aboutsummaryrefslogtreecommitdiffstats
path: root/drivers/char/hw_random/n2-drv.c
blob: 43ac61978d8b2661672418901bde4242462a6165 (plain)
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
/* n2-drv.c: Niagara-2 RNG driver.
 *
 * Copyright (C) 2008 David S. Miller <davem@davemloft.net>
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/types.h>
#include <linux/delay.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/workqueue.h>
#include <linux/preempt.h>
#include <linux/hw_random.h>

#include <linux/of.h>
#include <linux/of_device.h>

#include <asm/hypervisor.h>

#include "n2rng.h"

#define DRV_MODULE_NAME		"n2rng"
#define PFX DRV_MODULE_NAME	": "
#define DRV_MODULE_VERSION	"0.1"
#define DRV_MODULE_RELDATE	"May 15, 2008"

static char version[] __devinitdata =
	DRV_MODULE_NAME ".c:v" DRV_MODULE_VERSION " (" DRV_MODULE_RELDATE ")\n";

MODULE_AUTHOR("David S. Miller (davem@davemloft.net)");
MODULE_DESCRIPTION("Niagara2 RNG driver");
MODULE_LICENSE("GPL");
MODULE_VERSION(DRV_MODULE_VERSION);

/* The Niagara2 RNG provides a 64-bit read-only random number
 * register, plus a control register.  Access to the RNG is
 * virtualized through the hypervisor so that both guests and control
 * nodes can access the device.
 *
 * The entropy source consists of raw entropy sources, each
 * constructed from a voltage controlled oscillator whose phase is
 * jittered by thermal noise sources.
 *
 * The oscillator in each of the three raw entropy sources run at
 * different frequencies.  Normally, all three generator outputs are
 * gathered, xored together, and fed into a CRC circuit, the output of
 * which is the 64-bit read-only register.
 *
 * Some time is necessary for all the necessary entropy to build up
 * such that a full 64-bits of entropy are available in the register.
 * In normal operating mode (RNG_CTL_LFSR is set), the chip implements
 * an interlock which blocks register reads until sufficient entropy
 * is available.
 *
 * A control register is provided for adjusting various aspects of RNG
 * operation, and to enable diagnostic modes.  Each of the three raw
 * entropy sources has an enable bit (RNG_CTL_ES{1,2,3}).  Also
 * provided are fields for controlling the minimum time in cycles
 * between read accesses to the register (RNG_CTL_WAIT, this controls
 * the interlock described in the previous paragraph).
 *
 * The standard setting is to have the mode bit (RNG_CTL_LFSR) set,
 * all three entropy sources enabled, and the interlock time set
 * appropriately.
 *
 * The CRC polynomial used by the chip is:
 *
 * P(X) = x64 + x61 + x57 + x56 + x52 + x51 + x50 + x48 + x47 + x46 +
 *        x43 + x42 + x41 + x39 + x38 + x37 + x35 + x32 + x28 + x25 +
 *        x22 + x21 + x17 + x15 + x13 + x12 + x11 + x7 + x5 + x + 1
 *
 * The RNG_CTL_VCO value of each noise cell must be programmed
 * separately.  This is why 4 control register values must be provided
 * to the hypervisor.  During a write, the hypervisor writes them all,
 * one at a time, to the actual RNG_CTL register.  The first three
 * values are used to setup the desired RNG_CTL_VCO for each entropy
 * source, for example:
 *
 *	control 0: (1 << RNG_CTL_VCO_SHIFT) | RNG_CTL_ES1
 *	control 1: (2 << RNG_CTL_VCO_SHIFT) | RNG_CTL_ES2
 *	control 2: (3 << RNG_CTL_VCO_SHIFT) | RNG_CTL_ES3
 *
 * And then the fourth value sets the final chip state and enables
 * desired.
 */

static int n2rng_hv_err_trans(unsigned long hv_err)
{
	switch (hv_err) {
	case HV_EOK:
		return 0;
	case HV_EWOULDBLOCK:
		return -EAGAIN;
	case HV_ENOACCESS:
		return -EPERM;
	case HV_EIO:
		return -EIO;
	case HV_EBUSY:
		return -EBUSY;
	case HV_EBADALIGN:
	case HV_ENORADDR:
		return -EFAULT;
	default:
		return -EINVAL;
	}
}

static unsigned long n2rng_generic_read_control_v2(unsigned long ra,
						   unsigned long unit)
{
	unsigned long hv_err, state, ticks, watchdog_delta, watchdog_status;
	int block = 0, busy = 0;

	while (1) {
		hv_err = sun4v_rng_ctl_read_v2(ra, unit, &state,
					       &ticks,
					       &watchdog_delta,
					       &watchdog_status);
		if (hv_err == HV_EOK)
			break;

		if (hv_err == HV_EBUSY) {
			if (++busy >= N2RNG_BUSY_LIMIT)
				break;

			udelay(1);
		} else if (hv_err == HV_EWOULDBLOCK) {
			if (++block >= N2RNG_BLOCK_LIMIT)
				break;

			__delay(ticks);
		} else
			break;
	}

	return hv_err;
}

/* In multi-socket situations, the hypervisor might need to
 * queue up the RNG control register write if it's for a unit
 * that is on a cpu socket other than the one we are executing on.
 *
 * We poll here waiting for a successful read of that control
 * register to make sure the write has been actually performed.
 */
static unsigned long n2rng_control_settle_v2(struct n2rng *np, int unit)
{
	unsigned long ra = __pa(&np->scratch_control[0]);

	return n2rng_generic_read_control_v2(ra, unit);
}

static unsigned long n2rng_write_ctl_one(struct n2rng *np, int unit,
					 unsigned long state,
					 unsigned long control_ra,
					 unsigned long watchdog_timeout,
					 unsigned long *ticks)
{
	unsigned long hv_err;

	if (np->hvapi_major == 1) {
		hv_err = sun4v_rng_ctl_write_v1(control_ra, state,
						watchdog_timeout, ticks);
	} else {
		hv_err = sun4v_rng_ctl_write_v2(control_ra, state,
						watchdog_timeout, unit);
		if (hv_err == HV_EOK)
			hv_err = n2rng_control_settle_v2(np, unit);
		*ticks = N2RNG_ACCUM_CYCLES_DEFAULT;
	}

	return hv_err;
}

static int n2rng_generic_read_data(unsigned long data_ra)
{
	unsigned long ticks, hv_err;
	int block = 0, hcheck = 0;

	while (1) {
		hv_err = sun4v_rng_data_read(data_ra, &ticks);
		if (hv_err == HV_EOK)
			return 0;

		if (hv_err == HV_EWOULDBLOCK) {
			if (++block >= N2RNG_BLOCK_LIMIT)
				return -EWOULDBLOCK;
			__delay(ticks);
		} else if (hv_err == HV_ENOACCESS) {
			return -EPERM;
		} else if (hv_err == HV_EIO) {
			if (++hcheck >= N2RNG_HCHECK_LIMIT)
				return -EIO;
			udelay(10000);
		} else
			return -ENODEV;
	}
}

static unsigned long n2rng_read_diag_data_one(struct n2rng *np,
					      unsigned long unit,
					      unsigned long data_ra,
					      unsigned long data_len,
					      unsigned long *ticks)
{
	unsigned long hv_err;

	if (np->hvapi_major == 1) {
		hv_err = sun4v_rng_data_read_diag_v1(data_ra, data_len, ticks);
	} else {
		hv_err = sun4v_rng_data_read_diag_v2(data_ra, data_len,
						     unit, ticks);
		if (!*ticks)
			*ticks = N2RNG_ACCUM_CYCLES_DEFAULT;
	}
	return hv_err;
}

static int n2rng_generic_read_diag_data(struct n2rng *np,
					unsigned long unit,
					unsigned long data_ra,
					unsigned long data_len)
{
	unsigned long ticks, hv_err;
	int block = 0;

	while (1) {
		hv_err = n2rng_read_diag_data_one(np, unit,
						  data_ra, data_len,
						  &ticks);
		if (hv_err == HV_EOK)
			return 0;

		if (hv_err == HV_EWOULDBLOCK) {
			if (++block >= N2RNG_BLOCK_LIMIT)
				return -EWOULDBLOCK;
			__delay(ticks);
		} else if (hv_err == HV_ENOACCESS) {
			return -EPERM;
		} else if (hv_err == HV_EIO) {
			return -EIO;
		} else
			return -ENODEV;
	}
}


static int n2rng_generic_write_control(struct n2rng *np,
				       unsigned long control_ra,
				       unsigned long unit,
				       unsigned long state)
{
	unsigned long hv_err, ticks;
	int block = 0, busy = 0;

	while (1) {
		hv_err = n2rng_write_ctl_one(np, unit, state, control_ra,
					     np->wd_timeo, &ticks);
		if (hv_err == HV_EOK)
			return 0;

		if (hv_err == HV_EWOULDBLOCK) {
			if (++block >= N2RNG_BLOCK_LIMIT)
				return -EWOULDBLOCK;
			__delay(ticks);
		} else if (hv_err == HV_EBUSY) {
			if (++busy >= N2RNG_BUSY_LIMIT)
				return -EBUSY;
			udelay(1);
		} else
			return -ENODEV;
	}
}

/* Just try to see if we can successfully access the control register
 * of the RNG on the domain on which we are currently executing.
 */
static int n2rng_try_read_ctl(struct n2rng *np)
{
	unsigned long hv_err;
	unsigned long x;

	if (np->hvapi_major == 1) {
		hv_err = sun4v_rng_get_diag_ctl();
	} else {
		/* We purposefully give invalid arguments, HV_NOACCESS
		 * is higher priority than the errors we'd get from
		 * these other cases, and that's the error we are
		 * truly interested in.
		 */
		hv_err = sun4v_rng_ctl_read_v2(0UL, ~0UL, &x, &x, &x, &x);
		switch (hv_err) {
		case HV_EWOULDBLOCK:
		case HV_ENOACCESS:
			break;
		default:
			hv_err = HV_EOK;
			break;
		}
	}

	return n2rng_hv_err_trans(hv_err);
}

#define CONTROL_DEFAULT_BASE		\
	((2 << RNG_CTL_ASEL_SHIFT) |	\
	 (N2RNG_ACCUM_CYCLES_DEFAULT << RNG_CTL_WAIT_SHIFT) |	\
	 RNG_CTL_LFSR)

#define CONTROL_DEFAULT_0		\
	(CONTROL_DEFAULT_BASE |		\
	 (1 << RNG_CTL_VCO_SHIFT) |	\
	 RNG_CTL_ES1)
#define CONTROL_DEFAULT_1		\
	(CONTROL_DEFAULT_BASE |		\
	 (2 << RNG_CTL_VCO_SHIFT) |	\
	 RNG_CTL_ES2)
#define CONTROL_DEFAULT_2		\
	(CONTROL_DEFAULT_BASE |		\
	 (3 << RNG_CTL_VCO_SHIFT) |	\
	 RNG_CTL_ES3)
#define CONTROL_DEFAULT_3		\
	(CONTROL_DEFAULT_BASE |		\
	 RNG_CTL_ES1 | RNG_CTL_ES2 | RNG_CTL_ES3)

static void n2rng_control_swstate_init(struct n2rng *np)
{
	int i;

	np->flags |= N2RNG_FLAG_CONTROL;

	np->health_check_sec = N2RNG_HEALTH_CHECK_SEC_DEFAULT;
	np->accum_cycles = N2RNG_ACCUM_CYCLES_DEFAULT;
	np->wd_timeo = N2RNG_WD_TIMEO_DEFAULT;

	for (i = 0; i < np->num_units; i++) {
		struct n2rng_unit *up = &np->units[i];

		up->control[0] = CONTROL_DEFAULT_0;
		up->control[1] = CONTROL_DEFAULT_1;
		up->control[2] = CONTROL_DEFAULT_2;
		up->control[3] = CONTROL_DEFAULT_3;
	}

	np->hv_state = HV_RNG_STATE_UNCONFIGURED;
}

static int n2rng_grab_diag_control(struct n2rng *np)
{
	int i, busy_count, err = -ENODEV;

	busy_count = 0;
	for (i = 0; i < 100; i++) {
		err = n2rng_try_read_ctl(np);
		if (err != -EAGAIN)
			break;

		if (++busy_count > 100) {
			dev_err(&np->op->dev,
				"Grab diag control timeout.\n");
			return -ENODEV;
		}

		udelay(1);
	}

	return err;
}

static int n2rng_init_control(struct n2rng *np)
{
	int err = n2rng_grab_diag_control(np);

	/* Not in the control domain, that's OK we are only a consumer
	 * of the RNG data, we don't setup and program it.
	 */
	if (err == -EPERM)
		return 0;
	if (err)
		return err;

	n2rng_control_swstate_init(np);

	return 0;
}

static int n2rng_data_read(struct hwrng *rng, u32 *data)
{
	struct n2rng *np = (struct n2rng *) rng->priv;
	unsigned long ra = __pa(&np->test_data);
	int len;

	if (!(np->flags & N2RNG_FLAG_READY)) {
		len = 0;
	} else if (np->flags & N2RNG_FLAG_BUFFER_VALID) {
		np->flags &= ~N2RNG_FLAG_BUFFER_VALID;
		*data = np->buffer;
		len = 4;
	} else {
		int err = n2rng_generic_read_data(ra);
		if (!err) {
			np->buffer = np->test_data >> 32;
			*data = np->test_data & 0xffffffff;
			len = 4;
		} else {
			dev_err(&np->op->dev, "RNG error, restesting\n");
			np->flags &= ~N2RNG_FLAG_READY;
			if (!(np->flags & N2RNG_FLAG_SHUTDOWN))
				schedule_delayed_work(&np->work, 0);
			len = 0;
		}
	}

	return len;
}

/* On a guest node, just make sure we can read random data properly.
 * If a control node reboots or reloads it's n2rng driver, this won't
 * work during that time.  So we have to keep probing until the device
 * becomes usable.
 */
static int n2rng_guest_check(struct n2rng *np)
{
	unsigned long ra = __pa(&np->test_data);

	return n2rng_generic_read_data(ra);
}

static int n2rng_entropy_diag_read(struct n2rng *np, unsigned long unit,
				   u64 *pre_control, u64 pre_state,
				   u64 *buffer, unsigned long buf_len,
				   u64 *post_control, u64 post_state)
{
	unsigned long post_ctl_ra = __pa(post_control);
	unsigned long pre_ctl_ra = __pa(pre_control);
	unsigned long buffer_ra = __pa(buffer);
	int err;

	err = n2rng_generic_write_control(np, pre_ctl_ra, unit, pre_state);
	if (err)
		return err;

	err = n2rng_generic_read_diag_data(np, unit,
					   buffer_ra, buf_len);

	(void) n2rng_generic_write_control(np, post_ctl_ra, unit,
					   post_state);

	return err;
}

static u64 advance_polynomial(u64 poly, u64 val, int count)
{
	int i;

	for (i = 0; i < count; i++) {
		int highbit_set = ((s64)val < 0);

		val <<= 1;
		if (highbit_set)
			val ^= poly;
	}

	return val;
}

static int n2rng_test_buffer_find(struct n2rng *np, u64 val)
{
	int i, count = 0;

	/* Purposefully skip over the first word.  */
	for (i = 1; i < SELFTEST_BUFFER_WORDS; i++) {
		if (np->test_buffer[i] == val)
			count++;
	}
	return count;
}

static void n2rng_dump_test_buffer(struct n2rng *np)
{
	int i;

	for (i = 0; i < SELFTEST_BUFFER_WORDS; i++)
		dev_err(&np->op->dev, "Test buffer slot %d [0x%016llx]\n",
			i, np->test_buffer[i]);
}

static int n2rng_check_selftest_buffer(struct n2rng *np, unsigned long unit)
{
	u64 val = SELFTEST_VAL;
	int err, matches, limit;

	matches = 0;
	for (limit = 0; limit < SELFTEST_LOOPS_MAX; limit++) {
		matches += n2rng_test_buffer_find(np, val);
		if (matches >= SELFTEST_MATCH_GOAL)
			break;
		val = advance_polynomial(SELFTEST_POLY, val, 1);
	}

	err = 0;
	if (limit >= SELFTEST_LOOPS_MAX) {
		err = -ENODEV;
		dev_err(&np->op->dev, "Selftest failed on unit %lu\n", unit);
		n2rng_dump_test_buffer(np);
	} else
		dev_info(&np->op->dev, "Selftest passed on unit %lu\n", unit);

	return err;
}

static int n2rng_control_selftest(struct n2rng *np, unsigned long unit)
{
	int err;

	np->test_control[0] = (0x2 << RNG_CTL_ASEL_SHIFT);
	np->test_control[1] = (0x2 << RNG_CTL_ASEL_SHIFT);
	np->test_control[2] = (0x2 << RNG_CTL_ASEL_SHIFT);
	np->test_control[3] = ((0x2 << RNG_CTL_ASEL_SHIFT) |
			       RNG_CTL_LFSR |
			       ((SELFTEST_TICKS - 2) << RNG_CTL_WAIT_SHIFT));


	err = n2rng_entropy_diag_read(np, unit, np->test_control,
				      HV_RNG_STATE_HEALTHCHECK,
				      np->test_buffer,
				      sizeof(np->test_buffer),
				      &np->units[unit].control[0],
				      np->hv_state);
	if (err)
		return err;

	return n2rng_check_selftest_buffer(np, unit);
}

static int n2rng_control_check(struct n2rng *np)
{
	int i;

	for (i = 0; i < np->num_units; i++) {
		int err = n2rng_control_selftest(np, i);
		if (err)
			return err;
	}
	return 0;
}

/* The sanity checks passed, install the final configuration into the
 * chip, it's ready to use.
 */
static int n2rng_control_configure_units(struct n2rng *np)
{
	int unit, err;

	err = 0;
	for (unit = 0; unit < np->num_units; unit++) {
		struct n2rng_unit *up = &np->units[unit];
		unsigned long ctl_ra = __pa(&up->control[0]);
		int esrc;
		u64 base;

		base = ((np->accum_cycles << RNG_CTL_WAIT_SHIFT) |
			(2 << RNG_CTL_ASEL_SHIFT) |
			RNG_CTL_LFSR);

		/* XXX This isn't the best.  We should fetch a bunch
		 * XXX of words using each entropy source combined XXX
		 * with each VCO setting, and see which combinations
		 * XXX give the best random data.
		 */
		for (esrc = 0; esrc < 3; esrc++)
			up->control[esrc] = base |
				(esrc << RNG_CTL_VCO_SHIFT) |
				(RNG_CTL_ES1 << esrc);

		up->control[3] = base |
			(RNG_CTL_ES1 | RNG_CTL_ES2 | RNG_CTL_ES3);

		err = n2rng_generic_write_control(np, ctl_ra, unit,
						  HV_RNG_STATE_CONFIGURED);
		if (err)
			break;
	}

	return err;
}

static void n2rng_work(struct work_struct *work)
{
	struct n2rng *np = container_of(work, struct n2rng, work.work);
	int err = 0;

	if (!(np->flags & N2RNG_FLAG_CONTROL)) {
		err = n2rng_guest_check(np);
	} else {
		preempt_disable();
		err = n2rng_control_check(np);
		preempt_enable();

		if (!err)
			err = n2rng_control_configure_units(np);
	}

	if (!err) {
		np->flags |= N2RNG_FLAG_READY;
		dev_info(&np->op->dev, "RNG ready\n");
	}

	if (err && !(np->flags & N2RNG_FLAG_SHUTDOWN))
		schedule_delayed_work(&np->work, HZ * 2);
}

static void __devinit n2rng_driver_version(void)
{
	static int n2rng_version_printed;

	if (n2rng_version_printed++ == 0)
		pr_info("%s", version);
}

static int __devinit n2rng_probe(struct platform_device *op)
{
	int victoria_falls;
	int err = -ENOMEM;
	struct n2rng *np;

	if (!op->dev.of_match)
		return -EINVAL;
	victoria_falls = (op->dev.of_match->data != NULL);

	n2rng_driver_version();
	np = kzalloc(sizeof(*np), GFP_KERNEL);
	if (!np)
		goto out;
	np->op = op;

	INIT_DELAYED_WORK(&np->work, n2rng_work);

	if (victoria_falls)
		np->flags |= N2RNG_FLAG_VF;

	err = -ENODEV;
	np->hvapi_major = 2;
	if (sun4v_hvapi_register(HV_GRP_RNG,
				 np->hvapi_major,
				 &np->hvapi_minor)) {
		np->hvapi_major = 1;
		if (sun4v_hvapi_register(HV_GRP_RNG,
					 np->hvapi_major,
					 &np->hvapi_minor)) {
			dev_err(&op->dev, "Cannot register suitable "
				"HVAPI version.\n");
			goto out_free;
		}
	}

	if (np->flags & N2RNG_FLAG_VF) {
		if (np->hvapi_major < 2) {
			dev_err(&op->dev, "VF RNG requires HVAPI major "
				"version 2 or later, got %lu\n",
				np->hvapi_major);
			goto out_hvapi_unregister;
		}
		np->num_units = of_getintprop_default(op->dev.of_node,
						      "rng-#units", 0);
		if (!np->num_units) {
			dev_err(&op->dev, "VF RNG lacks rng-#units property\n");
			goto out_hvapi_unregister;
		}
	} else
		np->num_units = 1;

	dev_info(&op->dev, "Registered RNG HVAPI major %lu minor %lu\n",
		 np->hvapi_major, np->hvapi_minor);

	np->units = kzalloc(sizeof(struct n2rng_unit) * np->num_units,
			    GFP_KERNEL);
	err = -ENOMEM;
	if (!np->units)
		goto out_hvapi_unregister;

	err = n2rng_init_control(np);
	if (err)
		goto out_free_units;

	dev_info(&op->dev, "Found %s RNG, units: %d\n",
		 ((np->flags & N2RNG_FLAG_VF) ?
		  "Victoria Falls" : "Niagara2"),
		 np->num_units);

	np->hwrng.name = "n2rng";
	np->hwrng.data_read = n2rng_data_read;
	np->hwrng.priv = (unsigned long) np;

	err = hwrng_register(&np->hwrng);
	if (err)
		goto out_free_units;

	dev_set_drvdata(&op->dev, np);

	schedule_delayed_work(&np->work, 0);

	return 0;

out_free_units:
	kfree(np->units);
	np->units = NULL;

out_hvapi_unregister:
	sun4v_hvapi_unregister(HV_GRP_RNG);

out_free:
	kfree(np);
out:
	return err;
}

static int __devexit n2rng_remove(struct platform_device *op)
{
	struct n2rng *np = dev_get_drvdata(&op->dev);

	np->flags |= N2RNG_FLAG_SHUTDOWN;

	cancel_delayed_work_sync(&np->work);

	hwrng_unregister(&np->hwrng);

	sun4v_hvapi_unregister(HV_GRP_RNG);

	kfree(np->units);
	np->units = NULL;

	kfree(np);

	dev_set_drvdata(&op->dev, NULL);

	return 0;
}

static const struct of_device_id n2rng_match[] = {
	{
		.name		= "random-number-generator",
		.compatible	= "SUNW,n2-rng",
	},
	{
		.name		= "random-number-generator",
		.compatible	= "SUNW,vf-rng",
		.data		= (void *) 1,
	},
	{},
};
MODULE_DEVICE_TABLE(of, n2rng_match);

static struct platform_driver n2rng_driver = {
	.driver = {
		.name = "n2rng",
		.owner = THIS_MODULE,
		.of_match_table = n2rng_match,
	},
	.probe		= n2rng_probe,
	.remove		= __devexit_p(n2rng_remove),
};

static int __init n2rng_init(void)
{
	return platform_driver_register(&n2rng_driver);
}

static void __exit n2rng_exit(void)
{
	platform_driver_unregister(&n2rng_driver);
}

module_init(n2rng_init);
module_exit(n2rng_exit);