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  *   59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.             *
  22  ***************************************************************************/
  23 #ifdef HAVE_CONFIG_H
  24 #include "config.h"
  25 #endif
  26
  27 #include "bitbang.h"
  28 #include <jtag/interface.h>
  29 #include <jtag/commands.h>
  30
  31 /**
  32  * Function bitbang_stableclocks
  33  * issues a number of clock cycles while staying in a stable state.
  34  * Because the TMS value required to stay in the RESET state is a 1, whereas
  35  * the TMS value required to stay in any of the other stable states is a 0,
  36  * this function checks the current stable state to decide on the value of TMS
  37  * to use.
  38  */
  39 static void bitbang_stableclocks(int num_cycles);
  40
  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
  65 /* The bitbang driver leaves the TCK 0 when in idle */
  66 static void bitbang_end_state(tap_state_t state)
  67 {
  68         if (tap_is_state_stable(state))
  69                 tap_set_end_state(state);
  70         else
  71         {
  72                 LOG_ERROR("BUG: %i is not a valid end state", state);
  73                 exit(-1);
  74         }
  75 }
  76
  77 static void bitbang_state_move(int skip)
  78 {
  79         int i = 0, tms = 0;
  80         uint8_t tms_scan = tap_get_tms_path(tap_get_state(), tap_get_end_state());
  81         int tms_count = tap_get_tms_path_len(tap_get_state(), tap_get_end_state());
  82
  83         for (i = skip; i < tms_count; i++)
  84         {
  85                 tms = (tms_scan >> i) & 1;
  86                 bitbang_interface->write(0, tms, 0);
  87                 bitbang_interface->write(1, tms, 0);
  88         }
  89         bitbang_interface->write(CLOCK_IDLE(), tms, 0);
  90
  91         tap_set_state(tap_get_end_state());
  92 }
  93
  94
  95 /**
  96  * Clock a bunch of TMS (or SWDIO) transitions, to change the JTAG
  97  * (or SWD) state machine.
  98  */
  99 static int bitbang_execute_tms(struct jtag_command *cmd)
 100 {
 101         unsigned        num_bits = cmd->cmd.tms->num_bits;
 102         const uint8_t   *bits = cmd->cmd.tms->bits;
 103
 104         DEBUG_JTAG_IO("TMS: %d bits", num_bits);
 105
 106         int tms = 0;
 107         for (unsigned i = 0; i < num_bits; i++)
 108         {
 109                 tms = ((bits[i/8] >> (i % 8)) & 1);
 110                 bitbang_interface->write(0, tms, 0);
 111                 bitbang_interface->write(1, tms, 0);
 112         }
 113         bitbang_interface->write(CLOCK_IDLE(), tms, 0);
 114
 115         return ERROR_OK;
 116 }
 117
 118
 119 static void bitbang_path_move(struct pathmove_command *cmd)
 120 {
 121         int num_states = cmd->num_states;
 122         int state_count;
 123         int tms = 0;
 124
 125         state_count = 0;
 126         while (num_states)
 127         {
 128                 if (tap_state_transition(tap_get_state(), false) == cmd->path[state_count])
 129                 {
 130                         tms = 0;
 131                 }
 132                 else if (tap_state_transition(tap_get_state(), true) == cmd->path[state_count])
 133                 {
 134                         tms = 1;
 135                 }
 136                 else
 137                 {
 138                         LOG_ERROR("BUG: %s -> %s isn't a valid TAP transition", tap_state_name(tap_get_state()), tap_state_name(cmd->path[state_count]));
 139                         exit(-1);
 140                 }
 141
 142                 bitbang_interface->write(0, tms, 0);
 143                 bitbang_interface->write(1, tms, 0);
 144
 145                 tap_set_state(cmd->path[state_count]);
 146                 state_count++;
 147                 num_states--;
 148         }
 149
 150         bitbang_interface->write(CLOCK_IDLE(), tms, 0);
 151
 152         tap_set_end_state(tap_get_state());
 153 }
 154
 155 static void bitbang_runtest(int num_cycles)
 156 {
 157         int i;
 158
 159         tap_state_t saved_end_state = tap_get_end_state();
 160
 161         /* only do a state_move when we're not already in IDLE */
 162         if (tap_get_state() != TAP_IDLE)
 163         {
 164                 bitbang_end_state(TAP_IDLE);
 165                 bitbang_state_move(0);
 166         }
 167
 168         /* execute num_cycles */
 169         for (i = 0; i < num_cycles; i++)
 170         {
 171                 bitbang_interface->write(0, 0, 0);
 172                 bitbang_interface->write(1, 0, 0);
 173         }
 174         bitbang_interface->write(CLOCK_IDLE(), 0, 0);
 175
 176         /* finish in end_state */
 177         bitbang_end_state(saved_end_state);
 178         if (tap_get_state() != tap_get_end_state())
 179                 bitbang_state_move(0);
 180 }
 181
 182
 183 static void bitbang_stableclocks(int num_cycles)
 184 {
 185         int tms = (tap_get_state() == TAP_RESET ? 1 : 0);
 186         int i;
 187
 188         /* send num_cycles clocks onto the cable */
 189         for (i = 0; i < num_cycles; i++)
 190         {
 191                 bitbang_interface->write(1, tms, 0);
 192                 bitbang_interface->write(0, tms, 0);
 193         }
 194 }
 195
 196
 197
 198 static void bitbang_scan(bool ir_scan, enum scan_type type, uint8_t *buffer, int scan_size)
 199 {
 200         tap_state_t saved_end_state = tap_get_end_state();
 201         int bit_cnt;
 202
 203         if (!((!ir_scan && (tap_get_state() == TAP_DRSHIFT)) || (ir_scan && (tap_get_state() == TAP_IRSHIFT))))
 204         {
 205                 if (ir_scan)
 206                         bitbang_end_state(TAP_IRSHIFT);
 207                 else
 208                         bitbang_end_state(TAP_DRSHIFT);
 209
 210                 bitbang_state_move(0);
 211                 bitbang_end_state(saved_end_state);
 212         }
 213
 214         for (bit_cnt = 0; bit_cnt < scan_size; bit_cnt++)
 215         {
 216                 int val = 0;
 217                 int tms = (bit_cnt == scan_size-1) ? 1 : 0;
 218                 int tdi;
 219                 int bytec = bit_cnt/8;
 220                 int bcval = 1 << (bit_cnt % 8);
 221
 222                 /* if we're just reading the scan, but don't care about the output
 223                  * default to outputting 'low', this also makes valgrind traces more readable,
 224                  * as it removes the dependency on an uninitialised value
 225                  */
 226                 tdi = 0;
 227                 if ((type != SCAN_IN) && (buffer[bytec] & bcval))
 228                         tdi = 1;
 229
 230                 bitbang_interface->write(0, tms, tdi);
 231
 232                 if (type != SCAN_OUT)
 233                         val = bitbang_interface->read();
 234
 235                 bitbang_interface->write(1, tms, tdi);
 236
 237                 if (type != SCAN_OUT)
 238                 {
 239                         if (val)
 240                                 buffer[bytec] |= bcval;
 241                         else
 242                                 buffer[bytec] &= ~bcval;
 243                 }
 244         }
 245
 246         if (tap_get_state() != tap_get_end_state())
 247         {
 248                 /* we *KNOW* the above loop transitioned out of
 249                  * the shift state, so we skip the first state
 250                  * and move directly to the end state.
 251                  */
 252                 bitbang_state_move(1);
 253         }
 254 }
 255
 256 int bitbang_execute_queue(void)
 257 {
 258         struct jtag_command *cmd = jtag_command_queue; /* currently processed command */
 259         int scan_size;
 260         enum scan_type type;
 261         uint8_t *buffer;
 262         int retval;
 263
 264         if (!bitbang_interface)
 265         {
 266                 LOG_ERROR("BUG: Bitbang interface called, but not yet initialized");
 267                 exit(-1);
 268         }
 269
 270         /* return ERROR_OK, unless a jtag_read_buffer returns a failed check
 271          * that wasn't handled by a caller-provided error handler
 272          */
 273         retval = ERROR_OK;
 274
 275         if (bitbang_interface->blink)
 276                 bitbang_interface->blink(1);
 277
 278         while (cmd)
 279         {
 280                 switch (cmd->type)
 281                 {
 282                         case JTAG_RESET:
 283 #ifdef _DEBUG_JTAG_IO_
 284                                 LOG_DEBUG("reset trst: %i srst %i", cmd->cmd.reset->trst, cmd->cmd.reset->srst);
 285 #endif
 286                                 if ((cmd->cmd.reset->trst == 1) || (cmd->cmd.reset->srst && (jtag_get_reset_config() & RESET_SRST_PULLS_TRST)))
 287                                 {
 288                                         tap_set_state(TAP_RESET);
 289                                 }
 290                                 bitbang_interface->reset(cmd->cmd.reset->trst, cmd->cmd.reset->srst);
 291                                 break;
 292                         case JTAG_RUNTEST:
 293 #ifdef _DEBUG_JTAG_IO_
 294                                 LOG_DEBUG("runtest %i cycles, end in %s", cmd->cmd.runtest->num_cycles, tap_state_name(cmd->cmd.runtest->end_state));
 295 #endif
 296                                 bitbang_end_state(cmd->cmd.runtest->end_state);
 297                                 bitbang_runtest(cmd->cmd.runtest->num_cycles);
 298                                 break;
 299
 300                         case JTAG_STABLECLOCKS:
 301                                 /* this is only allowed while in a stable state.  A check for a stable
 302                                  * state was done in jtag_add_clocks()
 303                                  */
 304                                 bitbang_stableclocks(cmd->cmd.stableclocks->num_cycles);
 305                                 break;
 306
 307                         case JTAG_STATEMOVE:
 308 #ifdef _DEBUG_JTAG_IO_
 309                                 LOG_DEBUG("statemove end in %s", tap_state_name(cmd->cmd.statemove->end_state));
 310 #endif
 311                                 bitbang_end_state(cmd->cmd.statemove->end_state);
 312                                 bitbang_state_move(0);
 313                                 break;
 314                         case JTAG_PATHMOVE:
 315 #ifdef _DEBUG_JTAG_IO_
 316                                 LOG_DEBUG("pathmove: %i states, end in %s", cmd->cmd.pathmove->num_states,
 317                                         tap_state_name(cmd->cmd.pathmove->path[cmd->cmd.pathmove->num_states - 1]));
 318 #endif
 319                                 bitbang_path_move(cmd->cmd.pathmove);
 320                                 break;
 321                         case JTAG_SCAN:
 322 #ifdef _DEBUG_JTAG_IO_
 323                                 LOG_DEBUG("%s scan end in %s",  (cmd->cmd.scan->ir_scan) ? "IR" : "DR", tap_state_name(cmd->cmd.scan->end_state));
 324 #endif
 325                                 bitbang_end_state(cmd->cmd.scan->end_state);
 326                                 scan_size = jtag_build_buffer(cmd->cmd.scan, &buffer);
 327                                 type = jtag_scan_type(cmd->cmd.scan);
 328                                 bitbang_scan(cmd->cmd.scan->ir_scan, type, buffer, scan_size);
 329                                 if (jtag_read_buffer(buffer, cmd->cmd.scan) != ERROR_OK)
 330                                         retval = ERROR_JTAG_QUEUE_FAILED;
 331                                 if (buffer)
 332                                         free(buffer);
 333                                 break;
 334                         case JTAG_SLEEP:
 335 #ifdef _DEBUG_JTAG_IO_
 336                                 LOG_DEBUG("sleep %" PRIi32, cmd->cmd.sleep->us);
 337 #endif
 338                                 jtag_sleep(cmd->cmd.sleep->us);
 339                                 break;
 340                         case JTAG_TMS:
 341                                 retval = bitbang_execute_tms(cmd);
 342                                 break;
 343                         default:
 344                                 LOG_ERROR("BUG: unknown JTAG command type encountered");
 345                                 exit(-1);
 346                 }
 347                 cmd = cmd->next;
 348         }
 349         if (bitbang_interface->blink)
 350                 bitbang_interface->blink(0);
 351
 352         return retval;
 353 }