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  *   59 Temple Place - Suite 330, Boston, MA  02111-1307, 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 /* No speed control is implemented yet */
 262 static int sysfsgpio_speed(int speed)
 263 {
 264         return ERROR_OK;
 265 }
 266
 267 static int sysfsgpio_khz(int khz, int *jtag_speed)
 268 {
 269         /* no adaptive clocking */
 270         if (khz == 0)
 271                 return ERROR_FAIL;
 272
 273         *jtag_speed = 0;
 274         return ERROR_OK;
 275 }
 276
 277 static int sysfsgpio_speed_div(int speed, int *khz)
 278 {
 279         *khz = 1;
 280         return ERROR_OK;
 281 }
 282
 283 /* gpio numbers for each gpio. Negative values are invalid */
 284 static int tck_gpio = -1;
 285 static int tms_gpio = -1;
 286 static int tdi_gpio = -1;
 287 static int tdo_gpio = -1;
 288 static int trst_gpio = -1;
 289 static int srst_gpio = -1;
 290
 291 COMMAND_HANDLER(sysfsgpio_handle_jtag_gpionums)
 292 {
 293         if (CMD_ARGC == 4) {
 294                 COMMAND_PARSE_NUMBER(int, CMD_ARGV[0], tck_gpio);
 295                 COMMAND_PARSE_NUMBER(int, CMD_ARGV[1], tms_gpio);
 296                 COMMAND_PARSE_NUMBER(int, CMD_ARGV[2], tdi_gpio);
 297                 COMMAND_PARSE_NUMBER(int, CMD_ARGV[3], tdo_gpio);
 298         } else if (CMD_ARGC != 0) {
 299                 return ERROR_COMMAND_SYNTAX_ERROR;
 300         }
 301
 302         command_print(CMD_CTX,
 303                         "SysfsGPIO nums: tck = %d, tms = %d, tdi = %d, tdi = %d",
 304                         tck_gpio, tms_gpio, tdi_gpio, tdo_gpio);
 305
 306         return ERROR_OK;
 307 }
 308
 309 COMMAND_HANDLER(sysfsgpio_handle_jtag_gpionum_tck)
 310 {
 311         if (CMD_ARGC == 1)
 312                 COMMAND_PARSE_NUMBER(int, CMD_ARGV[0], tck_gpio);
 313
 314         command_print(CMD_CTX, "SysfsGPIO num: tck = %d", tck_gpio);
 315         return ERROR_OK;
 316 }
 317
 318 COMMAND_HANDLER(sysfsgpio_handle_jtag_gpionum_tms)
 319 {
 320         if (CMD_ARGC == 1)
 321                 COMMAND_PARSE_NUMBER(int, CMD_ARGV[0], tms_gpio);
 322
 323         command_print(CMD_CTX, "SysfsGPIO num: tms = %d", tms_gpio);
 324         return ERROR_OK;
 325 }
 326
 327 COMMAND_HANDLER(sysfsgpio_handle_jtag_gpionum_tdo)
 328 {
 329         if (CMD_ARGC == 1)
 330                 COMMAND_PARSE_NUMBER(int, CMD_ARGV[0], tdo_gpio);
 331
 332         command_print(CMD_CTX, "SysfsGPIO num: tdo = %d", tdo_gpio);
 333         return ERROR_OK;
 334 }
 335
 336 COMMAND_HANDLER(sysfsgpio_handle_jtag_gpionum_tdi)
 337 {
 338         if (CMD_ARGC == 1)
 339                 COMMAND_PARSE_NUMBER(int, CMD_ARGV[0], tdi_gpio);
 340
 341         command_print(CMD_CTX, "SysfsGPIO num: tdi = %d", tdi_gpio);
 342         return ERROR_OK;
 343 }
 344
 345 COMMAND_HANDLER(sysfsgpio_handle_jtag_gpionum_srst)
 346 {
 347         if (CMD_ARGC == 1)
 348                 COMMAND_PARSE_NUMBER(int, CMD_ARGV[0], srst_gpio);
 349
 350         command_print(CMD_CTX, "SysfsGPIO num: srst = %d", srst_gpio);
 351         return ERROR_OK;
 352 }
 353
 354 COMMAND_HANDLER(sysfsgpio_handle_jtag_gpionum_trst)
 355 {
 356         if (CMD_ARGC == 1)
 357                 COMMAND_PARSE_NUMBER(int, CMD_ARGV[0], trst_gpio);
 358
 359         command_print(CMD_CTX, "SysfsGPIO num: trst = %d", trst_gpio);
 360         return ERROR_OK;
 361 }
 362
 363 static const struct command_registration sysfsgpio_command_handlers[] = {
 364         {
 365                 .name = "sysfsgpio_jtag_nums",
 366                 .handler = &sysfsgpio_handle_jtag_gpionums,
 367                 .mode = COMMAND_CONFIG,
 368                 .help = "gpio numbers for tck, tms, tdi, tdo. (in that order)",
 369                 .usage = "(tck tms tdi tdo)* ",
 370         },
 371         {
 372                 .name = "sysfsgpio_tck_num",
 373                 .handler = &sysfsgpio_handle_jtag_gpionum_tck,
 374                 .mode = COMMAND_CONFIG,
 375                 .help = "gpio number for tck.",
 376         },
 377         {
 378                 .name = "sysfsgpio_tms_num",
 379                 .handler = &sysfsgpio_handle_jtag_gpionum_tms,
 380                 .mode = COMMAND_CONFIG,
 381                 .help = "gpio number for tms.",
 382         },
 383         {
 384                 .name = "sysfsgpio_tdo_num",
 385                 .handler = &sysfsgpio_handle_jtag_gpionum_tdo,
 386                 .mode = COMMAND_CONFIG,
 387                 .help = "gpio number for tdo.",
 388         },
 389         {
 390                 .name = "sysfsgpio_tdi_num",
 391                 .handler = &sysfsgpio_handle_jtag_gpionum_tdi,
 392                 .mode = COMMAND_CONFIG,
 393                 .help = "gpio number for tdi.",
 394         },
 395         {
 396                 .name = "sysfsgpio_srst_num",
 397                 .handler = &sysfsgpio_handle_jtag_gpionum_srst,
 398                 .mode = COMMAND_CONFIG,
 399                 .help = "gpio number for srst.",
 400         },
 401         {
 402                 .name = "sysfsgpio_trst_num",
 403                 .handler = &sysfsgpio_handle_jtag_gpionum_trst,
 404                 .mode = COMMAND_CONFIG,
 405                 .help = "gpio number for trst.",
 406         },
 407         COMMAND_REGISTRATION_DONE
 408 };
 409
 410 static int sysfsgpio_init(void);
 411 static int sysfsgpio_quit(void);
 412
 413 struct jtag_interface sysfsgpio_interface = {
 414         .name = "sysfsgpio",
 415         .supported = DEBUG_CAP_TMS_SEQ,
 416         .execute_queue = bitbang_execute_queue,
 417         .transports = jtag_only,
 418         .speed = sysfsgpio_speed,
 419         .khz = sysfsgpio_khz,
 420         .speed_div = sysfsgpio_speed_div,
 421         .commands = sysfsgpio_command_handlers,
 422         .init = sysfsgpio_init,
 423         .quit = sysfsgpio_quit,
 424 };
 425
 426 static struct bitbang_interface sysfsgpio_bitbang = {
 427         .read = sysfsgpio_read,
 428         .write = sysfsgpio_write,
 429         .reset = sysfsgpio_reset,
 430         .blink = 0
 431 };
 432
 433 /* helper func to close and cleanup files only if they were valid/ used */
 434 static void cleanup_fd(int fd, int gpio)
 435 {
 436         if (gpio >= 0) {
 437                 if (fd >= 0)
 438                         close(fd);
 439
 440                 unexport_sysfs_gpio(gpio);
 441         }
 442 }
 443
 444 static void cleanup_all_fds(void)
 445 {
 446         cleanup_fd(tck_fd, tck_gpio);
 447         cleanup_fd(tms_fd, tms_gpio);
 448         cleanup_fd(tdi_fd, tdi_gpio);
 449         cleanup_fd(tdo_fd, tdo_gpio);
 450         cleanup_fd(trst_fd, trst_gpio);
 451         cleanup_fd(srst_fd, srst_gpio);
 452 }
 453
 454 static int sysfsgpio_init(void)
 455 {
 456         bitbang_interface = &sysfsgpio_bitbang;
 457
 458         LOG_INFO("SysfsGPIO JTAG bitbang driver");
 459
 460         if (!(is_gpio_valid(tck_gpio)
 461                         && is_gpio_valid(tms_gpio)
 462                         && is_gpio_valid(tdi_gpio)
 463                         && is_gpio_valid(tdo_gpio))) {
 464                 if (!is_gpio_valid(tck_gpio))
 465                         LOG_ERROR("gpio num for tck is invalid");
 466                 if (!is_gpio_valid(tms_gpio))
 467                         LOG_ERROR("gpio num for tms is invalid");
 468                 if (!is_gpio_valid(tdo_gpio))
 469                         LOG_ERROR("gpio num for tdo is invalid");
 470                 if (!is_gpio_valid(tdi_gpio))
 471                         LOG_ERROR("gpio num for tdi is invalid");
 472
 473                 LOG_ERROR("Require tck, tms, tdi and tdo gpios to all be specified");
 474                 return ERROR_JTAG_INIT_FAILED;
 475         }
 476
 477         if (!is_gpio_valid(trst_gpio) && !is_gpio_valid(srst_gpio)) {
 478                 LOG_ERROR("Require at least one of trst or srst gpios to be specified");
 479                 return ERROR_JTAG_INIT_FAILED;
 480         }
 481
 482         /*
 483          * Configure TDO as an input, and TDI, TCK, TMS, TRST, SRST
 484          * as outputs.  Drive TDI and TCK low, and TMS/TRST/SRST high.
 485          */
 486         tck_fd = setup_sysfs_gpio(tck_gpio, 1, 0);
 487         if (tck_fd < 0)
 488                 goto out_error;
 489
 490         tms_fd = setup_sysfs_gpio(tms_gpio, 1, 1);
 491         if (tms_fd < 0)
 492                 goto out_error;
 493
 494         tdi_fd = setup_sysfs_gpio(tdi_gpio, 1, 0);
 495         if (tdi_fd < 0)
 496                 goto out_error;
 497
 498         tdo_fd = setup_sysfs_gpio(tdo_gpio, 0, 0);
 499         if (tdo_fd < 0)
 500                 goto out_error;
 501
 502         /* assume active low*/
 503         trst_fd = setup_sysfs_gpio(trst_gpio, 1, 1);
 504         if (trst_gpio > 0 && trst_fd < 0)
 505                 goto out_error;
 506
 507         /* assume active low*/
 508         srst_fd = setup_sysfs_gpio(srst_gpio, 1, 1);
 509         if (srst_gpio > 0 && srst_fd < 0)
 510                 goto out_error;
 511
 512         return ERROR_OK;
 513
 514 out_error:
 515         cleanup_all_fds();
 516         return ERROR_JTAG_INIT_FAILED;
 517 }
 518
 519 static int sysfsgpio_quit(void)
 520 {
 521         cleanup_all_fds();
 522         return ERROR_OK;
 523 }
 524