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
 203         if (!first_time) {
 204                 last_tck = !tck;
 205                 last_tms = !tms;
 206                 last_tdi = !tdi;
 207                 first_time = 1;
 208         }
 209
 210         if (tdi != last_tdi)
 211                 write(tdi_fd, tdi ? &one : &zero, 1);
 212         if (tms != last_tms)
 213                 write(tms_fd, tms ? &one : &zero, 1);
 214         /* write clk last */
 215         if (tck != last_tck)
 216                 write(tck_fd, tck ? &one : &zero, 1);
 217
 218         last_tdi = tdi;
 219         last_tms = tms;
 220         last_tck = tck;
 221 }
 222
 223 /*
 224  * Bitbang interface to manipulate reset lines SRST and TRST
 225  *
 226  * (1) assert or (0) deassert reset lines
 227  */
 228 static void sysfsgpio_reset(int trst, int srst)
 229 {
 230         const char one[] = "1";
 231         const char zero[] = "0";
 232
 233         /* assume active low */
 234         if (srst_fd >= 0)
 235                 write(srst_fd, srst ? &zero : &one, 1);
 236
 237         /* assume active low */
 238         if (trst_fd >= 0)
 239                 write(trst_fd, trst ? &zero : &one, 1);
 240 }
 241
 242 /* No speed control is implemented yet */
 243 static int sysfsgpio_speed(int speed)
 244 {
 245         return ERROR_OK;
 246 }
 247
 248 static int sysfsgpio_khz(int khz, int *jtag_speed)
 249 {
 250         /* no adaptive clocking */
 251         if (khz == 0)
 252                 return ERROR_FAIL;
 253
 254         *jtag_speed = 0;
 255         return ERROR_OK;
 256 }
 257
 258 static int sysfsgpio_speed_div(int speed, int *khz)
 259 {
 260         *khz = 1;
 261         return ERROR_OK;
 262 }
 263
 264 /* gpio numbers for each gpio. Negative values are invalid */
 265 static int tck_gpio = -1;
 266 static int tms_gpio = -1;
 267 static int tdi_gpio = -1;
 268 static int tdo_gpio = -1;
 269 static int trst_gpio = -1;
 270 static int srst_gpio = -1;
 271
 272 COMMAND_HANDLER(sysfsgpio_handle_jtag_gpionums)
 273 {
 274         if (CMD_ARGC == 4) {
 275                 COMMAND_PARSE_NUMBER(int, CMD_ARGV[0], tck_gpio);
 276                 COMMAND_PARSE_NUMBER(int, CMD_ARGV[1], tms_gpio);
 277                 COMMAND_PARSE_NUMBER(int, CMD_ARGV[2], tdi_gpio);
 278                 COMMAND_PARSE_NUMBER(int, CMD_ARGV[3], tdo_gpio);
 279         } else if (CMD_ARGC != 0) {
 280                 return ERROR_COMMAND_SYNTAX_ERROR;
 281         }
 282
 283         command_print(CMD_CTX,
 284                         "SysfsGPIO nums: tck = %d, tms = %d, tdi = %d, tdi = %d",
 285                         tck_gpio, tms_gpio, tdi_gpio, tdo_gpio);
 286
 287         return ERROR_OK;
 288 }
 289
 290 COMMAND_HANDLER(sysfsgpio_handle_jtag_gpionum_tck)
 291 {
 292         if (CMD_ARGC == 1)
 293                 COMMAND_PARSE_NUMBER(int, CMD_ARGV[0], tck_gpio);
 294
 295         command_print(CMD_CTX, "SysfsGPIO num: tck = %d", tck_gpio);
 296         return ERROR_OK;
 297 }
 298
 299 COMMAND_HANDLER(sysfsgpio_handle_jtag_gpionum_tms)
 300 {
 301         if (CMD_ARGC == 1)
 302                 COMMAND_PARSE_NUMBER(int, CMD_ARGV[0], tms_gpio);
 303
 304         command_print(CMD_CTX, "SysfsGPIO num: tms = %d", tms_gpio);
 305         return ERROR_OK;
 306 }
 307
 308 COMMAND_HANDLER(sysfsgpio_handle_jtag_gpionum_tdo)
 309 {
 310         if (CMD_ARGC == 1)
 311                 COMMAND_PARSE_NUMBER(int, CMD_ARGV[0], tdo_gpio);
 312
 313         command_print(CMD_CTX, "SysfsGPIO num: tdo = %d", tdo_gpio);
 314         return ERROR_OK;
 315 }
 316
 317 COMMAND_HANDLER(sysfsgpio_handle_jtag_gpionum_tdi)
 318 {
 319         if (CMD_ARGC == 1)
 320                 COMMAND_PARSE_NUMBER(int, CMD_ARGV[0], tdi_gpio);
 321
 322         command_print(CMD_CTX, "SysfsGPIO num: tdi = %d", tdi_gpio);
 323         return ERROR_OK;
 324 }
 325
 326 COMMAND_HANDLER(sysfsgpio_handle_jtag_gpionum_srst)
 327 {
 328         if (CMD_ARGC == 1)
 329                 COMMAND_PARSE_NUMBER(int, CMD_ARGV[0], srst_gpio);
 330
 331         command_print(CMD_CTX, "SysfsGPIO num: srst = %d", srst_gpio);
 332         return ERROR_OK;
 333 }
 334
 335 COMMAND_HANDLER(sysfsgpio_handle_jtag_gpionum_trst)
 336 {
 337         if (CMD_ARGC == 1)
 338                 COMMAND_PARSE_NUMBER(int, CMD_ARGV[0], trst_gpio);
 339
 340         command_print(CMD_CTX, "SysfsGPIO num: trst = %d", trst_gpio);
 341         return ERROR_OK;
 342 }
 343
 344 static const struct command_registration sysfsgpio_command_handlers[] = {
 345         {
 346                 .name = "sysfsgpio_jtag_nums",
 347                 .handler = &sysfsgpio_handle_jtag_gpionums,
 348                 .mode = COMMAND_CONFIG,
 349                 .help = "gpio numbers for tck, tms, tdi, tdo. (in that order)",
 350                 .usage = "(tck tms tdi tdo)* ",
 351         },
 352         {
 353                 .name = "sysfsgpio_tck_num",
 354                 .handler = &sysfsgpio_handle_jtag_gpionum_tck,
 355                 .mode = COMMAND_CONFIG,
 356                 .help = "gpio number for tck.",
 357         },
 358         {
 359                 .name = "sysfsgpio_tms_num",
 360                 .handler = &sysfsgpio_handle_jtag_gpionum_tms,
 361                 .mode = COMMAND_CONFIG,
 362                 .help = "gpio number for tms.",
 363         },
 364         {
 365                 .name = "sysfsgpio_tdo_num",
 366                 .handler = &sysfsgpio_handle_jtag_gpionum_tdo,
 367                 .mode = COMMAND_CONFIG,
 368                 .help = "gpio number for tdo.",
 369         },
 370         {
 371                 .name = "sysfsgpio_tdi_num",
 372                 .handler = &sysfsgpio_handle_jtag_gpionum_tdi,
 373                 .mode = COMMAND_CONFIG,
 374                 .help = "gpio number for tdi.",
 375         },
 376         {
 377                 .name = "sysfsgpio_srst_num",
 378                 .handler = &sysfsgpio_handle_jtag_gpionum_srst,
 379                 .mode = COMMAND_CONFIG,
 380                 .help = "gpio number for srst.",
 381         },
 382         {
 383                 .name = "sysfsgpio_trst_num",
 384                 .handler = &sysfsgpio_handle_jtag_gpionum_trst,
 385                 .mode = COMMAND_CONFIG,
 386                 .help = "gpio number for trst.",
 387         },
 388         COMMAND_REGISTRATION_DONE
 389 };
 390
 391 static int sysfsgpio_init(void);
 392 static int sysfsgpio_quit(void);
 393
 394 struct jtag_interface sysfsgpio_interface = {
 395         .name = "sysfsgpio",
 396         .supported = DEBUG_CAP_TMS_SEQ,
 397         .execute_queue = bitbang_execute_queue,
 398         .transports = jtag_only,
 399         .speed = sysfsgpio_speed,
 400         .khz = sysfsgpio_khz,
 401         .speed_div = sysfsgpio_speed_div,
 402         .commands = sysfsgpio_command_handlers,
 403         .init = sysfsgpio_init,
 404         .quit = sysfsgpio_quit,
 405 };
 406
 407 static struct bitbang_interface sysfsgpio_bitbang = {
 408         .read = sysfsgpio_read,
 409         .write = sysfsgpio_write,
 410         .reset = sysfsgpio_reset,
 411         .blink = 0
 412 };
 413
 414 /* helper func to close and cleanup files only if they were valid/ used */
 415 static void cleanup_fd(int fd, int gpio)
 416 {
 417         if (gpio >= 0) {
 418                 if (fd >= 0)
 419                         close(fd);
 420
 421                 unexport_sysfs_gpio(gpio);
 422         }
 423 }
 424
 425 static void cleanup_all_fds(void)
 426 {
 427         cleanup_fd(tck_fd, tck_gpio);
 428         cleanup_fd(tms_fd, tms_gpio);
 429         cleanup_fd(tdi_fd, tdi_gpio);
 430         cleanup_fd(tdo_fd, tdo_gpio);
 431         cleanup_fd(trst_fd, trst_gpio);
 432         cleanup_fd(srst_fd, srst_gpio);
 433 }
 434
 435 static int sysfsgpio_init(void)
 436 {
 437         bitbang_interface = &sysfsgpio_bitbang;
 438
 439         LOG_INFO("SysfsGPIO JTAG bitbang driver");
 440
 441         if (!(is_gpio_valid(tck_gpio)
 442                         && is_gpio_valid(tms_gpio)
 443                         && is_gpio_valid(tdi_gpio)
 444                         && is_gpio_valid(tdo_gpio))) {
 445                 if (!is_gpio_valid(tck_gpio))
 446                         LOG_ERROR("gpio num for tck is invalid");
 447                 if (!is_gpio_valid(tms_gpio))
 448                         LOG_ERROR("gpio num for tms is invalid");
 449                 if (!is_gpio_valid(tdo_gpio))
 450                         LOG_ERROR("gpio num for tdo is invalid");
 451                 if (!is_gpio_valid(tdi_gpio))
 452                         LOG_ERROR("gpio num for tdi is invalid");
 453
 454                 LOG_ERROR("Require tck, tms, tdi and tdo gpios to all be specified");
 455                 return ERROR_JTAG_INIT_FAILED;
 456         }
 457
 458         if (!is_gpio_valid(trst_gpio) && !is_gpio_valid(srst_gpio)) {
 459                 LOG_ERROR("Require at least one of trst or srst gpios to be specified");
 460                 return ERROR_JTAG_INIT_FAILED;
 461         }
 462
 463         /*
 464          * Configure TDO as an input, and TDI, TCK, TMS, TRST, SRST
 465          * as outputs.  Drive TDI and TCK low, and TMS/TRST/SRST high.
 466          */
 467         tck_fd = setup_sysfs_gpio(tck_gpio, 1, 0);
 468         if (tck_fd < 0)
 469                 goto out_error;
 470
 471         tms_fd = setup_sysfs_gpio(tms_gpio, 1, 1);
 472         if (tms_fd < 0)
 473                 goto out_error;
 474
 475         tdi_fd = setup_sysfs_gpio(tdi_gpio, 1, 0);
 476         if (tdi_fd < 0)
 477                 goto out_error;
 478
 479         tdo_fd = setup_sysfs_gpio(tdo_gpio, 0, 0);
 480         if (tdo_fd < 0)
 481                 goto out_error;
 482
 483         /* assume active low*/
 484         trst_fd = setup_sysfs_gpio(trst_gpio, 1, 1);
 485         if (trst_gpio > 0 && trst_fd < 0)
 486                 goto out_error;
 487
 488         /* assume active low*/
 489         srst_fd = setup_sysfs_gpio(srst_gpio, 1, 1);
 490         if (srst_gpio > 0 && srst_fd < 0)
 491                 goto out_error;
 492
 493         return ERROR_OK;
 494
 495 out_error:
 496         cleanup_all_fds();
 497         return ERROR_JTAG_INIT_FAILED;
 498 }
 499
 500 static int sysfsgpio_quit(void)
 501 {
 502         cleanup_all_fds();
 503         return ERROR_OK;
 504 }
 505