src/jtag/drivers/bitbang.c

   1 /***************************************************************************
   2  *   Copyright (C) 2005 by Dominic Rath                                    *
   3  *   Dominic.Rath@gmx.de                                                   *
   4  *                                                                         *
   5  *   Copyright (C) 2007,2008 Øyvind Harboe                                 *
   6  *   oyvind.harboe@zylin.com                                               *
   7  *                                                                         *
   8  *   This program is free software; you can redistribute it and/or modify  *
   9  *   it under the terms of the GNU General Public License as published by  *
  10  *   the Free Software Foundation; either version 2 of the License, or     *
  11  *   (at your option) any later version.                                   *
  12  *                                                                         *
  13  *   This program is distributed in the hope that it will be useful,       *
  14  *   but WITHOUT ANY WARRANTY; without even the implied warranty of        *
  15  *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         *
  16  *   GNU General Public License for more details.                          *
  17  *                                                                         *
  18  *   You should have received a copy of the GNU General Public License     *
  19  *   along with this program.  If not, see <http://www.gnu.org/licenses/>. *
  20  ***************************************************************************/
  21
  22 /* 2014-12: Addition of the SWD protocol support is based on the initial work
  23  * by Paul Fertser and modifications by Jean-Christian de Rivaz. */
  24
  25 #ifdef HAVE_CONFIG_H
  26 #include "config.h"
  27 #endif
  28
  29 #include "bitbang.h"
  30 #include <jtag/interface.h>
  31 #include <jtag/commands.h>
  32
  33 /* YUK! - but this is currently a global.... */
  34 extern struct jtag_interface *jtag_interface;
  35
  36 /**
  37  * Function bitbang_stableclocks
  38  * issues a number of clock cycles while staying in a stable state.
  39  * Because the TMS value required to stay in the RESET state is a 1, whereas
  40  * the TMS value required to stay in any of the other stable states is a 0,
  41  * this function checks the current stable state to decide on the value of TMS
  42  * to use.
  43  */
  44 static int bitbang_stableclocks(int num_cycles);
  45
  46 static void bitbang_swd_write_reg(uint8_t cmd, uint32_t value, uint32_t ap_delay_clk);
  47
  48 struct bitbang_interface *bitbang_interface;
  49
  50 /* DANGER!!!! clock absolutely *MUST* be 0 in idle or reset won't work!
  51  *
  52  * Set this to 1 and str912 reset halt will fail.
  53  *
  54  * If someone can submit a patch with an explanation it will be greatly
  55  * appreciated, but as far as I can tell (ØH) DCLK is generated upon
  56  * clk = 0 in TAP_IDLE. Good luck deducing that from the ARM documentation!
  57  * The ARM documentation uses the term "DCLK is asserted while in the TAP_IDLE
  58  * state". With hardware there is no such thing as *while* in a state. There
  59  * are only edges. So clk => 0 is in fact a very subtle state transition that
  60  * happens *while* in the TAP_IDLE state. "#&¤"#¤&"#&"#&
  61  *
  62  * For "reset halt" the last thing that happens before srst is asserted
  63  * is that the breakpoint is set up. If DCLK is not wiggled one last
  64  * time before the reset, then the breakpoint is not set up and
  65  * "reset halt" will fail to halt.
  66  *
  67  */
  68 #define CLOCK_IDLE() 0
  69
  70 /* The bitbang driver leaves the TCK 0 when in idle */
  71 static void bitbang_end_state(tap_state_t state)
  72 {
  73         assert(tap_is_state_stable(state));
  74         tap_set_end_state(state);
  75 }
  76
  77 static int bitbang_state_move(int skip)
  78 {
  79         int i = 0, tms = 0;
  80         uint8_t tms_scan = tap_get_tms_path(tap_get_state(), tap_get_end_state());
  81         int tms_count = tap_get_tms_path_len(tap_get_state(), tap_get_end_state());
  82
  83         for (i = skip; i < tms_count; i++) {
  84                 tms = (tms_scan >> i) & 1;
  85                 if (bitbang_interface->write(0, tms, 0) != ERROR_OK)
  86                         return ERROR_FAIL;
  87                 if (bitbang_interface->write(1, tms, 0) != ERROR_OK)
  88                         return ERROR_FAIL;
  89         }
  90         if (bitbang_interface->write(CLOCK_IDLE(), tms, 0) != ERROR_OK)
  91                 return ERROR_FAIL;
  92
  93         tap_set_state(tap_get_end_state());
  94         return ERROR_OK;
  95 }
  96
  97 /**
  98  * Clock a bunch of TMS (or SWDIO) transitions, to change the JTAG
  99  * (or SWD) state machine.
 100  */
 101 static int bitbang_execute_tms(struct jtag_command *cmd)
 102 {
 103         unsigned num_bits = cmd->cmd.tms->num_bits;
 104         const uint8_t *bits = cmd->cmd.tms->bits;
 105
 106         DEBUG_JTAG_IO("TMS: %d bits", num_bits);
 107
 108         int tms = 0;
 109         for (unsigned i = 0; i < num_bits; i++) {
 110                 tms = ((bits[i/8] >> (i % 8)) & 1);
 111                 if (bitbang_interface->write(0, tms, 0) != ERROR_OK)
 112                         return ERROR_FAIL;
 113                 if (bitbang_interface->write(1, tms, 0) != ERROR_OK)
 114                         return ERROR_FAIL;
 115         }
 116         if (bitbang_interface->write(CLOCK_IDLE(), tms, 0) != ERROR_OK)
 117                 return ERROR_FAIL;
 118
 119         return ERROR_OK;
 120 }
 121
 122 static int bitbang_path_move(struct pathmove_command *cmd)
 123 {
 124         int num_states = cmd->num_states;
 125         int state_count;
 126         int tms = 0;
 127
 128         state_count = 0;
 129         while (num_states) {
 130                 if (tap_state_transition(tap_get_state(), false) == cmd->path[state_count])
 131                         tms = 0;
 132                 else if (tap_state_transition(tap_get_state(), true) == cmd->path[state_count])
 133                         tms = 1;
 134                 else {
 135                         LOG_ERROR("BUG: %s -> %s isn't a valid TAP transition",
 136                                 tap_state_name(tap_get_state()),
 137                                 tap_state_name(cmd->path[state_count]));
 138                         exit(-1);
 139                 }
 140
 141                 if (bitbang_interface->write(0, tms, 0) != ERROR_OK)
 142                         return ERROR_FAIL;
 143                 if (bitbang_interface->write(1, tms, 0) != ERROR_OK)
 144                         return ERROR_FAIL;
 145
 146                 tap_set_state(cmd->path[state_count]);
 147                 state_count++;
 148                 num_states--;
 149         }
 150
 151         if (bitbang_interface->write(CLOCK_IDLE(), tms, 0) != ERROR_OK)
 152                 return ERROR_FAIL;
 153
 154         tap_set_end_state(tap_get_state());
 155         return ERROR_OK;
 156 }
 157
 158 static int bitbang_runtest(int num_cycles)
 159 {
 160         int i;
 161
 162         tap_state_t saved_end_state = tap_get_end_state();
 163
 164         /* only do a state_move when we're not already in IDLE */
 165         if (tap_get_state() != TAP_IDLE) {
 166                 bitbang_end_state(TAP_IDLE);
 167                 if (bitbang_state_move(0) != ERROR_OK)
 168                         return ERROR_FAIL;
 169         }
 170
 171         /* execute num_cycles */
 172         for (i = 0; i < num_cycles; i++) {
 173                 if (bitbang_interface->write(0, 0, 0) != ERROR_OK)
 174                         return ERROR_FAIL;
 175                 if (bitbang_interface->write(1, 0, 0) != ERROR_OK)
 176                         return ERROR_FAIL;
 177         }
 178         if (bitbang_interface->write(CLOCK_IDLE(), 0, 0) != ERROR_OK)
 179                 return ERROR_FAIL;
 180
 181         /* finish in end_state */
 182         bitbang_end_state(saved_end_state);
 183         if (tap_get_state() != tap_get_end_state())
 184                 if (bitbang_state_move(0) != ERROR_OK)
 185                         return ERROR_FAIL;
 186
 187         return ERROR_OK;
 188 }
 189
 190 static int bitbang_stableclocks(int num_cycles)
 191 {
 192         int tms = (tap_get_state() == TAP_RESET ? 1 : 0);
 193         int i;
 194
 195         /* send num_cycles clocks onto the cable */
 196         for (i = 0; i < num_cycles; i++) {
 197                 if (bitbang_interface->write(1, tms, 0) != ERROR_OK)
 198                         return ERROR_FAIL;
 199                 if (bitbang_interface->write(0, tms, 0) != ERROR_OK)
 200                         return ERROR_FAIL;
 201         }
 202
 203         return ERROR_OK;
 204 }
 205
 206 static int bitbang_scan(bool ir_scan, enum scan_type type, uint8_t *buffer,
 207                 unsigned scan_size)
 208 {
 209         tap_state_t saved_end_state = tap_get_end_state();
 210         unsigned bit_cnt;
 211
 212         if (!((!ir_scan &&
 213                         (tap_get_state() == TAP_DRSHIFT)) ||
 214                         (ir_scan && (tap_get_state() == TAP_IRSHIFT)))) {
 215                 if (ir_scan)
 216                         bitbang_end_state(TAP_IRSHIFT);
 217                 else
 218                         bitbang_end_state(TAP_DRSHIFT);
 219
 220                 if (bitbang_state_move(0) != ERROR_OK)
 221                         return ERROR_FAIL;
 222                 bitbang_end_state(saved_end_state);
 223         }
 224
 225         size_t buffered = 0;
 226         for (bit_cnt = 0; bit_cnt < scan_size; bit_cnt++) {
 227                 int tms = (bit_cnt == scan_size-1) ? 1 : 0;
 228                 int tdi;
 229                 int bytec = bit_cnt/8;
 230                 int bcval = 1 << (bit_cnt % 8);
 231
 232                 /* if we're just reading the scan, but don't care about the output
 233                  * default to outputting 'low', this also makes valgrind traces more readable,
 234                  * as it removes the dependency on an uninitialised value
 235                  */
 236                 tdi = 0;
 237                 if ((type != SCAN_IN) && (buffer[bytec] & bcval))
 238                         tdi = 1;
 239
 240                 if (bitbang_interface->write(0, tms, tdi) != ERROR_OK)
 241                         return ERROR_FAIL;
 242
 243                 if (type != SCAN_OUT) {
 244                         if (bitbang_interface->buf_size) {
 245                                 if (bitbang_interface->sample() != ERROR_OK)
 246                                         return ERROR_FAIL;
 247                                 buffered++;
 248                         } else {
 249                                 switch (bitbang_interface->read()) {
 250                                         case BB_LOW:
 251                                                 buffer[bytec] &= ~bcval;
 252                                                 break;
 253                                         case BB_HIGH:
 254                                                 buffer[bytec] |= bcval;
 255                                                 break;
 256                                         default:
 257                                                 return ERROR_FAIL;
 258                                 }
 259                         }
 260                 }
 261
 262                 if (bitbang_interface->write(1, tms, tdi) != ERROR_OK)
 263                         return ERROR_FAIL;
 264
 265                 if (type != SCAN_OUT && bitbang_interface->buf_size &&
 266                                 (buffered == bitbang_interface->buf_size ||
 267                                  bit_cnt == scan_size - 1)) {
 268                         for (unsigned i = bit_cnt + 1 - buffered; i <= bit_cnt; i++) {
 269                                 switch (bitbang_interface->read_sample()) {
 270                                         case BB_LOW:
 271                                                 buffer[i/8] &= ~(1 << (i % 8));
 272                                                 break;
 273                                         case BB_HIGH:
 274                                                 buffer[i/8] |= 1 << (i % 8);
 275                                                 break;
 276                                         default:
 277                                                 return ERROR_FAIL;
 278                                 }
 279                         }
 280                         buffered = 0;
 281                 }
 282         }
 283
 284         if (tap_get_state() != tap_get_end_state()) {
 285                 /* we *KNOW* the above loop transitioned out of
 286                  * the shift state, so we skip the first state
 287                  * and move directly to the end state.
 288                  */
 289                 if (bitbang_state_move(1) != ERROR_OK)
 290                         return ERROR_FAIL;
 291         }
 292         return ERROR_OK;
 293 }
 294
 295 int bitbang_execute_queue(void)
 296 {
 297         struct jtag_command *cmd = jtag_command_queue;  /* currently processed command */
 298         int scan_size;
 299         enum scan_type type;
 300         uint8_t *buffer;
 301         int retval;
 302
 303         if (!bitbang_interface) {
 304                 LOG_ERROR("BUG: Bitbang interface called, but not yet initialized");
 305                 exit(-1);
 306         }
 307
 308         /* return ERROR_OK, unless a jtag_read_buffer returns a failed check
 309          * that wasn't handled by a caller-provided error handler
 310          */
 311         retval = ERROR_OK;
 312
 313         if (bitbang_interface->blink) {
 314                 if (bitbang_interface->blink(1) != ERROR_OK)
 315                         return ERROR_FAIL;
 316         }
 317
 318         while (cmd) {
 319                 switch (cmd->type) {
 320                         case JTAG_RESET:
 321 #ifdef _DEBUG_JTAG_IO_
 322                                 LOG_DEBUG("reset trst: %i srst %i",
 323                                 cmd->cmd.reset->trst,
 324                                 cmd->cmd.reset->srst);
 325 #endif
 326                                 if ((cmd->cmd.reset->trst == 1) ||
 327                                                 (cmd->cmd.reset->srst && (jtag_get_reset_config() & RESET_SRST_PULLS_TRST)))
 328                                         tap_set_state(TAP_RESET);
 329                                 if (bitbang_interface->reset(cmd->cmd.reset->trst,
 330                                                         cmd->cmd.reset->srst) != ERROR_OK)
 331                                         return ERROR_FAIL;
 332                                 break;
 333                         case JTAG_RUNTEST:
 334 #ifdef _DEBUG_JTAG_IO_
 335                                 LOG_DEBUG("runtest %i cycles, end in %s",
 336                                                 cmd->cmd.runtest->num_cycles,
 337                                                 tap_state_name(cmd->cmd.runtest->end_state));
 338 #endif
 339                                 bitbang_end_state(cmd->cmd.runtest->end_state);
 340                                 if (bitbang_runtest(cmd->cmd.runtest->num_cycles) != ERROR_OK)
 341                                         return ERROR_FAIL;
 342                                 break;
 343
 344                         case JTAG_STABLECLOCKS:
 345                                 /* this is only allowed while in a stable state.  A check for a stable
 346                                  * state was done in jtag_add_clocks()
 347                                  */
 348                                 if (bitbang_stableclocks(cmd->cmd.stableclocks->num_cycles) != ERROR_OK)
 349                                         return ERROR_FAIL;
 350                                 break;
 351
 352                         case JTAG_TLR_RESET:
 353 #ifdef _DEBUG_JTAG_IO_
 354                                 LOG_DEBUG("statemove end in %s",
 355                                                 tap_state_name(cmd->cmd.statemove->end_state));
 356 #endif
 357                                 bitbang_end_state(cmd->cmd.statemove->end_state);
 358                                 if (bitbang_state_move(0) != ERROR_OK)
 359                                         return ERROR_FAIL;
 360                                 break;
 361                         case JTAG_PATHMOVE:
 362 #ifdef _DEBUG_JTAG_IO_
 363                                 LOG_DEBUG("pathmove: %i states, end in %s",
 364                                                 cmd->cmd.pathmove->num_states,
 365                                                 tap_state_name(cmd->cmd.pathmove->path[cmd->cmd.pathmove->num_states - 1]));
 366 #endif
 367                                 if (bitbang_path_move(cmd->cmd.pathmove) != ERROR_OK)
 368                                         return ERROR_FAIL;
 369                                 break;
 370                         case JTAG_SCAN:
 371                                 bitbang_end_state(cmd->cmd.scan->end_state);
 372                                 scan_size = jtag_build_buffer(cmd->cmd.scan, &buffer);
 373 #ifdef _DEBUG_JTAG_IO_
 374                                 LOG_DEBUG("%s scan %d bits; end in %s",
 375                                                 (cmd->cmd.scan->ir_scan) ? "IR" : "DR",
 376                                                 scan_size,
 377                                         tap_state_name(cmd->cmd.scan->end_state));
 378 #endif
 379                                 type = jtag_scan_type(cmd->cmd.scan);
 380                                 if (bitbang_scan(cmd->cmd.scan->ir_scan, type, buffer,
 381                                                         scan_size) != ERROR_OK)
 382                                         return ERROR_FAIL;
 383                                 if (jtag_read_buffer(buffer, cmd->cmd.scan) != ERROR_OK)
 384                                         retval = ERROR_JTAG_QUEUE_FAILED;
 385                                 if (buffer)
 386                                         free(buffer);
 387                                 break;
 388                         case JTAG_SLEEP:
 389 #ifdef _DEBUG_JTAG_IO_
 390                                 LOG_DEBUG("sleep %" PRIi32, cmd->cmd.sleep->us);
 391 #endif
 392                                 jtag_sleep(cmd->cmd.sleep->us);
 393                                 break;
 394                         case JTAG_TMS:
 395                                 retval = bitbang_execute_tms(cmd);
 396                                 break;
 397                         default:
 398                                 LOG_ERROR("BUG: unknown JTAG command type encountered");
 399                                 exit(-1);
 400                 }
 401                 cmd = cmd->next;
 402         }
 403         if (bitbang_interface->blink) {
 404                 if (bitbang_interface->blink(0) != ERROR_OK)
 405                         return ERROR_FAIL;
 406         }
 407
 408         return retval;
 409 }
 410
 411
 412 bool swd_mode;
 413 static int queued_retval;
 414
 415 static int bitbang_swd_init(void)
 416 {
 417         LOG_DEBUG("bitbang_swd_init");
 418         swd_mode = true;
 419         return ERROR_OK;
 420 }
 421
 422 static void bitbang_exchange(bool rnw, uint8_t buf[], unsigned int offset, unsigned int bit_cnt)
 423 {
 424         LOG_DEBUG("bitbang_exchange");
 425         int tdi;
 426
 427         for (unsigned int i = offset; i < bit_cnt + offset; i++) {
 428                 int bytec = i/8;
 429                 int bcval = 1 << (i % 8);
 430                 tdi = !rnw && (buf[bytec] & bcval);
 431
 432                 bitbang_interface->write(0, 0, tdi);
 433
 434                 if (rnw && buf) {
 435                         if (bitbang_interface->swdio_read())
 436                                 buf[bytec] |= bcval;
 437                         else
 438                                 buf[bytec] &= ~bcval;
 439                 }
 440
 441                 bitbang_interface->write(1, 0, tdi);
 442         }
 443 }
 444
 445 int bitbang_swd_switch_seq(enum swd_special_seq seq)
 446 {
 447         LOG_DEBUG("bitbang_swd_switch_seq");
 448
 449         switch (seq) {
 450         case LINE_RESET:
 451                 LOG_DEBUG("SWD line reset");
 452                 bitbang_exchange(false, (uint8_t *)swd_seq_line_reset, 0, swd_seq_line_reset_len);
 453                 break;
 454         case JTAG_TO_SWD:
 455                 LOG_DEBUG("JTAG-to-SWD");
 456                 bitbang_exchange(false, (uint8_t *)swd_seq_jtag_to_swd, 0, swd_seq_jtag_to_swd_len);
 457                 break;
 458         case SWD_TO_JTAG:
 459                 LOG_DEBUG("SWD-to-JTAG");
 460                 bitbang_exchange(false, (uint8_t *)swd_seq_swd_to_jtag, 0, swd_seq_swd_to_jtag_len);
 461                 break;
 462         default:
 463                 LOG_ERROR("Sequence %d not supported", seq);
 464                 return ERROR_FAIL;
 465         }
 466
 467         return ERROR_OK;
 468 }
 469
 470 void bitbang_switch_to_swd(void)
 471 {
 472         LOG_DEBUG("bitbang_switch_to_swd");
 473         bitbang_exchange(false, (uint8_t *)swd_seq_jtag_to_swd, 0, swd_seq_jtag_to_swd_len);
 474 }
 475
 476 static void swd_clear_sticky_errors(void)
 477 {
 478         bitbang_swd_write_reg(swd_cmd(false,  false, DP_ABORT),
 479                 STKCMPCLR | STKERRCLR | WDERRCLR | ORUNERRCLR, 0);
 480 }
 481
 482 static void bitbang_swd_read_reg(uint8_t cmd, uint32_t *value, uint32_t ap_delay_clk)
 483 {
 484         LOG_DEBUG("bitbang_swd_read_reg");
 485         assert(cmd & SWD_CMD_RnW);
 486
 487         if (queued_retval != ERROR_OK) {
 488                 LOG_DEBUG("Skip bitbang_swd_read_reg because queued_retval=%d", queued_retval);
 489                 return;
 490         }
 491
 492         for (;;) {
 493                 uint8_t trn_ack_data_parity_trn[DIV_ROUND_UP(4 + 3 + 32 + 1 + 4, 8)];
 494
 495                 cmd |= SWD_CMD_START | (1 << 7);
 496                 bitbang_exchange(false, &cmd, 0, 8);
 497
 498                 bitbang_interface->swdio_drive(false);
 499                 bitbang_exchange(true, trn_ack_data_parity_trn, 0, 1 + 3 + 32 + 1 + 1);
 500                 bitbang_interface->swdio_drive(true);
 501
 502                 int ack = buf_get_u32(trn_ack_data_parity_trn, 1, 3);
 503                 uint32_t data = buf_get_u32(trn_ack_data_parity_trn, 1 + 3, 32);
 504                 int parity = buf_get_u32(trn_ack_data_parity_trn, 1 + 3 + 32, 1);
 505
 506                 LOG_DEBUG("%s %s %s reg %X = %08"PRIx32,
 507                           ack == SWD_ACK_OK ? "OK" : ack == SWD_ACK_WAIT ? "WAIT" : ack == SWD_ACK_FAULT ? "FAULT" : "JUNK",
 508                           cmd & SWD_CMD_APnDP ? "AP" : "DP",
 509                           cmd & SWD_CMD_RnW ? "read" : "write",
 510                           (cmd & SWD_CMD_A32) >> 1,
 511                           data);
 512
 513                 switch (ack) {
 514                  case SWD_ACK_OK:
 515                         if (parity != parity_u32(data)) {
 516                                 LOG_DEBUG("Wrong parity detected");
 517                                 queued_retval = ERROR_FAIL;
 518                                 return;
 519                         }
 520                         if (value)
 521                                 *value = data;
 522                         if (cmd & SWD_CMD_APnDP)
 523                                 bitbang_exchange(true, NULL, 0, ap_delay_clk);
 524                         return;
 525                  case SWD_ACK_WAIT:
 526                         LOG_DEBUG("SWD_ACK_WAIT");
 527                         swd_clear_sticky_errors();
 528                         break;
 529                  case SWD_ACK_FAULT:
 530                         LOG_DEBUG("SWD_ACK_FAULT");
 531                         queued_retval = ack;
 532                         return;
 533                  default:
 534                         LOG_DEBUG("No valid acknowledge: ack=%d", ack);
 535                         queued_retval = ack;
 536                         return;
 537                 }
 538         }
 539 }
 540
 541 static void bitbang_swd_write_reg(uint8_t cmd, uint32_t value, uint32_t ap_delay_clk)
 542 {
 543         LOG_DEBUG("bitbang_swd_write_reg");
 544         assert(!(cmd & SWD_CMD_RnW));
 545
 546         if (queued_retval != ERROR_OK) {
 547                 LOG_DEBUG("Skip bitbang_swd_write_reg because queued_retval=%d", queued_retval);
 548                 return;
 549         }
 550
 551         for (;;) {
 552                 uint8_t trn_ack_data_parity_trn[DIV_ROUND_UP(4 + 3 + 32 + 1 + 4, 8)];
 553                 buf_set_u32(trn_ack_data_parity_trn, 1 + 3 + 1, 32, value);
 554                 buf_set_u32(trn_ack_data_parity_trn, 1 + 3 + 1 + 32, 1, parity_u32(value));
 555
 556                 cmd |= SWD_CMD_START | (1 << 7);
 557                 bitbang_exchange(false, &cmd, 0, 8);
 558
 559                 bitbang_interface->swdio_drive(false);
 560                 bitbang_exchange(true, trn_ack_data_parity_trn, 0, 1 + 3 + 1);
 561                 bitbang_interface->swdio_drive(true);
 562                 bitbang_exchange(false, trn_ack_data_parity_trn, 1 + 3 + 1, 32 + 1);
 563
 564                 int ack = buf_get_u32(trn_ack_data_parity_trn, 1, 3);
 565                 LOG_DEBUG("%s %s %s reg %X = %08"PRIx32,
 566                           ack == SWD_ACK_OK ? "OK" : ack == SWD_ACK_WAIT ? "WAIT" : ack == SWD_ACK_FAULT ? "FAULT" : "JUNK",
 567                           cmd & SWD_CMD_APnDP ? "AP" : "DP",
 568                           cmd & SWD_CMD_RnW ? "read" : "write",
 569                           (cmd & SWD_CMD_A32) >> 1,
 570                           buf_get_u32(trn_ack_data_parity_trn, 1 + 3 + 1, 32));
 571
 572                 switch (ack) {
 573                  case SWD_ACK_OK:
 574                         if (cmd & SWD_CMD_APnDP)
 575                                 bitbang_exchange(true, NULL, 0, ap_delay_clk);
 576                         return;
 577                  case SWD_ACK_WAIT:
 578                         LOG_DEBUG("SWD_ACK_WAIT");
 579                         swd_clear_sticky_errors();
 580                         break;
 581                  case SWD_ACK_FAULT:
 582                         LOG_DEBUG("SWD_ACK_FAULT");
 583                         queued_retval = ack;
 584                         return;
 585                  default:
 586                         LOG_DEBUG("No valid acknowledge: ack=%d", ack);
 587                         queued_retval = ack;
 588                         return;
 589                 }
 590         }
 591 }
 592
 593 static int bitbang_swd_run_queue(void)
 594 {
 595         LOG_DEBUG("bitbang_swd_run_queue");
 596         /* A transaction must be followed by another transaction or at least 8 idle cycles to
 597          * ensure that data is clocked through the AP. */
 598         bitbang_exchange(true, NULL, 0, 8);
 599
 600         int retval = queued_retval;
 601         queued_retval = ERROR_OK;
 602         LOG_DEBUG("SWD queue return value: %02x", retval);
 603         return retval;
 604 }
 605
 606 const struct swd_driver bitbang_swd = {
 607         .init = bitbang_swd_init,
 608         .switch_seq = bitbang_swd_switch_seq,
 609         .read_reg = bitbang_swd_read_reg,
 610         .write_reg = bitbang_swd_write_reg,
 611         .run = bitbang_swd_run_queue,
 612 };