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.,                                       *
 *   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] = "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 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 */
static int jtag_nsrst_assert_width = 0; /* width of assertion */
static int jtag_ntrst_assert_width = 0; /* width of assertion */

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;
/* speed to fallback to when RCLK is requested but not supported */
static int rclk_fallback_speed_khz = 0;
static enum {CLOCK_MODE_SPEED, CLOCK_MODE_KHZ, CLOCK_MODE_RCLK} clock_mode;
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;
}

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

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;
}

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

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;
}

/* returns a pointer to the n-th device in the scan chain */
static inline 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_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;

	/* 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;
}

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;
}

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)
	{
		jtag_event_callback_t *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_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)
{
	assert(state != TAP_RESET);

	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)
{
	assert(state != TAP_RESET);

	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, jtag_callback_data_t data0)
{
	interface_jtag_add_callback(f, data0);
}

void jtag_add_callback4(jtag_callback_t f, jtag_callback_data_t data0,
		jtag_callback_data_t data1, jtag_callback_data_t data2,
		jtag_callback_data_t data3)
{
	interface_jtag_add_callback4(f, data0, data1, data2, data3);
}

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(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, (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);
		}
		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)
{
	assert(state != TAP_RESET);

	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)
{
	assert(state != TAP_RESET);

	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 uint32_t* value,
		tap_state_t end_state)
{
	assert(end_state != TAP_RESET);
	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());

	/* NOTE: order here matches TRST path in jtag_add_reset() */
	jtag_call_event_callbacks(JTAG_TRST_ASSERTED);
	jtag_notify_event(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 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 < 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;
	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 %d", retval);
			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 (jtag_nsrst_assert_width)
				jtag_add_sleep(jtag_nsrst_assert_width * 1000);
		}
		else {
			LOG_DEBUG("SRST line released");
			if (jtag_nsrst_delay)
				jtag_add_sleep(jtag_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_set_end_state(TAP_RESET);
		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);
		}
	}
}

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(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 = 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) {
		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(scan_field_t *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());
}

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;

	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;
}

void jtag_sleep(uint32_t us)
{
	alive_sleep(us/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	0x000000ff

/* 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)
{
	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, END_OF_CHAIN_FLAG);

	jtag_add_plain_dr_scan(1, &field, 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__, __FUNCTION__,
				  "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 || 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.
 * 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_s *tap)
{
	/* ignore expected BYPASS codes; warn otherwise */
	if (0 == tap->expected_ids_cnt && !tap->idcode)
		return true;

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