src/jtag/drivers/sysfsgpio.c

   1 /***************************************************************************
   2  *   Copyright (C) 2012 by Creative Product Design, marc @ cpdesign.com.au *
   3  *                                                                         *
   4  *   This program is free software; you can redistribute it and/or modify  *
   5  *   it under the terms of the GNU General Public License as published by  *
   6  *   the Free Software Foundation; either version 2 of the License, or     *
   7  *   (at your option) any later version.                                   *
   8  *                                                                         *
   9  *   This program is distributed in the hope that it will be useful,       *
  10  *   but WITHOUT ANY WARRANTY; without even the implied warranty of        *
  11  *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         *
  12  *   GNU General Public License for more details.                          *
  13  *                                                                         *
  14  *   You should have received a copy of the GNU General Public License     *
  15  *   along with this program.  If not, see <http://www.gnu.org/licenses/>. *
  16  ***************************************************************************/
  17
  18 /* 2014-12: Addition of the SWD protocol support is based on the initial work
  19  * on bcm2835gpio.c by Paul Fertser and modifications by Jean-Christian de Rivaz. */
  20
  21 /**
  22  * @file
  23  * This driver implements a bitbang jtag interface using gpio lines via
  24  * sysfs.
  25  * The aim of this driver implementation is use system GPIOs but avoid the
  26  * need for a additional kernel driver.
  27  * (Note memory mapped IO is another option, however it doesn't mix well with
  28  * the kernel gpiolib driver - which makes sense I guess.)
  29  *
  30  * A gpio is required for tck, tms, tdi and tdo. One or both of srst and trst
  31  * must be also be specified. The required jtag gpios are specified via the
  32  * sysfsgpio_jtag_nums command or the relevant sysfsgpio_XXX_num commang.
  33  * The srst and trst gpios are set via the sysfsgpio_srst_num and
  34  * sysfsgpio_trst_num respectively. GPIO numbering follows the kernel
  35  * convention of starting from 0.
  36  *
  37  * The gpios should not be in use by another entity, and must not be requested
  38  * by a kernel driver without also being exported by it (otherwise they can't
  39  * be exported by sysfs).
  40  *
  41  * The sysfs gpio interface can only manipulate one gpio at a time, so the
  42  * bitbang write handler remembers the last state for tck, tms, tdi to avoid
  43  * superfluous writes.
  44  * For speed the sysfs "value" entry is opened at init and held open.
  45  * This results in considerable gains over open-write-close (45s vs 900s)
  46  *
  47  * Further work could address:
  48  *  -srst and trst open drain/ push pull
  49  *  -configurable active high/low for srst & trst
  50  */
  51 #ifdef HAVE_CONFIG_H
  52 #include "config.h"
  53 #endif
  54
  55 #include <jtag/interface.h>
  56 #include "bitbang.h"
  57
  58 /*
  59  * Helper func to determine if gpio number valid
  60  *
  61  * Assume here that there will be less than 1000 gpios on a system
  62  */
  63 static int is_gpio_valid(int gpio)
  64 {
  65         return gpio >= 0 && gpio < 1000;
  66 }
  67
  68 /*
  69  * Helper func to open, write to and close a file
  70  * name and valstr must be null terminated.
  71  *
  72  * Returns negative on failure.
  73  */
  74 static int open_write_close(const char *name, const char *valstr)
  75 {
  76         int ret;
  77         int fd = open(name, O_WRONLY);
  78         if (fd < 0)
  79                 return fd;
  80
  81         ret = write(fd, valstr, strlen(valstr));
  82         close(fd);
  83
  84         return ret;
  85 }
  86
  87 /*
  88  * Helper func to unexport gpio from sysfs
  89  */
  90 static void unexport_sysfs_gpio(int gpio)
  91 {
  92         char gpiostr[4];
  93
  94         if (!is_gpio_valid(gpio))
  95                 return;
  96
  97         snprintf(gpiostr, sizeof(gpiostr), "%d", gpio);
  98         if (open_write_close("/sys/class/gpio/unexport", gpiostr) < 0)
  99                 LOG_ERROR("Couldn't unexport gpio %d", gpio);
 100
 101         return;
 102 }
 103
 104 /*
 105  * Exports and sets up direction for gpio.
 106  * If the gpio is an output, it is initialized according to init_high,
 107  * otherwise it is ignored.
 108  *
 109  * If the gpio is already exported we just show a warning and continue; if
 110  * openocd happened to crash (or was killed by user) then the gpios will not
 111  * have been cleaned up.
 112  */
 113 static int setup_sysfs_gpio(int gpio, int is_output, int init_high)
 114 {
 115         char buf[40];
 116         char gpiostr[4];
 117         int ret;
 118
 119         if (!is_gpio_valid(gpio))
 120                 return ERROR_OK;
 121
 122         snprintf(gpiostr, sizeof(gpiostr), "%d", gpio);
 123         ret = open_write_close("/sys/class/gpio/export", gpiostr);
 124         if (ret < 0) {
 125                 if (errno == EBUSY) {
 126                         LOG_WARNING("gpio %d is already exported", gpio);
 127                 } else {
 128                         LOG_ERROR("Couldn't export gpio %d", gpio);
 129                         perror("sysfsgpio: ");
 130                         return ERROR_FAIL;
 131                 }
 132         }
 133
 134         snprintf(buf, sizeof(buf), "/sys/class/gpio/gpio%d/direction", gpio);
 135         ret = open_write_close(buf, is_output ? (init_high ? "high" : "low") : "in");
 136         if (ret < 0) {
 137                 LOG_ERROR("Couldn't set direction for gpio %d", gpio);
 138                 perror("sysfsgpio: ");
 139                 unexport_sysfs_gpio(gpio);
 140                 return ERROR_FAIL;
 141         }
 142
 143         snprintf(buf, sizeof(buf), "/sys/class/gpio/gpio%d/value", gpio);
 144         ret = open(buf, O_RDWR | O_NONBLOCK | O_SYNC);
 145         if (ret < 0) {
 146                 LOG_ERROR("Couldn't open value for gpio %d", gpio);
 147                 perror("sysfsgpio: ");
 148                 unexport_sysfs_gpio(gpio);
 149         }
 150
 151         return ret;
 152 }
 153
 154 /* gpio numbers for each gpio. Negative values are invalid */
 155 static int tck_gpio = -1;
 156 static int tms_gpio = -1;
 157 static int tdi_gpio = -1;
 158 static int tdo_gpio = -1;
 159 static int trst_gpio = -1;
 160 static int srst_gpio = -1;
 161 static int swclk_gpio = -1;
 162 static int swdio_gpio = -1;
 163
 164 /*
 165  * file descriptors for /sys/class/gpio/gpioXX/value
 166  * Set up during init.
 167  */
 168 static int tck_fd = -1;
 169 static int tms_fd = -1;
 170 static int tdi_fd = -1;
 171 static int tdo_fd = -1;
 172 static int trst_fd = -1;
 173 static int srst_fd = -1;
 174 static int swclk_fd = -1;
 175 static int swdio_fd = -1;
 176
 177 static int last_swclk;
 178 static int last_swdio;
 179 static bool last_stored;
 180 static bool swdio_input;
 181
 182 static void sysfsgpio_swdio_drive(bool is_output)
 183 {
 184         char buf[40];
 185         int ret;
 186
 187         snprintf(buf, sizeof(buf), "/sys/class/gpio/gpio%d/direction", swdio_gpio);
 188         ret = open_write_close(buf, is_output ? "high" : "in");
 189         if (ret < 0) {
 190                 LOG_ERROR("Couldn't set direction for gpio %d", swdio_gpio);
 191                 perror("sysfsgpio: ");
 192         }
 193
 194         last_stored = false;
 195         swdio_input = !is_output;
 196 }
 197
 198 static int sysfsgpio_swdio_read(void)
 199 {
 200         char buf[1];
 201
 202         /* important to seek to signal sysfs of new read */
 203         lseek(swdio_fd, 0, SEEK_SET);
 204         int ret = read(swdio_fd, &buf, sizeof(buf));
 205
 206         if (ret < 0) {
 207                 LOG_WARNING("reading swdio failed");
 208                 return 0;
 209         }
 210
 211         return buf[0] != '0';
 212 }
 213
 214 static void sysfsgpio_swdio_write(int swclk, int swdio)
 215 {
 216         const char one[] = "1";
 217         const char zero[] = "0";
 218
 219         size_t bytes_written;
 220
 221         if (!swdio_input) {
 222                 if (!last_stored || (swdio != last_swdio)) {
 223                         bytes_written = write(swdio_fd, swdio ? &one : &zero, 1);
 224                         if (bytes_written != 1)
 225                                 LOG_WARNING("writing swdio failed");
 226                 }
 227         }
 228
 229         /* write swclk last */
 230         if (!last_stored || (swclk != last_swclk)) {
 231                 bytes_written = write(swclk_fd, swclk ? &one : &zero, 1);
 232                 if (bytes_written != 1)
 233                         LOG_WARNING("writing swclk failed");
 234         }
 235
 236         last_swdio = swdio;
 237         last_swclk = swclk;
 238         last_stored = true;
 239 }
 240
 241 /*
 242  * Bitbang interface read of TDO
 243  *
 244  * The sysfs value will read back either '0' or '1'. The trick here is to call
 245  * lseek to bypass buffering in the sysfs kernel driver.
 246  */
 247 static int sysfsgpio_read(void)
 248 {
 249         char buf[1];
 250
 251         /* important to seek to signal sysfs of new read */
 252         lseek(tdo_fd, 0, SEEK_SET);
 253         int ret = read(tdo_fd, &buf, sizeof(buf));
 254
 255         if (ret < 0) {
 256                 LOG_WARNING("reading tdo failed");
 257                 return 0;
 258         }
 259
 260         return buf[0] != '0';
 261 }
 262
 263 /*
 264  * Bitbang interface write of TCK, TMS, TDI
 265  *
 266  * Seeing as this is the only function where the outputs are changed,
 267  * we can cache the old value to avoid needlessly writing it.
 268  */
 269 static void sysfsgpio_write(int tck, int tms, int tdi)
 270 {
 271         if (swd_mode) {
 272                 sysfsgpio_swdio_write(tck, tdi);
 273                 return;
 274         }
 275
 276         const char one[] = "1";
 277         const char zero[] = "0";
 278
 279         static int last_tck;
 280         static int last_tms;
 281         static int last_tdi;
 282
 283         static int first_time;
 284         size_t bytes_written;
 285
 286         if (!first_time) {
 287                 last_tck = !tck;
 288                 last_tms = !tms;
 289                 last_tdi = !tdi;
 290                 first_time = 1;
 291         }
 292
 293         if (tdi != last_tdi) {
 294                 bytes_written = write(tdi_fd, tdi ? &one : &zero, 1);
 295                 if (bytes_written != 1)
 296                         LOG_WARNING("writing tdi failed");
 297         }
 298
 299         if (tms != last_tms) {
 300                 bytes_written = write(tms_fd, tms ? &one : &zero, 1);
 301                 if (bytes_written != 1)
 302                         LOG_WARNING("writing tms failed");
 303         }
 304
 305         /* write clk last */
 306         if (tck != last_tck) {
 307                 bytes_written = write(tck_fd, tck ? &one : &zero, 1);
 308                 if (bytes_written != 1)
 309                         LOG_WARNING("writing tck failed");
 310         }
 311
 312         last_tdi = tdi;
 313         last_tms = tms;
 314         last_tck = tck;
 315 }
 316
 317 /*
 318  * Bitbang interface to manipulate reset lines SRST and TRST
 319  *
 320  * (1) assert or (0) deassert reset lines
 321  */
 322 static void sysfsgpio_reset(int trst, int srst)
 323 {
 324         LOG_DEBUG("sysfsgpio_reset");
 325         const char one[] = "1";
 326         const char zero[] = "0";
 327         size_t bytes_written;
 328
 329         /* assume active low */
 330         if (srst_fd >= 0) {
 331                 bytes_written = write(srst_fd, srst ? &zero : &one, 1);
 332                 if (bytes_written != 1)
 333                         LOG_WARNING("writing srst failed");
 334         }
 335
 336         /* assume active low */
 337         if (trst_fd >= 0) {
 338                 bytes_written = write(trst_fd, trst ? &zero : &one, 1);
 339                 if (bytes_written != 1)
 340                         LOG_WARNING("writing trst failed");
 341         }
 342 }
 343
 344 COMMAND_HANDLER(sysfsgpio_handle_jtag_gpionums)
 345 {
 346         if (CMD_ARGC == 4) {
 347                 COMMAND_PARSE_NUMBER(int, CMD_ARGV[0], tck_gpio);
 348                 COMMAND_PARSE_NUMBER(int, CMD_ARGV[1], tms_gpio);
 349                 COMMAND_PARSE_NUMBER(int, CMD_ARGV[2], tdi_gpio);
 350                 COMMAND_PARSE_NUMBER(int, CMD_ARGV[3], tdo_gpio);
 351         } else if (CMD_ARGC != 0) {
 352                 return ERROR_COMMAND_SYNTAX_ERROR;
 353         }
 354
 355         command_print(CMD_CTX,
 356                         "SysfsGPIO nums: tck = %d, tms = %d, tdi = %d, tdo = %d",
 357                         tck_gpio, tms_gpio, tdi_gpio, tdo_gpio);
 358
 359         return ERROR_OK;
 360 }
 361
 362 COMMAND_HANDLER(sysfsgpio_handle_jtag_gpionum_tck)
 363 {
 364         if (CMD_ARGC == 1)
 365                 COMMAND_PARSE_NUMBER(int, CMD_ARGV[0], tck_gpio);
 366
 367         command_print(CMD_CTX, "SysfsGPIO num: tck = %d", tck_gpio);
 368         return ERROR_OK;
 369 }
 370
 371 COMMAND_HANDLER(sysfsgpio_handle_jtag_gpionum_tms)
 372 {
 373         if (CMD_ARGC == 1)
 374                 COMMAND_PARSE_NUMBER(int, CMD_ARGV[0], tms_gpio);
 375
 376         command_print(CMD_CTX, "SysfsGPIO num: tms = %d", tms_gpio);
 377         return ERROR_OK;
 378 }
 379
 380 COMMAND_HANDLER(sysfsgpio_handle_jtag_gpionum_tdo)
 381 {
 382         if (CMD_ARGC == 1)
 383                 COMMAND_PARSE_NUMBER(int, CMD_ARGV[0], tdo_gpio);
 384
 385         command_print(CMD_CTX, "SysfsGPIO num: tdo = %d", tdo_gpio);
 386         return ERROR_OK;
 387 }
 388
 389 COMMAND_HANDLER(sysfsgpio_handle_jtag_gpionum_tdi)
 390 {
 391         if (CMD_ARGC == 1)
 392                 COMMAND_PARSE_NUMBER(int, CMD_ARGV[0], tdi_gpio);
 393
 394         command_print(CMD_CTX, "SysfsGPIO num: tdi = %d", tdi_gpio);
 395         return ERROR_OK;
 396 }
 397
 398 COMMAND_HANDLER(sysfsgpio_handle_jtag_gpionum_srst)
 399 {
 400         if (CMD_ARGC == 1)
 401                 COMMAND_PARSE_NUMBER(int, CMD_ARGV[0], srst_gpio);
 402
 403         command_print(CMD_CTX, "SysfsGPIO num: srst = %d", srst_gpio);
 404         return ERROR_OK;
 405 }
 406
 407 COMMAND_HANDLER(sysfsgpio_handle_jtag_gpionum_trst)
 408 {
 409         if (CMD_ARGC == 1)
 410                 COMMAND_PARSE_NUMBER(int, CMD_ARGV[0], trst_gpio);
 411
 412         command_print(CMD_CTX, "SysfsGPIO num: trst = %d", trst_gpio);
 413         return ERROR_OK;
 414 }
 415
 416 COMMAND_HANDLER(sysfsgpio_handle_swd_gpionums)
 417 {
 418         if (CMD_ARGC == 2) {
 419                 COMMAND_PARSE_NUMBER(int, CMD_ARGV[0], swclk_gpio);
 420                 COMMAND_PARSE_NUMBER(int, CMD_ARGV[1], swdio_gpio);
 421         } else if (CMD_ARGC != 0) {
 422                 return ERROR_COMMAND_SYNTAX_ERROR;
 423         }
 424
 425         command_print(CMD_CTX,
 426                         "SysfsGPIO nums: swclk = %d, swdio = %d",
 427                         swclk_gpio, swdio_gpio);
 428
 429         return ERROR_OK;
 430 }
 431
 432 COMMAND_HANDLER(sysfsgpio_handle_swd_gpionum_swclk)
 433 {
 434         if (CMD_ARGC == 1)
 435                 COMMAND_PARSE_NUMBER(int, CMD_ARGV[0], swclk_gpio);
 436
 437         command_print(CMD_CTX, "SysfsGPIO num: swclk = %d", swclk_gpio);
 438         return ERROR_OK;
 439 }
 440
 441 COMMAND_HANDLER(sysfsgpio_handle_swd_gpionum_swdio)
 442 {
 443         if (CMD_ARGC == 1)
 444                 COMMAND_PARSE_NUMBER(int, CMD_ARGV[0], swdio_gpio);
 445
 446         command_print(CMD_CTX, "SysfsGPIO num: swdio = %d", swdio_gpio);
 447         return ERROR_OK;
 448 }
 449
 450 static const struct command_registration sysfsgpio_command_handlers[] = {
 451         {
 452                 .name = "sysfsgpio_jtag_nums",
 453                 .handler = &sysfsgpio_handle_jtag_gpionums,
 454                 .mode = COMMAND_CONFIG,
 455                 .help = "gpio numbers for tck, tms, tdi, tdo. (in that order)",
 456                 .usage = "(tck tms tdi tdo)* ",
 457         },
 458         {
 459                 .name = "sysfsgpio_tck_num",
 460                 .handler = &sysfsgpio_handle_jtag_gpionum_tck,
 461                 .mode = COMMAND_CONFIG,
 462                 .help = "gpio number for tck.",
 463         },
 464         {
 465                 .name = "sysfsgpio_tms_num",
 466                 .handler = &sysfsgpio_handle_jtag_gpionum_tms,
 467                 .mode = COMMAND_CONFIG,
 468                 .help = "gpio number for tms.",
 469         },
 470         {
 471                 .name = "sysfsgpio_tdo_num",
 472                 .handler = &sysfsgpio_handle_jtag_gpionum_tdo,
 473                 .mode = COMMAND_CONFIG,
 474                 .help = "gpio number for tdo.",
 475         },
 476         {
 477                 .name = "sysfsgpio_tdi_num",
 478                 .handler = &sysfsgpio_handle_jtag_gpionum_tdi,
 479                 .mode = COMMAND_CONFIG,
 480                 .help = "gpio number for tdi.",
 481         },
 482         {
 483                 .name = "sysfsgpio_srst_num",
 484                 .handler = &sysfsgpio_handle_jtag_gpionum_srst,
 485                 .mode = COMMAND_CONFIG,
 486                 .help = "gpio number for srst.",
 487         },
 488         {
 489                 .name = "sysfsgpio_trst_num",
 490                 .handler = &sysfsgpio_handle_jtag_gpionum_trst,
 491                 .mode = COMMAND_CONFIG,
 492                 .help = "gpio number for trst.",
 493         },
 494         {
 495                 .name = "sysfsgpio_swd_nums",
 496                 .handler = &sysfsgpio_handle_swd_gpionums,
 497                 .mode = COMMAND_CONFIG,
 498                 .help = "gpio numbers for swclk, swdio. (in that order)",
 499                 .usage = "(swclk swdio)* ",
 500         },
 501         {
 502                 .name = "sysfsgpio_swclk_num",
 503                 .handler = &sysfsgpio_handle_swd_gpionum_swclk,
 504                 .mode = COMMAND_CONFIG,
 505                 .help = "gpio number for swclk.",
 506         },
 507         {
 508                 .name = "sysfsgpio_swdio_num",
 509                 .handler = &sysfsgpio_handle_swd_gpionum_swdio,
 510                 .mode = COMMAND_CONFIG,
 511                 .help = "gpio number for swdio.",
 512         },
 513         COMMAND_REGISTRATION_DONE
 514 };
 515
 516 static int sysfsgpio_init(void);
 517 static int sysfsgpio_quit(void);
 518
 519 static const char * const sysfsgpio_transports[] = { "jtag", "swd", NULL };
 520
 521 struct jtag_interface sysfsgpio_interface = {
 522         .name = "sysfsgpio",
 523         .supported = DEBUG_CAP_TMS_SEQ,
 524         .execute_queue = bitbang_execute_queue,
 525         .transports = sysfsgpio_transports,
 526         .swd = &bitbang_swd,
 527         .commands = sysfsgpio_command_handlers,
 528         .init = sysfsgpio_init,
 529         .quit = sysfsgpio_quit,
 530 };
 531
 532 static struct bitbang_interface sysfsgpio_bitbang = {
 533         .read = sysfsgpio_read,
 534         .write = sysfsgpio_write,
 535         .reset = sysfsgpio_reset,
 536         .swdio_read = sysfsgpio_swdio_read,
 537         .swdio_drive = sysfsgpio_swdio_drive,
 538         .blink = 0
 539 };
 540
 541 /* helper func to close and cleanup files only if they were valid/ used */
 542 static void cleanup_fd(int fd, int gpio)
 543 {
 544         if (gpio >= 0) {
 545                 if (fd >= 0)
 546                         close(fd);
 547
 548                 unexport_sysfs_gpio(gpio);
 549         }
 550 }
 551
 552 static void cleanup_all_fds(void)
 553 {
 554         cleanup_fd(tck_fd, tck_gpio);
 555         cleanup_fd(tms_fd, tms_gpio);
 556         cleanup_fd(tdi_fd, tdi_gpio);
 557         cleanup_fd(tdo_fd, tdo_gpio);
 558         cleanup_fd(trst_fd, trst_gpio);
 559         cleanup_fd(srst_fd, srst_gpio);
 560 }
 561
 562 static bool sysfsgpio_jtag_mode_possible(void)
 563 {
 564         if (!is_gpio_valid(tck_gpio))
 565                 return 0;
 566         if (!is_gpio_valid(tms_gpio))
 567                 return 0;
 568         if (!is_gpio_valid(tdi_gpio))
 569                 return 0;
 570         if (!is_gpio_valid(tdo_gpio))
 571                 return 0;
 572         return 1;
 573 }
 574
 575 static bool sysfsgpio_swd_mode_possible(void)
 576 {
 577         if (!is_gpio_valid(swclk_gpio))
 578                 return 0;
 579         if (!is_gpio_valid(swdio_gpio))
 580                 return 0;
 581         return 1;
 582 }
 583
 584 static int sysfsgpio_init(void)
 585 {
 586         bitbang_interface = &sysfsgpio_bitbang;
 587
 588         LOG_INFO("SysfsGPIO JTAG/SWD bitbang driver");
 589
 590         if (sysfsgpio_jtag_mode_possible()) {
 591                 if (sysfsgpio_swd_mode_possible())
 592                         LOG_INFO("JTAG and SWD modes enabled");
 593                 else
 594                         LOG_INFO("JTAG only mode enabled (specify swclk and swdio gpio to add SWD mode)");
 595                 if (!is_gpio_valid(trst_gpio) && !is_gpio_valid(srst_gpio)) {
 596                         LOG_ERROR("Require at least one of trst or srst gpios to be specified");
 597                         return ERROR_JTAG_INIT_FAILED;
 598                 }
 599         } else if (sysfsgpio_swd_mode_possible()) {
 600                 LOG_INFO("SWD only mode enabled (specify tck, tms, tdi and tdo gpios to add JTAG mode)");
 601         } else {
 602                 LOG_ERROR("Require tck, tms, tdi and tdo gpios for JTAG mode and/or swclk and swdio gpio for SWD mode");
 603                 return ERROR_JTAG_INIT_FAILED;
 604         }
 605
 606
 607         /*
 608          * Configure TDO as an input, and TDI, TCK, TMS, TRST, SRST
 609          * as outputs.  Drive TDI and TCK low, and TMS/TRST/SRST high.
 610          * For SWD, SWCLK and SWDIO are configures as output high.
 611          */
 612         if (tck_gpio >= 0) {
 613                 tck_fd = setup_sysfs_gpio(tck_gpio, 1, 0);
 614                 if (tck_fd < 0)
 615                         goto out_error;
 616         }
 617
 618         if (tms_gpio >= 0) {
 619                 tms_fd = setup_sysfs_gpio(tms_gpio, 1, 1);
 620                 if (tms_fd < 0)
 621                         goto out_error;
 622         }
 623
 624         if (tdi_gpio >= 0) {
 625                 tdi_fd = setup_sysfs_gpio(tdi_gpio, 1, 0);
 626                 if (tdi_fd < 0)
 627                         goto out_error;
 628         }
 629
 630         if (tdo_gpio >= 0) {
 631                 tdo_fd = setup_sysfs_gpio(tdo_gpio, 0, 0);
 632                 if (tdo_fd < 0)
 633                         goto out_error;
 634         }
 635
 636         /* assume active low*/
 637         if (trst_gpio >= 0) {
 638                 trst_fd = setup_sysfs_gpio(trst_gpio, 1, 1);
 639                 if (trst_fd < 0)
 640                         goto out_error;
 641         }
 642
 643         /* assume active low*/
 644         if (srst_gpio >= 0) {
 645                 srst_fd = setup_sysfs_gpio(srst_gpio, 1, 1);
 646                 if (srst_fd < 0)
 647                         goto out_error;
 648         }
 649
 650         if (swclk_gpio >= 0) {
 651                 swclk_fd = setup_sysfs_gpio(swclk_gpio, 1, 0);
 652                 if (swclk_fd < 0)
 653                         goto out_error;
 654         }
 655
 656         if (swdio_gpio >= 0) {
 657                 swdio_fd = setup_sysfs_gpio(swdio_gpio, 1, 0);
 658                 if (swdio_fd < 0)
 659                         goto out_error;
 660         }
 661
 662         if (sysfsgpio_swd_mode_possible()) {
 663                 if (swd_mode)
 664                         bitbang_swd_switch_seq(JTAG_TO_SWD);
 665                 else
 666                         bitbang_swd_switch_seq(SWD_TO_JTAG);
 667         }
 668
 669         return ERROR_OK;
 670
 671 out_error:
 672         cleanup_all_fds();
 673         return ERROR_JTAG_INIT_FAILED;
 674 }
 675
 676 static int sysfsgpio_quit(void)
 677 {
 678         cleanup_all_fds();
 679         return ERROR_OK;
 680 }
 681