src/jtag/drivers/bcm2835gpio.c

   1 /* SPDX-License-Identifier: GPL-2.0-or-later */
   2
   3 /***************************************************************************
   4  *   Copyright (C) 2013 by Paul Fertser, fercerpav@gmail.com               *
   5  *                                                                         *
   6  *   Copyright (C) 2012 by Creative Product Design, marc @ cpdesign.com.au *
   7  *   Based on at91rm9200.c (c) Anders Larsen                               *
   8  *   and RPi GPIO examples by Gert van Loo & Dom                           *
   9  ***************************************************************************/
  10
  11 #ifdef HAVE_CONFIG_H
  12 #include "config.h"
  13 #endif
  14
  15 #include <jtag/adapter.h>
  16 #include <jtag/interface.h>
  17 #include <transport/transport.h>
  18 #include "bitbang.h"
  19
  20 #include <sys/mman.h>
  21
  22 uint32_t bcm2835_peri_base = 0x20000000;
  23 #define BCM2835_GPIO_BASE       (bcm2835_peri_base + 0x200000) /* GPIO controller */
  24
  25 #define BCM2835_PADS_GPIO_0_27          (bcm2835_peri_base + 0x100000)
  26 #define BCM2835_PADS_GPIO_0_27_OFFSET   (0x2c / 4)
  27
  28 /* See "GPIO Function Select Registers (GPFSELn)" in "Broadcom BCM2835 ARM Peripherals" datasheet. */
  29 #define BCM2835_GPIO_MODE_INPUT 0
  30 #define BCM2835_GPIO_MODE_OUTPUT 1
  31
  32 /* GPIO setup macros */
  33 #define MODE_GPIO(g) (*(pio_base+((g)/10))>>(((g)%10)*3) & 7)
  34 #define INP_GPIO(g) do { *(pio_base+((g)/10)) &= ~(7<<(((g)%10)*3)); } while (0)
  35 #define SET_MODE_GPIO(g, m) do { /* clear the mode bits first, then set as necessary */ \
  36                 INP_GPIO(g);                                            \
  37                 *(pio_base+((g)/10)) |=  ((m)<<(((g)%10)*3)); } while (0)
  38 #define OUT_GPIO(g) SET_MODE_GPIO(g, BCM2835_GPIO_MODE_OUTPUT)
  39
  40 #define GPIO_SET (*(pio_base+7))  /* sets   bits which are 1, ignores bits which are 0 */
  41 #define GPIO_CLR (*(pio_base+10)) /* clears bits which are 1, ignores bits which are 0 */
  42 #define GPIO_LEV (*(pio_base+13)) /* current level of the pin */
  43
  44 static int dev_mem_fd;
  45 static volatile uint32_t *pio_base = MAP_FAILED;
  46 static volatile uint32_t *pads_base = MAP_FAILED;
  47
  48 /* Transition delay coefficients */
  49 static int speed_coeff = 113714;
  50 static int speed_offset = 28;
  51 static unsigned int jtag_delay;
  52
  53 static const struct adapter_gpio_config *adapter_gpio_config;
  54 static int initial_gpio_mode[ADAPTER_GPIO_IDX_NUM];
  55
  56 static bool is_gpio_config_valid(enum adapter_gpio_config_index idx)
  57 {
  58         /* Only chip 0 is supported, accept unset value (-1) too */
  59         return adapter_gpio_config[idx].chip_num >= -1
  60                 && adapter_gpio_config[idx].chip_num <= 0
  61                 && adapter_gpio_config[idx].gpio_num >= 0
  62                 && adapter_gpio_config[idx].gpio_num <= 31;
  63 }
  64
  65 static void set_gpio_value(const struct adapter_gpio_config *gpio_config, int value)
  66 {
  67         value = value ^ (gpio_config->active_low ? 1 : 0);
  68         switch (gpio_config->drive) {
  69         case ADAPTER_GPIO_DRIVE_MODE_PUSH_PULL:
  70                 if (value)
  71                         GPIO_SET = 1 << gpio_config->gpio_num;
  72                 else
  73                         GPIO_CLR = 1 << gpio_config->gpio_num;
  74                 /* For performance reasons assume the GPIO is already set as an output
  75                  * and therefore the call can be omitted here.
  76                  */
  77                 break;
  78         case ADAPTER_GPIO_DRIVE_MODE_OPEN_DRAIN:
  79                 if (value) {
  80                         INP_GPIO(gpio_config->gpio_num);
  81                 } else {
  82                         GPIO_CLR = 1 << gpio_config->gpio_num;
  83                         OUT_GPIO(gpio_config->gpio_num);
  84                 }
  85                 break;
  86         case ADAPTER_GPIO_DRIVE_MODE_OPEN_SOURCE:
  87                 if (value) {
  88                         GPIO_SET = 1 << gpio_config->gpio_num;
  89                         OUT_GPIO(gpio_config->gpio_num);
  90                 } else {
  91                         INP_GPIO(gpio_config->gpio_num);
  92                 }
  93                 break;
  94         }
  95 }
  96
  97 static void restore_gpio(enum adapter_gpio_config_index idx)
  98 {
  99         if (is_gpio_config_valid(idx))
 100                 SET_MODE_GPIO(adapter_gpio_config[idx].gpio_num, initial_gpio_mode[idx]);
 101 }
 102
 103 static void initialize_gpio(enum adapter_gpio_config_index idx)
 104 {
 105         if (!is_gpio_config_valid(idx))
 106                 return;
 107
 108         initial_gpio_mode[idx] = MODE_GPIO(adapter_gpio_config[idx].gpio_num);
 109         LOG_DEBUG("saved GPIO mode for %s (GPIO %d %d): %d",
 110                         adapter_gpio_get_name(idx), adapter_gpio_config[idx].chip_num, adapter_gpio_config[idx].gpio_num,
 111                         initial_gpio_mode[idx]);
 112
 113         if (adapter_gpio_config[idx].pull != ADAPTER_GPIO_PULL_NONE) {
 114                 LOG_WARNING("BCM2835 GPIO does not support pull-up or pull-down settings (signal %s)",
 115                         adapter_gpio_get_name(idx));
 116         }
 117
 118         switch (adapter_gpio_config[idx].init_state) {
 119         case ADAPTER_GPIO_INIT_STATE_INACTIVE:
 120                 set_gpio_value(&adapter_gpio_config[idx], 0);
 121                 break;
 122         case ADAPTER_GPIO_INIT_STATE_ACTIVE:
 123                 set_gpio_value(&adapter_gpio_config[idx], 1);
 124                 break;
 125         case ADAPTER_GPIO_INIT_STATE_INPUT:
 126                 INP_GPIO(adapter_gpio_config[idx].gpio_num);
 127                 break;
 128         }
 129
 130         /* Direction for non push-pull is already set by set_gpio_value() */
 131         if (adapter_gpio_config[idx].drive == ADAPTER_GPIO_DRIVE_MODE_PUSH_PULL)
 132                 OUT_GPIO(adapter_gpio_config[idx].gpio_num);
 133 }
 134
 135 static bb_value_t bcm2835gpio_read(void)
 136 {
 137         unsigned int shift = adapter_gpio_config[ADAPTER_GPIO_IDX_TDO].gpio_num;
 138         uint32_t value = (GPIO_LEV >> shift) & 1;
 139         return value ^ (adapter_gpio_config[ADAPTER_GPIO_IDX_TDO].active_low ? BB_HIGH : BB_LOW);
 140
 141 }
 142
 143 static int bcm2835gpio_write(int tck, int tms, int tdi)
 144 {
 145         uint32_t set = tck << adapter_gpio_config[ADAPTER_GPIO_IDX_TCK].gpio_num |
 146                         tms << adapter_gpio_config[ADAPTER_GPIO_IDX_TMS].gpio_num |
 147                         tdi << adapter_gpio_config[ADAPTER_GPIO_IDX_TDI].gpio_num;
 148         uint32_t clear = !tck << adapter_gpio_config[ADAPTER_GPIO_IDX_TCK].gpio_num |
 149                         !tms << adapter_gpio_config[ADAPTER_GPIO_IDX_TMS].gpio_num |
 150                         !tdi << adapter_gpio_config[ADAPTER_GPIO_IDX_TDI].gpio_num;
 151
 152         GPIO_SET = set;
 153         GPIO_CLR = clear;
 154
 155         for (unsigned int i = 0; i < jtag_delay; i++)
 156                 asm volatile ("");
 157
 158         return ERROR_OK;
 159 }
 160
 161 /* Requires push-pull drive mode for swclk and swdio */
 162 static int bcm2835gpio_swd_write_fast(int swclk, int swdio)
 163 {
 164         swclk = swclk ^ (adapter_gpio_config[ADAPTER_GPIO_IDX_SWCLK].active_low ? 1 : 0);
 165         swdio = swdio ^ (adapter_gpio_config[ADAPTER_GPIO_IDX_SWDIO].active_low ? 1 : 0);
 166
 167         uint32_t set = swclk << adapter_gpio_config[ADAPTER_GPIO_IDX_SWCLK].gpio_num |
 168                                         swdio << adapter_gpio_config[ADAPTER_GPIO_IDX_SWDIO].gpio_num;
 169         uint32_t clear = !swclk << adapter_gpio_config[ADAPTER_GPIO_IDX_SWCLK].gpio_num |
 170                                         !swdio << adapter_gpio_config[ADAPTER_GPIO_IDX_SWDIO].gpio_num;
 171
 172         GPIO_SET = set;
 173         GPIO_CLR = clear;
 174
 175         for (unsigned int i = 0; i < jtag_delay; i++)
 176                 asm volatile ("");
 177
 178         return ERROR_OK;
 179 }
 180
 181 /* Generic mode that works for open-drain/open-source drive modes, but slower */
 182 static int bcm2835gpio_swd_write_generic(int swclk, int swdio)
 183 {
 184         set_gpio_value(&adapter_gpio_config[ADAPTER_GPIO_IDX_SWDIO], swdio);
 185         set_gpio_value(&adapter_gpio_config[ADAPTER_GPIO_IDX_SWCLK], swclk); /* Write clock last */
 186
 187         for (unsigned int i = 0; i < jtag_delay; ++i)
 188                 asm volatile ("");
 189
 190         return ERROR_OK;
 191 }
 192
 193 /* (1) assert or (0) deassert reset lines */
 194 static int bcm2835gpio_reset(int trst, int srst)
 195 {
 196         /* As the "adapter reset_config" command keeps the srst and trst gpio drive
 197          * mode settings in sync we can use our standard set_gpio_value() function
 198          * that honours drive mode and active low.
 199          */
 200         if (is_gpio_config_valid(ADAPTER_GPIO_IDX_SRST))
 201                 set_gpio_value(&adapter_gpio_config[ADAPTER_GPIO_IDX_SRST], srst);
 202
 203         if (is_gpio_config_valid(ADAPTER_GPIO_IDX_TRST))
 204                 set_gpio_value(&adapter_gpio_config[ADAPTER_GPIO_IDX_TRST], trst);
 205
 206         LOG_DEBUG("BCM2835 GPIO: bcm2835gpio_reset(%d, %d), trst_gpio: %d %d, srst_gpio: %d %d",
 207                 trst, srst,
 208                 adapter_gpio_config[ADAPTER_GPIO_IDX_TRST].chip_num, adapter_gpio_config[ADAPTER_GPIO_IDX_TRST].gpio_num,
 209                 adapter_gpio_config[ADAPTER_GPIO_IDX_SRST].chip_num, adapter_gpio_config[ADAPTER_GPIO_IDX_SRST].gpio_num);
 210         return ERROR_OK;
 211 }
 212
 213 static void bcm2835_swdio_drive(bool is_output)
 214 {
 215         if (is_output) {
 216                 if (is_gpio_config_valid(ADAPTER_GPIO_IDX_SWDIO_DIR))
 217                         set_gpio_value(&adapter_gpio_config[ADAPTER_GPIO_IDX_SWDIO_DIR], 1);
 218                 OUT_GPIO(adapter_gpio_config[ADAPTER_GPIO_IDX_SWDIO].gpio_num);
 219         } else {
 220                 INP_GPIO(adapter_gpio_config[ADAPTER_GPIO_IDX_SWDIO].gpio_num);
 221                 if (is_gpio_config_valid(ADAPTER_GPIO_IDX_SWDIO_DIR))
 222                         set_gpio_value(&adapter_gpio_config[ADAPTER_GPIO_IDX_SWDIO_DIR], 0);
 223         }
 224 }
 225
 226 static int bcm2835_swdio_read(void)
 227 {
 228         unsigned int shift = adapter_gpio_config[ADAPTER_GPIO_IDX_SWDIO].gpio_num;
 229         uint32_t value = (GPIO_LEV >> shift) & 1;
 230         return value ^ (adapter_gpio_config[ADAPTER_GPIO_IDX_SWDIO].active_low ? 1 : 0);
 231 }
 232
 233 static int bcm2835gpio_khz(int khz, int *jtag_speed)
 234 {
 235         if (!khz) {
 236                 LOG_DEBUG("BCM2835 GPIO: RCLK not supported");
 237                 return ERROR_FAIL;
 238         }
 239         *jtag_speed = speed_coeff/khz - speed_offset;
 240         if (*jtag_speed < 0)
 241                 *jtag_speed = 0;
 242         return ERROR_OK;
 243 }
 244
 245 static int bcm2835gpio_speed_div(int speed, int *khz)
 246 {
 247         *khz = speed_coeff/(speed + speed_offset);
 248         return ERROR_OK;
 249 }
 250
 251 static int bcm2835gpio_speed(int speed)
 252 {
 253         jtag_delay = speed;
 254         return ERROR_OK;
 255 }
 256
 257 COMMAND_HANDLER(bcm2835gpio_handle_speed_coeffs)
 258 {
 259         if (CMD_ARGC == 2) {
 260                 COMMAND_PARSE_NUMBER(int, CMD_ARGV[0], speed_coeff);
 261                 COMMAND_PARSE_NUMBER(int, CMD_ARGV[1], speed_offset);
 262         }
 263
 264         command_print(CMD, "BCM2835 GPIO: speed_coeffs = %d, speed_offset = %d",
 265                                   speed_coeff, speed_offset);
 266         return ERROR_OK;
 267 }
 268
 269 COMMAND_HANDLER(bcm2835gpio_handle_peripheral_base)
 270 {
 271         if (CMD_ARGC == 1)
 272                 COMMAND_PARSE_NUMBER(u32, CMD_ARGV[0], bcm2835_peri_base);
 273
 274         command_print(CMD, "BCM2835 GPIO: peripheral_base = 0x%08x",
 275                                   bcm2835_peri_base);
 276         return ERROR_OK;
 277 }
 278
 279 static const struct command_registration bcm2835gpio_subcommand_handlers[] = {
 280         {
 281                 .name = "speed_coeffs",
 282                 .handler = &bcm2835gpio_handle_speed_coeffs,
 283                 .mode = COMMAND_CONFIG,
 284                 .help = "SPEED_COEFF and SPEED_OFFSET for delay calculations.",
 285                 .usage = "[SPEED_COEFF SPEED_OFFSET]",
 286         },
 287         {
 288                 .name = "peripheral_base",
 289                 .handler = &bcm2835gpio_handle_peripheral_base,
 290                 .mode = COMMAND_CONFIG,
 291                 .help = "peripheral base to access GPIOs (RPi1 0x20000000, RPi2 0x3F000000).",
 292                 .usage = "[base]",
 293         },
 294
 295         COMMAND_REGISTRATION_DONE
 296 };
 297
 298 static const struct command_registration bcm2835gpio_command_handlers[] = {
 299         {
 300                 .name = "bcm2835gpio",
 301                 .mode = COMMAND_ANY,
 302                 .help = "perform bcm2835gpio management",
 303                 .chain = bcm2835gpio_subcommand_handlers,
 304                 .usage = "",
 305         },
 306         COMMAND_REGISTRATION_DONE
 307 };
 308
 309 static bool bcm2835gpio_jtag_mode_possible(void)
 310 {
 311         if (!is_gpio_config_valid(ADAPTER_GPIO_IDX_TCK))
 312                 return false;
 313         if (!is_gpio_config_valid(ADAPTER_GPIO_IDX_TMS))
 314                 return false;
 315         if (!is_gpio_config_valid(ADAPTER_GPIO_IDX_TDI))
 316                 return false;
 317         if (!is_gpio_config_valid(ADAPTER_GPIO_IDX_TDO))
 318                 return false;
 319         return true;
 320 }
 321
 322 static bool bcm2835gpio_swd_mode_possible(void)
 323 {
 324         if (!is_gpio_config_valid(ADAPTER_GPIO_IDX_SWCLK))
 325                 return false;
 326         if (!is_gpio_config_valid(ADAPTER_GPIO_IDX_SWDIO))
 327                 return false;
 328         return true;
 329 }
 330
 331 static void bcm2835gpio_munmap(void)
 332 {
 333         if (pio_base != MAP_FAILED) {
 334                 munmap((void *)pio_base, sysconf(_SC_PAGE_SIZE));
 335                 pio_base = MAP_FAILED;
 336         }
 337
 338         if (pads_base != MAP_FAILED) {
 339                 munmap((void *)pads_base, sysconf(_SC_PAGE_SIZE));
 340                 pads_base = MAP_FAILED;
 341         }
 342 }
 343
 344 static struct bitbang_interface bcm2835gpio_bitbang = {
 345         .read = bcm2835gpio_read,
 346         .write = bcm2835gpio_write,
 347         .swdio_read = bcm2835_swdio_read,
 348         .swdio_drive = bcm2835_swdio_drive,
 349         .swd_write = bcm2835gpio_swd_write_generic,
 350         .blink = NULL
 351 };
 352
 353 static int bcm2835gpio_init(void)
 354 {
 355         LOG_INFO("BCM2835 GPIO JTAG/SWD bitbang driver");
 356
 357         bitbang_interface = &bcm2835gpio_bitbang;
 358         adapter_gpio_config = adapter_gpio_get_config();
 359
 360         if (transport_is_jtag() && !bcm2835gpio_jtag_mode_possible()) {
 361                 LOG_ERROR("Require tck, tms, tdi and tdo gpios for JTAG mode");
 362                 return ERROR_JTAG_INIT_FAILED;
 363         }
 364
 365         if (transport_is_swd() && !bcm2835gpio_swd_mode_possible()) {
 366                 LOG_ERROR("Require swclk and swdio gpio for SWD mode");
 367                 return ERROR_JTAG_INIT_FAILED;
 368         }
 369
 370         dev_mem_fd = open("/dev/gpiomem", O_RDWR | O_SYNC);
 371         if (dev_mem_fd < 0) {
 372                 LOG_DEBUG("Cannot open /dev/gpiomem, fallback to /dev/mem");
 373                 dev_mem_fd = open("/dev/mem", O_RDWR | O_SYNC);
 374         }
 375         if (dev_mem_fd < 0) {
 376                 LOG_ERROR("open: %s", strerror(errno));
 377                 return ERROR_JTAG_INIT_FAILED;
 378         }
 379
 380         pio_base = mmap(NULL, sysconf(_SC_PAGE_SIZE), PROT_READ | PROT_WRITE,
 381                                 MAP_SHARED, dev_mem_fd, BCM2835_GPIO_BASE);
 382
 383         if (pio_base == MAP_FAILED) {
 384                 LOG_ERROR("mmap: %s", strerror(errno));
 385                 close(dev_mem_fd);
 386                 return ERROR_JTAG_INIT_FAILED;
 387         }
 388
 389         pads_base = mmap(NULL, sysconf(_SC_PAGE_SIZE), PROT_READ | PROT_WRITE,
 390                                 MAP_SHARED, dev_mem_fd, BCM2835_PADS_GPIO_0_27);
 391
 392         if (pads_base == MAP_FAILED) {
 393                 LOG_ERROR("mmap: %s", strerror(errno));
 394                 bcm2835gpio_munmap();
 395                 close(dev_mem_fd);
 396                 return ERROR_JTAG_INIT_FAILED;
 397         }
 398
 399         close(dev_mem_fd);
 400
 401         /* set 4mA drive strength, slew rate limited, hysteresis on */
 402         pads_base[BCM2835_PADS_GPIO_0_27_OFFSET] = 0x5a000008 + 1;
 403
 404         /* Configure JTAG/SWD signals. Default directions and initial states are handled
 405          * by adapter.c and "adapter gpio" command.
 406          */
 407         if (transport_is_jtag()) {
 408                 initialize_gpio(ADAPTER_GPIO_IDX_TDO);
 409                 initialize_gpio(ADAPTER_GPIO_IDX_TDI);
 410                 initialize_gpio(ADAPTER_GPIO_IDX_TMS);
 411                 initialize_gpio(ADAPTER_GPIO_IDX_TCK);
 412                 initialize_gpio(ADAPTER_GPIO_IDX_TRST);
 413         }
 414
 415         if (transport_is_swd()) {
 416                 /* swdio and its buffer should be initialized in the order that prevents
 417                  * two outputs from being connected together. This will occur if the
 418                  * swdio GPIO of the AM335x is configured as an output while its
 419                  * external buffer is configured to send the swdio signal from the
 420                  * target to the AM335x.
 421                  */
 422                 if (adapter_gpio_config[ADAPTER_GPIO_IDX_SWDIO].init_state == ADAPTER_GPIO_INIT_STATE_INPUT) {
 423                         initialize_gpio(ADAPTER_GPIO_IDX_SWDIO);
 424                         initialize_gpio(ADAPTER_GPIO_IDX_SWDIO_DIR);
 425                 } else {
 426                         initialize_gpio(ADAPTER_GPIO_IDX_SWDIO_DIR);
 427                         initialize_gpio(ADAPTER_GPIO_IDX_SWDIO);
 428                 }
 429
 430                 initialize_gpio(ADAPTER_GPIO_IDX_SWCLK);
 431
 432                 if (adapter_gpio_config[ADAPTER_GPIO_IDX_SWCLK].drive == ADAPTER_GPIO_DRIVE_MODE_PUSH_PULL &&
 433                                 adapter_gpio_config[ADAPTER_GPIO_IDX_SWDIO].drive == ADAPTER_GPIO_DRIVE_MODE_PUSH_PULL) {
 434                         LOG_DEBUG("BCM2835 GPIO using fast mode for SWD write");
 435                         bcm2835gpio_bitbang.swd_write = bcm2835gpio_swd_write_fast;
 436                 } else {
 437                         LOG_DEBUG("BCM2835 GPIO using generic mode for SWD write");
 438                         bcm2835gpio_bitbang.swd_write = bcm2835gpio_swd_write_generic;
 439                 }
 440         }
 441
 442         initialize_gpio(ADAPTER_GPIO_IDX_SRST);
 443
 444         return ERROR_OK;
 445 }
 446
 447 static int bcm2835gpio_quit(void)
 448 {
 449         if (transport_is_jtag()) {
 450                 restore_gpio(ADAPTER_GPIO_IDX_TDO);
 451                 restore_gpio(ADAPTER_GPIO_IDX_TDI);
 452                 restore_gpio(ADAPTER_GPIO_IDX_TCK);
 453                 restore_gpio(ADAPTER_GPIO_IDX_TMS);
 454                 restore_gpio(ADAPTER_GPIO_IDX_TRST);
 455         }
 456
 457         if (transport_is_swd()) {
 458                 /* Restore swdio/swdio_dir to their initial modes, even if that means
 459                  * connecting two outputs. Begin by making swdio an input so that the
 460                  * current and final states of swdio and swdio_dir do not have to be
 461                  * considered to calculate the safe restoration order.
 462                  */
 463                 INP_GPIO(adapter_gpio_config[ADAPTER_GPIO_IDX_SWDIO].gpio_num);
 464                 restore_gpio(ADAPTER_GPIO_IDX_SWDIO_DIR);
 465                 restore_gpio(ADAPTER_GPIO_IDX_SWDIO);
 466                 restore_gpio(ADAPTER_GPIO_IDX_SWCLK);
 467         }
 468
 469         restore_gpio(ADAPTER_GPIO_IDX_SRST);
 470
 471         bcm2835gpio_munmap();
 472
 473         return ERROR_OK;
 474 }
 475
 476
 477 static const char * const bcm2835_transports[] = { "jtag", "swd", NULL };
 478
 479 static struct jtag_interface bcm2835gpio_interface = {
 480         .supported = DEBUG_CAP_TMS_SEQ,
 481         .execute_queue = bitbang_execute_queue,
 482 };
 483 struct adapter_driver bcm2835gpio_adapter_driver = {
 484         .name = "bcm2835gpio",
 485         .transports = bcm2835_transports,
 486         .commands = bcm2835gpio_command_handlers,
 487
 488         .init = bcm2835gpio_init,
 489         .quit = bcm2835gpio_quit,
 490         .reset = bcm2835gpio_reset,
 491         .speed = bcm2835gpio_speed,
 492         .khz = bcm2835gpio_khz,
 493         .speed_div = bcm2835gpio_speed_div,
 494
 495         .jtag_ops = &bcm2835gpio_interface,
 496         .swd_ops = &bitbang_swd,
 497 };