drivers/bitbang: add support for SWD multidrop
[fw/openocd] / src / jtag / drivers / bitbang.c
index c9ec9c9d6fa33b4b2ede7d329a8c276e3c696209..898d6d3df9c5d482d167348d8f6b8a8e45416023 100644 (file)
@@ -30,9 +30,6 @@
 #include <jtag/interface.h>
 #include <jtag/commands.h>
 
-/* YUK! - but this is currently a global.... */
-extern struct jtag_interface *jtag_interface;
-
 /**
  * Function bitbang_stableclocks
  * issues a number of clock cycles while staying in a stable state.
@@ -41,7 +38,7 @@ extern struct jtag_interface *jtag_interface;
  * this function checks the current stable state to decide on the value of TMS
  * to use.
  */
-static void bitbang_stableclocks(int num_cycles);
+static int bitbang_stableclocks(int num_cycles);
 
 static void bitbang_swd_write_reg(uint8_t cmd, uint32_t value, uint32_t ap_delay_clk);
 
@@ -70,15 +67,11 @@ struct bitbang_interface *bitbang_interface;
 /* The bitbang driver leaves the TCK 0 when in idle */
 static void bitbang_end_state(tap_state_t state)
 {
-       if (tap_is_state_stable(state))
-               tap_set_end_state(state);
-       else {
-               LOG_ERROR("BUG: %i is not a valid end state", state);
-               exit(-1);
-       }
+       assert(tap_is_state_stable(state));
+       tap_set_end_state(state);
 }
 
-static void bitbang_state_move(int skip)
+static int bitbang_state_move(int skip)
 {
        int i = 0, tms = 0;
        uint8_t tms_scan = tap_get_tms_path(tap_get_state(), tap_get_end_state());
@@ -86,12 +79,16 @@ static void bitbang_state_move(int skip)
 
        for (i = skip; i < tms_count; i++) {
                tms = (tms_scan >> i) & 1;
-               bitbang_interface->write(0, tms, 0);
-               bitbang_interface->write(1, tms, 0);
+               if (bitbang_interface->write(0, tms, 0) != ERROR_OK)
+                       return ERROR_FAIL;
+               if (bitbang_interface->write(1, tms, 0) != ERROR_OK)
+                       return ERROR_FAIL;
        }
-       bitbang_interface->write(CLOCK_IDLE(), tms, 0);
+       if (bitbang_interface->write(CLOCK_IDLE(), tms, 0) != ERROR_OK)
+               return ERROR_FAIL;
 
        tap_set_state(tap_get_end_state());
+       return ERROR_OK;
 }
 
 /**
@@ -103,20 +100,23 @@ static int bitbang_execute_tms(struct jtag_command *cmd)
        unsigned num_bits = cmd->cmd.tms->num_bits;
        const uint8_t *bits = cmd->cmd.tms->bits;
 
-       DEBUG_JTAG_IO("TMS: %d bits", num_bits);
+       LOG_DEBUG_IO("TMS: %d bits", num_bits);
 
        int tms = 0;
        for (unsigned i = 0; i < num_bits; i++) {
                tms = ((bits[i/8] >> (i % 8)) & 1);
-               bitbang_interface->write(0, tms, 0);
-               bitbang_interface->write(1, tms, 0);
+               if (bitbang_interface->write(0, tms, 0) != ERROR_OK)
+                       return ERROR_FAIL;
+               if (bitbang_interface->write(1, tms, 0) != ERROR_OK)
+                       return ERROR_FAIL;
        }
-       bitbang_interface->write(CLOCK_IDLE(), tms, 0);
+       if (bitbang_interface->write(CLOCK_IDLE(), tms, 0) != ERROR_OK)
+               return ERROR_FAIL;
 
        return ERROR_OK;
 }
 
-static void bitbang_path_move(struct pathmove_command *cmd)
+static int bitbang_path_move(struct pathmove_command *cmd)
 {
        int num_states = cmd->num_states;
        int state_count;
@@ -135,20 +135,24 @@ static void bitbang_path_move(struct pathmove_command *cmd)
                        exit(-1);
                }
 
-               bitbang_interface->write(0, tms, 0);
-               bitbang_interface->write(1, tms, 0);
+               if (bitbang_interface->write(0, tms, 0) != ERROR_OK)
+                       return ERROR_FAIL;
+               if (bitbang_interface->write(1, tms, 0) != ERROR_OK)
+                       return ERROR_FAIL;
 
                tap_set_state(cmd->path[state_count]);
                state_count++;
                num_states--;
        }
 
-       bitbang_interface->write(CLOCK_IDLE(), tms, 0);
+       if (bitbang_interface->write(CLOCK_IDLE(), tms, 0) != ERROR_OK)
+               return ERROR_FAIL;
 
        tap_set_end_state(tap_get_state());
+       return ERROR_OK;
 }
 
-static void bitbang_runtest(int num_cycles)
+static int bitbang_runtest(int num_cycles)
 {
        int i;
 
@@ -157,38 +161,50 @@ static void bitbang_runtest(int num_cycles)
        /* only do a state_move when we're not already in IDLE */
        if (tap_get_state() != TAP_IDLE) {
                bitbang_end_state(TAP_IDLE);
-               bitbang_state_move(0);
+               if (bitbang_state_move(0) != ERROR_OK)
+                       return ERROR_FAIL;
        }
 
        /* execute num_cycles */
        for (i = 0; i < num_cycles; i++) {
-               bitbang_interface->write(0, 0, 0);
-               bitbang_interface->write(1, 0, 0);
+               if (bitbang_interface->write(0, 0, 0) != ERROR_OK)
+                       return ERROR_FAIL;
+               if (bitbang_interface->write(1, 0, 0) != ERROR_OK)
+                       return ERROR_FAIL;
        }
-       bitbang_interface->write(CLOCK_IDLE(), 0, 0);
+       if (bitbang_interface->write(CLOCK_IDLE(), 0, 0) != ERROR_OK)
+               return ERROR_FAIL;
 
        /* finish in end_state */
        bitbang_end_state(saved_end_state);
        if (tap_get_state() != tap_get_end_state())
-               bitbang_state_move(0);
+               if (bitbang_state_move(0) != ERROR_OK)
+                       return ERROR_FAIL;
+
+       return ERROR_OK;
 }
 
-static void bitbang_stableclocks(int num_cycles)
+static int bitbang_stableclocks(int num_cycles)
 {
        int tms = (tap_get_state() == TAP_RESET ? 1 : 0);
        int i;
 
        /* send num_cycles clocks onto the cable */
        for (i = 0; i < num_cycles; i++) {
-               bitbang_interface->write(1, tms, 0);
-               bitbang_interface->write(0, tms, 0);
+               if (bitbang_interface->write(1, tms, 0) != ERROR_OK)
+                       return ERROR_FAIL;
+               if (bitbang_interface->write(0, tms, 0) != ERROR_OK)
+                       return ERROR_FAIL;
        }
+
+       return ERROR_OK;
 }
 
-static void bitbang_scan(bool ir_scan, enum scan_type type, uint8_t *buffer, int scan_size)
+static int bitbang_scan(bool ir_scan, enum scan_type type, uint8_t *buffer,
+               unsigned scan_size)
 {
        tap_state_t saved_end_state = tap_get_end_state();
-       int bit_cnt;
+       unsigned bit_cnt;
 
        if (!((!ir_scan &&
                        (tap_get_state() == TAP_DRSHIFT)) ||
@@ -198,12 +214,13 @@ static void bitbang_scan(bool ir_scan, enum scan_type type, uint8_t *buffer, int
                else
                        bitbang_end_state(TAP_DRSHIFT);
 
-               bitbang_state_move(0);
+               if (bitbang_state_move(0) != ERROR_OK)
+                       return ERROR_FAIL;
                bitbang_end_state(saved_end_state);
        }
 
+       size_t buffered = 0;
        for (bit_cnt = 0; bit_cnt < scan_size; bit_cnt++) {
-               int val = 0;
                int tms = (bit_cnt == scan_size-1) ? 1 : 0;
                int tdi;
                int bytec = bit_cnt/8;
@@ -217,18 +234,47 @@ static void bitbang_scan(bool ir_scan, enum scan_type type, uint8_t *buffer, int
                if ((type != SCAN_IN) && (buffer[bytec] & bcval))
                        tdi = 1;
 
-               bitbang_interface->write(0, tms, tdi);
-
-               if (type != SCAN_OUT)
-                       val = bitbang_interface->read();
-
-               bitbang_interface->write(1, tms, tdi);
+               if (bitbang_interface->write(0, tms, tdi) != ERROR_OK)
+                       return ERROR_FAIL;
 
                if (type != SCAN_OUT) {
-                       if (val)
-                               buffer[bytec] |= bcval;
-                       else
-                               buffer[bytec] &= ~bcval;
+                       if (bitbang_interface->buf_size) {
+                               if (bitbang_interface->sample() != ERROR_OK)
+                                       return ERROR_FAIL;
+                               buffered++;
+                       } else {
+                               switch (bitbang_interface->read()) {
+                                       case BB_LOW:
+                                               buffer[bytec] &= ~bcval;
+                                               break;
+                                       case BB_HIGH:
+                                               buffer[bytec] |= bcval;
+                                               break;
+                                       default:
+                                               return ERROR_FAIL;
+                               }
+                       }
+               }
+
+               if (bitbang_interface->write(1, tms, tdi) != ERROR_OK)
+                       return ERROR_FAIL;
+
+               if (type != SCAN_OUT && bitbang_interface->buf_size &&
+                               (buffered == bitbang_interface->buf_size ||
+                                bit_cnt == scan_size - 1)) {
+                       for (unsigned i = bit_cnt + 1 - buffered; i <= bit_cnt; i++) {
+                               switch (bitbang_interface->read_sample()) {
+                                       case BB_LOW:
+                                               buffer[i/8] &= ~(1 << (i % 8));
+                                               break;
+                                       case BB_HIGH:
+                                               buffer[i/8] |= 1 << (i % 8);
+                                               break;
+                                       default:
+                                               return ERROR_FAIL;
+                               }
+                       }
+                       buffered = 0;
                }
        }
 
@@ -237,8 +283,10 @@ static void bitbang_scan(bool ir_scan, enum scan_type type, uint8_t *buffer, int
                 * the shift state, so we skip the first state
                 * and move directly to the end state.
                 */
-               bitbang_state_move(1);
+               if (bitbang_state_move(1) != ERROR_OK)
+                       return ERROR_FAIL;
        }
+       return ERROR_OK;
 }
 
 int bitbang_execute_queue(void)
@@ -259,74 +307,61 @@ int bitbang_execute_queue(void)
         */
        retval = ERROR_OK;
 
-       if (bitbang_interface->blink)
-               bitbang_interface->blink(1);
+       if (bitbang_interface->blink) {
+               if (bitbang_interface->blink(1) != ERROR_OK)
+                       return ERROR_FAIL;
+       }
 
        while (cmd) {
                switch (cmd->type) {
-                       case JTAG_RESET:
-#ifdef _DEBUG_JTAG_IO_
-                               LOG_DEBUG("reset trst: %i srst %i",
-                               cmd->cmd.reset->trst,
-                               cmd->cmd.reset->srst);
-#endif
-                               if ((cmd->cmd.reset->trst == 1) ||
-                                               (cmd->cmd.reset->srst && (jtag_get_reset_config() & RESET_SRST_PULLS_TRST)))
-                                       tap_set_state(TAP_RESET);
-                               bitbang_interface->reset(cmd->cmd.reset->trst, cmd->cmd.reset->srst);
-                               break;
                        case JTAG_RUNTEST:
-#ifdef _DEBUG_JTAG_IO_
-                               LOG_DEBUG("runtest %i cycles, end in %s",
+                               LOG_DEBUG_IO("runtest %i cycles, end in %s",
                                                cmd->cmd.runtest->num_cycles,
                                                tap_state_name(cmd->cmd.runtest->end_state));
-#endif
                                bitbang_end_state(cmd->cmd.runtest->end_state);
-                               bitbang_runtest(cmd->cmd.runtest->num_cycles);
+                               if (bitbang_runtest(cmd->cmd.runtest->num_cycles) != ERROR_OK)
+                                       return ERROR_FAIL;
                                break;
 
                        case JTAG_STABLECLOCKS:
                                /* this is only allowed while in a stable state.  A check for a stable
                                 * state was done in jtag_add_clocks()
                                 */
-                               bitbang_stableclocks(cmd->cmd.stableclocks->num_cycles);
+                               if (bitbang_stableclocks(cmd->cmd.stableclocks->num_cycles) != ERROR_OK)
+                                       return ERROR_FAIL;
                                break;
 
                        case JTAG_TLR_RESET:
-#ifdef _DEBUG_JTAG_IO_
-                               LOG_DEBUG("statemove end in %s",
+                               LOG_DEBUG_IO("statemove end in %s",
                                                tap_state_name(cmd->cmd.statemove->end_state));
-#endif
                                bitbang_end_state(cmd->cmd.statemove->end_state);
-                               bitbang_state_move(0);
+                               if (bitbang_state_move(0) != ERROR_OK)
+                                       return ERROR_FAIL;
                                break;
                        case JTAG_PATHMOVE:
-#ifdef _DEBUG_JTAG_IO_
-                               LOG_DEBUG("pathmove: %i states, end in %s",
+                               LOG_DEBUG_IO("pathmove: %i states, end in %s",
                                                cmd->cmd.pathmove->num_states,
                                                tap_state_name(cmd->cmd.pathmove->path[cmd->cmd.pathmove->num_states - 1]));
-#endif
-                               bitbang_path_move(cmd->cmd.pathmove);
+                               if (bitbang_path_move(cmd->cmd.pathmove) != ERROR_OK)
+                                       return ERROR_FAIL;
                                break;
                        case JTAG_SCAN:
-#ifdef _DEBUG_JTAG_IO_
-                               LOG_DEBUG("%s scan end in %s",
-                                               (cmd->cmd.scan->ir_scan) ? "IR" : "DR",
-                                       tap_state_name(cmd->cmd.scan->end_state));
-#endif
                                bitbang_end_state(cmd->cmd.scan->end_state);
                                scan_size = jtag_build_buffer(cmd->cmd.scan, &buffer);
+                               LOG_DEBUG_IO("%s scan %d bits; end in %s",
+                                               (cmd->cmd.scan->ir_scan) ? "IR" : "DR",
+                                               scan_size,
+                                       tap_state_name(cmd->cmd.scan->end_state));
                                type = jtag_scan_type(cmd->cmd.scan);
-                               bitbang_scan(cmd->cmd.scan->ir_scan, type, buffer, scan_size);
+                               if (bitbang_scan(cmd->cmd.scan->ir_scan, type, buffer,
+                                                       scan_size) != ERROR_OK)
+                                       return ERROR_FAIL;
                                if (jtag_read_buffer(buffer, cmd->cmd.scan) != ERROR_OK)
                                        retval = ERROR_JTAG_QUEUE_FAILED;
-                               if (buffer)
-                                       free(buffer);
+                               free(buffer);
                                break;
                        case JTAG_SLEEP:
-#ifdef _DEBUG_JTAG_IO_
-                               LOG_DEBUG("sleep %" PRIi32, cmd->cmd.sleep->us);
-#endif
+                               LOG_DEBUG_IO("sleep %" PRIu32, cmd->cmd.sleep->us);
                                jtag_sleep(cmd->cmd.sleep->us);
                                break;
                        case JTAG_TMS:
@@ -338,34 +373,37 @@ int bitbang_execute_queue(void)
                }
                cmd = cmd->next;
        }
-       if (bitbang_interface->blink)
-               bitbang_interface->blink(0);
+       if (bitbang_interface->blink) {
+               if (bitbang_interface->blink(0) != ERROR_OK)
+                       return ERROR_FAIL;
+       }
 
        return retval;
 }
 
-
-bool swd_mode;
 static int queued_retval;
 
 static int bitbang_swd_init(void)
 {
        LOG_DEBUG("bitbang_swd_init");
-       swd_mode = true;
        return ERROR_OK;
 }
 
-static void bitbang_exchange(bool rnw, uint8_t buf[], unsigned int offset, unsigned int bit_cnt)
+static void bitbang_swd_exchange(bool rnw, uint8_t buf[], unsigned int offset, unsigned int bit_cnt)
 {
-       LOG_DEBUG("bitbang_exchange");
-       int tdi;
+       LOG_DEBUG("bitbang_swd_exchange");
+
+       if (bitbang_interface->blink) {
+               /* FIXME: we should manage errors */
+               bitbang_interface->blink(1);
+       }
 
        for (unsigned int i = offset; i < bit_cnt + offset; i++) {
                int bytec = i/8;
                int bcval = 1 << (i % 8);
-               tdi = !rnw && (buf[bytec] & bcval);
+               int swdio = !rnw && (buf[bytec] & bcval);
 
-               bitbang_interface->write(0, 0, tdi);
+               bitbang_interface->swd_write(0, swdio);
 
                if (rnw && buf) {
                        if (bitbang_interface->swdio_read())
@@ -374,26 +412,47 @@ static void bitbang_exchange(bool rnw, uint8_t buf[], unsigned int offset, unsig
                                buf[bytec] &= ~bcval;
                }
 
-               bitbang_interface->write(1, 0, tdi);
+               bitbang_interface->swd_write(1, swdio);
+       }
+
+       if (bitbang_interface->blink) {
+               /* FIXME: we should manage errors */
+               bitbang_interface->blink(0);
        }
 }
 
-int bitbang_swd_switch_seq(enum swd_special_seq seq)
+static int bitbang_swd_switch_seq(enum swd_special_seq seq)
 {
        LOG_DEBUG("bitbang_swd_switch_seq");
 
        switch (seq) {
        case LINE_RESET:
                LOG_DEBUG("SWD line reset");
-               bitbang_exchange(false, (uint8_t *)swd_seq_line_reset, 0, swd_seq_line_reset_len);
+               bitbang_swd_exchange(false, (uint8_t *)swd_seq_line_reset, 0, swd_seq_line_reset_len);
                break;
        case JTAG_TO_SWD:
                LOG_DEBUG("JTAG-to-SWD");
-               bitbang_exchange(false, (uint8_t *)swd_seq_jtag_to_swd, 0, swd_seq_jtag_to_swd_len);
+               bitbang_swd_exchange(false, (uint8_t *)swd_seq_jtag_to_swd, 0, swd_seq_jtag_to_swd_len);
+               break;
+       case JTAG_TO_DORMANT:
+               LOG_DEBUG("JTAG-to-DORMANT");
+               bitbang_swd_exchange(false, (uint8_t *)swd_seq_jtag_to_dormant, 0, swd_seq_jtag_to_dormant_len);
                break;
        case SWD_TO_JTAG:
                LOG_DEBUG("SWD-to-JTAG");
-               bitbang_exchange(false, (uint8_t *)swd_seq_swd_to_jtag, 0, swd_seq_swd_to_jtag_len);
+               bitbang_swd_exchange(false, (uint8_t *)swd_seq_swd_to_jtag, 0, swd_seq_swd_to_jtag_len);
+               break;
+       case SWD_TO_DORMANT:
+               LOG_DEBUG("SWD-to-DORMANT");
+               bitbang_swd_exchange(false, (uint8_t *)swd_seq_swd_to_dormant, 0, swd_seq_swd_to_dormant_len);
+               break;
+       case DORMANT_TO_SWD:
+               LOG_DEBUG("DORMANT-to-SWD");
+               bitbang_swd_exchange(false, (uint8_t *)swd_seq_dormant_to_swd, 0, swd_seq_dormant_to_swd_len);
+               break;
+       case DORMANT_TO_JTAG:
+               LOG_DEBUG("DORMANT-to-JTAG");
+               bitbang_swd_exchange(false, (uint8_t *)swd_seq_dormant_to_jtag, 0, swd_seq_dormant_to_jtag_len);
                break;
        default:
                LOG_ERROR("Sequence %d not supported", seq);
@@ -403,12 +462,6 @@ int bitbang_swd_switch_seq(enum swd_special_seq seq)
        return ERROR_OK;
 }
 
-void bitbang_switch_to_swd(void)
-{
-       LOG_DEBUG("bitbang_switch_to_swd");
-       bitbang_exchange(false, (uint8_t *)swd_seq_jtag_to_swd, 0, swd_seq_jtag_to_swd_len);
-}
-
 static void swd_clear_sticky_errors(void)
 {
        bitbang_swd_write_reg(swd_cmd(false,  false, DP_ABORT),
@@ -418,7 +471,7 @@ static void swd_clear_sticky_errors(void)
 static void bitbang_swd_read_reg(uint8_t cmd, uint32_t *value, uint32_t ap_delay_clk)
 {
        LOG_DEBUG("bitbang_swd_read_reg");
-       assert(cmd & SWD_CMD_RnW);
+       assert(cmd & SWD_CMD_RNW);
 
        if (queued_retval != ERROR_OK) {
                LOG_DEBUG("Skip bitbang_swd_read_reg because queued_retval=%d", queued_retval);
@@ -428,101 +481,92 @@ static void bitbang_swd_read_reg(uint8_t cmd, uint32_t *value, uint32_t ap_delay
        for (;;) {
                uint8_t trn_ack_data_parity_trn[DIV_ROUND_UP(4 + 3 + 32 + 1 + 4, 8)];
 
-               cmd |= SWD_CMD_START | (1 << 7);
-               bitbang_exchange(false, &cmd, 0, 8);
+               cmd |= SWD_CMD_START | SWD_CMD_PARK;
+               bitbang_swd_exchange(false, &cmd, 0, 8);
 
                bitbang_interface->swdio_drive(false);
-               bitbang_exchange(true, trn_ack_data_parity_trn, 0, 1 + 3 + 32 + 1 + 1);
+               bitbang_swd_exchange(true, trn_ack_data_parity_trn, 0, 1 + 3 + 32 + 1 + 1);
                bitbang_interface->swdio_drive(true);
 
                int ack = buf_get_u32(trn_ack_data_parity_trn, 1, 3);
                uint32_t data = buf_get_u32(trn_ack_data_parity_trn, 1 + 3, 32);
                int parity = buf_get_u32(trn_ack_data_parity_trn, 1 + 3 + 32, 1);
 
-               LOG_DEBUG("%s %s %s reg %X = %08"PRIx32,
+               LOG_DEBUG("%s %s read reg %X = %08"PRIx32,
                          ack == SWD_ACK_OK ? "OK" : ack == SWD_ACK_WAIT ? "WAIT" : ack == SWD_ACK_FAULT ? "FAULT" : "JUNK",
-                         cmd & SWD_CMD_APnDP ? "AP" : "DP",
-                         cmd & SWD_CMD_RnW ? "read" : "write",
+                         cmd & SWD_CMD_APNDP ? "AP" : "DP",
                          (cmd & SWD_CMD_A32) >> 1,
                          data);
 
-               switch (ack) {
-                case SWD_ACK_OK:
-                       if (parity != parity_u32(data)) {
-                               LOG_DEBUG("Wrong parity detected");
-                               queued_retval = ERROR_FAIL;
-                               return;
-                       }
-                       if (value)
-                               *value = data;
-                       if (cmd & SWD_CMD_APnDP)
-                               bitbang_exchange(true, NULL, 0, ap_delay_clk);
-                       return;
-                case SWD_ACK_WAIT:
-                       LOG_DEBUG("SWD_ACK_WAIT");
+               if (ack == SWD_ACK_WAIT) {
                        swd_clear_sticky_errors();
-                       break;
-                case SWD_ACK_FAULT:
-                       LOG_DEBUG("SWD_ACK_FAULT");
-                       queued_retval = ack;
+                       continue;
+               } else if (ack != SWD_ACK_OK) {
+                       queued_retval = swd_ack_to_error_code(ack);
                        return;
-                default:
-                       LOG_DEBUG("No valid acknowledge: ack=%d", ack);
-                       queued_retval = ack;
+               }
+
+               if (parity != parity_u32(data)) {
+                       LOG_ERROR("Wrong parity detected");
+                       queued_retval = ERROR_FAIL;
                        return;
                }
+               if (value)
+                       *value = data;
+               if (cmd & SWD_CMD_APNDP)
+                       bitbang_swd_exchange(true, NULL, 0, ap_delay_clk);
+               return;
        }
 }
 
 static void bitbang_swd_write_reg(uint8_t cmd, uint32_t value, uint32_t ap_delay_clk)
 {
        LOG_DEBUG("bitbang_swd_write_reg");
-       assert(!(cmd & SWD_CMD_RnW));
+       assert(!(cmd & SWD_CMD_RNW));
 
        if (queued_retval != ERROR_OK) {
                LOG_DEBUG("Skip bitbang_swd_write_reg because queued_retval=%d", queued_retval);
                return;
        }
 
+       /* Devices do not reply to DP_TARGETSEL write cmd, ignore received ack */
+       bool check_ack = swd_cmd_returns_ack(cmd);
+
        for (;;) {
                uint8_t trn_ack_data_parity_trn[DIV_ROUND_UP(4 + 3 + 32 + 1 + 4, 8)];
                buf_set_u32(trn_ack_data_parity_trn, 1 + 3 + 1, 32, value);
                buf_set_u32(trn_ack_data_parity_trn, 1 + 3 + 1 + 32, 1, parity_u32(value));
 
-               cmd |= SWD_CMD_START | (1 << 7);
-               bitbang_exchange(false, &cmd, 0, 8);
+               cmd |= SWD_CMD_START | SWD_CMD_PARK;
+               bitbang_swd_exchange(false, &cmd, 0, 8);
 
                bitbang_interface->swdio_drive(false);
-               bitbang_exchange(true, trn_ack_data_parity_trn, 0, 1 + 3 + 1);
+               bitbang_swd_exchange(true, trn_ack_data_parity_trn, 0, 1 + 3 + 1);
                bitbang_interface->swdio_drive(true);
-               bitbang_exchange(false, trn_ack_data_parity_trn, 1 + 3 + 1, 32 + 1);
+               bitbang_swd_exchange(false, trn_ack_data_parity_trn, 1 + 3 + 1, 32 + 1);
 
                int ack = buf_get_u32(trn_ack_data_parity_trn, 1, 3);
-               LOG_DEBUG("%s %s %s reg %X = %08"PRIx32,
+
+               LOG_DEBUG("%s%s %s write reg %X = %08"PRIx32,
+                         check_ack ? "" : "ack ignored ",
                          ack == SWD_ACK_OK ? "OK" : ack == SWD_ACK_WAIT ? "WAIT" : ack == SWD_ACK_FAULT ? "FAULT" : "JUNK",
-                         cmd & SWD_CMD_APnDP ? "AP" : "DP",
-                         cmd & SWD_CMD_RnW ? "read" : "write",
+                         cmd & SWD_CMD_APNDP ? "AP" : "DP",
                          (cmd & SWD_CMD_A32) >> 1,
                          buf_get_u32(trn_ack_data_parity_trn, 1 + 3 + 1, 32));
 
-               switch (ack) {
-                case SWD_ACK_OK:
-                       if (cmd & SWD_CMD_APnDP)
-                               bitbang_exchange(true, NULL, 0, ap_delay_clk);
-                       return;
-                case SWD_ACK_WAIT:
-                       LOG_DEBUG("SWD_ACK_WAIT");
-                       swd_clear_sticky_errors();
-                       break;
-                case SWD_ACK_FAULT:
-                       LOG_DEBUG("SWD_ACK_FAULT");
-                       queued_retval = ack;
-                       return;
-                default:
-                       LOG_DEBUG("No valid acknowledge: ack=%d", ack);
-                       queued_retval = ack;
-                       return;
+               if (check_ack) {
+                       if (ack == SWD_ACK_WAIT) {
+                               swd_clear_sticky_errors();
+                               continue;
+                       } else if (ack != SWD_ACK_OK) {
+                               queued_retval = swd_ack_to_error_code(ack);
+                               return;
+                       }
                }
+
+               if (cmd & SWD_CMD_APNDP)
+                       bitbang_swd_exchange(true, NULL, 0, ap_delay_clk);
+               return;
        }
 }
 
@@ -531,7 +575,7 @@ static int bitbang_swd_run_queue(void)
        LOG_DEBUG("bitbang_swd_run_queue");
        /* A transaction must be followed by another transaction or at least 8 idle cycles to
         * ensure that data is clocked through the AP. */
-       bitbang_exchange(true, NULL, 0, 8);
+       bitbang_swd_exchange(true, NULL, 0, 8);
 
        int retval = queued_retval;
        queued_retval = ERROR_OK;