq)) {
				error = CPUFREQ_SET(devs[n], &levels[i],
				    CPUFREQ_PRIO_USER);
				break;
			}
		}
		if (i == count) {
			error = EINVAL;
			break;
		}
	}

out:
	if (devs)
		free(devs, M_TEMP);
	if (levels)
		free(levels, M_TEMP);
	return (error);
}

static int
cpufreq_levels_sysctl(SYSCTL_HANDLER_ARGS)
{
	struct cpufreq_softc *sc;
	struct cf_level *levels;
	struct cf_setting *set;
	struct sbuf sb;
	int count, error, i;

	sc = oidp->oid_arg1;
	sbuf_new(&sb, NULL, 128, SBUF_AUTOEXTEND);

	/* Get settings from the device and generate the output string. */
	count = CF_MAX_LEVELS;
	levels = malloc(count * sizeof(*levels), M_TEMP, M_NOWAIT);
	if (levels == NULL)
		return (ENOMEM);
	error = CPUFREQ_LEVELS(sc->dev, levels, &count);
	if (error) {
		if (error == E2BIG)
			printf("cpufreq: need to increase CF_MAX_LEVELS\n");
		goto out;
	}
	if (count) {
		for (i = 0; i < count; i++) {
			set = &levels[i].total_set;
			sbuf_printf(&sb, "%d/%d ", set->freq, set->power);
		}
	} else
		sbuf_cpy(&sb, "0");
	sbuf_trim(&sb);
	sbuf_finish(&sb);
	error = sysctl_handle_string(oidp, sbuf_data(&sb), sbuf_len(&sb), req);

out:
	free(levels, M_TEMP);
	sbuf_delete(&sb);
	return (error);
}

static int
cpufreq_settings_sysctl(SYSCTL_HANDLER_ARGS)
{
	device_t dev;
	struct cf_setting *sets;
	struct sbuf sb;
	int error, i, set_count;

	dev = oidp->oid_arg1;
	sbuf_new(&sb, NULL, 128, SBUF_AUTOEXTEND);

	/* Get settings from the device and generate the output string. */
	set_count = MAX_SETTINGS;
	sets = malloc(set_count * sizeof(*sets), M_TEMP, M_NOWAIT);
	if (sets == NULL)
		return (ENOMEM);
	error = CPUFREQ_DRV_SETTINGS(dev, sets, &set_count);
	if (error)
		goto out;
	if (set_count) {
		for (i = 0; i < set_count; i++)
			sbuf_printf(&sb, "%d/%d ", sets[i].freq, sets[i].power);
	} else
		sbuf_cpy(&sb, "0");
	sbuf_trim(&sb);
	sbuf_finish(&sb);
	error = sysctl_handle_string(oidp, sbuf_data(&sb), sbuf_len(&sb), req);

out:
	free(sets, M_TEMP);
	sbuf_delete(&sb);
	return (error);
}

int
cpufreq_register(device_t dev)
{
	struct cpufreq_softc *sc;
	device_t cf_dev, cpu_dev;

	/* Add a sysctl to get each driver's settings separately. */
	SYSCTL_ADD_PROC(device_get_sysctl_ctx(dev),
	    SYSCTL_CHILDREN(device_get_sysctl_tree(dev)),
	    OID_AUTO, "freq_settings", CTLTYPE_STRING | CTLFLAG_RD, dev, 0,
	    cpufreq_settings_sysctl, "A", "CPU frequency driver settings");

	/*
	 * Add only one cpufreq device to each CPU.  Currently, all CPUs
	 * must offer the same levels and be switched at the same time.
	 */
	cpu_dev = device_get_parent(dev);
	if ((cf_dev = device_find_child(cpu_dev, "cpufreq", -1))) {
		sc = device_get_softc(cf_dev);
		sc->max_mhz = CPUFREQ_VAL_UNKNOWN;
		return (0);
	}

	/* Add the child device and possibly sysctls. */
	cf_dev = BUS_ADD_CHILD(cpu_dev, 0, "cpufreq", -1);
	if (cf_dev == NULL)
		return (ENOMEM);
	device_quiet(cf_dev);

	return (device_probe_and_attach(cf_dev));
}

int
cpufreq_unregister(device_t dev)
{
	device_t cf_dev, *devs;
	int cfcount, devcount, error, i, type;

	/*
	 * If this is the last cpufreq child device, remove the control
	 * device as well.  We identify cpufreq children by calling a method
	 * they support.
	 */
	error = device_get_children(device_get_parent(dev), &devs, &devcount);
	if (error)
		return (error);
	cf_dev = device_find_child(device_get_parent(dev), "cpufreq", -1);
	if (cf_dev == NULL) {
		device_printf(dev,
	"warning: cpufreq_unregister called with no cpufreq device active\n");
		return (0);
	}
	cfcount = 0;
	for (i = 0; i < devcount; i++) {
		if (!device_is_attached(devs[i]))
			continue;
		if (CPUFREQ_DRV_TYPE(devs[i], &type) == 0)
			cfcount++;
	}
	if (cfcount <= 1)
		device_delete_child(device_get_parent(cf_dev), cf_dev);
	free(devs, M_TEMP);

	return (0);
}