src/jtag/drivers/bitbang.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2
   3 /***************************************************************************
   4  *   Copyright (C) 2005 by Dominic Rath                                    *
   5  *   Dominic.Rath@gmx.de                                                   *
   6  *                                                                         *
   7  *   Copyright (C) 2007,2008 Øyvind Harboe                                 *
   8  *   oyvind.harboe@zylin.com                                               *
   9  ***************************************************************************/
  10
  11 /* 2014-12: Addition of the SWD protocol support is based on the initial work
  12  * by Paul Fertser and modifications by Jean-Christian de Rivaz. */
  13
  14 #ifdef HAVE_CONFIG_H
  15 #include "config.h"
  16 #endif
  17
  18 #include <jtag/jtag.h>      /* Added to avoid include loop in commands.h */
  19 #include "bitbang.h"
  20 #include <jtag/interface.h>
  21 #include <jtag/commands.h>
  22
  23 /**
  24  * Function bitbang_stableclocks
  25  * issues a number of clock cycles while staying in a stable state.
  26  * Because the TMS value required to stay in the RESET state is a 1, whereas
  27  * the TMS value required to stay in any of the other stable states is a 0,
  28  * this function checks the current stable state to decide on the value of TMS
  29  * to use.
  30  */
  31 static int bitbang_stableclocks(int num_cycles);
  32
  33 static void bitbang_swd_write_reg(uint8_t cmd, uint32_t value, uint32_t ap_delay_clk);
  34
  35 struct bitbang_interface *bitbang_interface;
  36
  37 /* DANGER!!!! clock absolutely *MUST* be 0 in idle or reset won't work!
  38  *
  39  * Set this to 1 and str912 reset halt will fail.
  40  *
  41  * If someone can submit a patch with an explanation it will be greatly
  42  * appreciated, but as far as I can tell (ØH) DCLK is generated upon
  43  * clk = 0 in TAP_IDLE. Good luck deducing that from the ARM documentation!
  44  * The ARM documentation uses the term "DCLK is asserted while in the TAP_IDLE
  45  * state". With hardware there is no such thing as *while* in a state. There
  46  * are only edges. So clk => 0 is in fact a very subtle state transition that
  47  * happens *while* in the TAP_IDLE state. "#&¤"#¤&"#&"#&
  48  *
  49  * For "reset halt" the last thing that happens before srst is asserted
  50  * is that the breakpoint is set up. If DCLK is not wiggled one last
  51  * time before the reset, then the breakpoint is not set up and
  52  * "reset halt" will fail to halt.
  53  *
  54  */
  55 #define CLOCK_IDLE() 0
  56
  57 /* The bitbang driver leaves the TCK 0 when in idle */
  58 static void bitbang_end_state(tap_state_t state)
  59 {
  60         assert(tap_is_state_stable(state));
  61         tap_set_end_state(state);
  62 }
  63
  64 static int bitbang_state_move(int skip)
  65 {
  66         int i = 0, tms = 0;
  67         uint8_t tms_scan = tap_get_tms_path(tap_get_state(), tap_get_end_state());
  68         int tms_count = tap_get_tms_path_len(tap_get_state(), tap_get_end_state());
  69
  70         for (i = skip; i < tms_count; i++) {
  71                 tms = (tms_scan >> i) & 1;
  72                 if (bitbang_interface->write(0, tms, 0) != ERROR_OK)
  73                         return ERROR_FAIL;
  74                 if (bitbang_interface->write(1, tms, 0) != ERROR_OK)
  75                         return ERROR_FAIL;
  76         }
  77         if (bitbang_interface->write(CLOCK_IDLE(), tms, 0) != ERROR_OK)
  78                 return ERROR_FAIL;
  79
  80         tap_set_state(tap_get_end_state());
  81         return ERROR_OK;
  82 }
  83
  84 /**
  85  * Clock a bunch of TMS (or SWDIO) transitions, to change the JTAG
  86  * (or SWD) state machine.
  87  */
  88 static int bitbang_execute_tms(struct jtag_command *cmd)
  89 {
  90         unsigned num_bits = cmd->cmd.tms->num_bits;
  91         const uint8_t *bits = cmd->cmd.tms->bits;
  92
  93         LOG_DEBUG_IO("TMS: %d bits", num_bits);
  94
  95         int tms = 0;
  96         for (unsigned i = 0; i < num_bits; i++) {
  97                 tms = ((bits[i/8] >> (i % 8)) & 1);
  98                 if (bitbang_interface->write(0, tms, 0) != ERROR_OK)
  99                         return ERROR_FAIL;
 100                 if (bitbang_interface->write(1, tms, 0) != ERROR_OK)
 101                         return ERROR_FAIL;
 102         }
 103         if (bitbang_interface->write(CLOCK_IDLE(), tms, 0) != ERROR_OK)
 104                 return ERROR_FAIL;
 105
 106         return ERROR_OK;
 107 }
 108
 109 static int bitbang_path_move(struct pathmove_command *cmd)
 110 {
 111         int num_states = cmd->num_states;
 112         int state_count;
 113         int tms = 0;
 114
 115         state_count = 0;
 116         while (num_states) {
 117                 if (tap_state_transition(tap_get_state(), false) == cmd->path[state_count])
 118                         tms = 0;
 119                 else if (tap_state_transition(tap_get_state(), true) == cmd->path[state_count])
 120                         tms = 1;
 121                 else {
 122                         LOG_ERROR("BUG: %s -> %s isn't a valid TAP transition",
 123                                 tap_state_name(tap_get_state()),
 124                                 tap_state_name(cmd->path[state_count]));
 125                         exit(-1);
 126                 }
 127
 128                 if (bitbang_interface->write(0, tms, 0) != ERROR_OK)
 129                         return ERROR_FAIL;
 130                 if (bitbang_interface->write(1, tms, 0) != ERROR_OK)
 131                         return ERROR_FAIL;
 132
 133                 tap_set_state(cmd->path[state_count]);
 134                 state_count++;
 135                 num_states--;
 136         }
 137
 138         if (bitbang_interface->write(CLOCK_IDLE(), tms, 0) != ERROR_OK)
 139                 return ERROR_FAIL;
 140
 141         tap_set_end_state(tap_get_state());
 142         return ERROR_OK;
 143 }
 144
 145 static int bitbang_runtest(int num_cycles)
 146 {
 147         int i;
 148
 149         tap_state_t saved_end_state = tap_get_end_state();
 150
 151         /* only do a state_move when we're not already in IDLE */
 152         if (tap_get_state() != TAP_IDLE) {
 153                 bitbang_end_state(TAP_IDLE);
 154                 if (bitbang_state_move(0) != ERROR_OK)
 155                         return ERROR_FAIL;
 156         }
 157
 158         /* execute num_cycles */
 159         for (i = 0; i < num_cycles; i++) {
 160                 if (bitbang_interface->write(0, 0, 0) != ERROR_OK)
 161                         return ERROR_FAIL;
 162                 if (bitbang_interface->write(1, 0, 0) != ERROR_OK)
 163                         return ERROR_FAIL;
 164         }
 165         if (bitbang_interface->write(CLOCK_IDLE(), 0, 0) != ERROR_OK)
 166                 return ERROR_FAIL;
 167
 168         /* finish in end_state */
 169         bitbang_end_state(saved_end_state);
 170         if (tap_get_state() != tap_get_end_state())
 171                 if (bitbang_state_move(0) != ERROR_OK)
 172                         return ERROR_FAIL;
 173
 174         return ERROR_OK;
 175 }
 176
 177 static int bitbang_stableclocks(int num_cycles)
 178 {
 179         int tms = (tap_get_state() == TAP_RESET ? 1 : 0);
 180         int i;
 181
 182         /* send num_cycles clocks onto the cable */
 183         for (i = 0; i < num_cycles; i++) {
 184                 if (bitbang_interface->write(1, tms, 0) != ERROR_OK)
 185                         return ERROR_FAIL;
 186                 if (bitbang_interface->write(0, tms, 0) != ERROR_OK)
 187                         return ERROR_FAIL;
 188         }
 189
 190         return ERROR_OK;
 191 }
 192
 193 static int bitbang_scan(bool ir_scan, enum scan_type type, uint8_t *buffer,
 194                 unsigned scan_size)
 195 {
 196         tap_state_t saved_end_state = tap_get_end_state();
 197         unsigned bit_cnt;
 198
 199         if (!((!ir_scan &&
 200                         (tap_get_state() == TAP_DRSHIFT)) ||
 201                         (ir_scan && (tap_get_state() == TAP_IRSHIFT)))) {
 202                 if (ir_scan)
 203                         bitbang_end_state(TAP_IRSHIFT);
 204                 else
 205                         bitbang_end_state(TAP_DRSHIFT);
 206
 207                 if (bitbang_state_move(0) != ERROR_OK)
 208                         return ERROR_FAIL;
 209                 bitbang_end_state(saved_end_state);
 210         }
 211
 212         size_t buffered = 0;
 213         for (bit_cnt = 0; bit_cnt < scan_size; bit_cnt++) {
 214                 int tms = (bit_cnt == scan_size-1) ? 1 : 0;
 215                 int tdi;
 216                 int bytec = bit_cnt/8;
 217                 int bcval = 1 << (bit_cnt % 8);
 218
 219                 /* if we're just reading the scan, but don't care about the output
 220                  * default to outputting 'low', this also makes valgrind traces more readable,
 221                  * as it removes the dependency on an uninitialised value
 222                  */
 223                 tdi = 0;
 224                 if ((type != SCAN_IN) && (buffer[bytec] & bcval))
 225                         tdi = 1;
 226
 227                 if (bitbang_interface->write(0, tms, tdi) != ERROR_OK)
 228                         return ERROR_FAIL;
 229
 230                 if (type != SCAN_OUT) {
 231                         if (bitbang_interface->buf_size) {
 232                                 if (bitbang_interface->sample() != ERROR_OK)
 233                                         return ERROR_FAIL;
 234                                 buffered++;
 235                         } else {
 236                                 switch (bitbang_interface->read()) {
 237                                         case BB_LOW:
 238                                                 buffer[bytec] &= ~bcval;
 239                                                 break;
 240                                         case BB_HIGH:
 241                                                 buffer[bytec] |= bcval;
 242                                                 break;
 243                                         default:
 244                                                 return ERROR_FAIL;
 245                                 }
 246                         }
 247                 }
 248
 249                 if (bitbang_interface->write(1, tms, tdi) != ERROR_OK)
 250                         return ERROR_FAIL;
 251
 252                 if (type != SCAN_OUT && bitbang_interface->buf_size &&
 253                                 (buffered == bitbang_interface->buf_size ||
 254                                  bit_cnt == scan_size - 1)) {
 255                         for (unsigned i = bit_cnt + 1 - buffered; i <= bit_cnt; i++) {
 256                                 switch (bitbang_interface->read_sample()) {
 257                                         case BB_LOW:
 258                                                 buffer[i/8] &= ~(1 << (i % 8));
 259                                                 break;
 260                                         case BB_HIGH:
 261                                                 buffer[i/8] |= 1 << (i % 8);
 262                                                 break;
 263                                         default:
 264                                                 return ERROR_FAIL;
 265                                 }
 266                         }
 267                         buffered = 0;
 268                 }
 269         }
 270
 271         if (tap_get_state() != tap_get_end_state()) {
 272                 /* we *KNOW* the above loop transitioned out of
 273                  * the shift state, so we skip the first state
 274                  * and move directly to the end state.
 275                  */
 276                 if (bitbang_state_move(1) != ERROR_OK)
 277                         return ERROR_FAIL;
 278         }
 279         return ERROR_OK;
 280 }
 281
 282 static void bitbang_sleep(unsigned int microseconds)
 283 {
 284         if (bitbang_interface->sleep) {
 285                 bitbang_interface->sleep(microseconds);
 286         } else {
 287                 jtag_sleep(microseconds);
 288         }
 289 }
 290
 291 int bitbang_execute_queue(struct jtag_command *cmd_queue)
 292 {
 293         struct jtag_command *cmd = cmd_queue;   /* currently processed command */
 294         int scan_size;
 295         enum scan_type type;
 296         uint8_t *buffer;
 297         int retval;
 298
 299         if (!bitbang_interface) {
 300                 LOG_ERROR("BUG: Bitbang interface called, but not yet initialized");
 301                 exit(-1);
 302         }
 303
 304         /* return ERROR_OK, unless a jtag_read_buffer returns a failed check
 305          * that wasn't handled by a caller-provided error handler
 306          */
 307         retval = ERROR_OK;
 308
 309         if (bitbang_interface->blink) {
 310                 if (bitbang_interface->blink(1) != ERROR_OK)
 311                         return ERROR_FAIL;
 312         }
 313
 314         while (cmd) {
 315                 switch (cmd->type) {
 316                         case JTAG_RUNTEST:
 317                                 LOG_DEBUG_IO("runtest %i cycles, end in %s",
 318                                                 cmd->cmd.runtest->num_cycles,
 319                                                 tap_state_name(cmd->cmd.runtest->end_state));
 320                                 bitbang_end_state(cmd->cmd.runtest->end_state);
 321                                 if (bitbang_runtest(cmd->cmd.runtest->num_cycles) != ERROR_OK)
 322                                         return ERROR_FAIL;
 323                                 break;
 324
 325                         case JTAG_STABLECLOCKS:
 326                                 /* this is only allowed while in a stable state.  A check for a stable
 327                                  * state was done in jtag_add_clocks()
 328                                  */
 329                                 if (bitbang_stableclocks(cmd->cmd.stableclocks->num_cycles) != ERROR_OK)
 330                                         return ERROR_FAIL;
 331                                 break;
 332
 333                         case JTAG_TLR_RESET:
 334                                 LOG_DEBUG_IO("statemove end in %s",
 335                                                 tap_state_name(cmd->cmd.statemove->end_state));
 336                                 bitbang_end_state(cmd->cmd.statemove->end_state);
 337                                 if (bitbang_state_move(0) != ERROR_OK)
 338                                         return ERROR_FAIL;
 339                                 break;
 340                         case JTAG_PATHMOVE:
 341                                 LOG_DEBUG_IO("pathmove: %i states, end in %s",
 342                                                 cmd->cmd.pathmove->num_states,
 343                                                 tap_state_name(cmd->cmd.pathmove->path[cmd->cmd.pathmove->num_states - 1]));
 344                                 if (bitbang_path_move(cmd->cmd.pathmove) != ERROR_OK)
 345                                         return ERROR_FAIL;
 346                                 break;
 347                         case JTAG_SCAN:
 348                                 bitbang_end_state(cmd->cmd.scan->end_state);
 349                                 scan_size = jtag_build_buffer(cmd->cmd.scan, &buffer);
 350                                 LOG_DEBUG_IO("%s scan %d bits; end in %s",
 351                                                 (cmd->cmd.scan->ir_scan) ? "IR" : "DR",
 352                                                 scan_size,
 353                                         tap_state_name(cmd->cmd.scan->end_state));
 354                                 type = jtag_scan_type(cmd->cmd.scan);
 355                                 if (bitbang_scan(cmd->cmd.scan->ir_scan, type, buffer,
 356                                                         scan_size) != ERROR_OK)
 357                                         return ERROR_FAIL;
 358                                 if (jtag_read_buffer(buffer, cmd->cmd.scan) != ERROR_OK)
 359                                         retval = ERROR_JTAG_QUEUE_FAILED;
 360                                 free(buffer);
 361                                 break;
 362                         case JTAG_SLEEP:
 363                                 LOG_DEBUG_IO("sleep %" PRIu32, cmd->cmd.sleep->us);
 364                                 if (bitbang_interface->flush && (bitbang_interface->flush() != ERROR_OK))
 365                                         return ERROR_FAIL;
 366                                 bitbang_sleep(cmd->cmd.sleep->us);
 367                                 break;
 368                         case JTAG_TMS:
 369                                 retval = bitbang_execute_tms(cmd);
 370                                 break;
 371                         default:
 372                                 LOG_ERROR("BUG: unknown JTAG command type encountered");
 373                                 exit(-1);
 374                 }
 375                 cmd = cmd->next;
 376         }
 377         if (bitbang_interface->blink) {
 378                 if (bitbang_interface->blink(0) != ERROR_OK)
 379                         return ERROR_FAIL;
 380         }
 381
 382         return retval;
 383 }
 384
 385 static int queued_retval;
 386
 387 static int bitbang_swd_init(void)
 388 {
 389         LOG_DEBUG("bitbang_swd_init");
 390         return ERROR_OK;
 391 }
 392
 393 static void bitbang_swd_exchange(bool rnw, uint8_t buf[], unsigned int offset, unsigned int bit_cnt)
 394 {
 395         if (bitbang_interface->blink) {
 396                 /* FIXME: we should manage errors */
 397                 bitbang_interface->blink(1);
 398         }
 399
 400         for (unsigned int i = offset; i < bit_cnt + offset; i++) {
 401                 int bytec = i/8;
 402                 int bcval = 1 << (i % 8);
 403                 int swdio = !rnw && (buf[bytec] & bcval);
 404
 405                 bitbang_interface->swd_write(0, swdio);
 406
 407                 if (rnw && buf) {
 408                         if (bitbang_interface->swdio_read())
 409                                 buf[bytec] |= bcval;
 410                         else
 411                                 buf[bytec] &= ~bcval;
 412                 }
 413
 414                 bitbang_interface->swd_write(1, swdio);
 415         }
 416
 417         if (bitbang_interface->blink) {
 418                 /* FIXME: we should manage errors */
 419                 bitbang_interface->blink(0);
 420         }
 421 }
 422
 423 static int bitbang_swd_switch_seq(enum swd_special_seq seq)
 424 {
 425         switch (seq) {
 426         case LINE_RESET:
 427                 LOG_DEBUG_IO("SWD line reset");
 428                 bitbang_swd_exchange(false, (uint8_t *)swd_seq_line_reset, 0, swd_seq_line_reset_len);
 429                 break;
 430         case JTAG_TO_SWD:
 431                 LOG_DEBUG("JTAG-to-SWD");
 432                 bitbang_swd_exchange(false, (uint8_t *)swd_seq_jtag_to_swd, 0, swd_seq_jtag_to_swd_len);
 433                 break;
 434         case JTAG_TO_DORMANT:
 435                 LOG_DEBUG("JTAG-to-DORMANT");
 436                 bitbang_swd_exchange(false, (uint8_t *)swd_seq_jtag_to_dormant, 0, swd_seq_jtag_to_dormant_len);
 437                 break;
 438         case SWD_TO_JTAG:
 439                 LOG_DEBUG("SWD-to-JTAG");
 440                 bitbang_swd_exchange(false, (uint8_t *)swd_seq_swd_to_jtag, 0, swd_seq_swd_to_jtag_len);
 441                 break;
 442         case SWD_TO_DORMANT:
 443                 LOG_DEBUG("SWD-to-DORMANT");
 444                 bitbang_swd_exchange(false, (uint8_t *)swd_seq_swd_to_dormant, 0, swd_seq_swd_to_dormant_len);
 445                 break;
 446         case DORMANT_TO_SWD:
 447                 LOG_DEBUG("DORMANT-to-SWD");
 448                 bitbang_swd_exchange(false, (uint8_t *)swd_seq_dormant_to_swd, 0, swd_seq_dormant_to_swd_len);
 449                 break;
 450         case DORMANT_TO_JTAG:
 451                 LOG_DEBUG("DORMANT-to-JTAG");
 452                 bitbang_swd_exchange(false, (uint8_t *)swd_seq_dormant_to_jtag, 0, swd_seq_dormant_to_jtag_len);
 453                 break;
 454         default:
 455                 LOG_ERROR("Sequence %d not supported", seq);
 456                 return ERROR_FAIL;
 457         }
 458
 459         return ERROR_OK;
 460 }
 461
 462 static void swd_clear_sticky_errors(void)
 463 {
 464         bitbang_swd_write_reg(swd_cmd(false,  false, DP_ABORT),
 465                 STKCMPCLR | STKERRCLR | WDERRCLR | ORUNERRCLR, 0);
 466 }
 467
 468 static void bitbang_swd_read_reg(uint8_t cmd, uint32_t *value, uint32_t ap_delay_clk)
 469 {
 470         assert(cmd & SWD_CMD_RNW);
 471
 472         if (queued_retval != ERROR_OK) {
 473                 LOG_DEBUG("Skip bitbang_swd_read_reg because queued_retval=%d", queued_retval);
 474                 return;
 475         }
 476
 477         for (;;) {
 478                 uint8_t trn_ack_data_parity_trn[DIV_ROUND_UP(4 + 3 + 32 + 1 + 4, 8)];
 479
 480                 cmd |= SWD_CMD_START | SWD_CMD_PARK;
 481                 bitbang_swd_exchange(false, &cmd, 0, 8);
 482
 483                 bitbang_interface->swdio_drive(false);
 484                 bitbang_swd_exchange(true, trn_ack_data_parity_trn, 0, 1 + 3 + 32 + 1 + 1);
 485                 bitbang_interface->swdio_drive(true);
 486
 487                 int ack = buf_get_u32(trn_ack_data_parity_trn, 1, 3);
 488                 uint32_t data = buf_get_u32(trn_ack_data_parity_trn, 1 + 3, 32);
 489                 int parity = buf_get_u32(trn_ack_data_parity_trn, 1 + 3 + 32, 1);
 490
 491                 LOG_DEBUG_IO("%s %s read reg %X = %08" PRIx32,
 492                           ack == SWD_ACK_OK ? "OK" : ack == SWD_ACK_WAIT ? "WAIT" : ack == SWD_ACK_FAULT ? "FAULT" : "JUNK",
 493                           cmd & SWD_CMD_APNDP ? "AP" : "DP",
 494                           (cmd & SWD_CMD_A32) >> 1,
 495                           data);
 496
 497                 if (ack == SWD_ACK_WAIT) {
 498                         swd_clear_sticky_errors();
 499                         continue;
 500                 } else if (ack != SWD_ACK_OK) {
 501                         queued_retval = swd_ack_to_error_code(ack);
 502                         return;
 503                 }
 504
 505                 if (parity != parity_u32(data)) {
 506                         LOG_ERROR("Wrong parity detected");
 507                         queued_retval = ERROR_FAIL;
 508                         return;
 509                 }
 510                 if (value)
 511                         *value = data;
 512                 if (cmd & SWD_CMD_APNDP)
 513                         bitbang_swd_exchange(true, NULL, 0, ap_delay_clk);
 514                 return;
 515         }
 516 }
 517
 518 static void bitbang_swd_write_reg(uint8_t cmd, uint32_t value, uint32_t ap_delay_clk)
 519 {
 520         assert(!(cmd & SWD_CMD_RNW));
 521
 522         if (queued_retval != ERROR_OK) {
 523                 LOG_DEBUG("Skip bitbang_swd_write_reg because queued_retval=%d", queued_retval);
 524                 return;
 525         }
 526
 527         /* Devices do not reply to DP_TARGETSEL write cmd, ignore received ack */
 528         bool check_ack = swd_cmd_returns_ack(cmd);
 529
 530         /* init the array to silence scan-build */
 531         uint8_t trn_ack_data_parity_trn[DIV_ROUND_UP(4 + 3 + 32 + 1 + 4, 8)] = {0};
 532         for (;;) {
 533                 buf_set_u32(trn_ack_data_parity_trn, 1 + 3 + 1, 32, value);
 534                 buf_set_u32(trn_ack_data_parity_trn, 1 + 3 + 1 + 32, 1, parity_u32(value));
 535
 536                 cmd |= SWD_CMD_START | SWD_CMD_PARK;
 537                 bitbang_swd_exchange(false, &cmd, 0, 8);
 538
 539                 bitbang_interface->swdio_drive(false);
 540                 bitbang_swd_exchange(true, trn_ack_data_parity_trn, 0, 1 + 3);
 541
 542                 /* Avoid a glitch on SWDIO when changing the direction to output.
 543                  * To keep performance penalty minimal, pre-write the first data
 544                  * bit to SWDIO GPIO output buffer while clocking the turnaround bit.
 545                  * Following swdio_drive(true) outputs the pre-written value
 546                  * and the same value is rewritten by the next swd_write()
 547                  * instead of glitching SWDIO
 548                  * HiZ/pull-up --------------> 0 -------------> 1
 549                  *           swdio_drive(true)   swd_write(0,1)
 550                  * in case of data bit 0 = 1
 551                  */
 552                 bitbang_swd_exchange(false, trn_ack_data_parity_trn, 1 + 3 + 1, 1);
 553                 bitbang_interface->swdio_drive(true);
 554                 bitbang_swd_exchange(false, trn_ack_data_parity_trn, 1 + 3 + 1, 32 + 1);
 555
 556                 int ack = buf_get_u32(trn_ack_data_parity_trn, 1, 3);
 557
 558                 LOG_DEBUG_IO("%s%s %s write reg %X = %08" PRIx32,
 559                           check_ack ? "" : "ack ignored ",
 560                           ack == SWD_ACK_OK ? "OK" : ack == SWD_ACK_WAIT ? "WAIT" : ack == SWD_ACK_FAULT ? "FAULT" : "JUNK",
 561                           cmd & SWD_CMD_APNDP ? "AP" : "DP",
 562                           (cmd & SWD_CMD_A32) >> 1,
 563                           buf_get_u32(trn_ack_data_parity_trn, 1 + 3 + 1, 32));
 564
 565                 if (check_ack) {
 566                         if (ack == SWD_ACK_WAIT) {
 567                                 swd_clear_sticky_errors();
 568                                 continue;
 569                         } else if (ack != SWD_ACK_OK) {
 570                                 queued_retval = swd_ack_to_error_code(ack);
 571                                 return;
 572                         }
 573                 }
 574
 575                 if (cmd & SWD_CMD_APNDP)
 576                         bitbang_swd_exchange(true, NULL, 0, ap_delay_clk);
 577                 return;
 578         }
 579 }
 580
 581 static int bitbang_swd_run_queue(void)
 582 {
 583         /* A transaction must be followed by another transaction or at least 8 idle cycles to
 584          * ensure that data is clocked through the AP. */
 585         bitbang_swd_exchange(true, NULL, 0, 8);
 586
 587         int retval = queued_retval;
 588         queued_retval = ERROR_OK;
 589         LOG_DEBUG_IO("SWD queue return value: %02x", retval);
 590         return retval;
 591 }
 592
 593 const struct swd_driver bitbang_swd = {
 594         .init = bitbang_swd_init,
 595         .switch_seq = bitbang_swd_switch_seq,
 596         .read_reg = bitbang_swd_read_reg,
 597         .write_reg = bitbang_swd_write_reg,
 598         .run = bitbang_swd_run_queue,
 599 };