src/jtag/drivers/bitbang.c

   1 /***************************************************************************
   2  *   Copyright (C) 2005 by Dominic Rath                                    *
   3  *   Dominic.Rath@gmx.de                                                   *
   4  *                                                                         *
   5  *   Copyright (C) 2007,2008 Øyvind Harboe                                 *
   6  *   oyvind.harboe@zylin.com                                               *
   7  *                                                                         *
   8  *   This program is free software; you can redistribute it and/or modify  *
   9  *   it under the terms of the GNU General Public License as published by  *
  10  *   the Free Software Foundation; either version 2 of the License, or     *
  11  *   (at your option) any later version.                                   *
  12  *                                                                         *
  13  *   This program is distributed in the hope that it will be useful,       *
  14  *   but WITHOUT ANY WARRANTY; without even the implied warranty of        *
  15  *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         *
  16  *   GNU General Public License for more details.                          *
  17  *                                                                         *
  18  *   You should have received a copy of the GNU General Public License     *
  19  *   along with this program; if not, write to the                         *
  20  *   Free Software Foundation, Inc.,                                       *
  21  *   51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.           *
  22  ***************************************************************************/
  23
  24 #ifdef HAVE_CONFIG_H
  25 #include "config.h"
  26 #endif
  27
  28 #include "bitbang.h"
  29 #include <jtag/interface.h>
  30 #include <jtag/commands.h>
  31
  32 /**
  33  * Function bitbang_stableclocks
  34  * issues a number of clock cycles while staying in a stable state.
  35  * Because the TMS value required to stay in the RESET state is a 1, whereas
  36  * the TMS value required to stay in any of the other stable states is a 0,
  37  * this function checks the current stable state to decide on the value of TMS
  38  * to use.
  39  */
  40 static void bitbang_stableclocks(int num_cycles);
  41
  42 struct bitbang_interface *bitbang_interface;
  43
  44 /* DANGER!!!! clock absolutely *MUST* be 0 in idle or reset won't work!
  45  *
  46  * Set this to 1 and str912 reset halt will fail.
  47  *
  48  * If someone can submit a patch with an explanation it will be greatly
  49  * appreciated, but as far as I can tell (ØH) DCLK is generated upon
  50  * clk = 0 in TAP_IDLE. Good luck deducing that from the ARM documentation!
  51  * The ARM documentation uses the term "DCLK is asserted while in the TAP_IDLE
  52  * state". With hardware there is no such thing as *while* in a state. There
  53  * are only edges. So clk => 0 is in fact a very subtle state transition that
  54  * happens *while* in the TAP_IDLE state. "#&¤"#¤&"#&"#&
  55  *
  56  * For "reset halt" the last thing that happens before srst is asserted
  57  * is that the breakpoint is set up. If DCLK is not wiggled one last
  58  * time before the reset, then the breakpoint is not set up and
  59  * "reset halt" will fail to halt.
  60  *
  61  */
  62 #define CLOCK_IDLE() 0
  63
  64 /* The bitbang driver leaves the TCK 0 when in idle */
  65 static void bitbang_end_state(tap_state_t state)
  66 {
  67         if (tap_is_state_stable(state))
  68                 tap_set_end_state(state);
  69         else {
  70                 LOG_ERROR("BUG: %i is not a valid end state", state);
  71                 exit(-1);
  72         }
  73 }
  74
  75 static void bitbang_state_move(int skip)
  76 {
  77         int i = 0, tms = 0;
  78         uint8_t tms_scan = tap_get_tms_path(tap_get_state(), tap_get_end_state());
  79         int tms_count = tap_get_tms_path_len(tap_get_state(), tap_get_end_state());
  80
  81         for (i = skip; i < tms_count; i++) {
  82                 tms = (tms_scan >> i) & 1;
  83                 bitbang_interface->write(0, tms, 0);
  84                 bitbang_interface->write(1, tms, 0);
  85         }
  86         bitbang_interface->write(CLOCK_IDLE(), tms, 0);
  87
  88         tap_set_state(tap_get_end_state());
  89 }
  90
  91 /**
  92  * Clock a bunch of TMS (or SWDIO) transitions, to change the JTAG
  93  * (or SWD) state machine.
  94  */
  95 static int bitbang_execute_tms(struct jtag_command *cmd)
  96 {
  97         unsigned num_bits = cmd->cmd.tms->num_bits;
  98         const uint8_t *bits = cmd->cmd.tms->bits;
  99
 100         DEBUG_JTAG_IO("TMS: %d bits", num_bits);
 101
 102         int tms = 0;
 103         for (unsigned i = 0; i < num_bits; i++) {
 104                 tms = ((bits[i/8] >> (i % 8)) & 1);
 105                 bitbang_interface->write(0, tms, 0);
 106                 bitbang_interface->write(1, tms, 0);
 107         }
 108         bitbang_interface->write(CLOCK_IDLE(), tms, 0);
 109
 110         return ERROR_OK;
 111 }
 112
 113 static void bitbang_path_move(struct pathmove_command *cmd)
 114 {
 115         int num_states = cmd->num_states;
 116         int state_count;
 117         int tms = 0;
 118
 119         state_count = 0;
 120         while (num_states) {
 121                 if (tap_state_transition(tap_get_state(), false) == cmd->path[state_count])
 122                         tms = 0;
 123                 else if (tap_state_transition(tap_get_state(), true) == cmd->path[state_count])
 124                         tms = 1;
 125                 else {
 126                         LOG_ERROR("BUG: %s -> %s isn't a valid TAP transition",
 127                                 tap_state_name(tap_get_state()),
 128                                 tap_state_name(cmd->path[state_count]));
 129                         exit(-1);
 130                 }
 131
 132                 bitbang_interface->write(0, tms, 0);
 133                 bitbang_interface->write(1, tms, 0);
 134
 135                 tap_set_state(cmd->path[state_count]);
 136                 state_count++;
 137                 num_states--;
 138         }
 139
 140         bitbang_interface->write(CLOCK_IDLE(), tms, 0);
 141
 142         tap_set_end_state(tap_get_state());
 143 }
 144
 145 static void bitbang_runtest(int num_cycles)
 146 {
 147         int i;
 148
 149         tap_state_t saved_end_state = tap_get_end_state();
 150
 151         /* only do a state_move when we're not already in IDLE */
 152         if (tap_get_state() != TAP_IDLE) {
 153                 bitbang_end_state(TAP_IDLE);
 154                 bitbang_state_move(0);
 155         }
 156
 157         /* execute num_cycles */
 158         for (i = 0; i < num_cycles; i++) {
 159                 bitbang_interface->write(0, 0, 0);
 160                 bitbang_interface->write(1, 0, 0);
 161         }
 162         bitbang_interface->write(CLOCK_IDLE(), 0, 0);
 163
 164         /* finish in end_state */
 165         bitbang_end_state(saved_end_state);
 166         if (tap_get_state() != tap_get_end_state())
 167                 bitbang_state_move(0);
 168 }
 169
 170 static void bitbang_stableclocks(int num_cycles)
 171 {
 172         int tms = (tap_get_state() == TAP_RESET ? 1 : 0);
 173         int i;
 174
 175         /* send num_cycles clocks onto the cable */
 176         for (i = 0; i < num_cycles; i++) {
 177                 bitbang_interface->write(1, tms, 0);
 178                 bitbang_interface->write(0, tms, 0);
 179         }
 180 }
 181
 182 static void bitbang_scan(bool ir_scan, enum scan_type type, uint8_t *buffer, int scan_size)
 183 {
 184         tap_state_t saved_end_state = tap_get_end_state();
 185         int bit_cnt;
 186
 187         if (!((!ir_scan &&
 188                         (tap_get_state() == TAP_DRSHIFT)) ||
 189                         (ir_scan && (tap_get_state() == TAP_IRSHIFT)))) {
 190                 if (ir_scan)
 191                         bitbang_end_state(TAP_IRSHIFT);
 192                 else
 193                         bitbang_end_state(TAP_DRSHIFT);
 194
 195                 bitbang_state_move(0);
 196                 bitbang_end_state(saved_end_state);
 197         }
 198
 199         for (bit_cnt = 0; bit_cnt < scan_size; bit_cnt++) {
 200                 int val = 0;
 201                 int tms = (bit_cnt == scan_size-1) ? 1 : 0;
 202                 int tdi;
 203                 int bytec = bit_cnt/8;
 204                 int bcval = 1 << (bit_cnt % 8);
 205
 206                 /* if we're just reading the scan, but don't care about the output
 207                  * default to outputting 'low', this also makes valgrind traces more readable,
 208                  * as it removes the dependency on an uninitialised value
 209                  */
 210                 tdi = 0;
 211                 if ((type != SCAN_IN) && (buffer[bytec] & bcval))
 212                         tdi = 1;
 213
 214                 bitbang_interface->write(0, tms, tdi);
 215
 216                 if (type != SCAN_OUT)
 217                         val = bitbang_interface->read();
 218
 219                 bitbang_interface->write(1, tms, tdi);
 220
 221                 if (type != SCAN_OUT) {
 222                         if (val)
 223                                 buffer[bytec] |= bcval;
 224                         else
 225                                 buffer[bytec] &= ~bcval;
 226                 }
 227         }
 228
 229         if (tap_get_state() != tap_get_end_state()) {
 230                 /* we *KNOW* the above loop transitioned out of
 231                  * the shift state, so we skip the first state
 232                  * and move directly to the end state.
 233                  */
 234                 bitbang_state_move(1);
 235         }
 236 }
 237
 238 int bitbang_execute_queue(void)
 239 {
 240         struct jtag_command *cmd = jtag_command_queue;  /* currently processed command */
 241         int scan_size;
 242         enum scan_type type;
 243         uint8_t *buffer;
 244         int retval;
 245
 246         if (!bitbang_interface) {
 247                 LOG_ERROR("BUG: Bitbang interface called, but not yet initialized");
 248                 exit(-1);
 249         }
 250
 251         /* return ERROR_OK, unless a jtag_read_buffer returns a failed check
 252          * that wasn't handled by a caller-provided error handler
 253          */
 254         retval = ERROR_OK;
 255
 256         if (bitbang_interface->blink)
 257                 bitbang_interface->blink(1);
 258
 259         while (cmd) {
 260                 switch (cmd->type) {
 261                         case JTAG_RESET:
 262 #ifdef _DEBUG_JTAG_IO_
 263                                 LOG_DEBUG("reset trst: %i srst %i",
 264                                 cmd->cmd.reset->trst,
 265                                 cmd->cmd.reset->srst);
 266 #endif
 267                                 if ((cmd->cmd.reset->trst == 1) ||
 268                                                 (cmd->cmd.reset->srst && (jtag_get_reset_config() & RESET_SRST_PULLS_TRST)))
 269                                         tap_set_state(TAP_RESET);
 270                                 bitbang_interface->reset(cmd->cmd.reset->trst, cmd->cmd.reset->srst);
 271                                 break;
 272                         case JTAG_RUNTEST:
 273 #ifdef _DEBUG_JTAG_IO_
 274                                 LOG_DEBUG("runtest %i cycles, end in %s",
 275                                                 cmd->cmd.runtest->num_cycles,
 276                                                 tap_state_name(cmd->cmd.runtest->end_state));
 277 #endif
 278                                 bitbang_end_state(cmd->cmd.runtest->end_state);
 279                                 bitbang_runtest(cmd->cmd.runtest->num_cycles);
 280                                 break;
 281
 282                         case JTAG_STABLECLOCKS:
 283                                 /* this is only allowed while in a stable state.  A check for a stable
 284                                  * state was done in jtag_add_clocks()
 285                                  */
 286                                 bitbang_stableclocks(cmd->cmd.stableclocks->num_cycles);
 287                                 break;
 288
 289                         case JTAG_TLR_RESET:
 290 #ifdef _DEBUG_JTAG_IO_
 291                                 LOG_DEBUG("statemove end in %s",
 292                                                 tap_state_name(cmd->cmd.statemove->end_state));
 293 #endif
 294                                 bitbang_end_state(cmd->cmd.statemove->end_state);
 295                                 bitbang_state_move(0);
 296                                 break;
 297                         case JTAG_PATHMOVE:
 298 #ifdef _DEBUG_JTAG_IO_
 299                                 LOG_DEBUG("pathmove: %i states, end in %s",
 300                                                 cmd->cmd.pathmove->num_states,
 301                                                 tap_state_name(cmd->cmd.pathmove->path[cmd->cmd.pathmove->num_states - 1]));
 302 #endif
 303                                 bitbang_path_move(cmd->cmd.pathmove);
 304                                 break;
 305                         case JTAG_SCAN:
 306 #ifdef _DEBUG_JTAG_IO_
 307                                 LOG_DEBUG("%s scan end in %s",
 308                                                 (cmd->cmd.scan->ir_scan) ? "IR" : "DR",
 309                                         tap_state_name(cmd->cmd.scan->end_state));
 310 #endif
 311                                 bitbang_end_state(cmd->cmd.scan->end_state);
 312                                 scan_size = jtag_build_buffer(cmd->cmd.scan, &buffer);
 313                                 type = jtag_scan_type(cmd->cmd.scan);
 314                                 bitbang_scan(cmd->cmd.scan->ir_scan, type, buffer, scan_size);
 315                                 if (jtag_read_buffer(buffer, cmd->cmd.scan) != ERROR_OK)
 316                                         retval = ERROR_JTAG_QUEUE_FAILED;
 317                                 if (buffer)
 318                                         free(buffer);
 319                                 break;
 320                         case JTAG_SLEEP:
 321 #ifdef _DEBUG_JTAG_IO_
 322                                 LOG_DEBUG("sleep %" PRIi32, cmd->cmd.sleep->us);
 323 #endif
 324                                 jtag_sleep(cmd->cmd.sleep->us);
 325                                 break;
 326                         case JTAG_TMS:
 327                                 retval = bitbang_execute_tms(cmd);
 328                                 break;
 329                         default:
 330                                 LOG_ERROR("BUG: unknown JTAG command type encountered");
 331                                 exit(-1);
 332                 }
 333                 cmd = cmd->next;
 334         }
 335         if (bitbang_interface->blink)
 336                 bitbang_interface->blink(0);
 337
 338         return retval;
 339 }