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   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2
   3 /***************************************************************************
   4  *
   5  *   Copyright (C) 2010 by David Brownell
   6  ***************************************************************************/
   7
   8 /**
   9  * @file
  10  * Utilities to support ARM "Serial Wire Debug" (SWD), a low pin-count debug
  11  * link protocol used in cases where JTAG is not wanted.  This is coupled to
  12  * recent versions of ARM's "CoreSight" debug framework.  This specific code
  13  * is a transport level interface, with "target/arm_adi_v5.[hc]" code
  14  * understanding operation semantics, shared with the JTAG transport.
  15  *
  16  * Single-DAP support only.
  17  *
  18  * for details, see "ARM IHI 0031A"
  19  * ARM Debug Interface v5 Architecture Specification
  20  * especially section 5.3 for SWD protocol
  21  * and "ARM IHI 0074C" ARM Debug Interface Architecture Specification ADIv6.0
  22  *
  23  * On many chips (most current Cortex-M3 parts) SWD is a run-time alternative
  24  * to JTAG.  Boards may support one or both.  There are also SWD-only chips,
  25  * (using SW-DP not SWJ-DP).
  26  *
  27  * Even boards that also support JTAG can benefit from SWD support, because
  28  * usually there's no way to access the SWO trace view mechanism in JTAG mode.
  29  * That is, trace access may require SWD support.
  30  *
  31  */
  32
  33 #ifdef HAVE_CONFIG_H
  34 #include "config.h"
  35 #endif
  36
  37 #include "arm.h"
  38 #include "arm_adi_v5.h"
  39 #include <helper/time_support.h>
  40
  41 #include <transport/transport.h>
  42 #include <jtag/interface.h>
  43
  44 #include <jtag/swd.h>
  45
  46 /* for debug, set do_sync to true to force synchronous transfers */
  47 static bool do_sync;
  48
  49 static struct adiv5_dap *swd_multidrop_selected_dap;
  50
  51
  52 static int swd_queue_dp_write_inner(struct adiv5_dap *dap, unsigned int reg,
  53                 uint32_t data);
  54
  55
  56 static int swd_send_sequence(struct adiv5_dap *dap, enum swd_special_seq seq)
  57 {
  58         const struct swd_driver *swd = adiv5_dap_swd_driver(dap);
  59         assert(swd);
  60
  61         return swd->switch_seq(seq);
  62 }
  63
  64 static void swd_finish_read(struct adiv5_dap *dap)
  65 {
  66         const struct swd_driver *swd = adiv5_dap_swd_driver(dap);
  67         if (dap->last_read) {
  68                 swd->read_reg(swd_cmd(true, false, DP_RDBUFF), dap->last_read, 0);
  69                 dap->last_read = NULL;
  70         }
  71 }
  72
  73 static void swd_clear_sticky_errors(struct adiv5_dap *dap)
  74 {
  75         const struct swd_driver *swd = adiv5_dap_swd_driver(dap);
  76         assert(swd);
  77
  78         swd->write_reg(swd_cmd(false, false, DP_ABORT),
  79                 STKCMPCLR | STKERRCLR | WDERRCLR | ORUNERRCLR, 0);
  80 }
  81
  82 static int swd_run_inner(struct adiv5_dap *dap)
  83 {
  84         const struct swd_driver *swd = adiv5_dap_swd_driver(dap);
  85         int retval;
  86
  87         retval = swd->run();
  88
  89         if (retval != ERROR_OK) {
  90                 /* fault response */
  91                 dap->do_reconnect = true;
  92         }
  93
  94         return retval;
  95 }
  96
  97 static inline int check_sync(struct adiv5_dap *dap)
  98 {
  99         return do_sync ? swd_run_inner(dap) : ERROR_OK;
 100 }
 101
 102 /** Select the DP register bank matching bits 7:4 of reg. */
 103 static int swd_queue_dp_bankselect(struct adiv5_dap *dap, unsigned int reg)
 104 {
 105         /* Only register address 0 and 4 are banked. */
 106         if ((reg & 0xf) > 4)
 107                 return ERROR_OK;
 108
 109         uint64_t sel = (reg & 0x000000F0) >> 4;
 110         if (dap->select != DP_SELECT_INVALID)
 111                 sel |= dap->select & ~0xfULL;
 112
 113         if (sel == dap->select)
 114                 return ERROR_OK;
 115
 116         dap->select = sel;
 117
 118         int retval = swd_queue_dp_write_inner(dap, DP_SELECT, (uint32_t)sel);
 119         if (retval != ERROR_OK)
 120                 dap->select = DP_SELECT_INVALID;
 121
 122         return retval;
 123 }
 124
 125 static int swd_queue_dp_read_inner(struct adiv5_dap *dap, unsigned int reg,
 126                 uint32_t *data)
 127 {
 128         const struct swd_driver *swd = adiv5_dap_swd_driver(dap);
 129         assert(swd);
 130
 131         int retval = swd_queue_dp_bankselect(dap, reg);
 132         if (retval != ERROR_OK)
 133                 return retval;
 134
 135         swd->read_reg(swd_cmd(true, false, reg), data, 0);
 136
 137         return check_sync(dap);
 138 }
 139
 140 static int swd_queue_dp_write_inner(struct adiv5_dap *dap, unsigned int reg,
 141                 uint32_t data)
 142 {
 143         int retval;
 144         const struct swd_driver *swd = adiv5_dap_swd_driver(dap);
 145         assert(swd);
 146
 147         swd_finish_read(dap);
 148
 149         if (reg == DP_SELECT) {
 150                 dap->select = data & (DP_SELECT_APSEL | DP_SELECT_APBANK | DP_SELECT_DPBANK);
 151
 152                 swd->write_reg(swd_cmd(false, false, reg), data, 0);
 153
 154                 retval = check_sync(dap);
 155                 if (retval != ERROR_OK)
 156                         dap->select = DP_SELECT_INVALID;
 157
 158                 return retval;
 159         }
 160
 161         retval = swd_queue_dp_bankselect(dap, reg);
 162         if (retval != ERROR_OK)
 163                 return retval;
 164
 165         swd->write_reg(swd_cmd(false, false, reg), data, 0);
 166
 167         return check_sync(dap);
 168 }
 169
 170
 171 static int swd_multidrop_select_inner(struct adiv5_dap *dap, uint32_t *dpidr_ptr,
 172                 uint32_t *dlpidr_ptr, bool clear_sticky)
 173 {
 174         int retval;
 175         uint32_t dpidr, dlpidr;
 176
 177         assert(dap_is_multidrop(dap));
 178
 179         swd_send_sequence(dap, LINE_RESET);
 180         /* From ARM IHI 0074C ADIv6.0, chapter B4.3.3 "Connection and line reset
 181          * sequence":
 182          * - line reset sets DP_SELECT_DPBANK to zero;
 183          * - read of DP_DPIDR takes the connection out of reset;
 184          * - write of DP_TARGETSEL keeps the connection in reset;
 185          * - other accesses return protocol error (SWDIO not driven by target).
 186          *
 187          * Read DP_DPIDR to get out of reset. Initialize dap->select to zero to
 188          * skip the write to DP_SELECT, avoiding the protocol error. Set again
 189          * dap->select to DP_SELECT_INVALID because the rest of the register is
 190          * unknown after line reset.
 191          */
 192         dap->select = 0;
 193
 194         retval = swd_queue_dp_write_inner(dap, DP_TARGETSEL, dap->multidrop_targetsel);
 195         if (retval != ERROR_OK)
 196                 return retval;
 197
 198         retval = swd_queue_dp_read_inner(dap, DP_DPIDR, &dpidr);
 199         if (retval != ERROR_OK)
 200                 return retval;
 201
 202         if (clear_sticky) {
 203                 /* Clear all sticky errors (including ORUN) */
 204                 swd_clear_sticky_errors(dap);
 205         } else {
 206                 /* Ideally just clear ORUN flag which is set by reset */
 207                 retval = swd_queue_dp_write_inner(dap, DP_ABORT, ORUNERRCLR);
 208                 if (retval != ERROR_OK)
 209                         return retval;
 210         }
 211
 212         dap->select = DP_SELECT_INVALID;
 213
 214         retval = swd_queue_dp_read_inner(dap, DP_DLPIDR, &dlpidr);
 215         if (retval != ERROR_OK)
 216                 return retval;
 217
 218         retval = swd_run_inner(dap);
 219         if (retval != ERROR_OK)
 220                 return retval;
 221
 222         if ((dpidr & DP_DPIDR_VERSION_MASK) < (2UL << DP_DPIDR_VERSION_SHIFT)) {
 223                 LOG_INFO("Read DPIDR 0x%08" PRIx32
 224                                  " has version < 2. A non multidrop capable device connected?",
 225                                  dpidr);
 226                 return ERROR_FAIL;
 227         }
 228
 229         /* TODO: check TARGETID if DLIPDR is same for more than one DP */
 230         uint32_t expected_dlpidr = DP_DLPIDR_PROTVSN |
 231                         (dap->multidrop_targetsel & DP_TARGETSEL_INSTANCEID_MASK);
 232         if (dlpidr != expected_dlpidr) {
 233                 LOG_INFO("Read incorrect DLPIDR 0x%08" PRIx32
 234                                  " (possibly CTRL/STAT value)",
 235                                  dlpidr);
 236                 return ERROR_FAIL;
 237         }
 238
 239         LOG_DEBUG_IO("Selected DP_TARGETSEL 0x%08" PRIx32, dap->multidrop_targetsel);
 240         swd_multidrop_selected_dap = dap;
 241
 242         if (dpidr_ptr)
 243                 *dpidr_ptr = dpidr;
 244
 245         if (dlpidr_ptr)
 246                 *dlpidr_ptr = dlpidr;
 247
 248         return retval;
 249 }
 250
 251 static int swd_multidrop_select(struct adiv5_dap *dap)
 252 {
 253         if (!dap_is_multidrop(dap))
 254                 return ERROR_OK;
 255
 256         if (swd_multidrop_selected_dap == dap)
 257                 return ERROR_OK;
 258
 259         int retval = ERROR_OK;
 260         for (unsigned int retry = 0; ; retry++) {
 261                 bool clear_sticky = retry > 0;
 262
 263                 retval = swd_multidrop_select_inner(dap, NULL, NULL, clear_sticky);
 264                 if (retval == ERROR_OK)
 265                         break;
 266
 267                 swd_multidrop_selected_dap = NULL;
 268                 if (retry > 3) {
 269                         LOG_ERROR("Failed to select multidrop %s", adiv5_dap_name(dap));
 270                         return retval;
 271                 }
 272
 273                 LOG_DEBUG("Failed to select multidrop %s, retrying...",
 274                                   adiv5_dap_name(dap));
 275                 /* we going to retry localy, do not ask for full reconnect */
 276                 dap->do_reconnect = false;
 277         }
 278
 279         return retval;
 280 }
 281
 282 static int swd_connect_multidrop(struct adiv5_dap *dap)
 283 {
 284         int retval;
 285         uint32_t dpidr = 0xdeadbeef;
 286         uint32_t dlpidr = 0xdeadbeef;
 287         int64_t timeout = timeval_ms() + 500;
 288
 289         do {
 290                 swd_send_sequence(dap, JTAG_TO_DORMANT);
 291                 swd_send_sequence(dap, DORMANT_TO_SWD);
 292
 293                 /* Clear link state, including the SELECT cache. */
 294                 dap->do_reconnect = false;
 295                 dap_invalidate_cache(dap);
 296                 swd_multidrop_selected_dap = NULL;
 297
 298                 retval = swd_multidrop_select_inner(dap, &dpidr, &dlpidr, true);
 299                 if (retval == ERROR_OK)
 300                         break;
 301
 302                 alive_sleep(1);
 303
 304         } while (timeval_ms() < timeout);
 305
 306         if (retval != ERROR_OK) {
 307                 swd_multidrop_selected_dap = NULL;
 308                 LOG_ERROR("Failed to connect multidrop %s", adiv5_dap_name(dap));
 309                 return retval;
 310         }
 311
 312         LOG_INFO("SWD DPIDR 0x%08" PRIx32 ", DLPIDR 0x%08" PRIx32,
 313                           dpidr, dlpidr);
 314
 315         return retval;
 316 }
 317
 318 static int swd_connect_single(struct adiv5_dap *dap)
 319 {
 320         int retval;
 321         uint32_t dpidr = 0xdeadbeef;
 322         int64_t timeout = timeval_ms() + 500;
 323
 324         do {
 325                 if (dap->switch_through_dormant) {
 326                         swd_send_sequence(dap, JTAG_TO_DORMANT);
 327                         swd_send_sequence(dap, DORMANT_TO_SWD);
 328                 } else {
 329                         swd_send_sequence(dap, JTAG_TO_SWD);
 330                 }
 331
 332                 /* Clear link state, including the SELECT cache. */
 333                 dap->do_reconnect = false;
 334                 dap_invalidate_cache(dap);
 335
 336                 /* The sequences to enter in SWD (JTAG_TO_SWD and DORMANT_TO_SWD) end
 337                  * with a SWD line reset sequence (50 clk with SWDIO high).
 338                  * From ARM IHI 0074C ADIv6.0, chapter B4.3.3 "Connection and line reset
 339                  * sequence":
 340                  * - line reset sets DP_SELECT_DPBANK to zero;
 341                  * - read of DP_DPIDR takes the connection out of reset;
 342                  * - write of DP_TARGETSEL keeps the connection in reset;
 343                  * - other accesses return protocol error (SWDIO not driven by target).
 344                  *
 345                  * Read DP_DPIDR to get out of reset. Initialize dap->select to zero to
 346                  * skip the write to DP_SELECT, avoiding the protocol error. Set again
 347                  * dap->select to DP_SELECT_INVALID because the rest of the register is
 348                  * unknown after line reset.
 349                  */
 350                 dap->select = 0;
 351                 retval = swd_queue_dp_read_inner(dap, DP_DPIDR, &dpidr);
 352                 if (retval == ERROR_OK) {
 353                         retval = swd_run_inner(dap);
 354                         if (retval == ERROR_OK)
 355                                 break;
 356                 }
 357
 358                 alive_sleep(1);
 359
 360                 dap->switch_through_dormant = !dap->switch_through_dormant;
 361         } while (timeval_ms() < timeout);
 362
 363         dap->select = DP_SELECT_INVALID;
 364
 365         if (retval != ERROR_OK) {
 366                 LOG_ERROR("Error connecting DP: cannot read IDR");
 367                 return retval;
 368         }
 369
 370         LOG_INFO("SWD DPIDR 0x%08" PRIx32, dpidr);
 371
 372         do {
 373                 dap->do_reconnect = false;
 374
 375                 /* force clear all sticky faults */
 376                 swd_clear_sticky_errors(dap);
 377
 378                 retval = swd_run_inner(dap);
 379                 if (retval != ERROR_WAIT)
 380                         break;
 381
 382                 alive_sleep(10);
 383
 384         } while (timeval_ms() < timeout);
 385
 386         return retval;
 387 }
 388
 389 static int swd_connect(struct adiv5_dap *dap)
 390 {
 391         int status;
 392
 393         /* FIXME validate transport config ... is the
 394          * configured DAP present (check IDCODE)?
 395          */
 396
 397         /* Check if we should reset srst already when connecting, but not if reconnecting. */
 398         if (!dap->do_reconnect) {
 399                 enum reset_types jtag_reset_config = jtag_get_reset_config();
 400
 401                 if (jtag_reset_config & RESET_CNCT_UNDER_SRST) {
 402                         if (jtag_reset_config & RESET_SRST_NO_GATING)
 403                                 adapter_assert_reset();
 404                         else
 405                                 LOG_WARNING("\'srst_nogate\' reset_config option is required");
 406                 }
 407         }
 408
 409         if (dap_is_multidrop(dap))
 410                 status = swd_connect_multidrop(dap);
 411         else
 412                 status = swd_connect_single(dap);
 413
 414         /* IHI 0031E B4.3.2:
 415          * "A WAIT response must not be issued to the ...
 416          * ... writes to the ABORT register"
 417          * swd_clear_sticky_errors() writes to the ABORT register only.
 418          *
 419          * Unfortunately at least Microchip SAMD51/E53/E54 returns WAIT
 420          * in a corner case. Just try if ABORT resolves the problem.
 421          */
 422         if (status == ERROR_WAIT) {
 423                 LOG_WARNING("Connecting DP: stalled AP operation, issuing ABORT");
 424
 425                 dap->do_reconnect = false;
 426
 427                 status = swd_queue_dp_write_inner(dap, DP_ABORT,
 428                         DAPABORT | STKCMPCLR | STKERRCLR | WDERRCLR | ORUNERRCLR);
 429
 430                 if (status == ERROR_OK)
 431                         status = swd_run_inner(dap);
 432         }
 433
 434         if (status == ERROR_OK)
 435                 status = dap_dp_init(dap);
 436
 437         return status;
 438 }
 439
 440 static int swd_check_reconnect(struct adiv5_dap *dap)
 441 {
 442         if (dap->do_reconnect)
 443                 return swd_connect(dap);
 444
 445         return ERROR_OK;
 446 }
 447
 448 static int swd_queue_ap_abort(struct adiv5_dap *dap, uint8_t *ack)
 449 {
 450         const struct swd_driver *swd = adiv5_dap_swd_driver(dap);
 451         assert(swd);
 452
 453         /* TODO: Send DAPABORT in swd_multidrop_select_inner()
 454          * in the case the multidrop dap is not selected?
 455          * swd_queue_ap_abort() is not currently used anyway...
 456          */
 457         int retval = swd_multidrop_select(dap);
 458         if (retval != ERROR_OK)
 459                 return retval;
 460
 461         swd->write_reg(swd_cmd(false, false, DP_ABORT),
 462                 DAPABORT | STKCMPCLR | STKERRCLR | WDERRCLR | ORUNERRCLR, 0);
 463         return check_sync(dap);
 464 }
 465
 466 static int swd_queue_dp_read(struct adiv5_dap *dap, unsigned reg,
 467                 uint32_t *data)
 468 {
 469         int retval = swd_check_reconnect(dap);
 470         if (retval != ERROR_OK)
 471                 return retval;
 472
 473         retval = swd_multidrop_select(dap);
 474         if (retval != ERROR_OK)
 475                 return retval;
 476
 477         return swd_queue_dp_read_inner(dap, reg, data);
 478 }
 479
 480 static int swd_queue_dp_write(struct adiv5_dap *dap, unsigned reg,
 481                 uint32_t data)
 482 {
 483         const struct swd_driver *swd = adiv5_dap_swd_driver(dap);
 484         assert(swd);
 485
 486         int retval = swd_check_reconnect(dap);
 487         if (retval != ERROR_OK)
 488                 return retval;
 489
 490         retval = swd_multidrop_select(dap);
 491         if (retval != ERROR_OK)
 492                 return retval;
 493
 494         return swd_queue_dp_write_inner(dap, reg, data);
 495 }
 496
 497 /** Select the AP register bank matching bits 7:4 of reg. */
 498 static int swd_queue_ap_bankselect(struct adiv5_ap *ap, unsigned reg)
 499 {
 500         int retval;
 501         struct adiv5_dap *dap = ap->dap;
 502         uint64_t sel;
 503
 504         if (is_adiv6(dap)) {
 505                 sel = ap->ap_num | (reg & 0x00000FF0);
 506                 if (sel == (dap->select & ~0xfULL))
 507                         return ERROR_OK;
 508
 509                 if (dap->select != DP_SELECT_INVALID)
 510                         sel |= dap->select & 0xf;
 511                 dap->select = sel;
 512                 LOG_DEBUG("AP BANKSEL: %" PRIx64, sel);
 513
 514                 retval = swd_queue_dp_write(dap, DP_SELECT, (uint32_t)sel);
 515
 516                 if (retval == ERROR_OK && dap->asize > 32)
 517                         retval = swd_queue_dp_write(dap, DP_SELECT1, (uint32_t)(sel >> 32));
 518
 519                 if (retval != ERROR_OK)
 520                         dap->select = DP_SELECT_INVALID;
 521
 522                 return retval;
 523         }
 524
 525         /* ADIv5 */
 526         sel = (ap->ap_num << 24) | (reg & 0x000000F0);
 527         if (dap->select != DP_SELECT_INVALID)
 528                 sel |= dap->select & DP_SELECT_DPBANK;
 529
 530         if (sel == dap->select)
 531                 return ERROR_OK;
 532
 533         dap->select = sel;
 534
 535         retval = swd_queue_dp_write_inner(dap, DP_SELECT, sel);
 536         if (retval != ERROR_OK)
 537                 dap->select = DP_SELECT_INVALID;
 538
 539         return retval;
 540 }
 541
 542 static int swd_queue_ap_read(struct adiv5_ap *ap, unsigned reg,
 543                 uint32_t *data)
 544 {
 545         struct adiv5_dap *dap = ap->dap;
 546         const struct swd_driver *swd = adiv5_dap_swd_driver(dap);
 547         assert(swd);
 548
 549         int retval = swd_check_reconnect(dap);
 550         if (retval != ERROR_OK)
 551                 return retval;
 552
 553         retval = swd_multidrop_select(dap);
 554         if (retval != ERROR_OK)
 555                 return retval;
 556
 557         retval = swd_queue_ap_bankselect(ap, reg);
 558         if (retval != ERROR_OK)
 559                 return retval;
 560
 561         swd->read_reg(swd_cmd(true, true, reg), dap->last_read, ap->memaccess_tck);
 562         dap->last_read = data;
 563
 564         return check_sync(dap);
 565 }
 566
 567 static int swd_queue_ap_write(struct adiv5_ap *ap, unsigned reg,
 568                 uint32_t data)
 569 {
 570         struct adiv5_dap *dap = ap->dap;
 571         const struct swd_driver *swd = adiv5_dap_swd_driver(dap);
 572         assert(swd);
 573
 574         int retval = swd_check_reconnect(dap);
 575         if (retval != ERROR_OK)
 576                 return retval;
 577
 578         retval = swd_multidrop_select(dap);
 579         if (retval != ERROR_OK)
 580                 return retval;
 581
 582         swd_finish_read(dap);
 583
 584         retval = swd_queue_ap_bankselect(ap, reg);
 585         if (retval != ERROR_OK)
 586                 return retval;
 587
 588         swd->write_reg(swd_cmd(false, true, reg), data, ap->memaccess_tck);
 589
 590         return check_sync(dap);
 591 }
 592
 593 /** Executes all queued DAP operations. */
 594 static int swd_run(struct adiv5_dap *dap)
 595 {
 596         int retval = swd_multidrop_select(dap);
 597         if (retval != ERROR_OK)
 598                 return retval;
 599
 600         swd_finish_read(dap);
 601
 602         return swd_run_inner(dap);
 603 }
 604
 605 /** Put the SWJ-DP back to JTAG mode */
 606 static void swd_quit(struct adiv5_dap *dap)
 607 {
 608         const struct swd_driver *swd = adiv5_dap_swd_driver(dap);
 609         static bool done;
 610
 611         /* There is no difference if the sequence is sent at the last
 612          * or the first swd_quit() call, send it just once */
 613         if (done)
 614                 return;
 615
 616         done = true;
 617         if (dap_is_multidrop(dap)) {
 618                 swd->switch_seq(SWD_TO_DORMANT);
 619                 /* Revisit!
 620                  * Leaving DPs in dormant state was tested and offers some safety
 621                  * against DPs mismatch in case of unintentional use of non-multidrop SWD.
 622                  * To put SWJ-DPs to power-on state issue
 623                  * swd->switch_seq(DORMANT_TO_JTAG);
 624                  */
 625         } else {
 626                 if (dap->switch_through_dormant) {
 627                         swd->switch_seq(SWD_TO_DORMANT);
 628                         swd->switch_seq(DORMANT_TO_JTAG);
 629                 } else {
 630                         swd->switch_seq(SWD_TO_JTAG);
 631                 }
 632         }
 633
 634         /* flush the queue to shift out the sequence before exit */
 635         swd->run();
 636 }
 637
 638 const struct dap_ops swd_dap_ops = {
 639         .connect = swd_connect,
 640         .send_sequence = swd_send_sequence,
 641         .queue_dp_read = swd_queue_dp_read,
 642         .queue_dp_write = swd_queue_dp_write,
 643         .queue_ap_read = swd_queue_ap_read,
 644         .queue_ap_write = swd_queue_ap_write,
 645         .queue_ap_abort = swd_queue_ap_abort,
 646         .run = swd_run,
 647         .quit = swd_quit,
 648 };
 649
 650 static const struct command_registration swd_commands[] = {
 651         {
 652                 /*
 653                  * Set up SWD and JTAG targets identically, unless/until
 654                  * infrastructure improves ...  meanwhile, ignore all
 655                  * JTAG-specific stuff like IR length for SWD.
 656                  *
 657                  * REVISIT can we verify "just one SWD DAP" here/early?
 658                  */
 659                 .name = "newdap",
 660                 .jim_handler = jim_jtag_newtap,
 661                 .mode = COMMAND_CONFIG,
 662                 .help = "declare a new SWD DAP"
 663         },
 664         COMMAND_REGISTRATION_DONE
 665 };
 666
 667 static const struct command_registration swd_handlers[] = {
 668         {
 669                 .name = "swd",
 670                 .mode = COMMAND_ANY,
 671                 .help = "SWD command group",
 672                 .chain = swd_commands,
 673                 .usage = "",
 674         },
 675         COMMAND_REGISTRATION_DONE
 676 };
 677
 678 static int swd_select(struct command_context *ctx)
 679 {
 680         /* FIXME: only place where global 'adapter_driver' is still needed */
 681         extern struct adapter_driver *adapter_driver;
 682         const struct swd_driver *swd = adapter_driver->swd_ops;
 683         int retval;
 684
 685         retval = register_commands(ctx, NULL, swd_handlers);
 686         if (retval != ERROR_OK)
 687                 return retval;
 688
 689          /* be sure driver is in SWD mode; start
 690           * with hardware default TRN (1), it can be changed later
 691           */
 692         if (!swd || !swd->read_reg || !swd->write_reg || !swd->init) {
 693                 LOG_DEBUG("no SWD driver?");
 694                 return ERROR_FAIL;
 695         }
 696
 697         retval = swd->init();
 698         if (retval != ERROR_OK) {
 699                 LOG_DEBUG("can't init SWD driver");
 700                 return retval;
 701         }
 702
 703         return retval;
 704 }
 705
 706 static int swd_init(struct command_context *ctx)
 707 {
 708         /* nothing done here, SWD is initialized
 709          * together with the DAP */
 710         return ERROR_OK;
 711 }
 712
 713 static struct transport swd_transport = {
 714         .name = "swd",
 715         .select = swd_select,
 716         .init = swd_init,
 717 };
 718
 719 static void swd_constructor(void) __attribute__((constructor));
 720 static void swd_constructor(void)
 721 {
 722         transport_register(&swd_transport);
 723 }
 724
 725 /** Returns true if the current debug session
 726  * is using SWD as its transport.
 727  */
 728 bool transport_is_swd(void)
 729 {
 730         return get_current_transport() == &swd_transport;
 731 }