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, write to the                         *
  16  *   Free Software Foundation, Inc.,                                       *
  17  *   51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.           *
  18  ***************************************************************************/
  19 /**
  20  * @file
  21  * This driver implements a bitbang jtag interface using gpio lines via
  22  * sysfs.
  23  * The aim of this driver implementation is use system GPIOs but avoid the
  24  * need for a additional kernel driver.
  25  * (Note memory mapped IO is another option, however it doesn't mix well with
  26  * the kernel gpiolib driver - which makes sense I guess.)
  27  *
  28  * A gpio is required for tck, tms, tdi and tdo. One or both of srst and trst
  29  * must be also be specified. The required jtag gpios are specified via the
  30  * sysfsgpio_jtag_nums command or the relevant sysfsgpio_XXX_num commang.
  31  * The srst and trst gpios are set via the sysfsgpio_srst_num and
  32  * sysfsgpio_trst_num respectively. GPIO numbering follows the kernel
  33  * convention of starting from 0.
  34  *
  35  * The gpios should not be in use by another entity, and must not be requested
  36  * by a kernel driver without also being exported by it (otherwise they can't
  37  * be exported by sysfs).
  38  *
  39  * The sysfs gpio interface can only manipulate one gpio at a time, so the
  40  * bitbang write handler remembers the last state for tck, tms, tdi to avoid
  41  * superfluous writes.
  42  * For speed the sysfs "value" entry is opened at init and held open.
  43  * This results in considerable gains over open-write-close (45s vs 900s)
  44  *
  45  * Further work could address:
  46  *  -srst and trst open drain/ push pull
  47  *  -configurable active high/low for srst & trst
  48  */
  49 #ifdef HAVE_CONFIG_H
  50 #include "config.h"
  51 #endif
  52
  53 #include <jtag/interface.h>
  54 #include "bitbang.h"
  55
  56 /*
  57  * Helper func to determine if gpio number valid
  58  *
  59  * Assume here that there will be less than 1000 gpios on a system
  60  */
  61 static int is_gpio_valid(int gpio)
  62 {
  63         return gpio >= 0 && gpio < 1000;
  64 }
  65
  66 /*
  67  * Helper func to open, write to and close a file
  68  * name and valstr must be null terminated.
  69  *
  70  * Returns negative on failure.
  71  */
  72 static int open_write_close(const char *name, const char *valstr)
  73 {
  74         int ret;
  75         int fd = open(name, O_WRONLY);
  76         if (fd < 0)
  77                 return fd;
  78
  79         ret = write(fd, valstr, strlen(valstr));
  80         close(fd);
  81
  82         return ret;
  83 }
  84
  85 /*
  86  * Helper func to unexport gpio from sysfs
  87  */
  88 static void unexport_sysfs_gpio(int gpio)
  89 {
  90         char gpiostr[4];
  91
  92         if (!is_gpio_valid(gpio))
  93                 return;
  94
  95         snprintf(gpiostr, sizeof(gpiostr), "%d", gpio);
  96         if (open_write_close("/sys/class/gpio/unexport", gpiostr) < 0)
  97                 LOG_ERROR("Couldn't unexport gpio %d", gpio);
  98
  99         return;
 100 }
 101
 102 /*
 103  * Exports and sets up direction for gpio.
 104  * If the gpio is an output, it is initialized according to init_high,
 105  * otherwise it is ignored.
 106  *
 107  * If the gpio is already exported we just show a warning and continue; if
 108  * openocd happened to crash (or was killed by user) then the gpios will not
 109  * have been cleaned up.
 110  */
 111 static int setup_sysfs_gpio(int gpio, int is_output, int init_high)
 112 {
 113         char buf[40];
 114         char gpiostr[4];
 115         int ret;
 116
 117         if (!is_gpio_valid(gpio))
 118                 return ERROR_OK;
 119
 120         snprintf(gpiostr, sizeof(gpiostr), "%d", gpio);
 121         ret = open_write_close("/sys/class/gpio/export", gpiostr);
 122         if (ret < 0) {
 123                 if (errno == EBUSY) {
 124                         LOG_WARNING("gpio %d is already exported", gpio);
 125                 } else {
 126                         LOG_ERROR("Couldn't export gpio %d", gpio);
 127                         perror("sysfsgpio: ");
 128                         return ERROR_FAIL;
 129                 }
 130         }
 131
 132         snprintf(buf, sizeof(buf), "/sys/class/gpio/gpio%d/direction", gpio);
 133         ret = open_write_close(buf, is_output ? (init_high ? "high" : "low") : "in");
 134         if (ret < 0) {
 135                 LOG_ERROR("Couldn't set direction for gpio %d", gpio);
 136                 perror("sysfsgpio: ");
 137                 unexport_sysfs_gpio(gpio);
 138                 return ERROR_FAIL;
 139         }
 140
 141         snprintf(buf, sizeof(buf), "/sys/class/gpio/gpio%d/value", gpio);
 142         if (is_output)
 143                 ret = open(buf, O_WRONLY | O_NONBLOCK | O_SYNC);
 144         else
 145                 ret = open(buf, O_RDONLY | O_NONBLOCK | O_SYNC);
 146
 147         if (ret < 0)
 148                 unexport_sysfs_gpio(gpio);
 149
 150         return ret;
 151 }
 152
 153 /*
 154  * file descriptors for /sys/class/gpio/gpioXX/value
 155  * Set up during init.
 156  */
 157 static int tck_fd = -1;
 158 static int tms_fd = -1;
 159 static int tdi_fd = -1;
 160 static int tdo_fd = -1;
 161 static int trst_fd = -1;
 162 static int srst_fd = -1;
 163
 164 /*
 165  * Bitbang interface read of TDO
 166  *
 167  * The sysfs value will read back either '0' or '1'. The trick here is to call
 168  * lseek to bypass buffering in the sysfs kernel driver.
 169  */
 170 static int sysfsgpio_read(void)
 171 {
 172         char buf[1];
 173
 174         /* important to seek to signal sysfs of new read */
 175         lseek(tdo_fd, 0, SEEK_SET);
 176         int ret = read(tdo_fd, &buf, sizeof(buf));
 177
 178         if (ret < 0) {
 179                 LOG_WARNING("reading tdo failed");
 180                 return 0;
 181         }
 182
 183         return buf[0] == '1';
 184 }
 185
 186 /*
 187  * Bitbang interface write of TCK, TMS, TDI
 188  *
 189  * Seeing as this is the only function where the outputs are changed,
 190  * we can cache the old value to avoid needlessly writing it.
 191  */
 192 static void sysfsgpio_write(int tck, int tms, int tdi)
 193 {
 194         const char one[] = "1";
 195         const char zero[] = "0";
 196
 197         static int last_tck;
 198         static int last_tms;
 199         static int last_tdi;
 200
 201         static int first_time;
 202         size_t bytes_written;
 203
 204         if (!first_time) {
 205                 last_tck = !tck;
 206                 last_tms = !tms;
 207                 last_tdi = !tdi;
 208                 first_time = 1;
 209         }
 210
 211         if (tdi != last_tdi) {
 212                 bytes_written = write(tdi_fd, tdi ? &one : &zero, 1);
 213                 if (bytes_written != 1)
 214                         LOG_WARNING("writing tdi failed");
 215         }
 216
 217         if (tms != last_tms) {
 218                 bytes_written = write(tms_fd, tms ? &one : &zero, 1);
 219                 if (bytes_written != 1)
 220                         LOG_WARNING("writing tms failed");
 221         }
 222
 223         /* write clk last */
 224         if (tck != last_tck) {
 225                 bytes_written = write(tck_fd, tck ? &one : &zero, 1);
 226                 if (bytes_written != 1)
 227                         LOG_WARNING("writing tck failed");
 228         }
 229
 230         last_tdi = tdi;
 231         last_tms = tms;
 232         last_tck = tck;
 233 }
 234
 235 /*
 236  * Bitbang interface to manipulate reset lines SRST and TRST
 237  *
 238  * (1) assert or (0) deassert reset lines
 239  */
 240 static void sysfsgpio_reset(int trst, int srst)
 241 {
 242         const char one[] = "1";
 243         const char zero[] = "0";
 244         size_t bytes_written;
 245
 246         /* assume active low */
 247         if (srst_fd >= 0) {
 248                 bytes_written = write(srst_fd, srst ? &zero : &one, 1);
 249                 if (bytes_written != 1)
 250                         LOG_WARNING("writing srst failed");
 251         }
 252
 253         /* assume active low */
 254         if (trst_fd >= 0) {
 255                 bytes_written = write(trst_fd, trst ? &zero : &one, 1);
 256                 if (bytes_written != 1)
 257                         LOG_WARNING("writing trst failed");
 258         }
 259 }
 260
 261 /* gpio numbers for each gpio. Negative values are invalid */
 262 static int tck_gpio = -1;
 263 static int tms_gpio = -1;
 264 static int tdi_gpio = -1;
 265 static int tdo_gpio = -1;
 266 static int trst_gpio = -1;
 267 static int srst_gpio = -1;
 268
 269 COMMAND_HANDLER(sysfsgpio_handle_jtag_gpionums)
 270 {
 271         if (CMD_ARGC == 4) {
 272                 COMMAND_PARSE_NUMBER(int, CMD_ARGV[0], tck_gpio);
 273                 COMMAND_PARSE_NUMBER(int, CMD_ARGV[1], tms_gpio);
 274                 COMMAND_PARSE_NUMBER(int, CMD_ARGV[2], tdi_gpio);
 275                 COMMAND_PARSE_NUMBER(int, CMD_ARGV[3], tdo_gpio);
 276         } else if (CMD_ARGC != 0) {
 277                 return ERROR_COMMAND_SYNTAX_ERROR;
 278         }
 279
 280         command_print(CMD_CTX,
 281                         "SysfsGPIO nums: tck = %d, tms = %d, tdi = %d, tdo = %d",
 282                         tck_gpio, tms_gpio, tdi_gpio, tdo_gpio);
 283
 284         return ERROR_OK;
 285 }
 286
 287 COMMAND_HANDLER(sysfsgpio_handle_jtag_gpionum_tck)
 288 {
 289         if (CMD_ARGC == 1)
 290                 COMMAND_PARSE_NUMBER(int, CMD_ARGV[0], tck_gpio);
 291
 292         command_print(CMD_CTX, "SysfsGPIO num: tck = %d", tck_gpio);
 293         return ERROR_OK;
 294 }
 295
 296 COMMAND_HANDLER(sysfsgpio_handle_jtag_gpionum_tms)
 297 {
 298         if (CMD_ARGC == 1)
 299                 COMMAND_PARSE_NUMBER(int, CMD_ARGV[0], tms_gpio);
 300
 301         command_print(CMD_CTX, "SysfsGPIO num: tms = %d", tms_gpio);
 302         return ERROR_OK;
 303 }
 304
 305 COMMAND_HANDLER(sysfsgpio_handle_jtag_gpionum_tdo)
 306 {
 307         if (CMD_ARGC == 1)
 308                 COMMAND_PARSE_NUMBER(int, CMD_ARGV[0], tdo_gpio);
 309
 310         command_print(CMD_CTX, "SysfsGPIO num: tdo = %d", tdo_gpio);
 311         return ERROR_OK;
 312 }
 313
 314 COMMAND_HANDLER(sysfsgpio_handle_jtag_gpionum_tdi)
 315 {
 316         if (CMD_ARGC == 1)
 317                 COMMAND_PARSE_NUMBER(int, CMD_ARGV[0], tdi_gpio);
 318
 319         command_print(CMD_CTX, "SysfsGPIO num: tdi = %d", tdi_gpio);
 320         return ERROR_OK;
 321 }
 322
 323 COMMAND_HANDLER(sysfsgpio_handle_jtag_gpionum_srst)
 324 {
 325         if (CMD_ARGC == 1)
 326                 COMMAND_PARSE_NUMBER(int, CMD_ARGV[0], srst_gpio);
 327
 328         command_print(CMD_CTX, "SysfsGPIO num: srst = %d", srst_gpio);
 329         return ERROR_OK;
 330 }
 331
 332 COMMAND_HANDLER(sysfsgpio_handle_jtag_gpionum_trst)
 333 {
 334         if (CMD_ARGC == 1)
 335                 COMMAND_PARSE_NUMBER(int, CMD_ARGV[0], trst_gpio);
 336
 337         command_print(CMD_CTX, "SysfsGPIO num: trst = %d", trst_gpio);
 338         return ERROR_OK;
 339 }
 340
 341 static const struct command_registration sysfsgpio_command_handlers[] = {
 342         {
 343                 .name = "sysfsgpio_jtag_nums",
 344                 .handler = &sysfsgpio_handle_jtag_gpionums,
 345                 .mode = COMMAND_CONFIG,
 346                 .help = "gpio numbers for tck, tms, tdi, tdo. (in that order)",
 347                 .usage = "(tck tms tdi tdo)* ",
 348         },
 349         {
 350                 .name = "sysfsgpio_tck_num",
 351                 .handler = &sysfsgpio_handle_jtag_gpionum_tck,
 352                 .mode = COMMAND_CONFIG,
 353                 .help = "gpio number for tck.",
 354         },
 355         {
 356                 .name = "sysfsgpio_tms_num",
 357                 .handler = &sysfsgpio_handle_jtag_gpionum_tms,
 358                 .mode = COMMAND_CONFIG,
 359                 .help = "gpio number for tms.",
 360         },
 361         {
 362                 .name = "sysfsgpio_tdo_num",
 363                 .handler = &sysfsgpio_handle_jtag_gpionum_tdo,
 364                 .mode = COMMAND_CONFIG,
 365                 .help = "gpio number for tdo.",
 366         },
 367         {
 368                 .name = "sysfsgpio_tdi_num",
 369                 .handler = &sysfsgpio_handle_jtag_gpionum_tdi,
 370                 .mode = COMMAND_CONFIG,
 371                 .help = "gpio number for tdi.",
 372         },
 373         {
 374                 .name = "sysfsgpio_srst_num",
 375                 .handler = &sysfsgpio_handle_jtag_gpionum_srst,
 376                 .mode = COMMAND_CONFIG,
 377                 .help = "gpio number for srst.",
 378         },
 379         {
 380                 .name = "sysfsgpio_trst_num",
 381                 .handler = &sysfsgpio_handle_jtag_gpionum_trst,
 382                 .mode = COMMAND_CONFIG,
 383                 .help = "gpio number for trst.",
 384         },
 385         COMMAND_REGISTRATION_DONE
 386 };
 387
 388 static int sysfsgpio_init(void);
 389 static int sysfsgpio_quit(void);
 390
 391 struct jtag_interface sysfsgpio_interface = {
 392         .name = "sysfsgpio",
 393         .supported = DEBUG_CAP_TMS_SEQ,
 394         .execute_queue = bitbang_execute_queue,
 395         .transports = jtag_only,
 396         .commands = sysfsgpio_command_handlers,
 397         .init = sysfsgpio_init,
 398         .quit = sysfsgpio_quit,
 399 };
 400
 401 static struct bitbang_interface sysfsgpio_bitbang = {
 402         .read = sysfsgpio_read,
 403         .write = sysfsgpio_write,
 404         .reset = sysfsgpio_reset,
 405         .blink = 0
 406 };
 407
 408 /* helper func to close and cleanup files only if they were valid/ used */
 409 static void cleanup_fd(int fd, int gpio)
 410 {
 411         if (gpio >= 0) {
 412                 if (fd >= 0)
 413                         close(fd);
 414
 415                 unexport_sysfs_gpio(gpio);
 416         }
 417 }
 418
 419 static void cleanup_all_fds(void)
 420 {
 421         cleanup_fd(tck_fd, tck_gpio);
 422         cleanup_fd(tms_fd, tms_gpio);
 423         cleanup_fd(tdi_fd, tdi_gpio);
 424         cleanup_fd(tdo_fd, tdo_gpio);
 425         cleanup_fd(trst_fd, trst_gpio);
 426         cleanup_fd(srst_fd, srst_gpio);
 427 }
 428
 429 static int sysfsgpio_init(void)
 430 {
 431         bitbang_interface = &sysfsgpio_bitbang;
 432
 433         LOG_INFO("SysfsGPIO JTAG bitbang driver");
 434
 435         if (!(is_gpio_valid(tck_gpio)
 436                         && is_gpio_valid(tms_gpio)
 437                         && is_gpio_valid(tdi_gpio)
 438                         && is_gpio_valid(tdo_gpio))) {
 439                 if (!is_gpio_valid(tck_gpio))
 440                         LOG_ERROR("gpio num for tck is invalid");
 441                 if (!is_gpio_valid(tms_gpio))
 442                         LOG_ERROR("gpio num for tms is invalid");
 443                 if (!is_gpio_valid(tdo_gpio))
 444                         LOG_ERROR("gpio num for tdo is invalid");
 445                 if (!is_gpio_valid(tdi_gpio))
 446                         LOG_ERROR("gpio num for tdi is invalid");
 447
 448                 LOG_ERROR("Require tck, tms, tdi and tdo gpios to all be specified");
 449                 return ERROR_JTAG_INIT_FAILED;
 450         }
 451
 452         if (!is_gpio_valid(trst_gpio) && !is_gpio_valid(srst_gpio)) {
 453                 LOG_ERROR("Require at least one of trst or srst gpios to be specified");
 454                 return ERROR_JTAG_INIT_FAILED;
 455         }
 456
 457         /*
 458          * Configure TDO as an input, and TDI, TCK, TMS, TRST, SRST
 459          * as outputs.  Drive TDI and TCK low, and TMS/TRST/SRST high.
 460          */
 461         tck_fd = setup_sysfs_gpio(tck_gpio, 1, 0);
 462         if (tck_fd < 0)
 463                 goto out_error;
 464
 465         tms_fd = setup_sysfs_gpio(tms_gpio, 1, 1);
 466         if (tms_fd < 0)
 467                 goto out_error;
 468
 469         tdi_fd = setup_sysfs_gpio(tdi_gpio, 1, 0);
 470         if (tdi_fd < 0)
 471                 goto out_error;
 472
 473         tdo_fd = setup_sysfs_gpio(tdo_gpio, 0, 0);
 474         if (tdo_fd < 0)
 475                 goto out_error;
 476
 477         /* assume active low*/
 478         if (trst_gpio > 0) {
 479                 trst_fd = setup_sysfs_gpio(trst_gpio, 1, 1);
 480                 if (trst_fd < 0)
 481                         goto out_error;
 482         }
 483
 484         /* assume active low*/
 485         if (srst_gpio > 0) {
 486                 srst_fd = setup_sysfs_gpio(srst_gpio, 1, 1);
 487                 if (srst_fd < 0)
 488                         goto out_error;
 489         }
 490
 491         return ERROR_OK;
 492
 493 out_error:
 494         cleanup_all_fds();
 495         return ERROR_JTAG_INIT_FAILED;
 496 }
 497
 498 static int sysfsgpio_quit(void)
 499 {
 500         cleanup_all_fds();
 501         return ERROR_OK;
 502 }
 503