David Brownell <david-b@pacbell.net>:

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

/***************************************************************************
 *   Copyright (C) 2005 by Dominic Rath                                    *
 *   Dominic.Rath@gmx.de                                                   *
 *                                                                         *
 *   Copyright (C) 2007,2008 Øyvind Harboe                                 *
 *   oyvind.harboe@zylin.com                                               *
 *                                                                         *
 *   Copyright (C) 2009 SoftPLC Corporation                                *
 *       http://softplc.com                                                *
 *   dick@softplc.com                                                      *
 *                                                                         *
 *   Copyright (C) 2009 Zachary T Welch                                    *
 *   zw@superlucidity.net                                                  *
 *                                                                         *
 *   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.,                                       *
 *   59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.             *
 ***************************************************************************/
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include "jtag.h"
#include "minidriver.h"
#include "interface.h"

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


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

static void jtag_add_scan_check(void (*jtag_add_scan)(int in_num_fields, const scan_field_t *in_fields, tap_state_t state),
                int in_num_fields, scan_field_t *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().
 *
 * Tts value may be checked with jtag_get_error() and cleared with
 * jtag_error_clear().  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] = "JTAG controller reset (RESET or TRST)",
        [JTAG_TAP_EVENT_ENABLE] = "TAP enabled",
        [JTAG_TAP_EVENT_DISABLE] = "TAP disabled",
};

static int jtag_trst = 0;
static int jtag_srst = 0;

/**
 * List all TAPs that have been created.
 */
static jtag_tap_t *__jtag_all_taps = NULL;
/**
 * 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 = 0;

static enum reset_types jtag_reset_config = RESET_NONE;
static tap_state_t cmd_queue_end_state = TAP_RESET;
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 jtag_nsrst_delay = 0; /* default to no nSRST delay */
static int jtag_ntrst_delay = 0; /* default to no nTRST delay */

typedef struct jtag_event_callback_s
{
        jtag_event_handler_t          callback;
        void*                         priv;
        struct jtag_event_callback_s* next;
} jtag_event_callback_t;

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

/* speed in kHz*/
static int speed_khz = 0;
/* flag if the kHz speed was defined */
static bool hasKHz = false;
static int jtag_speed = 0;

static struct jtag_interface_s *jtag = NULL;

/* configuration */
jtag_interface_t *jtag_interface = NULL;

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


jtag_tap_t *jtag_all_taps(void)
{
        return __jtag_all_taps;
};

unsigned jtag_tap_count(void)
{
        return jtag_num_taps;
}

unsigned jtag_tap_count_enabled(void)
{
        jtag_tap_t *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_s *t)
{
        t->abs_chain_position = jtag_num_taps++;

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

jtag_tap_t *jtag_tap_by_string(const char *s)
{
        /* try by name first */
        jtag_tap_t *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;

        return jtag_tap_by_position(n);
}

jtag_tap_t *jtag_tap_by_jim_obj(Jim_Interp *interp, Jim_Obj *o)
{
        const char *cp = Jim_GetString(o, NULL);
        jtag_tap_t *t = cp ? jtag_tap_by_string(cp) : NULL;
        if (NULL == cp)
                cp = "(unknown)";
        if (NULL == t)
                Jim_SetResult_sprintf(interp, "Tap '%s' could not be found", cp);
        return t;
}

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

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

        return t;
}

jtag_tap_t* jtag_tap_next_enabled(jtag_tap_t* 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 jtag_tap_t *tap)
{
        return (tap == NULL) ? "(unknown)" : tap->dotted_name;
}


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

        if (callback == NULL)
        {
                return ERROR_INVALID_ARGUMENTS;
        }

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

        (*callbacks_p) = malloc(sizeof(jtag_event_callback_t));
        (*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)
{
        jtag_event_callback_t **callbacks_p;
        jtag_event_callback_t **next;

        if (callback == NULL)
        {
                return ERROR_INVALID_ARGUMENTS;
        }

        for (callbacks_p = &jtag_event_callbacks;
                        *callbacks_p != NULL;
                        callbacks_p = next)
        {
                next = &((*callbacks_p)->next);

                if ((*callbacks_p)->priv != priv)
                        continue;

                if ((*callbacks_p)->callback == callback)
                {
                        free(*callbacks_p);
                        *callbacks_p = *next;
                }
        }

        return ERROR_OK;
}

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

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

        while (callback)
        {
                callback->callback(event, callback->priv);
                callback = 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_alloc_in_value32(scan_field_t *field)
{
        interface_jtag_alloc_in_value32(field);
}

void jtag_add_ir_scan_noverify(int in_count, const scan_field_t *in_fields,
                tap_state_t state)
{
        jtag_prelude(state);

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


void jtag_add_ir_scan(int in_num_fields, scan_field_t *in_fields, tap_state_t state)
{
        if (jtag_verify&&jtag_verify_capture_ir)
        {
                /* 8 x 32 bit id's is enough for all invocations */

                for (int j = 0; j < in_num_fields; j++)
                {
                        /* 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[j].check_value=in_fields[j].tap->expected;
                        in_fields[j].check_mask=in_fields[j].tap->expected_mask;
                }
                jtag_add_scan_check(jtag_add_ir_scan_noverify, in_num_fields, in_fields, state);
        } else
        {
                jtag_add_ir_scan_noverify(in_num_fields, in_fields, state);
        }
}

void jtag_add_plain_ir_scan(int in_num_fields, const scan_field_t *in_fields,
                tap_state_t state)
{
        jtag_prelude(state);

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

void jtag_add_callback(jtag_callback1_t f, u8 *in)
{
        interface_jtag_add_callback(f, in);
}

void jtag_add_callback4(jtag_callback_t f, u8 *in,
                jtag_callback_data_t data1, jtag_callback_data_t data2,
                jtag_callback_data_t data3)
{
        interface_jtag_add_callback4(f, in, data1, data2, data3);
}

int jtag_check_value_inner(u8 *captured, u8 *in_check_value, u8 *in_check_mask, int num_bits);

static int jtag_check_value_mask_callback(u8 *in, jtag_callback_data_t data1, jtag_callback_data_t data2, jtag_callback_data_t data3)
{
        return jtag_check_value_inner(in, (u8 *)data1, (u8 *)data2, (int)data3);
}

static void jtag_add_scan_check(void (*jtag_add_scan)(int in_num_fields, const scan_field_t *in_fields, tap_state_t state),
                int in_num_fields, scan_field_t *in_fields, tap_state_t state)
{
        for (int i = 0; i < in_num_fields; i++)
        {
                struct scan_field_s *field = &in_fields[i];
                field->allocated = 0;
                field->modified = 0;
                if (field->check_value || field->in_value)
                        continue;
                interface_jtag_add_scan_check_alloc(field);
                field->modified = 1;
        }

        jtag_add_scan(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, 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);
                }
                if (in_fields[i].allocated)
                {
                        free(in_fields[i].in_value);
                }
                if (in_fields[i].modified)
                {
                        in_fields[i].in_value = NULL;
                }
        }
}

void jtag_add_dr_scan_check(int in_num_fields, scan_field_t *in_fields, tap_state_t state)
{
        if (jtag_verify)
        {
                jtag_add_scan_check(jtag_add_dr_scan, in_num_fields, in_fields, state);
        } else
        {
                jtag_add_dr_scan(in_num_fields, in_fields, state);
        }
}


void jtag_add_dr_scan(int in_num_fields, const scan_field_t *in_fields,
                tap_state_t state)
{
        jtag_prelude(state);

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

void jtag_add_plain_dr_scan(int in_num_fields, const scan_field_t *in_fields,
                tap_state_t state)
{
        jtag_prelude(state);

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

void jtag_add_dr_out(jtag_tap_t* tap,
                int num_fields, const int* num_bits, const u32* value,
                tap_state_t end_state)
{
        assert(end_state != TAP_INVALID);

        cmd_queue_cur_state = end_state;

        interface_jtag_add_dr_out(tap,
                        num_fields, num_bits, value,
                        end_state);
}

void jtag_add_tlr(void)
{
        jtag_prelude(TAP_RESET);
        jtag_set_error(interface_jtag_add_tlr());
        jtag_call_event_callbacks(JTAG_TRST_ASSERTED);
}

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;

        LOG_DEBUG( "cur_state=%s goal_state=%s",
                tap_state_name(cur_state),
                tap_state_name(goal_state) );


        if (goal_state==cur_state )
                ;       /* nothing to do */
        else if( goal_state==TAP_RESET )
        {
                jtag_add_tlr();
        }
        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 < DIM(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 jtag_add_reset(int req_tlr_or_trst, int req_srst)
{
        int trst_with_tlr = 0;

        /* FIX!!! there are *many* different cases here. A better
         * approach is needed for legal combinations of transitions...
         */
        if ((jtag_reset_config & RESET_HAS_SRST)&&
                        (jtag_reset_config & RESET_HAS_TRST)&&
                        ((jtag_reset_config & RESET_SRST_PULLS_TRST)==0))
        {
                if (((req_tlr_or_trst&&!jtag_trst)||
                                (!req_tlr_or_trst&&jtag_trst))&&
                                ((req_srst&&!jtag_srst)||
                                                (!req_srst&&jtag_srst)))
                {
                        /* FIX!!! srst_pulls_trst allows 1,1 => 0,0 transition.... */
                        //LOG_ERROR("BUG: transition of req_tlr_or_trst and req_srst in the same jtag_add_reset() call is undefined");
                }
        }

        /* Make sure that jtag_reset_config allows the requested reset */
        /* if SRST pulls TRST, we can't fulfill srst == 1 with trst == 0 */
        if (((jtag_reset_config & RESET_SRST_PULLS_TRST) && (req_srst == 1)) && (!req_tlr_or_trst))
        {
                LOG_ERROR("BUG: requested reset would assert trst");
                jtag_set_error(ERROR_FAIL);
                return;
        }

        /* if TRST pulls SRST, we reset with TAP T-L-R */
        if (((jtag_reset_config & RESET_TRST_PULLS_SRST) && (req_tlr_or_trst)) && (req_srst == 0))
        {
                trst_with_tlr = 1;
        }

        if (req_srst && !(jtag_reset_config & RESET_HAS_SRST))
        {
                LOG_ERROR("BUG: requested SRST assertion, but the current configuration doesn't support this");
                jtag_set_error(ERROR_FAIL);
                return;
        }

        if (req_tlr_or_trst)
        {
                if (!trst_with_tlr && (jtag_reset_config & RESET_HAS_TRST))
                {
                        jtag_trst = 1;
                } else
                {
                        trst_with_tlr = 1;
                }
        } else
        {
                jtag_trst = 0;
        }

        jtag_srst = req_srst;

        int retval = interface_jtag_add_reset(jtag_trst, jtag_srst);
        if (retval != ERROR_OK)
        {
                jtag_set_error(retval);
                return;
        }
        jtag_execute_queue();

        if (jtag_srst)
        {
                LOG_DEBUG("SRST line asserted");
        }
        else
        {
                LOG_DEBUG("SRST line released");
                if (jtag_nsrst_delay)
                        jtag_add_sleep(jtag_nsrst_delay * 1000);
        }

        if (trst_with_tlr)
        {
                LOG_DEBUG("JTAG reset with RESET instead of TRST");
                jtag_set_end_state(TAP_RESET);
                jtag_add_tlr();
                return;
        }

        if (jtag_trst)
        {
                /* we just asserted nTRST, so we're now in Test-Logic-Reset,
                 * and inform possible listeners about this
                 */
                LOG_DEBUG("TRST line asserted");
                tap_set_state(TAP_RESET);
                jtag_call_event_callbacks(JTAG_TRST_ASSERTED);
        }
        else
        {
                if (jtag_ntrst_delay)
                        jtag_add_sleep(jtag_ntrst_delay * 1000);
        }
}

tap_state_t jtag_set_end_state(tap_state_t state)
{
        if ((state == TAP_DRSHIFT)||(state == TAP_IRSHIFT))
        {
                LOG_ERROR("BUG: TAP_DRSHIFT/IRSHIFT can't be end state. Calling code should use a larger scan field");
        }

        if (state!=TAP_INVALID)
                cmd_queue_end_state = state;
        return cmd_queue_end_state;
}

tap_state_t jtag_get_end_state(void)
{
        return cmd_queue_end_state;
}

void jtag_add_sleep(u32 us)
{
        /// @todo Here, keep_alive() appears to be a layering violation!!!
        keep_alive();
        jtag_set_error(interface_jtag_add_sleep(us));
}

int jtag_check_value_inner(u8 *captured, u8 *in_check_value, u8 *in_check_mask, int num_bits)
{
        int retval = ERROR_OK;

        int compare_failed = 0;

        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){
                /* An error handler could have caught the failing check
                 * only report a problem when there wasn't a handler, or if the handler
                 * acknowledged the error
                 */
                /*
                LOG_WARNING("TAP %s:",
                                        jtag_tap_name(field->tap));
                                        */
                if (compare_failed)
                {
                        char *captured_char = buf_to_str(captured, (num_bits > DEBUG_JTAG_IOZ) ? DEBUG_JTAG_IOZ : num_bits, 16);
                        char *in_check_value_char = buf_to_str(in_check_value, (num_bits > DEBUG_JTAG_IOZ) ? DEBUG_JTAG_IOZ : num_bits, 16);

                        if (in_check_mask)
                        {
                                char *in_check_mask_char;
                                in_check_mask_char = buf_to_str(in_check_mask, (num_bits > DEBUG_JTAG_IOZ) ? DEBUG_JTAG_IOZ : num_bits, 16);
                                LOG_WARNING("value captured during scan didn't pass the requested check:");
                                LOG_WARNING("captured: 0x%s check_value: 0x%s check_mask: 0x%s",
                                                        captured_char, in_check_value_char, in_check_mask_char);
                                free(in_check_mask_char);
                        }
                        else
                        {
                                LOG_WARNING("value captured during scan didn't pass the requested check: captured: 0x%s check_value: 0x%s", captured_char, in_check_value_char);
                        }

                        free(captured_char);
                        free(in_check_value_char);

                        retval = ERROR_JTAG_QUEUE_FAILED;
                }

        }
        return retval;
}

void jtag_check_value_mask(scan_field_t *field, u8 *value, u8 *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());
}

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)
{
        jtag_tap_t *tap = priv;

        LOG_DEBUG("-");

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

                buf_set_ones(tap->cur_instr, tap->ir_length);
                tap->bypass = 1;
        }

        return ERROR_OK;
}

void jtag_sleep(u32 us)
{
        alive_sleep(us/1000);
}

/// maximum number of JTAG devices expected in the chain
#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)

static int jtag_examine_chain_execute(u8 *idcode_buffer, unsigned num_idcode)
{
        scan_field_t field = {
                        .tap = NULL,
                        .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, 0x000000FF);

        jtag_add_plain_dr_scan(1, &field, TAP_RESET);
        return jtag_execute_queue();
}

static bool jtag_examine_chain_check(u8 *idcodes, unsigned count)
{
        u8 zero_check = 0x0;
        u8 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 */
        if (zero_check == 0x00 || one_check == 0xff)
        {
                LOG_ERROR("JTAG communication failure: check connection, "
                        "JTAG interface, target power etc.");
                return false;
        }
        return true;
}

static void jtag_examine_chain_display(enum log_levels level, const char *msg,
                const char *name, u32 idcode)
{
        log_printf_lf(level, __FILE__, __LINE__, __FUNCTION__,
                        "JTAG tap: %s %16.16s: 0x%08x "
                        "(mfg: 0x%3.3x, part: 0x%4.4x, ver: 0x%1.1x)",
                name, msg, idcode,
                EXTRACT_MFG(idcode), EXTRACT_PART(idcode), EXTRACT_VER(idcode) );
}

static bool jtag_idcode_is_final(u32 idcode)
{
                return idcode == 0x000000FF || idcode == 0xFFFFFFFF;
}

/**
 * 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.
 */
static void jtag_examine_chain_end(u8 *idcodes, unsigned count, unsigned max)
{
        bool triggered = false;
        for ( ; count < max - 31; count += 32)
        {
                u32 idcode = buf_get_u32(idcodes, count, 32);
                // do not trigger the warning if the data looks good
                if (!triggered && jtag_idcode_is_final(idcode))
                        continue;
                LOG_WARNING("Unexpected idcode after end of chain: %d 0x%08x",
                                count, idcode);
                triggered = true;
        }
}

static bool jtag_examine_chain_match_tap(const struct jtag_tap_s *tap)
{
        if (0 == tap->expected_ids_cnt)
        {
                /// @todo Enable LOG_INFO to ask for reports about unknown TAP IDs.
#if 0
                LOG_INFO("Uknown JTAG TAP ID: 0x%08x", tap->idcode)
                LOG_INFO("Please report the chip name and reported ID code to the openocd project");
#endif
                return true;
        }

        /* Loop over the expected identification codes and test for a match */
        u8 ii;
        for (ii = 0; ii < tap->expected_ids_cnt; ii++)
        {
                if (tap->idcode == tap->expected_ids[ii])
                        break;
        }

        /* If none of the expected ids matched, log an error */
        if (ii != tap->expected_ids_cnt)
        {
                LOG_INFO("JTAG Tap/device matched");
                return true;
        }
        jtag_examine_chain_display(LOG_LVL_ERROR, "got",
                        tap->dotted_name, tap->idcode);
        for (ii = 0; ii < tap->expected_ids_cnt; ii++)
        {
                char msg[32];
                snprintf(msg, sizeof(msg), "expected %hhu of %hhu",
                                ii + 1, tap->expected_ids_cnt);
                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
 */
int jtag_examine_chain(void)
{
        u8 idcode_buffer[JTAG_MAX_CHAIN_SIZE * 4];
        unsigned device_count = 0;

        jtag_examine_chain_execute(idcode_buffer, JTAG_MAX_CHAIN_SIZE);

        if (!jtag_examine_chain_check(idcode_buffer, JTAG_MAX_CHAIN_SIZE))
                return ERROR_JTAG_INIT_FAILED;

        /* point at the 1st tap */
        jtag_tap_t *tap = jtag_tap_next_enabled(NULL);
        if (tap == NULL)
        {
                LOG_ERROR("JTAG: No taps enabled?");
                return ERROR_JTAG_INIT_FAILED;
        }

        for (unsigned bit_count = 0; bit_count < (JTAG_MAX_CHAIN_SIZE * 32) - 31;)
        {
                u32 idcode = buf_get_u32(idcode_buffer, bit_count, 32);
                if ((idcode & 1) == 0)
                {
                        /* LSB must not be 0, this indicates a device in bypass */
                        LOG_WARNING("Tap/Device does not have IDCODE");
                        idcode = 0;

                        bit_count += 1;
                }
                else
                {
                        /*
                         * End of chain (invalid manufacturer ID) some devices, such
                         * as AVR will output all 1's instead of TDI input value at
                         * end of chain.
                         */
                        if (jtag_idcode_is_final(idcode))
                        {
                                jtag_examine_chain_end(idcode_buffer,
                                                bit_count + 32, JTAG_MAX_CHAIN_SIZE * 32);
                                break;
                        }

                        jtag_examine_chain_display(LOG_LVL_INFO, "tap/device found",
                                        tap ? tap->dotted_name : "(not-named)",
                                        idcode);

                        bit_count += 32;
                }
                device_count++;
                if (!tap)
                        continue;

                tap->idcode = idcode;

                // ensure the TAP ID does matches what was expected
                if (!jtag_examine_chain_match_tap(tap))
                        return ERROR_JTAG_INIT_FAILED;

                tap = jtag_tap_next_enabled(tap);
        }

        /* see if number of discovered devices matches configuration */
        if (device_count != jtag_tap_count_enabled())
        {
                LOG_ERROR("number of discovered devices in JTAG chain (%i) "
                                "does not match (enabled) configuration (%i), total taps: %d",
                                device_count, jtag_tap_count_enabled(), jtag_tap_count());
                LOG_ERROR("check the config file and ensure proper JTAG communication"
                                " (connections, speed, ...)");
                return ERROR_JTAG_INIT_FAILED;
        }

        return ERROR_OK;
}

int jtag_validate_chain(void)
{
        jtag_tap_t *tap;
        int total_ir_length = 0;
        u8 *ir_test = NULL;
        scan_field_t field;
        int chain_pos = 0;

        tap = NULL;
        total_ir_length = 0;
        for(;;){
                tap = jtag_tap_next_enabled(tap);
                if( tap == NULL ){
                        break;
                }
                total_ir_length += tap->ir_length;
        }

        total_ir_length += 2;
        ir_test = malloc(CEIL(total_ir_length, 8));
        buf_set_ones(ir_test, total_ir_length);

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


        jtag_add_plain_ir_scan(1, &field, TAP_RESET);
        jtag_execute_queue();

        tap = NULL;
        chain_pos = 0;
        int val;
        for(;;){
                tap = jtag_tap_next_enabled(tap);
                if( tap == NULL ){
                        break;
                }

                val = buf_get_u32(ir_test, chain_pos, 2);
                if (val != 0x1)
                {
                        char *cbuf = buf_to_str(ir_test, total_ir_length, 16);
                        LOG_ERROR("Could not validate JTAG scan chain, IR mismatch, scan returned 0x%s. tap=%s pos=%d expected 0x1 got %0x", cbuf, jtag_tap_name(tap), chain_pos, val);
                        free(cbuf);
                        free(ir_test);
                        return ERROR_JTAG_INIT_FAILED;
                }
                chain_pos += tap->ir_length;
        }

        val = buf_get_u32(ir_test, chain_pos, 2);
        if (val != 0x3)
        {
                char *cbuf = buf_to_str(ir_test, total_ir_length, 16);
                LOG_ERROR("Could not validate end of JTAG scan chain, IR mismatch, scan returned 0x%s. pos=%d expected 0x3 got %0x", cbuf, chain_pos, val);
                free(cbuf);
                free(ir_test);
                return ERROR_JTAG_INIT_FAILED;
        }

        free(ir_test);

        return ERROR_OK;
}


void jtag_tap_init(jtag_tap_t *tap)
{
        assert(0 != tap->ir_length);

        tap->expected = malloc(tap->ir_length);
        tap->expected_mask = malloc(tap->ir_length);
        tap->cur_instr = malloc(tap->ir_length);

        /// @todo cope sanely with ir_length bigger than 32 bits
        buf_set_u32(tap->expected, 0, tap->ir_length, tap->ir_capture_value);
        buf_set_u32(tap->expected_mask, 0, tap->ir_length, tap->ir_capture_mask);
        buf_set_ones(tap->cur_instr, tap->ir_length);

        // place TAP in bypass mode
        tap->bypass = 1;
        // register the reset callback for the TAP
        jtag_register_event_callback(&jtag_reset_callback, 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,
                                tap->ir_capture_value, tap->ir_capture_mask);
        jtag_tap_add(tap);
}

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

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

int jtag_interface_init(struct command_context_s *cmd_ctx)
{
        if (jtag)
                return ERROR_OK;

        if (!jtag_interface)
        {
                /* nothing was previously specified by "interface" command */
                LOG_ERROR("JTAG interface has to be specified, see \"interface\" command");
                return ERROR_JTAG_INVALID_INTERFACE;
        }
        if(hasKHz)
        {
                jtag_interface->khz(jtag_get_speed_khz(), &jtag_speed);
                hasKHz = false;
        }

        if (jtag_interface->init() != ERROR_OK)
                return ERROR_JTAG_INIT_FAILED;

        jtag = jtag_interface;
        return ERROR_OK;
}

static int jtag_init_inner(struct command_context_s *cmd_ctx)
{
        jtag_tap_t *tap;
        int retval;

        LOG_DEBUG("Init JTAG chain");

        tap = jtag_tap_next_enabled(NULL);
        if( tap == NULL ){
                LOG_ERROR("There are no enabled taps?");
                return ERROR_JTAG_INIT_FAILED;
        }

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

        /* examine chain first, as this could discover the real chain layout */
        if (jtag_examine_chain() != ERROR_OK)
        {
                LOG_ERROR("trying to validate configured JTAG chain anyway...");
        }

        if (jtag_validate_chain() != ERROR_OK)
        {
                LOG_WARNING("Could not validate JTAG chain, continuing anyway...");
        }

        return ERROR_OK;
}

int jtag_interface_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 jtag_init_reset(struct command_context_s *cmd_ctx)
{
        int retval;

        if ((retval=jtag_interface_init(cmd_ctx)) != ERROR_OK)
                return retval;

        LOG_DEBUG("Trying to bring the JTAG controller to life by asserting TRST / RESET");

        /* Reset can happen after a power cycle.
         *
         * Ideally we would only assert TRST or run RESET before the target reset.
         *
         * However w/srst_pulls_trst, trst is asserted together with the target
         * reset whether we want it or not.
         *
         * NB! Some targets have JTAG circuitry disabled until a
         * trst & srst has been asserted.
         *
         * NB! here we assume nsrst/ntrst delay are sufficient!
         *
         * NB! order matters!!!! srst *can* disconnect JTAG circuitry
         *
         */
        jtag_add_reset(1, 0); /* RESET 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);
        }
        jtag_add_reset(0, 0);
        if ((retval = jtag_execute_queue()) != 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_s *cmd_ctx)
{
        int retval;
        if ((retval=jtag_interface_init(cmd_ctx)) != ERROR_OK)
                return retval;
        if (jtag_init_inner(cmd_ctx)==ERROR_OK)
        {
                return ERROR_OK;
        }
        return jtag_init_reset(cmd_ctx);
}

void jtag_set_speed_khz(unsigned khz)
{
        speed_khz = khz;
}
unsigned jtag_get_speed_khz(void)
{
        return speed_khz;
}
int jtag_config_khz(unsigned khz)
{
        LOG_DEBUG("handle jtag khz");
        jtag_set_speed_khz(khz);

        int cur_speed = 0;
        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)
                {
                        jtag_set_speed_khz(0);
                        return retval;
                }
                cur_speed = speed_div1;
        }
        return jtag_set_speed(cur_speed);
}

int jtag_get_speed(void)
{
        return jtag_speed;
}

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

int jtag_get_speed_readable(int *speed)
{
        return jtag ? jtag->speed_div(jtag_get_speed(), speed) : 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)
{
        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)
{
        jtag_nsrst_delay = delay;
}
unsigned jtag_get_nsrst_delay(void)
{
        return jtag_nsrst_delay;
}
void jtag_set_ntrst_delay(unsigned delay)
{
        jtag_ntrst_delay = delay;
}
unsigned jtag_get_ntrst_delay(void)
{
        return jtag_ntrst_delay;
}