cmsis-dap: add initial cmsis-dap support

[fw/openocd] / src / jtag / core.c

/***************************************************************************
 *   Copyright (C) 2009 Zachary T Welch                                    *
 *   zw@superlucidity.net                                                  *
 *                                                                         *
 *   Copyright (C) 2007,2008,2009 Øyvind Harboe                            *
 *   oyvind.harboe@zylin.com                                               *
 *                                                                         *
 *   Copyright (C) 2009 SoftPLC Corporation                                *
 *       http://softplc.com                                                *
 *   dick@softplc.com                                                      *
 *                                                                         *
 *   Copyright (C) 2005 by Dominic Rath                                    *
 *   Dominic.Rath@gmx.de                                                   *
 *                                                                         *
 *   This program is free software; you can redistribute it and/or modify  *
 *   it under the terms of the GNU General Public License as published by  *
 *   the Free Software Foundation; either version 2 of the License, or     *
 *   (at your option) any later version.                                   *
 *                                                                         *
 *   This program is distributed in the hope that it will be useful,       *
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of        *
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         *
 *   GNU General Public License for more details.                          *
 *                                                                         *
 *   You should have received a copy of the GNU General Public License     *
 *   along with this program; if not, write to the                         *
 *   Free Software Foundation, Inc.,                                       *
 *   51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.           *
 ***************************************************************************/

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include "jtag.h"
#include "swd.h"
#include "interface.h"
#include <transport/transport.h>

#ifdef HAVE_STRINGS_H
#include <strings.h>
#endif

/* SVF and XSVF are higher level JTAG command sets (for boundary scan) */
#include "svf/svf.h"
#include "xsvf/xsvf.h"

/** The number of JTAG queue flushes (for profiling and debugging purposes). */
static int jtag_flush_queue_count;

/* Sleep this # of ms after flushing the queue */
static int jtag_flush_queue_sleep;

static void jtag_add_scan_check(struct jtag_tap *active,
                void (*jtag_add_scan)(struct jtag_tap *active,
                int in_num_fields,
                const struct scan_field *in_fields,
                tap_state_t state),
                int in_num_fields, struct scan_field *in_fields, tap_state_t state);

/**
 * The jtag_error variable is set when an error occurs while executing
 * the queue.  Application code may set this using jtag_set_error(),
 * when an error occurs during processing that should be reported during
 * jtag_execute_queue().
 *
 * The value is set and cleared, but never read by normal application code.
 *
 * This value is returned (and cleared) by jtag_execute_queue().
 */
static int jtag_error = ERROR_OK;

static const char *jtag_event_strings[] = {
        [JTAG_TRST_ASSERTED] = "TAP reset",
        [JTAG_TAP_EVENT_SETUP] = "TAP setup",
        [JTAG_TAP_EVENT_ENABLE] = "TAP enabled",
        [JTAG_TAP_EVENT_DISABLE] = "TAP disabled",
};

/*
 * JTAG adapters must initialize with TRST and SRST de-asserted
 * (they're negative logic, so that means *high*).  But some
 * hardware doesn't necessarily work that way ... so set things
 * up so that jtag_init() always forces that state.
 */
static int jtag_trst = -1;
static int jtag_srst = -1;

/**
 * List all TAPs that have been created.
 */
static struct jtag_tap *__jtag_all_taps;
/**
 * The number of TAPs in the __jtag_all_taps list, used to track the
 * assigned chain position to new TAPs
 */
static unsigned jtag_num_taps;

static enum reset_types jtag_reset_config = RESET_NONE;
tap_state_t cmd_queue_cur_state = TAP_RESET;

static bool jtag_verify_capture_ir = true;
static int jtag_verify = 1;

/* how long the OpenOCD should wait before attempting JTAG communication after reset lines
 *deasserted (in ms) */
static int adapter_nsrst_delay; /* default to no nSRST delay */
static int jtag_ntrst_delay;/* default to no nTRST delay */
static int adapter_nsrst_assert_width;  /* width of assertion */
static int jtag_ntrst_assert_width;     /* width of assertion */

/**
 * Contains a single callback along with a pointer that will be passed
 * when an event occurs.
 */
struct jtag_event_callback {
        /** a event callback */
        jtag_event_handler_t callback;
        /** the private data to pass to the callback */
        void *priv;
        /** the next callback */
        struct jtag_event_callback *next;
};

/* callbacks to inform high-level handlers about JTAG state changes */
static struct jtag_event_callback *jtag_event_callbacks;

/* speed in kHz*/
static int speed_khz;
/* speed to fallback to when RCLK is requested but not supported */
static int rclk_fallback_speed_khz;
static enum {CLOCK_MODE_UNSELECTED, CLOCK_MODE_KHZ, CLOCK_MODE_RCLK} clock_mode;
static int jtag_speed;

static struct jtag_interface *jtag;

/* configuration */
struct jtag_interface *jtag_interface;

void jtag_set_flush_queue_sleep(int ms)
{
        jtag_flush_queue_sleep = ms;
}

void jtag_set_error(int error)
{
        if ((error == ERROR_OK) || (jtag_error != ERROR_OK))
                return;
        jtag_error = error;
}

int jtag_error_clear(void)
{
        int temp = jtag_error;
        jtag_error = ERROR_OK;
        return temp;
}

/************/

static bool jtag_poll = 1;

bool is_jtag_poll_safe(void)
{
        /* Polling can be disabled explicitly with set_enabled(false).
         * It is also implicitly disabled while TRST is active and
         * while SRST is gating the JTAG clock.
         */
        if (!jtag_poll || jtag_trst != 0)
                return false;
        return jtag_srst == 0 || (jtag_reset_config & RESET_SRST_NO_GATING);
}

bool jtag_poll_get_enabled(void)
{
        return jtag_poll;
}

void jtag_poll_set_enabled(bool value)
{
        jtag_poll = value;
}

/************/

struct jtag_tap *jtag_all_taps(void)
{
        return __jtag_all_taps;
};

unsigned jtag_tap_count(void)
{
        return jtag_num_taps;
}

unsigned jtag_tap_count_enabled(void)
{
        struct jtag_tap *t = jtag_all_taps();
        unsigned n = 0;
        while (t) {
                if (t->enabled)
                        n++;
                t = t->next_tap;
        }
        return n;
}

/** Append a new TAP to the chain of all taps. */
void jtag_tap_add(struct jtag_tap *t)
{
        t->abs_chain_position = jtag_num_taps++;

        struct jtag_tap **tap = &__jtag_all_taps;
        while (*tap != NULL)
                tap = &(*tap)->next_tap;
        *tap = t;
}

/* returns a pointer to the n-th device in the scan chain */
struct jtag_tap *jtag_tap_by_position(unsigned n)
{
        struct jtag_tap *t = jtag_all_taps();

        while (t && n-- > 0)
                t = t->next_tap;

        return t;
}

struct jtag_tap *jtag_tap_by_string(const char *s)
{
        /* try by name first */
        struct jtag_tap *t = jtag_all_taps();

        while (t) {
                if (0 == strcmp(t->dotted_name, s))
                        return t;
                t = t->next_tap;
        }

        /* no tap found by name, so try to parse the name as a number */
        unsigned n;
        if (parse_uint(s, &n) != ERROR_OK)
                return NULL;

        /* FIXME remove this numeric fallback code late June 2010, along
         * with all info in the User's Guide that TAPs have numeric IDs.
         * Also update "scan_chain" output to not display the numbers.
         */
        t = jtag_tap_by_position(n);
        if (t)
                LOG_WARNING("Specify TAP '%s' by name, not number %u",
                        t->dotted_name, n);

        return t;
}

struct jtag_tap *jtag_tap_next_enabled(struct jtag_tap *p)
{
        p = p ? p->next_tap : jtag_all_taps();
        while (p) {
                if (p->enabled)
                        return p;
                p = p->next_tap;
        }
        return NULL;
}

const char *jtag_tap_name(const struct jtag_tap *tap)
{
        return (tap == NULL) ? "(unknown)" : tap->dotted_name;
}


int jtag_register_event_callback(jtag_event_handler_t callback, void *priv)
{
        struct jtag_event_callback **callbacks_p = &jtag_event_callbacks;

        if (callback == NULL)
                return ERROR_COMMAND_SYNTAX_ERROR;

        if (*callbacks_p) {
                while ((*callbacks_p)->next)
                        callbacks_p = &((*callbacks_p)->next);
                callbacks_p = &((*callbacks_p)->next);
        }

        (*callbacks_p) = malloc(sizeof(struct jtag_event_callback));
        (*callbacks_p)->callback = callback;
        (*callbacks_p)->priv = priv;
        (*callbacks_p)->next = NULL;

        return ERROR_OK;
}

int jtag_unregister_event_callback(jtag_event_handler_t callback, void *priv)
{
        struct jtag_event_callback **p = &jtag_event_callbacks, *temp;

        if (callback == NULL)
                return ERROR_COMMAND_SYNTAX_ERROR;

        while (*p) {
                if (((*p)->priv != priv) || ((*p)->callback != callback)) {
                        p = &(*p)->next;
                        continue;
                }

                temp = *p;
                *p = (*p)->next;
                free(temp);
        }

        return ERROR_OK;
}

int jtag_call_event_callbacks(enum jtag_event event)
{
        struct jtag_event_callback *callback = jtag_event_callbacks;

        LOG_DEBUG("jtag event: %s", jtag_event_strings[event]);

        while (callback) {
                struct jtag_event_callback *next;

                /* callback may remove itself */
                next = callback->next;
                callback->callback(event, callback->priv);
                callback = next;
        }

        return ERROR_OK;
}

static void jtag_checks(void)
{
        assert(jtag_trst == 0);
}

static void jtag_prelude(tap_state_t state)
{
        jtag_checks();

        assert(state != TAP_INVALID);

        cmd_queue_cur_state = state;
}

void jtag_add_ir_scan_noverify(struct jtag_tap *active, const struct scan_field *in_fields,
        tap_state_t state)
{
        jtag_prelude(state);

        int retval = interface_jtag_add_ir_scan(active, in_fields, state);
        jtag_set_error(retval);
}

static void jtag_add_ir_scan_noverify_callback(struct jtag_tap *active,
        int dummy,
        const struct scan_field *in_fields,
        tap_state_t state)
{
        jtag_add_ir_scan_noverify(active, in_fields, state);
}

/* If fields->in_value is filled out, then the captured IR value will be checked */
void jtag_add_ir_scan(struct jtag_tap *active, struct scan_field *in_fields, tap_state_t state)
{
        assert(state != TAP_RESET);

        if (jtag_verify && jtag_verify_capture_ir) {
                /* 8 x 32 bit id's is enough for all invocations */

                /* if we are to run a verification of the ir scan, we need to get the input back.
                 * We may have to allocate space if the caller didn't ask for the input back.
                 */
                in_fields->check_value = active->expected;
                in_fields->check_mask = active->expected_mask;
                jtag_add_scan_check(active, jtag_add_ir_scan_noverify_callback, 1, in_fields,
                        state);
        } else
                jtag_add_ir_scan_noverify(active, in_fields, state);
}

void jtag_add_plain_ir_scan(int num_bits, const uint8_t *out_bits, uint8_t *in_bits,
        tap_state_t state)
{
        assert(out_bits != NULL);
        assert(state != TAP_RESET);

        jtag_prelude(state);

        int retval = interface_jtag_add_plain_ir_scan(
                        num_bits, out_bits, in_bits, state);
        jtag_set_error(retval);
}

static int jtag_check_value_inner(uint8_t *captured, uint8_t *in_check_value,
                                  uint8_t *in_check_mask, int num_bits);

static int jtag_check_value_mask_callback(jtag_callback_data_t data0,
        jtag_callback_data_t data1,
        jtag_callback_data_t data2,
        jtag_callback_data_t data3)
{
        return jtag_check_value_inner((uint8_t *)data0,
                (uint8_t *)data1,
                (uint8_t *)data2,
                (int)data3);
}

static void jtag_add_scan_check(struct jtag_tap *active, void (*jtag_add_scan)(
                struct jtag_tap *active,
                int in_num_fields,
                const struct scan_field *in_fields,
                tap_state_t state),
        int in_num_fields, struct scan_field *in_fields, tap_state_t state)
{
        jtag_add_scan(active, in_num_fields, in_fields, state);

        for (int i = 0; i < in_num_fields; i++) {
                if ((in_fields[i].check_value != NULL) && (in_fields[i].in_value != NULL)) {
                        /* this is synchronous for a minidriver */
                        jtag_add_callback4(jtag_check_value_mask_callback,
                                (jtag_callback_data_t)in_fields[i].in_value,
                                (jtag_callback_data_t)in_fields[i].check_value,
                                (jtag_callback_data_t)in_fields[i].check_mask,
                                (jtag_callback_data_t)in_fields[i].num_bits);
                }
        }
}

void jtag_add_dr_scan_check(struct jtag_tap *active,
        int in_num_fields,
        struct scan_field *in_fields,
        tap_state_t state)
{
        if (jtag_verify)
                jtag_add_scan_check(active, jtag_add_dr_scan, in_num_fields, in_fields, state);
        else
                jtag_add_dr_scan(active, in_num_fields, in_fields, state);
}


void jtag_add_dr_scan(struct jtag_tap *active,
        int in_num_fields,
        const struct scan_field *in_fields,
        tap_state_t state)
{
        assert(state != TAP_RESET);

        jtag_prelude(state);

        int retval;
        retval = interface_jtag_add_dr_scan(active, in_num_fields, in_fields, state);
        jtag_set_error(retval);
}

void jtag_add_plain_dr_scan(int num_bits, const uint8_t *out_bits, uint8_t *in_bits,
        tap_state_t state)
{
        assert(out_bits != NULL);
        assert(state != TAP_RESET);

        jtag_prelude(state);

        int retval;
        retval = interface_jtag_add_plain_dr_scan(num_bits, out_bits, in_bits, state);
        jtag_set_error(retval);
}

void jtag_add_tlr(void)
{
        jtag_prelude(TAP_RESET);
        jtag_set_error(interface_jtag_add_tlr());

        /* NOTE: order here matches TRST path in jtag_add_reset() */
        jtag_call_event_callbacks(JTAG_TRST_ASSERTED);
        jtag_notify_event(JTAG_TRST_ASSERTED);
}

/**
 * If supported by the underlying adapter, this clocks a raw bit sequence
 * onto TMS for switching betwen JTAG and SWD modes.
 *
 * DO NOT use this to bypass the integrity checks and logging provided
 * by the jtag_add_pathmove() and jtag_add_statemove() calls.
 *
 * @param nbits How many bits to clock out.
 * @param seq The bit sequence.  The LSB is bit 0 of seq[0].
 * @param state The JTAG tap state to record on completion.  Use
 *      TAP_INVALID to represent being in in SWD mode.
 *
 * @todo Update naming conventions to stop assuming everything is JTAG.
 */
int jtag_add_tms_seq(unsigned nbits, const uint8_t *seq, enum tap_state state)
{
        int retval;

        if (!(jtag->supported & DEBUG_CAP_TMS_SEQ))
                return ERROR_JTAG_NOT_IMPLEMENTED;

        jtag_checks();
        cmd_queue_cur_state = state;

        retval = interface_add_tms_seq(nbits, seq, state);
        jtag_set_error(retval);
        return retval;
}

void jtag_add_pathmove(int num_states, const tap_state_t *path)
{
        tap_state_t cur_state = cmd_queue_cur_state;

        /* the last state has to be a stable state */
        if (!tap_is_state_stable(path[num_states - 1])) {
                LOG_ERROR("BUG: TAP path doesn't finish in a stable state");
                jtag_set_error(ERROR_JTAG_NOT_STABLE_STATE);
                return;
        }

        for (int i = 0; i < num_states; i++) {
                if (path[i] == TAP_RESET) {
                        LOG_ERROR("BUG: TAP_RESET is not a valid state for pathmove sequences");
                        jtag_set_error(ERROR_JTAG_STATE_INVALID);
                        return;
                }

                if (tap_state_transition(cur_state, true) != path[i] &&
                                tap_state_transition(cur_state, false) != path[i]) {
                        LOG_ERROR("BUG: %s -> %s isn't a valid TAP transition",
                                tap_state_name(cur_state), tap_state_name(path[i]));
                        jtag_set_error(ERROR_JTAG_TRANSITION_INVALID);
                        return;
                }
                cur_state = path[i];
        }

        jtag_checks();

        jtag_set_error(interface_jtag_add_pathmove(num_states, path));
        cmd_queue_cur_state = path[num_states - 1];
}

int jtag_add_statemove(tap_state_t goal_state)
{
        tap_state_t cur_state = cmd_queue_cur_state;

        if (goal_state != cur_state) {
                LOG_DEBUG("cur_state=%s goal_state=%s",
                        tap_state_name(cur_state),
                        tap_state_name(goal_state));
        }

        /* If goal is RESET, be paranoid and force that that transition
         * (e.g. five TCK cycles, TMS high).  Else trust "cur_state".
         */
        if (goal_state == TAP_RESET)
                jtag_add_tlr();
        else if (goal_state == cur_state)
                /* nothing to do */;

        else if (tap_is_state_stable(cur_state) && tap_is_state_stable(goal_state)) {
                unsigned tms_bits  = tap_get_tms_path(cur_state, goal_state);
                unsigned tms_count = tap_get_tms_path_len(cur_state, goal_state);
                tap_state_t moves[8];
                assert(tms_count < ARRAY_SIZE(moves));

                for (unsigned i = 0; i < tms_count; i++, tms_bits >>= 1) {
                        bool bit = tms_bits & 1;

                        cur_state = tap_state_transition(cur_state, bit);
                        moves[i] = cur_state;
                }

                jtag_add_pathmove(tms_count, moves);
        } else if (tap_state_transition(cur_state, true)  == goal_state
                        || tap_state_transition(cur_state, false) == goal_state)
                jtag_add_pathmove(1, &goal_state);
        else
                return ERROR_FAIL;

        return ERROR_OK;
}

void jtag_add_runtest(int num_cycles, tap_state_t state)
{
        jtag_prelude(state);
        jtag_set_error(interface_jtag_add_runtest(num_cycles, state));
}


void jtag_add_clocks(int num_cycles)
{
        if (!tap_is_state_stable(cmd_queue_cur_state)) {
                LOG_ERROR("jtag_add_clocks() called with TAP in unstable state \"%s\"",
                        tap_state_name(cmd_queue_cur_state));
                jtag_set_error(ERROR_JTAG_NOT_STABLE_STATE);
                return;
        }

        if (num_cycles > 0) {
                jtag_checks();
                jtag_set_error(interface_jtag_add_clocks(num_cycles));
        }
}

void swd_add_reset(int req_srst)
{
        if (req_srst) {
                if (!(jtag_reset_config & RESET_HAS_SRST)) {
                        LOG_ERROR("BUG: can't assert SRST");
                        jtag_set_error(ERROR_FAIL);
                        return;
                }
                req_srst = 1;
        }

        /* Maybe change SRST signal state */
        if (jtag_srst != req_srst) {
                int retval;

                retval = interface_jtag_add_reset(0, req_srst);
                if (retval != ERROR_OK)
                        jtag_set_error(retval);
                else
                        retval = jtag_execute_queue();

                if (retval != ERROR_OK) {
                        LOG_ERROR("TRST/SRST error");
                        return;
                }

                /* SRST resets everything hooked up to that signal */
                jtag_srst = req_srst;
                if (jtag_srst) {
                        LOG_DEBUG("SRST line asserted");
                        if (adapter_nsrst_assert_width)
                                jtag_add_sleep(adapter_nsrst_assert_width * 1000);
                } else {
                        LOG_DEBUG("SRST line released");
                        if (adapter_nsrst_delay)
                                jtag_add_sleep(adapter_nsrst_delay * 1000);
                }
        }
}

void jtag_add_reset(int req_tlr_or_trst, int req_srst)
{
        int trst_with_tlr = 0;
        int new_srst = 0;
        int new_trst = 0;

        /* Without SRST, we must use target-specific JTAG operations
         * on each target; callers should not be requesting SRST when
         * that signal doesn't exist.
         *
         * RESET_SRST_PULLS_TRST is a board or chip level quirk, which
         * can kick in even if the JTAG adapter can't drive TRST.
         */
        if (req_srst) {
                if (!(jtag_reset_config & RESET_HAS_SRST)) {
                        LOG_ERROR("BUG: can't assert SRST");
                        jtag_set_error(ERROR_FAIL);
                        return;
                }
                if ((jtag_reset_config & RESET_SRST_PULLS_TRST) != 0
                                && !req_tlr_or_trst) {
                        LOG_ERROR("BUG: can't assert only SRST");
                        jtag_set_error(ERROR_FAIL);
                        return;
                }
                new_srst = 1;
        }

        /* JTAG reset (entry to TAP_RESET state) can always be achieved
         * using TCK and TMS; that may go through a TAP_{IR,DR}UPDATE
         * state first.  TRST accelerates it, and bypasses those states.
         *
         * RESET_TRST_PULLS_SRST is a board or chip level quirk, which
         * can kick in even if the JTAG adapter can't drive SRST.
         */
        if (req_tlr_or_trst) {
                if (!(jtag_reset_config & RESET_HAS_TRST))
                        trst_with_tlr = 1;
                else if ((jtag_reset_config & RESET_TRST_PULLS_SRST) != 0
                         && !req_srst)
                        trst_with_tlr = 1;
                else
                        new_trst = 1;
        }

        /* Maybe change TRST and/or SRST signal state */
        if (jtag_srst != new_srst || jtag_trst != new_trst) {
                int retval;

                retval = interface_jtag_add_reset(new_trst, new_srst);
                if (retval != ERROR_OK)
                        jtag_set_error(retval);
                else
                        retval = jtag_execute_queue();

                if (retval != ERROR_OK) {
                        LOG_ERROR("TRST/SRST error");
                        return;
                }
        }

        /* SRST resets everything hooked up to that signal */
        if (jtag_srst != new_srst) {
                jtag_srst = new_srst;
                if (jtag_srst) {
                        LOG_DEBUG("SRST line asserted");
                        if (adapter_nsrst_assert_width)
                                jtag_add_sleep(adapter_nsrst_assert_width * 1000);
                } else {
                        LOG_DEBUG("SRST line released");
                        if (adapter_nsrst_delay)
                                jtag_add_sleep(adapter_nsrst_delay * 1000);
                }
        }

        /* Maybe enter the JTAG TAP_RESET state ...
         *  - using only TMS, TCK, and the JTAG state machine
         *  - or else more directly, using TRST
         *
         * TAP_RESET should be invisible to non-debug parts of the system.
         */
        if (trst_with_tlr) {
                LOG_DEBUG("JTAG reset with TLR instead of TRST");
                jtag_add_tlr();

        } else if (jtag_trst != new_trst) {
                jtag_trst = new_trst;
                if (jtag_trst) {
                        LOG_DEBUG("TRST line asserted");
                        tap_set_state(TAP_RESET);
                        if (jtag_ntrst_assert_width)
                                jtag_add_sleep(jtag_ntrst_assert_width * 1000);
                } else {
                        LOG_DEBUG("TRST line released");
                        if (jtag_ntrst_delay)
                                jtag_add_sleep(jtag_ntrst_delay * 1000);

                        /* We just asserted nTRST, so we're now in TAP_RESET.
                         * Inform possible listeners about this, now that
                         * JTAG instructions and data can be shifted.  This
                         * sequence must match jtag_add_tlr().
                         */
                        jtag_call_event_callbacks(JTAG_TRST_ASSERTED);
                        jtag_notify_event(JTAG_TRST_ASSERTED);
                }
        }
}

void jtag_add_sleep(uint32_t us)
{
        /** @todo Here, keep_alive() appears to be a layering violation!!! */
        keep_alive();
        jtag_set_error(interface_jtag_add_sleep(us));
}

static int jtag_check_value_inner(uint8_t *captured, uint8_t *in_check_value,
        uint8_t *in_check_mask, int num_bits)
{
        int retval = ERROR_OK;
        int compare_failed;

        if (in_check_mask)
                compare_failed = buf_cmp_mask(captured, in_check_value, in_check_mask, num_bits);
        else
                compare_failed = buf_cmp(captured, in_check_value, num_bits);

        if (compare_failed) {
                char *captured_str, *in_check_value_str;
                int bits = (num_bits > DEBUG_JTAG_IOZ) ? DEBUG_JTAG_IOZ : num_bits;

                /* NOTE:  we've lost diagnostic context here -- 'which tap' */

                captured_str = buf_to_str(captured, bits, 16);
                in_check_value_str = buf_to_str(in_check_value, bits, 16);

                LOG_WARNING("Bad value '%s' captured during DR or IR scan:",
                        captured_str);
                LOG_WARNING(" check_value: 0x%s", in_check_value_str);

                free(captured_str);
                free(in_check_value_str);

                if (in_check_mask) {
                        char *in_check_mask_str;

                        in_check_mask_str = buf_to_str(in_check_mask, bits, 16);
                        LOG_WARNING(" check_mask: 0x%s", in_check_mask_str);
                        free(in_check_mask_str);
                }

                retval = ERROR_JTAG_QUEUE_FAILED;
        }
        return retval;
}

void jtag_check_value_mask(struct scan_field *field, uint8_t *value, uint8_t *mask)
{
        assert(field->in_value != NULL);

        if (value == NULL) {
                /* no checking to do */
                return;
        }

        jtag_execute_queue_noclear();

        int retval = jtag_check_value_inner(field->in_value, value, mask, field->num_bits);
        jtag_set_error(retval);
}

int default_interface_jtag_execute_queue(void)
{
        if (NULL == jtag) {
                LOG_ERROR("No JTAG interface configured yet.  "
                        "Issue 'init' command in startup scripts "
                        "before communicating with targets.");
                return ERROR_FAIL;
        }

        return jtag->execute_queue();
}

void jtag_execute_queue_noclear(void)
{
        jtag_flush_queue_count++;
        jtag_set_error(interface_jtag_execute_queue());

        if (jtag_flush_queue_sleep > 0) {
                /* For debug purposes it can be useful to test performance
                 * or behavior when delaying after flushing the queue,
                 * e.g. to simulate long roundtrip times.
                 */
                usleep(jtag_flush_queue_sleep * 1000);
        }
}

int jtag_get_flush_queue_count(void)
{
        return jtag_flush_queue_count;
}

int jtag_execute_queue(void)
{
        jtag_execute_queue_noclear();
        return jtag_error_clear();
}

static int jtag_reset_callback(enum jtag_event event, void *priv)
{
        struct jtag_tap *tap = priv;

        if (event == JTAG_TRST_ASSERTED) {
                tap->enabled = !tap->disabled_after_reset;

                /* current instruction is either BYPASS or IDCODE */
                buf_set_ones(tap->cur_instr, tap->ir_length);
                tap->bypass = 1;
        }

        return ERROR_OK;
}

/* sleep at least us microseconds. When we sleep more than 1000ms we
 * do an alive sleep, i.e. keep GDB alive. Note that we could starve
 * GDB if we slept for <1000ms many times.
 */
void jtag_sleep(uint32_t us)
{
        if (us < 1000)
                usleep(us);
        else
                alive_sleep((us+999)/1000);
}

/* Maximum number of enabled JTAG devices we expect in the scan chain,
 * plus one (to detect garbage at the end).  Devices that don't support
 * IDCODE take up fewer bits, possibly allowing a few more devices.
 */
#define JTAG_MAX_CHAIN_SIZE 20

#define EXTRACT_MFG(X)  (((X) & 0xffe) >> 1)
#define EXTRACT_PART(X) (((X) & 0xffff000) >> 12)
#define EXTRACT_VER(X)  (((X) & 0xf0000000) >> 28)

/* A reserved manufacturer ID is used in END_OF_CHAIN_FLAG, so we
 * know that no valid TAP will have it as an IDCODE value.
 */
#define END_OF_CHAIN_FLAG       0xffffffff

/* a larger IR length than we ever expect to autoprobe */
#define JTAG_IRLEN_MAX          60

static int jtag_examine_chain_execute(uint8_t *idcode_buffer, unsigned num_idcode)
{
        struct scan_field field = {
                .num_bits = num_idcode * 32,
                .out_value = idcode_buffer,
                .in_value = idcode_buffer,
        };

        /* initialize to the end of chain ID value */
        for (unsigned i = 0; i < JTAG_MAX_CHAIN_SIZE; i++)
                buf_set_u32(idcode_buffer, i * 32, 32, END_OF_CHAIN_FLAG);

        jtag_add_plain_dr_scan(field.num_bits, field.out_value, field.in_value, TAP_DRPAUSE);
        jtag_add_tlr();
        return jtag_execute_queue();
}

static bool jtag_examine_chain_check(uint8_t *idcodes, unsigned count)
{
        uint8_t zero_check = 0x0;
        uint8_t one_check = 0xff;

        for (unsigned i = 0; i < count * 4; i++) {
                zero_check |= idcodes[i];
                one_check &= idcodes[i];
        }

        /* if there wasn't a single non-zero bit or if all bits were one,
         * the scan is not valid.  We wrote a mix of both values; either
         *
         *  - There's a hardware issue (almost certainly):
         *     + all-zeroes can mean a target stuck in JTAG reset
         *     + all-ones tends to mean no target
         *  - The scan chain is WAY longer than we can handle, *AND* either
         *     + there are several hundreds of TAPs in bypass, or
         *     + at least a few dozen TAPs all have an all-ones IDCODE
         */
        if (zero_check == 0x00 || one_check == 0xff) {
                LOG_ERROR("JTAG scan chain interrogation failed: all %s",
                        (zero_check == 0x00) ? "zeroes" : "ones");
                LOG_ERROR("Check JTAG interface, timings, target power, etc.");
                return false;
        }
        return true;
}

static void jtag_examine_chain_display(enum log_levels level, const char *msg,
        const char *name, uint32_t idcode)
{
        log_printf_lf(level, __FILE__, __LINE__, __func__,
                "JTAG tap: %s %16.16s: 0x%08x "
                "(mfg: 0x%3.3x, part: 0x%4.4x, ver: 0x%1.1x)",
                name, msg,
                (unsigned int)idcode,
                (unsigned int)EXTRACT_MFG(idcode),
                (unsigned int)EXTRACT_PART(idcode),
                (unsigned int)EXTRACT_VER(idcode));
}

static bool jtag_idcode_is_final(uint32_t idcode)
{
        /*
         * Some devices, such as AVR8, will output all 1's instead
         * of TDI input value at end of chain. Allow those values
         * instead of failing.
         */
        return idcode == END_OF_CHAIN_FLAG;
}

/**
 * This helper checks that remaining bits in the examined chain data are
 * all as expected, but a single JTAG device requires only 64 bits to be
 * read back correctly.  This can help identify and diagnose problems
 * with the JTAG chain earlier, gives more helpful/explicit error messages.
 * Returns TRUE iff garbage was found.
 */
static bool jtag_examine_chain_end(uint8_t *idcodes, unsigned count, unsigned max)
{
        bool triggered = false;
        for (; count < max - 31; count += 32) {
                uint32_t idcode = buf_get_u32(idcodes, count, 32);

                /* do not trigger the warning if the data looks good */
                if (jtag_idcode_is_final(idcode))
                        continue;
                LOG_WARNING("Unexpected idcode after end of chain: %d 0x%08x",
                        count, (unsigned int)idcode);
                triggered = true;
        }
        return triggered;
}

static bool jtag_examine_chain_match_tap(const struct jtag_tap *tap)
{
        uint32_t idcode = tap->idcode;

        /* ignore expected BYPASS codes; warn otherwise */
        if (0 == tap->expected_ids_cnt && !idcode)
                return true;

        /* optionally ignore the JTAG version field - bits 28-31 of IDCODE */
        uint32_t mask = tap->ignore_version ? ~(0xf << 28) : ~0;

        idcode &= mask;

        /* Loop over the expected identification codes and test for a match */
        unsigned ii, limit = tap->expected_ids_cnt;

        for (ii = 0; ii < limit; ii++) {
                uint32_t expected = tap->expected_ids[ii] & mask;

                if (idcode == expected)
                        return true;

                /* treat "-expected-id 0" as a "don't-warn" wildcard */
                if (0 == tap->expected_ids[ii])
                        return true;
        }

        /* If none of the expected ids matched, warn */
        jtag_examine_chain_display(LOG_LVL_WARNING, "UNEXPECTED",
                tap->dotted_name, tap->idcode);
        for (ii = 0; ii < limit; ii++) {
                char msg[32];

                snprintf(msg, sizeof(msg), "expected %u of %u", ii + 1, limit);
                jtag_examine_chain_display(LOG_LVL_ERROR, msg,
                        tap->dotted_name, tap->expected_ids[ii]);
        }
        return false;
}

/* Try to examine chain layout according to IEEE 1149.1 §12
 * This is called a "blind interrogation" of the scan chain.
 */
static int jtag_examine_chain(void)
{
        uint8_t idcode_buffer[JTAG_MAX_CHAIN_SIZE * 4];
        unsigned bit_count;
        int retval;
        int tapcount = 0;
        bool autoprobe = false;

        /* DR scan to collect BYPASS or IDCODE register contents.
         * Then make sure the scan data has both ones and zeroes.
         */
        LOG_DEBUG("DR scan interrogation for IDCODE/BYPASS");
        retval = jtag_examine_chain_execute(idcode_buffer, JTAG_MAX_CHAIN_SIZE);
        if (retval != ERROR_OK)
                return retval;
        if (!jtag_examine_chain_check(idcode_buffer, JTAG_MAX_CHAIN_SIZE))
                return ERROR_JTAG_INIT_FAILED;

        /* point at the 1st tap */
        struct jtag_tap *tap = jtag_tap_next_enabled(NULL);

        if (!tap)
                autoprobe = true;

        for (bit_count = 0;
             tap && bit_count < (JTAG_MAX_CHAIN_SIZE * 32) - 31;
             tap = jtag_tap_next_enabled(tap)) {
                uint32_t idcode = buf_get_u32(idcode_buffer, bit_count, 32);

                if ((idcode & 1) == 0) {
                        /* Zero for LSB indicates a device in bypass */
                        LOG_INFO("TAP %s does not have IDCODE",
                                tap->dotted_name);
                        idcode = 0;
                        tap->hasidcode = false;

                        bit_count += 1;
                } else {
                        /* Friendly devices support IDCODE */
                        tap->hasidcode = true;
                        jtag_examine_chain_display(LOG_LVL_INFO,
                                "tap/device found",
                                tap->dotted_name, idcode);

                        bit_count += 32;
                }
                tap->idcode = idcode;

                /* ensure the TAP ID matches what was expected */
                if (!jtag_examine_chain_match_tap(tap))
                        retval = ERROR_JTAG_INIT_SOFT_FAIL;
        }

        /* Fail if too many TAPs were enabled for us to verify them all. */
        if (tap) {
                LOG_ERROR("Too many TAPs enabled; '%s' ignored.",
                        tap->dotted_name);
                return ERROR_JTAG_INIT_FAILED;
        }

        /* if autoprobing, the tap list is still empty ... populate it! */
        while (autoprobe && bit_count < (JTAG_MAX_CHAIN_SIZE * 32) - 31) {
                uint32_t idcode;
                char buf[12];

                /* Is there another TAP? */
                idcode = buf_get_u32(idcode_buffer, bit_count, 32);
                if (jtag_idcode_is_final(idcode))
                        break;

                /* Default everything in this TAP except IR length.
                 *
                 * REVISIT create a jtag_alloc(chip, tap) routine, and
                 * share it with jim_newtap_cmd().
                 */
                tap = calloc(1, sizeof *tap);
                if (!tap)
                        return ERROR_FAIL;

                sprintf(buf, "auto%d", tapcount++);
                tap->chip = strdup(buf);
                tap->tapname = strdup("tap");

                sprintf(buf, "%s.%s", tap->chip, tap->tapname);
                tap->dotted_name = strdup(buf);

                /* tap->ir_length == 0 ... signifying irlen autoprobe */
                tap->ir_capture_mask = 0x03;
                tap->ir_capture_value = 0x01;

                tap->enabled = true;

                if ((idcode & 1) == 0) {
                        bit_count += 1;
                        tap->hasidcode = false;
                } else {
                        bit_count += 32;
                        tap->hasidcode = true;
                        tap->idcode = idcode;

                        tap->expected_ids_cnt = 1;
                        tap->expected_ids = malloc(sizeof(uint32_t));
                        tap->expected_ids[0] = idcode;
                }

                LOG_WARNING("AUTO %s - use \"jtag newtap "
                        "%s %s -expected-id 0x%8.8" PRIx32 " ...\"",
                        tap->dotted_name, tap->chip, tap->tapname,
                        tap->idcode);

                jtag_tap_init(tap);
        }

        /* After those IDCODE or BYPASS register values should be
         * only the data we fed into the scan chain.
         */
        if (jtag_examine_chain_end(idcode_buffer, bit_count,
                    8 * sizeof(idcode_buffer))) {
                LOG_ERROR("double-check your JTAG setup (interface, "
                        "speed, missing TAPs, ...)");
                return ERROR_JTAG_INIT_FAILED;
        }

        /* Return success or, for backwards compatibility if only
         * some IDCODE values mismatched, a soft/continuable fault.
         */
        return retval;
}

/*
 * Validate the date loaded by entry to the Capture-IR state, to help
 * find errors related to scan chain configuration (wrong IR lengths)
 * or communication.
 *
 * Entry state can be anything.  On non-error exit, all TAPs are in
 * bypass mode.  On error exits, the scan chain is reset.
 */
static int jtag_validate_ircapture(void)
{
        struct jtag_tap *tap;
        int total_ir_length = 0;
        uint8_t *ir_test = NULL;
        struct scan_field field;
        uint64_t val;
        int chain_pos = 0;
        int retval;

        /* when autoprobing, accomodate huge IR lengths */
        for (tap = NULL, total_ir_length = 0;
                        (tap = jtag_tap_next_enabled(tap)) != NULL;
                        total_ir_length += tap->ir_length) {
                if (tap->ir_length == 0)
                        total_ir_length += JTAG_IRLEN_MAX;
        }

        /* increase length to add 2 bit sentinel after scan */
        total_ir_length += 2;

        ir_test = malloc(DIV_ROUND_UP(total_ir_length, 8));
        if (ir_test == NULL)
                return ERROR_FAIL;

        /* after this scan, all TAPs will capture BYPASS instructions */
        buf_set_ones(ir_test, total_ir_length);

        field.num_bits = total_ir_length;
        field.out_value = ir_test;
        field.in_value = ir_test;

        jtag_add_plain_ir_scan(field.num_bits, field.out_value, field.in_value, TAP_IDLE);

        LOG_DEBUG("IR capture validation scan");
        retval = jtag_execute_queue();
        if (retval != ERROR_OK)
                goto done;

        tap = NULL;
        chain_pos = 0;

        for (;; ) {
                tap = jtag_tap_next_enabled(tap);
                if (tap == NULL)
                        break;

                /* If we're autoprobing, guess IR lengths.  They must be at
                 * least two bits.  Guessing will fail if (a) any TAP does
                 * not conform to the JTAG spec; or (b) when the upper bits
                 * captured from some conforming TAP are nonzero.  Or if
                 * (c) an IR length is longer than 32 bits -- which is only
                 * an implementation limit, which could someday be raised.
                 *
                 * REVISIT optimization:  if there's a *single* TAP we can
                 * lift restrictions (a) and (b) by scanning a recognizable
                 * pattern before the all-ones BYPASS.  Check for where the
                 * pattern starts in the result, instead of an 0...01 value.
                 *
                 * REVISIT alternative approach: escape to some tcl code
                 * which could provide more knowledge, based on IDCODE; and
                 * only guess when that has no success.
                 */
                if (tap->ir_length == 0) {
                        tap->ir_length = 2;
                        while ((val = buf_get_u64(ir_test, chain_pos, tap->ir_length + 1)) == 1
                                        && tap->ir_length <= 64) {
                                tap->ir_length++;
                        }
                        LOG_WARNING("AUTO %s - use \"... -irlen %d\"",
                                jtag_tap_name(tap), tap->ir_length);
                }

                /* Validate the two LSBs, which must be 01 per JTAG spec.
                 *
                 * Or ... more bits could be provided by TAP declaration.
                 * Plus, some taps (notably in i.MX series chips) violate
                 * this part of the JTAG spec, so their capture mask/value
                 * attributes might disable this test.
                 */
                val = buf_get_u64(ir_test, chain_pos, tap->ir_length);
                if ((val & tap->ir_capture_mask) != tap->ir_capture_value) {
                        LOG_ERROR("%s: IR capture error; saw 0x%0*" PRIx64 " not 0x%0*" PRIx32,
                                jtag_tap_name(tap),
                                (tap->ir_length + 7) / tap->ir_length, val,
                                (tap->ir_length + 7) / tap->ir_length, tap->ir_capture_value);

                        retval = ERROR_JTAG_INIT_FAILED;
                        goto done;
                }
                LOG_DEBUG("%s: IR capture 0x%0*" PRIx64, jtag_tap_name(tap),
                        (tap->ir_length + 7) / tap->ir_length, val);
                chain_pos += tap->ir_length;
        }

        /* verify the '11' sentinel we wrote is returned at the end */
        val = buf_get_u64(ir_test, chain_pos, 2);
        if (val != 0x3) {
                char *cbuf = buf_to_str(ir_test, total_ir_length, 16);

                LOG_ERROR("IR capture error at bit %d, saw 0x%s not 0x...3",
                        chain_pos, cbuf);
                free(cbuf);
                retval = ERROR_JTAG_INIT_FAILED;
        }

done:
        free(ir_test);
        if (retval != ERROR_OK) {
                jtag_add_tlr();
                jtag_execute_queue();
        }
        return retval;
}

void jtag_tap_init(struct jtag_tap *tap)
{
        unsigned ir_len_bits;
        unsigned ir_len_bytes;

        /* if we're autoprobing, cope with potentially huge ir_length */
        ir_len_bits = tap->ir_length ? : JTAG_IRLEN_MAX;
        ir_len_bytes = DIV_ROUND_UP(ir_len_bits, 8);

        tap->expected = calloc(1, ir_len_bytes);
        tap->expected_mask = calloc(1, ir_len_bytes);
        tap->cur_instr = malloc(ir_len_bytes);

        /** @todo cope better with ir_length bigger than 32 bits */
        if (ir_len_bits > 32)
                ir_len_bits = 32;

        buf_set_u32(tap->expected, 0, ir_len_bits, tap->ir_capture_value);
        buf_set_u32(tap->expected_mask, 0, ir_len_bits, tap->ir_capture_mask);

        /* TAP will be in bypass mode after jtag_validate_ircapture() */
        tap->bypass = 1;
        buf_set_ones(tap->cur_instr, tap->ir_length);

        /* register the reset callback for the TAP */
        jtag_register_event_callback(&jtag_reset_callback, tap);
        jtag_tap_add(tap);

        LOG_DEBUG("Created Tap: %s @ abs position %d, "
                        "irlen %d, capture: 0x%x mask: 0x%x", tap->dotted_name,
                        tap->abs_chain_position, tap->ir_length,
                        (unsigned) tap->ir_capture_value,
                        (unsigned) tap->ir_capture_mask);
}

void jtag_tap_free(struct jtag_tap *tap)
{
        jtag_unregister_event_callback(&jtag_reset_callback, tap);

        /** @todo is anything missing? no memory leaks please */
        free(tap->expected);
        free(tap->expected_ids);
        free(tap->chip);
        free(tap->tapname);
        free(tap->dotted_name);
        free(tap);
}

/**
 * Do low-level setup like initializing registers, output signals,
 * and clocking.
 */
int adapter_init(struct command_context *cmd_ctx)
{
        if (jtag)
                return ERROR_OK;

        if (!jtag_interface) {
                /* nothing was previously specified by "interface" command */
                LOG_ERROR("Debug Adapter has to be specified, "
                        "see \"interface\" command");
                return ERROR_JTAG_INVALID_INTERFACE;
        }

        int retval;
        retval = jtag_interface->init();
        if (retval != ERROR_OK)
                return retval;
        jtag = jtag_interface;

        /* LEGACY SUPPORT ... adapter drivers  must declare what
         * transports they allow.  Until they all do so, assume
         * the legacy drivers are JTAG-only
         */
        if (!transports_are_declared()) {
                LOG_ERROR("Adapter driver '%s' did not declare "
                        "which transports it allows; assuming "
                        "JTAG-only", jtag->name);
                retval = allow_transports(cmd_ctx, jtag_only);
                if (retval != ERROR_OK)
                        return retval;
        }

        if (jtag->speed == NULL) {
                LOG_INFO("This adapter doesn't support configurable speed");
                return ERROR_OK;
        }

        if (CLOCK_MODE_UNSELECTED == clock_mode) {
                LOG_ERROR("An adapter speed is not selected in the init script."
                        " Insert a call to adapter_khz or jtag_rclk to proceed.");
                return ERROR_JTAG_INIT_FAILED;
        }

        int requested_khz = jtag_get_speed_khz();
        int actual_khz = requested_khz;
        int jtag_speed_var = 0;
        retval = jtag_get_speed(&jtag_speed_var);
        if (retval != ERROR_OK)
                return retval;
        retval = jtag->speed(jtag_speed_var);
        if (retval != ERROR_OK)
                return retval;
        retval = jtag_get_speed_readable(&actual_khz);
        if (ERROR_OK != retval)
                LOG_INFO("adapter-specific clock speed value %d", jtag_speed_var);
        else if (actual_khz) {
                /* Adaptive clocking -- JTAG-specific */
                if ((CLOCK_MODE_RCLK == clock_mode)
                                || ((CLOCK_MODE_KHZ == clock_mode) && !requested_khz)) {
                        LOG_INFO("RCLK (adaptive clock speed) not supported - fallback to %d kHz"
                        , actual_khz);
                } else
                        LOG_INFO("clock speed %d kHz", actual_khz);
        } else
                LOG_INFO("RCLK (adaptive clock speed)");

        return ERROR_OK;
}

int jtag_init_inner(struct command_context *cmd_ctx)
{
        struct jtag_tap *tap;
        int retval;
        bool issue_setup = true;

        LOG_DEBUG("Init JTAG chain");

        tap = jtag_tap_next_enabled(NULL);
        if (tap == NULL) {
                /* Once JTAG itself is properly set up, and the scan chain
                 * isn't absurdly large, IDCODE autoprobe should work fine.
                 *
                 * But ... IRLEN autoprobe can fail even on systems which
                 * are fully conformant to JTAG.  Also, JTAG setup can be
                 * quite finicky on some systems.
                 *
                 * REVISIT: if TAP autoprobe works OK, then in many cases
                 * we could escape to tcl code and set up targets based on
                 * the TAP's IDCODE values.
                 */
                LOG_WARNING("There are no enabled taps.  "
                        "AUTO PROBING MIGHT NOT WORK!!");

                /* REVISIT default clock will often be too fast ... */
        }

        jtag_add_tlr();
        retval = jtag_execute_queue();
        if (retval != ERROR_OK)
                return retval;

        /* Examine DR values first.  This discovers problems which will
         * prevent communication ... hardware issues like TDO stuck, or
         * configuring the wrong number of (enabled) TAPs.
         */
        retval = jtag_examine_chain();
        switch (retval) {
                case ERROR_OK:
                        /* complete success */
                        break;
                default:
                        /* For backward compatibility reasons, try coping with
                         * configuration errors involving only ID mismatches.
                         * We might be able to talk to the devices.
                         *
                         * Also the device might be powered down during startup.
                         *
                         * After OpenOCD starts, we can try to power on the device
                         * and run a reset.
                         */
                        LOG_ERROR("Trying to use configured scan chain anyway...");
                        issue_setup = false;
                        break;
        }

        /* Now look at IR values.  Problems here will prevent real
         * communication.  They mostly mean that the IR length is
         * wrong ... or that the IR capture value is wrong.  (The
         * latter is uncommon, but easily worked around:  provide
         * ircapture/irmask values during TAP setup.)
         */
        retval = jtag_validate_ircapture();
        if (retval != ERROR_OK) {
                /* The target might be powered down. The user
                 * can power it up and reset it after firing
                 * up OpenOCD.
                 */
                issue_setup = false;
        }

        if (issue_setup)
                jtag_notify_event(JTAG_TAP_EVENT_SETUP);
        else
                LOG_WARNING("Bypassing JTAG setup events due to errors");


        return ERROR_OK;
}

int adapter_quit(void)
{
        if (!jtag || !jtag->quit)
                return ERROR_OK;

        /* close the JTAG interface */
        int result = jtag->quit();
        if (ERROR_OK != result)
                LOG_ERROR("failed: %d", result);

        return ERROR_OK;
}

int swd_init_reset(struct command_context *cmd_ctx)
{
        int retval = adapter_init(cmd_ctx);
        if (retval != ERROR_OK)
                return retval;

        LOG_DEBUG("Initializing with hard SRST reset");

        if (jtag_reset_config & RESET_HAS_SRST)
                swd_add_reset(1);
        swd_add_reset(0);
        retval = jtag_execute_queue();
        return retval;
}

int jtag_init_reset(struct command_context *cmd_ctx)
{
        int retval = adapter_init(cmd_ctx);
        if (retval != ERROR_OK)
                return retval;

        LOG_DEBUG("Initializing with hard TRST+SRST reset");

        /*
         * This procedure is used by default when OpenOCD triggers a reset.
         * It's now done through an overridable Tcl "init_reset" wrapper.
         *
         * This started out as a more powerful "get JTAG working" reset than
         * jtag_init_inner(), applying TRST because some chips won't activate
         * JTAG without a TRST cycle (presumed to be async, though some of
         * those chips synchronize JTAG activation using TCK).
         *
         * But some chips only activate JTAG as part of an SRST cycle; SRST
         * got mixed in.  So it became a hard reset routine, which got used
         * in more places, and which coped with JTAG reset being forced as
         * part of SRST (srst_pulls_trst).
         *
         * And even more corner cases started to surface:  TRST and/or SRST
         * assertion timings matter; some chips need other JTAG operations;
         * TRST/SRST sequences can need to be different from these, etc.
         *
         * Systems should override that wrapper to support system-specific
         * requirements that this not-fully-generic code doesn't handle.
         *
         * REVISIT once Tcl code can read the reset_config modes, this won't
         * need to be a C routine at all...
         */
        jtag_add_reset(1, 0);   /* TAP_RESET, using TMS+TCK or TRST */
        if (jtag_reset_config & RESET_HAS_SRST) {
                jtag_add_reset(1, 1);
                if ((jtag_reset_config & RESET_SRST_PULLS_TRST) == 0)
                        jtag_add_reset(0, 1);
        }

        /* some targets enable us to connect with srst asserted */
        if (jtag_reset_config & RESET_CNCT_UNDER_SRST) {
                if (jtag_reset_config & RESET_SRST_NO_GATING)
                        jtag_add_reset(0, 1);
                else {
                        LOG_WARNING("\'srst_nogate\' reset_config option is required");
                        jtag_add_reset(0, 0);
                }
        } else
                jtag_add_reset(0, 0);
        retval = jtag_execute_queue();
        if (retval != ERROR_OK)
                return retval;

        /* Check that we can communication on the JTAG chain + eventually we want to
         * be able to perform enumeration only after OpenOCD has started
         * telnet and GDB server
         *
         * That would allow users to more easily perform any magic they need to before
         * reset happens.
         */
        return jtag_init_inner(cmd_ctx);
}

int jtag_init(struct command_context *cmd_ctx)
{
        int retval = adapter_init(cmd_ctx);
        if (retval != ERROR_OK)
                return retval;

        /* guard against oddball hardware: force resets to be inactive */
        jtag_add_reset(0, 0);

        /* some targets enable us to connect with srst asserted */
        if (jtag_reset_config & RESET_CNCT_UNDER_SRST) {
                if (jtag_reset_config & RESET_SRST_NO_GATING)
                        jtag_add_reset(0, 1);
                else
                        LOG_WARNING("\'srst_nogate\' reset_config option is required");
        }
        retval = jtag_execute_queue();
        if (retval != ERROR_OK)
                return retval;

        if (Jim_Eval_Named(cmd_ctx->interp, "jtag_init", __FILE__, __LINE__) != JIM_OK)
                return ERROR_FAIL;

        return ERROR_OK;
}

unsigned jtag_get_speed_khz(void)
{
        return speed_khz;
}

static int adapter_khz_to_speed(unsigned khz, int *speed)
{
        LOG_DEBUG("convert khz to interface specific speed value");
        speed_khz = khz;
        if (jtag != NULL) {
                LOG_DEBUG("have interface set up");
                int speed_div1;
                int retval = jtag->khz(jtag_get_speed_khz(), &speed_div1);
                if (ERROR_OK != retval)
                        return retval;
                *speed = speed_div1;
        }
        return ERROR_OK;
}

static int jtag_rclk_to_speed(unsigned fallback_speed_khz, int *speed)
{
        int retval = adapter_khz_to_speed(0, speed);
        if ((ERROR_OK != retval) && fallback_speed_khz) {
                LOG_DEBUG("trying fallback speed...");
                retval = adapter_khz_to_speed(fallback_speed_khz, speed);
        }
        return retval;
}

static int jtag_set_speed(int speed)
{
        jtag_speed = speed;
        /* this command can be called during CONFIG,
         * in which case jtag isn't initialized */
        return jtag ? jtag->speed(speed) : ERROR_OK;
}

int jtag_config_khz(unsigned khz)
{
        LOG_DEBUG("handle jtag khz");
        clock_mode = CLOCK_MODE_KHZ;
        int speed = 0;
        int retval = adapter_khz_to_speed(khz, &speed);
        return (ERROR_OK != retval) ? retval : jtag_set_speed(speed);
}

int jtag_config_rclk(unsigned fallback_speed_khz)
{
        LOG_DEBUG("handle jtag rclk");
        clock_mode = CLOCK_MODE_RCLK;
        rclk_fallback_speed_khz = fallback_speed_khz;
        int speed = 0;
        int retval = jtag_rclk_to_speed(fallback_speed_khz, &speed);
        return (ERROR_OK != retval) ? retval : jtag_set_speed(speed);
}

int jtag_get_speed(int *speed)
{
        switch (clock_mode) {
                case CLOCK_MODE_KHZ:
                        adapter_khz_to_speed(jtag_get_speed_khz(), speed);
                        break;
                case CLOCK_MODE_RCLK:
                        jtag_rclk_to_speed(rclk_fallback_speed_khz, speed);
                        break;
                default:
                        LOG_ERROR("BUG: unknown jtag clock mode");
                        return ERROR_FAIL;
        }
        return ERROR_OK;
}

int jtag_get_speed_readable(int *khz)
{
        int jtag_speed_var = 0;
        int retval = jtag_get_speed(&jtag_speed_var);
        if (retval != ERROR_OK)
                return retval;
        return jtag ? jtag->speed_div(jtag_speed_var, khz) : ERROR_OK;
}

void jtag_set_verify(bool enable)
{
        jtag_verify = enable;
}

bool jtag_will_verify()
{
        return jtag_verify;
}

void jtag_set_verify_capture_ir(bool enable)
{
        jtag_verify_capture_ir = enable;
}

bool jtag_will_verify_capture_ir()
{
        return jtag_verify_capture_ir;
}

int jtag_power_dropout(int *dropout)
{
        if (jtag == NULL) {
                /* TODO: as the jtag interface is not valid all
                 * we can do at the moment is exit OpenOCD */
                LOG_ERROR("No Valid JTAG Interface Configured.");
                exit(-1);
        }
        return jtag->power_dropout(dropout);
}

int jtag_srst_asserted(int *srst_asserted)
{
        return jtag->srst_asserted(srst_asserted);
}

enum reset_types jtag_get_reset_config(void)
{
        return jtag_reset_config;
}
void jtag_set_reset_config(enum reset_types type)
{
        jtag_reset_config = type;
}

int jtag_get_trst(void)
{
        return jtag_trst;
}
int jtag_get_srst(void)
{
        return jtag_srst;
}

void jtag_set_nsrst_delay(unsigned delay)
{
        adapter_nsrst_delay = delay;
}
unsigned jtag_get_nsrst_delay(void)
{
        return adapter_nsrst_delay;
}
void jtag_set_ntrst_delay(unsigned delay)
{
        jtag_ntrst_delay = delay;
}
unsigned jtag_get_ntrst_delay(void)
{
        return jtag_ntrst_delay;
}


void jtag_set_nsrst_assert_width(unsigned delay)
{
        adapter_nsrst_assert_width = delay;
}
unsigned jtag_get_nsrst_assert_width(void)
{
        return adapter_nsrst_assert_width;
}
void jtag_set_ntrst_assert_width(unsigned delay)
{
        jtag_ntrst_assert_width = delay;
}
unsigned jtag_get_ntrst_assert_width(void)
{
        return jtag_ntrst_assert_width;
}

static int jtag_select(struct command_context *ctx)
{
        int retval;

        /* NOTE:  interface init must already have been done.
         * That works with only C code ... no Tcl glue required.
         */

        retval = jtag_register_commands(ctx);

        if (retval != ERROR_OK)
                return retval;

        retval = svf_register_commands(ctx);

        if (retval != ERROR_OK)
                return retval;

        return xsvf_register_commands(ctx);
}

static struct transport jtag_transport = {
        .name = "jtag",
        .select = jtag_select,
        .init = jtag_init,
};

static void jtag_constructor(void) __attribute__((constructor));
static void jtag_constructor(void)
{
        transport_register(&jtag_transport);
}

/** Returns true if the current debug session
 * is using JTAG as its transport.
 */
bool transport_is_jtag(void)
{
        return get_current_transport() == &jtag_transport;
}

void adapter_assert_reset(void)
{
        if (transport_is_jtag()) {
                if (jtag_reset_config & RESET_SRST_PULLS_TRST)
                        jtag_add_reset(1, 1);
                else
                        jtag_add_reset(0, 1);
        } else if (transport_is_swd())
                swd_add_reset(1);
        else if (transport_is_cmsis_dap())
                swd_add_reset(1);  /* FIXME */
        else if (get_current_transport() != NULL)
                LOG_ERROR("reset is not supported on %s",
                        get_current_transport()->name);
        else
                LOG_ERROR("transport is not selected");
}

void adapter_deassert_reset(void)
{
        if (transport_is_jtag())
                jtag_add_reset(0, 0);
        else if (transport_is_swd())
                swd_add_reset(0);
        else if (transport_is_cmsis_dap())
                swd_add_reset(0);  /* FIXME */
        else if (get_current_transport() != NULL)
                LOG_ERROR("reset is not supported on %s",
                        get_current_transport()->name);
        else
                LOG_ERROR("transport is not selected");
}