drivers/char/hw_random/n2-drv.c

   1 /* n2-drv.c: Niagara-2 RNG driver.
   2  *
   3  * Copyright (C) 2008 David S. Miller <davem@davemloft.net>
   4  */
   5
   6 #include <linux/kernel.h>
   7 #include <linux/module.h>
   8 #include <linux/types.h>
   9 #include <linux/delay.h>
  10 #include <linux/init.h>
  11 #include <linux/slab.h>
  12 #include <linux/workqueue.h>
  13 #include <linux/preempt.h>
  14 #include <linux/hw_random.h>
  15
  16 #include <linux/of.h>
  17 #include <linux/of_device.h>
  18
  19 #include <asm/hypervisor.h>
  20
  21 #include "n2rng.h"
  22
  23 #define DRV_MODULE_NAME         "n2rng"
  24 #define PFX DRV_MODULE_NAME     ": "
  25 #define DRV_MODULE_VERSION      "0.1"
  26 #define DRV_MODULE_RELDATE      "May 15, 2008"
  27
  28 static char version[] __devinitdata =
  29         DRV_MODULE_NAME ".c:v" DRV_MODULE_VERSION " (" DRV_MODULE_RELDATE ")\n";
  30
  31 MODULE_AUTHOR("David S. Miller (davem@davemloft.net)");
  32 MODULE_DESCRIPTION("Niagara2 RNG driver");
  33 MODULE_LICENSE("GPL");
  34 MODULE_VERSION(DRV_MODULE_VERSION);
  35
  36 /* The Niagara2 RNG provides a 64-bit read-only random number
  37  * register, plus a control register.  Access to the RNG is
  38  * virtualized through the hypervisor so that both guests and control
  39  * nodes can access the device.
  40  *
  41  * The entropy source consists of raw entropy sources, each
  42  * constructed from a voltage controlled oscillator whose phase is
  43  * jittered by thermal noise sources.
  44  *
  45  * The oscillator in each of the three raw entropy sources run at
  46  * different frequencies.  Normally, all three generator outputs are
  47  * gathered, xored together, and fed into a CRC circuit, the output of
  48  * which is the 64-bit read-only register.
  49  *
  50  * Some time is necessary for all the necessary entropy to build up
  51  * such that a full 64-bits of entropy are available in the register.
  52  * In normal operating mode (RNG_CTL_LFSR is set), the chip implements
  53  * an interlock which blocks register reads until sufficient entropy
  54  * is available.
  55  *
  56  * A control register is provided for adjusting various aspects of RNG
  57  * operation, and to enable diagnostic modes.  Each of the three raw
  58  * entropy sources has an enable bit (RNG_CTL_ES{1,2,3}).  Also
  59  * provided are fields for controlling the minimum time in cycles
  60  * between read accesses to the register (RNG_CTL_WAIT, this controls
  61  * the interlock described in the previous paragraph).
  62  *
  63  * The standard setting is to have the mode bit (RNG_CTL_LFSR) set,
  64  * all three entropy sources enabled, and the interlock time set
  65  * appropriately.
  66  *
  67  * The CRC polynomial used by the chip is:
  68  *
  69  * P(X) = x64 + x61 + x57 + x56 + x52 + x51 + x50 + x48 + x47 + x46 +
  70  *        x43 + x42 + x41 + x39 + x38 + x37 + x35 + x32 + x28 + x25 +
  71  *        x22 + x21 + x17 + x15 + x13 + x12 + x11 + x7 + x5 + x + 1
  72  *
  73  * The RNG_CTL_VCO value of each noise cell must be programmed
  74  * separately.  This is why 4 control register values must be provided
  75  * to the hypervisor.  During a write, the hypervisor writes them all,
  76  * one at a time, to the actual RNG_CTL register.  The first three
  77  * values are used to setup the desired RNG_CTL_VCO for each entropy
  78  * source, for example:
  79  *
  80  *      control 0: (1 << RNG_CTL_VCO_SHIFT) | RNG_CTL_ES1
  81  *      control 1: (2 << RNG_CTL_VCO_SHIFT) | RNG_CTL_ES2
  82  *      control 2: (3 << RNG_CTL_VCO_SHIFT) | RNG_CTL_ES3
  83  *
  84  * And then the fourth value sets the final chip state and enables
  85  * desired.
  86  */
  87
  88 static int n2rng_hv_err_trans(unsigned long hv_err)
  89 {
  90         switch (hv_err) {
  91         case HV_EOK:
  92                 return 0;
  93         case HV_EWOULDBLOCK:
  94                 return -EAGAIN;
  95         case HV_ENOACCESS:
  96                 return -EPERM;
  97         case HV_EIO:
  98                 return -EIO;
  99         case HV_EBUSY:
 100                 return -EBUSY;
 101         case HV_EBADALIGN:
 102         case HV_ENORADDR:
 103                 return -EFAULT;
 104         default:
 105                 return -EINVAL;
 106         }
 107 }
 108
 109 static unsigned long n2rng_generic_read_control_v2(unsigned long ra,
 110                                                    unsigned long unit)
 111 {
 112         unsigned long hv_err, state, ticks, watchdog_delta, watchdog_status;
 113         int block = 0, busy = 0;
 114
 115         while (1) {
 116                 hv_err = sun4v_rng_ctl_read_v2(ra, unit, &state,
 117                                                &ticks,
 118                                                &watchdog_delta,
 119                                                &watchdog_status);
 120                 if (hv_err == HV_EOK)
 121                         break;
 122
 123                 if (hv_err == HV_EBUSY) {
 124                         if (++busy >= N2RNG_BUSY_LIMIT)
 125                                 break;
 126
 127                         udelay(1);
 128                 } else if (hv_err == HV_EWOULDBLOCK) {
 129                         if (++block >= N2RNG_BLOCK_LIMIT)
 130                                 break;
 131
 132                         __delay(ticks);
 133                 } else
 134                         break;
 135         }
 136
 137         return hv_err;
 138 }
 139
 140 /* In multi-socket situations, the hypervisor might need to
 141  * queue up the RNG control register write if it's for a unit
 142  * that is on a cpu socket other than the one we are executing on.
 143  *
 144  * We poll here waiting for a successful read of that control
 145  * register to make sure the write has been actually performed.
 146  */
 147 static unsigned long n2rng_control_settle_v2(struct n2rng *np, int unit)
 148 {
 149         unsigned long ra = __pa(&np->scratch_control[0]);
 150
 151         return n2rng_generic_read_control_v2(ra, unit);
 152 }
 153
 154 static unsigned long n2rng_write_ctl_one(struct n2rng *np, int unit,
 155                                          unsigned long state,
 156                                          unsigned long control_ra,
 157                                          unsigned long watchdog_timeout,
 158                                          unsigned long *ticks)
 159 {
 160         unsigned long hv_err;
 161
 162         if (np->hvapi_major == 1) {
 163                 hv_err = sun4v_rng_ctl_write_v1(control_ra, state,
 164                                                 watchdog_timeout, ticks);
 165         } else {
 166                 hv_err = sun4v_rng_ctl_write_v2(control_ra, state,
 167                                                 watchdog_timeout, unit);
 168                 if (hv_err == HV_EOK)
 169                         hv_err = n2rng_control_settle_v2(np, unit);
 170                 *ticks = N2RNG_ACCUM_CYCLES_DEFAULT;
 171         }
 172
 173         return hv_err;
 174 }
 175
 176 static int n2rng_generic_read_data(unsigned long data_ra)
 177 {
 178         unsigned long ticks, hv_err;
 179         int block = 0, hcheck = 0;
 180
 181         while (1) {
 182                 hv_err = sun4v_rng_data_read(data_ra, &ticks);
 183                 if (hv_err == HV_EOK)
 184                         return 0;
 185
 186                 if (hv_err == HV_EWOULDBLOCK) {
 187                         if (++block >= N2RNG_BLOCK_LIMIT)
 188                                 return -EWOULDBLOCK;
 189                         __delay(ticks);
 190                 } else if (hv_err == HV_ENOACCESS) {
 191                         return -EPERM;
 192                 } else if (hv_err == HV_EIO) {
 193                         if (++hcheck >= N2RNG_HCHECK_LIMIT)
 194                                 return -EIO;
 195                         udelay(10000);
 196                 } else
 197                         return -ENODEV;
 198         }
 199 }
 200
 201 static unsigned long n2rng_read_diag_data_one(struct n2rng *np,
 202                                               unsigned long unit,
 203                                               unsigned long data_ra,
 204                                               unsigned long data_len,
 205                                               unsigned long *ticks)
 206 {
 207         unsigned long hv_err;
 208
 209         if (np->hvapi_major == 1) {
 210                 hv_err = sun4v_rng_data_read_diag_v1(data_ra, data_len, ticks);
 211         } else {
 212                 hv_err = sun4v_rng_data_read_diag_v2(data_ra, data_len,
 213                                                      unit, ticks);
 214                 if (!*ticks)
 215                         *ticks = N2RNG_ACCUM_CYCLES_DEFAULT;
 216         }
 217         return hv_err;
 218 }
 219
 220 static int n2rng_generic_read_diag_data(struct n2rng *np,
 221                                         unsigned long unit,
 222                                         unsigned long data_ra,
 223                                         unsigned long data_len)
 224 {
 225         unsigned long ticks, hv_err;
 226         int block = 0;
 227
 228         while (1) {
 229                 hv_err = n2rng_read_diag_data_one(np, unit,
 230                                                   data_ra, data_len,
 231                                                   &ticks);
 232                 if (hv_err == HV_EOK)
 233                         return 0;
 234
 235                 if (hv_err == HV_EWOULDBLOCK) {
 236                         if (++block >= N2RNG_BLOCK_LIMIT)
 237                                 return -EWOULDBLOCK;
 238                         __delay(ticks);
 239                 } else if (hv_err == HV_ENOACCESS) {
 240                         return -EPERM;
 241                 } else if (hv_err == HV_EIO) {
 242                         return -EIO;
 243                 } else
 244                         return -ENODEV;
 245         }
 246 }
 247
 248
 249 static int n2rng_generic_write_control(struct n2rng *np,
 250                                        unsigned long control_ra,
 251                                        unsigned long unit,
 252                                        unsigned long state)
 253 {
 254         unsigned long hv_err, ticks;
 255         int block = 0, busy = 0;
 256
 257         while (1) {
 258                 hv_err = n2rng_write_ctl_one(np, unit, state, control_ra,
 259                                              np->wd_timeo, &ticks);
 260                 if (hv_err == HV_EOK)
 261                         return 0;
 262
 263                 if (hv_err == HV_EWOULDBLOCK) {
 264                         if (++block >= N2RNG_BLOCK_LIMIT)
 265                                 return -EWOULDBLOCK;
 266                         __delay(ticks);
 267                 } else if (hv_err == HV_EBUSY) {
 268                         if (++busy >= N2RNG_BUSY_LIMIT)
 269                                 return -EBUSY;
 270                         udelay(1);
 271                 } else
 272                         return -ENODEV;
 273         }
 274 }
 275
 276 /* Just try to see if we can successfully access the control register
 277  * of the RNG on the domain on which we are currently executing.
 278  */
 279 static int n2rng_try_read_ctl(struct n2rng *np)
 280 {
 281         unsigned long hv_err;
 282         unsigned long x;
 283
 284         if (np->hvapi_major == 1) {
 285                 hv_err = sun4v_rng_get_diag_ctl();
 286         } else {
 287                 /* We purposefully give invalid arguments, HV_NOACCESS
 288                  * is higher priority than the errors we'd get from
 289                  * these other cases, and that's the error we are
 290                  * truly interested in.
 291                  */
 292                 hv_err = sun4v_rng_ctl_read_v2(0UL, ~0UL, &x, &x, &x, &x);
 293                 switch (hv_err) {
 294                 case HV_EWOULDBLOCK:
 295                 case HV_ENOACCESS:
 296                         break;
 297                 default:
 298                         hv_err = HV_EOK;
 299                         break;
 300                 }
 301         }
 302
 303         return n2rng_hv_err_trans(hv_err);
 304 }
 305
 306 #define CONTROL_DEFAULT_BASE            \
 307         ((2 << RNG_CTL_ASEL_SHIFT) |    \
 308          (N2RNG_ACCUM_CYCLES_DEFAULT << RNG_CTL_WAIT_SHIFT) |   \
 309          RNG_CTL_LFSR)
 310
 311 #define CONTROL_DEFAULT_0               \
 312         (CONTROL_DEFAULT_BASE |         \
 313          (1 << RNG_CTL_VCO_SHIFT) |     \
 314          RNG_CTL_ES1)
 315 #define CONTROL_DEFAULT_1               \
 316         (CONTROL_DEFAULT_BASE |         \
 317          (2 << RNG_CTL_VCO_SHIFT) |     \
 318          RNG_CTL_ES2)
 319 #define CONTROL_DEFAULT_2               \
 320         (CONTROL_DEFAULT_BASE |         \
 321          (3 << RNG_CTL_VCO_SHIFT) |     \
 322          RNG_CTL_ES3)
 323 #define CONTROL_DEFAULT_3               \
 324         (CONTROL_DEFAULT_BASE |         \
 325          RNG_CTL_ES1 | RNG_CTL_ES2 | RNG_CTL_ES3)
 326
 327 static void n2rng_control_swstate_init(struct n2rng *np)
 328 {
 329         int i;
 330
 331         np->flags |= N2RNG_FLAG_CONTROL;
 332
 333         np->health_check_sec = N2RNG_HEALTH_CHECK_SEC_DEFAULT;
 334         np->accum_cycles = N2RNG_ACCUM_CYCLES_DEFAULT;
 335         np->wd_timeo = N2RNG_WD_TIMEO_DEFAULT;
 336
 337         for (i = 0; i < np->num_units; i++) {
 338                 struct n2rng_unit *up = &np->units[i];
 339
 340                 up->control[0] = CONTROL_DEFAULT_0;
 341                 up->control[1] = CONTROL_DEFAULT_1;
 342                 up->control[2] = CONTROL_DEFAULT_2;
 343                 up->control[3] = CONTROL_DEFAULT_3;
 344         }
 345
 346         np->hv_state = HV_RNG_STATE_UNCONFIGURED;
 347 }
 348
 349 static int n2rng_grab_diag_control(struct n2rng *np)
 350 {
 351         int i, busy_count, err = -ENODEV;
 352
 353         busy_count = 0;
 354         for (i = 0; i < 100; i++) {
 355                 err = n2rng_try_read_ctl(np);
 356                 if (err != -EAGAIN)
 357                         break;
 358
 359                 if (++busy_count > 100) {
 360                         dev_err(&np->op->dev,
 361                                 "Grab diag control timeout.\n");
 362                         return -ENODEV;
 363                 }
 364
 365                 udelay(1);
 366         }
 367
 368         return err;
 369 }
 370
 371 static int n2rng_init_control(struct n2rng *np)
 372 {
 373         int err = n2rng_grab_diag_control(np);
 374
 375         /* Not in the control domain, that's OK we are only a consumer
 376          * of the RNG data, we don't setup and program it.
 377          */
 378         if (err == -EPERM)
 379                 return 0;
 380         if (err)
 381                 return err;
 382
 383         n2rng_control_swstate_init(np);
 384
 385         return 0;
 386 }
 387
 388 static int n2rng_data_read(struct hwrng *rng, u32 *data)
 389 {
 390         struct n2rng *np = (struct n2rng *) rng->priv;
 391         unsigned long ra = __pa(&np->test_data);
 392         int len;
 393
 394         if (!(np->flags & N2RNG_FLAG_READY)) {
 395                 len = 0;
 396         } else if (np->flags & N2RNG_FLAG_BUFFER_VALID) {
 397                 np->flags &= ~N2RNG_FLAG_BUFFER_VALID;
 398                 *data = np->buffer;
 399                 len = 4;
 400         } else {
 401                 int err = n2rng_generic_read_data(ra);
 402                 if (!err) {
 403                         np->buffer = np->test_data >> 32;
 404                         *data = np->test_data & 0xffffffff;
 405                         len = 4;
 406                 } else {
 407                         dev_err(&np->op->dev, "RNG error, restesting\n");
 408                         np->flags &= ~N2RNG_FLAG_READY;
 409                         if (!(np->flags & N2RNG_FLAG_SHUTDOWN))
 410                                 schedule_delayed_work(&np->work, 0);
 411                         len = 0;
 412                 }
 413         }
 414
 415         return len;
 416 }
 417
 418 /* On a guest node, just make sure we can read random data properly.
 419  * If a control node reboots or reloads it's n2rng driver, this won't
 420  * work during that time.  So we have to keep probing until the device
 421  * becomes usable.
 422  */
 423 static int n2rng_guest_check(struct n2rng *np)
 424 {
 425         unsigned long ra = __pa(&np->test_data);
 426
 427         return n2rng_generic_read_data(ra);
 428 }
 429
 430 static int n2rng_entropy_diag_read(struct n2rng *np, unsigned long unit,
 431                                    u64 *pre_control, u64 pre_state,
 432                                    u64 *buffer, unsigned long buf_len,
 433                                    u64 *post_control, u64 post_state)
 434 {
 435         unsigned long post_ctl_ra = __pa(post_control);
 436         unsigned long pre_ctl_ra = __pa(pre_control);
 437         unsigned long buffer_ra = __pa(buffer);
 438         int err;
 439
 440         err = n2rng_generic_write_control(np, pre_ctl_ra, unit, pre_state);
 441         if (err)
 442                 return err;
 443
 444         err = n2rng_generic_read_diag_data(np, unit,
 445                                            buffer_ra, buf_len);
 446
 447         (void) n2rng_generic_write_control(np, post_ctl_ra, unit,
 448                                            post_state);
 449
 450         return err;
 451 }
 452
 453 static u64 advance_polynomial(u64 poly, u64 val, int count)
 454 {
 455         int i;
 456
 457         for (i = 0; i < count; i++) {
 458                 int highbit_set = ((s64)val < 0);
 459
 460                 val <<= 1;
 461                 if (highbit_set)
 462                         val ^= poly;
 463         }
 464
 465         return val;
 466 }
 467
 468 static int n2rng_test_buffer_find(struct n2rng *np, u64 val)
 469 {
 470         int i, count = 0;
 471
 472         /* Purposefully skip over the first word.  */
 473         for (i = 1; i < SELFTEST_BUFFER_WORDS; i++) {
 474                 if (np->test_buffer[i] == val)
 475                         count++;
 476         }
 477         return count;
 478 }
 479
 480 static void n2rng_dump_test_buffer(struct n2rng *np)
 481 {
 482         int i;
 483
 484         for (i = 0; i < SELFTEST_BUFFER_WORDS; i++)
 485                 dev_err(&np->op->dev, "Test buffer slot %d [0x%016llx]\n",
 486                         i, np->test_buffer[i]);
 487 }
 488
 489 static int n2rng_check_selftest_buffer(struct n2rng *np, unsigned long unit)
 490 {
 491         u64 val = SELFTEST_VAL;
 492         int err, matches, limit;
 493
 494         matches = 0;
 495         for (limit = 0; limit < SELFTEST_LOOPS_MAX; limit++) {
 496                 matches += n2rng_test_buffer_find(np, val);
 497                 if (matches >= SELFTEST_MATCH_GOAL)
 498                         break;
 499                 val = advance_polynomial(SELFTEST_POLY, val, 1);
 500         }
 501
 502         err = 0;
 503         if (limit >= SELFTEST_LOOPS_MAX) {
 504                 err = -ENODEV;
 505                 dev_err(&np->op->dev, "Selftest failed on unit %lu\n", unit);
 506                 n2rng_dump_test_buffer(np);
 507         } else
 508                 dev_info(&np->op->dev, "Selftest passed on unit %lu\n", unit);
 509
 510         return err;
 511 }
 512
 513 static int n2rng_control_selftest(struct n2rng *np, unsigned long unit)
 514 {
 515         int err;
 516
 517         np->test_control[0] = (0x2 << RNG_CTL_ASEL_SHIFT);
 518         np->test_control[1] = (0x2 << RNG_CTL_ASEL_SHIFT);
 519         np->test_control[2] = (0x2 << RNG_CTL_ASEL_SHIFT);
 520         np->test_control[3] = ((0x2 << RNG_CTL_ASEL_SHIFT) |
 521                                RNG_CTL_LFSR |
 522                                ((SELFTEST_TICKS - 2) << RNG_CTL_WAIT_SHIFT));
 523
 524
 525         err = n2rng_entropy_diag_read(np, unit, np->test_control,
 526                                       HV_RNG_STATE_HEALTHCHECK,
 527                                       np->test_buffer,
 528                                       sizeof(np->test_buffer),
 529                                       &np->units[unit].control[0],
 530                                       np->hv_state);
 531         if (err)
 532                 return err;
 533
 534         return n2rng_check_selftest_buffer(np, unit);
 535 }
 536
 537 static int n2rng_control_check(struct n2rng *np)
 538 {
 539         int i;
 540
 541         for (i = 0; i < np->num_units; i++) {
 542                 int err = n2rng_control_selftest(np, i);
 543                 if (err)
 544                         return err;
 545         }
 546         return 0;
 547 }
 548
 549 /* The sanity checks passed, install the final configuration into the
 550  * chip, it's ready to use.
 551  */
 552 static int n2rng_control_configure_units(struct n2rng *np)
 553 {
 554         int unit, err;
 555
 556         err = 0;
 557         for (unit = 0; unit < np->num_units; unit++) {
 558                 struct n2rng_unit *up = &np->units[unit];
 559                 unsigned long ctl_ra = __pa(&up->control[0]);
 560                 int esrc;
 561                 u64 base;
 562
 563                 base = ((np->accum_cycles << RNG_CTL_WAIT_SHIFT) |
 564                         (2 << RNG_CTL_ASEL_SHIFT) |
 565                         RNG_CTL_LFSR);
 566
 567                 /* XXX This isn't the best.  We should fetch a bunch
 568                  * XXX of words using each entropy source combined XXX
 569                  * with each VCO setting, and see which combinations
 570                  * XXX give the best random data.
 571                  */
 572                 for (esrc = 0; esrc < 3; esrc++)
 573                         up->control[esrc] = base |
 574                                 (esrc << RNG_CTL_VCO_SHIFT) |
 575                                 (RNG_CTL_ES1 << esrc);
 576
 577                 up->control[3] = base |
 578                         (RNG_CTL_ES1 | RNG_CTL_ES2 | RNG_CTL_ES3);
 579
 580                 err = n2rng_generic_write_control(np, ctl_ra, unit,
 581                                                   HV_RNG_STATE_CONFIGURED);
 582                 if (err)
 583                         break;
 584         }
 585
 586         return err;
 587 }
 588
 589 static void n2rng_work(struct work_struct *work)
 590 {
 591         struct n2rng *np = container_of(work, struct n2rng, work.work);
 592         int err = 0;
 593
 594         if (!(np->flags & N2RNG_FLAG_CONTROL)) {
 595                 err = n2rng_guest_check(np);
 596         } else {
 597                 preempt_disable();
 598                 err = n2rng_control_check(np);
 599                 preempt_enable();
 600
 601                 if (!err)
 602                         err = n2rng_control_configure_units(np);
 603         }
 604
 605         if (!err) {
 606                 np->flags |= N2RNG_FLAG_READY;
 607                 dev_info(&np->op->dev, "RNG ready\n");
 608         }
 609
 610         if (err && !(np->flags & N2RNG_FLAG_SHUTDOWN))
 611                 schedule_delayed_work(&np->work, HZ * 2);
 612 }
 613
 614 static void __devinit n2rng_driver_version(void)
 615 {
 616         static int n2rng_version_printed;
 617
 618         if (n2rng_version_printed++ == 0)
 619                 pr_info("%s", version);
 620 }
 621
 622 static int __devinit n2rng_probe(struct of_device *op,
 623                                  const struct of_device_id *match)
 624 {
 625         int victoria_falls = (match->data != NULL);
 626         int err = -ENOMEM;
 627         struct n2rng *np;
 628
 629         n2rng_driver_version();
 630
 631         np = kzalloc(sizeof(*np), GFP_KERNEL);
 632         if (!np)
 633                 goto out;
 634         np->op = op;
 635
 636         INIT_DELAYED_WORK(&np->work, n2rng_work);
 637
 638         if (victoria_falls)
 639                 np->flags |= N2RNG_FLAG_VF;
 640
 641         err = -ENODEV;
 642         np->hvapi_major = 2;
 643         if (sun4v_hvapi_register(HV_GRP_RNG,
 644                                  np->hvapi_major,
 645                                  &np->hvapi_minor)) {
 646                 np->hvapi_major = 1;
 647                 if (sun4v_hvapi_register(HV_GRP_RNG,
 648                                          np->hvapi_major,
 649                                          &np->hvapi_minor)) {
 650                         dev_err(&op->dev, "Cannot register suitable "
 651                                 "HVAPI version.\n");
 652                         goto out_free;
 653                 }
 654         }
 655
 656         if (np->flags & N2RNG_FLAG_VF) {
 657                 if (np->hvapi_major < 2) {
 658                         dev_err(&op->dev, "VF RNG requires HVAPI major "
 659                                 "version 2 or later, got %lu\n",
 660                                 np->hvapi_major);
 661                         goto out_hvapi_unregister;
 662                 }
 663                 np->num_units = of_getintprop_default(op->dev.of_node,
 664                                                       "rng-#units", 0);
 665                 if (!np->num_units) {
 666                         dev_err(&op->dev, "VF RNG lacks rng-#units property\n");
 667                         goto out_hvapi_unregister;
 668                 }
 669         } else
 670                 np->num_units = 1;
 671
 672         dev_info(&op->dev, "Registered RNG HVAPI major %lu minor %lu\n",
 673                  np->hvapi_major, np->hvapi_minor);
 674
 675         np->units = kzalloc(sizeof(struct n2rng_unit) * np->num_units,
 676                             GFP_KERNEL);
 677         err = -ENOMEM;
 678         if (!np->units)
 679                 goto out_hvapi_unregister;
 680
 681         err = n2rng_init_control(np);
 682         if (err)
 683                 goto out_free_units;
 684
 685         dev_info(&op->dev, "Found %s RNG, units: %d\n",
 686                  ((np->flags & N2RNG_FLAG_VF) ?
 687                   "Victoria Falls" : "Niagara2"),
 688                  np->num_units);
 689
 690         np->hwrng.name = "n2rng";
 691         np->hwrng.data_read = n2rng_data_read;
 692         np->hwrng.priv = (unsigned long) np;
 693
 694         err = hwrng_register(&np->hwrng);
 695         if (err)
 696                 goto out_free_units;
 697
 698         dev_set_drvdata(&op->dev, np);
 699
 700         schedule_delayed_work(&np->work, 0);
 701
 702         return 0;
 703
 704 out_free_units:
 705         kfree(np->units);
 706         np->units = NULL;
 707
 708 out_hvapi_unregister:
 709         sun4v_hvapi_unregister(HV_GRP_RNG);
 710
 711 out_free:
 712         kfree(np);
 713 out:
 714         return err;
 715 }
 716
 717 static int __devexit n2rng_remove(struct of_device *op)
 718 {
 719         struct n2rng *np = dev_get_drvdata(&op->dev);
 720
 721         np->flags |= N2RNG_FLAG_SHUTDOWN;
 722
 723         cancel_delayed_work_sync(&np->work);
 724
 725         hwrng_unregister(&np->hwrng);
 726
 727         sun4v_hvapi_unregister(HV_GRP_RNG);
 728
 729         kfree(np->units);
 730         np->units = NULL;
 731
 732         kfree(np);
 733
 734         dev_set_drvdata(&op->dev, NULL);
 735
 736         return 0;
 737 }
 738
 739 static const struct of_device_id n2rng_match[] = {
 740         {
 741                 .name           = "random-number-generator",
 742                 .compatible     = "SUNW,n2-rng",
 743         },
 744         {
 745                 .name           = "random-number-generator",
 746                 .compatible     = "SUNW,vf-rng",
 747                 .data           = (void *) 1,
 748         },
 749         {},
 750 };
 751 MODULE_DEVICE_TABLE(of, n2rng_match);
 752
 753 static struct of_platform_driver n2rng_driver = {
 754         .driver = {
 755                 .name = "n2rng",
 756                 .owner = THIS_MODULE,
 757                 .of_match_table = n2rng_match,
 758         },
 759         .probe          = n2rng_probe,
 760         .remove         = __devexit_p(n2rng_remove),
 761 };
 762
 763 static int __init n2rng_init(void)
 764 {
 765         return of_register_platform_driver(&n2rng_driver);
 766 }
 767
 768 static void __exit n2rng_exit(void)
 769 {
 770         of_unregister_platform_driver(&n2rng_driver);
 771 }
 772
 773 module_init(n2rng_init);
 774 module_exit(n2rng_exit);