Updates to the initial scanchain validation code:
[fw/openocd] / src / jtag / core.c
index b13b48809f421a7a752c7a664690c03d24375160..b1d3ca0f1abb107b0aa1d4067ed7b83b79fe9151 100644 (file)
@@ -2,7 +2,7 @@
  *   Copyright (C) 2005 by Dominic Rath                                    *
  *   Dominic.Rath@gmx.de                                                   *
  *                                                                         *
- *   Copyright (C) 2007,2008 Øyvind Harboe                                 *
+ *   Copyright (C) 2007,2008 Øyvind Harboe                                 *
  *   oyvind.harboe@zylin.com                                               *
  *                                                                         *
  *   Copyright (C) 2009 SoftPLC Corporation                                *
@@ -60,11 +60,16 @@ static int jtag_error = ERROR_OK;
 
 static const char *jtag_event_strings[] =
 {
-       [JTAG_TRST_ASSERTED] = "JTAG controller reset (RESET or TRST)",
+       [JTAG_TRST_ASSERTED] = "TAP reset",
        [JTAG_TAP_EVENT_ENABLE] = "TAP enabled",
+       [JTAG_TAP_EVENT_POST_RESET] = "TAP post reset",
        [JTAG_TAP_EVENT_DISABLE] = "TAP disabled",
 };
 
+/*
+ * JTAG adapters must initialize with TRST and SRST de-asserted
+ * (they're negative logic, so that means *high*)
+ */
 static int jtag_trst = 0;
 static int jtag_srst = 0;
 
@@ -101,8 +106,9 @@ 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;
+/* 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;
@@ -162,10 +168,22 @@ void jtag_tap_add(struct jtag_tap_s *t)
        *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))
@@ -178,7 +196,16 @@ jtag_tap_t *jtag_tap_by_string(const char *s)
        if (parse_uint(s, &n) != ERROR_OK)
                return NULL;
 
-       return jtag_tap_by_position(n);
+       /* 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)
@@ -192,17 +219,6 @@ jtag_tap_t *jtag_tap_by_jim_obj(Jim_Interp *interp, Jim_Obj *o)
        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();
@@ -324,6 +340,8 @@ void jtag_add_ir_scan_noverify(int in_count, const scan_field_t *in_fields,
 
 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 */
@@ -346,6 +364,8 @@ void jtag_add_ir_scan(int in_num_fields, scan_field_t *in_fields, tap_state_t st
 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(
@@ -365,7 +385,8 @@ void jtag_add_callback4(jtag_callback_t f, jtag_callback_data_t data0,
        interface_jtag_add_callback4(f, data0, data1, data2, data3);
 }
 
-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_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)
 {
@@ -424,6 +445,8 @@ void jtag_add_dr_scan_check(int in_num_fields, scan_field_t *in_fields, tap_stat
 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;
@@ -434,6 +457,8 @@ void jtag_add_dr_scan(int in_num_fields, const scan_field_t *in_fields,
 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;
@@ -445,6 +470,7 @@ 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;
@@ -458,7 +484,10 @@ 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_reset();
 }
 
 void jtag_add_pathmove(int num_states, const tap_state_t *path)
@@ -570,102 +599,105 @@ void jtag_add_clocks(int 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;
 
-       /* FIX!!! there are *many* different cases here. A better
-        * approach is needed for legal combinations of transitions...
+       /* 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 ((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");
+       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;
        }
 
-       /* 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;
+       /* 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;
        }
 
-       /* 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;
-       }
+       /* Maybe change TRST and/or SRST signal state */
+       if (jtag_srst != new_srst || jtag_trst != new_trst) {
+               int retval;
 
-       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;
-       }
+               retval = interface_jtag_add_reset(new_trst, new_srst);
+               if (retval != ERROR_OK)
+                       jtag_set_error(retval);
+               else
+                       retval = jtag_execute_queue();
 
-       if (req_tlr_or_trst)
-       {
-               if (!trst_with_tlr && (jtag_reset_config & RESET_HAS_TRST))
-               {
-                       jtag_trst = 1;
-               } else
-               {
-                       trst_with_tlr = 1;
+               if (retval != ERROR_OK) {
+                       LOG_ERROR("TRST/SRST error %d", retval);
+                       return;
                }
-       } 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);
+       /* 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");
+               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");
+       /* 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();
-               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);
+       } else if (jtag_trst != new_trst) {
+               jtag_trst = new_trst;
+               if (jtag_trst) {
+                       LOG_DEBUG("TRST line asserted");
+                       tap_set_state(TAP_RESET);
+               } 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_reset();
+               }
        }
 }
 
@@ -693,7 +725,8 @@ void jtag_add_sleep(uint32_t us)
        jtag_set_error(interface_jtag_add_sleep(us));
 }
 
-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_inner(uint8_t *captured, uint8_t *in_check_value,
+               uint8_t *in_check_mask, int num_bits)
 {
        int retval = ERROR_OK;
 
@@ -705,39 +738,32 @@ int jtag_check_value_inner(uint8_t *captured, uint8_t *in_check_value, uint8_t *
                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);
-                       }
+               char *captured_str, *in_check_value_str;
+               int bits = (num_bits > DEBUG_JTAG_IOZ)
+                               ? DEBUG_JTAG_IOZ
+                               : num_bits;
 
-                       free(captured_char);
-                       free(in_check_value_char);
+               /* NOTE:  we've lost diagnostic context here -- 'which tap' */
 
-                       retval = ERROR_JTAG_QUEUE_FAILED;
+               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;
 }
@@ -794,12 +820,11 @@ 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;
 
+               /* current instruction is either BYPASS or IDCODE */
                buf_set_ones(tap->cur_instr, tap->ir_length);
                tap->bypass = 1;
        }
@@ -812,13 +837,21 @@ void jtag_sleep(uint32_t us)
        alive_sleep(us/1000);
 }
 
-/// maximum number of JTAG devices expected in the chain
+/* 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
+
 static int jtag_examine_chain_execute(uint8_t *idcode_buffer, unsigned num_idcode)
 {
        scan_field_t field = {
@@ -830,9 +863,10 @@ static int jtag_examine_chain_execute(uint8_t *idcode_buffer, unsigned num_idcod
 
        // 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);
+               buf_set_u32(idcode_buffer, i * 32, 32, END_OF_CHAIN_FLAG);
 
-       jtag_add_plain_dr_scan(1, &field, TAP_RESET);
+       jtag_add_plain_dr_scan(1, &field, TAP_DRPAUSE);
+       jtag_add_tlr();
        return jtag_execute_queue();
 }
 
@@ -864,16 +898,21 @@ static void jtag_examine_chain_display(enum log_levels level, const char *msg,
        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, 
+                                 name, msg,
                                  (unsigned int)idcode,
-                                 (unsigned int)EXTRACT_MFG(idcode), 
-                                 (unsigned int)EXTRACT_PART(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)
 {
-               return idcode == 0x000000FF || idcode == 0xFFFFFFFF;
+       /*
+        * 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;
 }
 
 /**
@@ -881,8 +920,9 @@ static bool jtag_idcode_is_final(uint32_t idcode)
  * 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 void jtag_examine_chain_end(uint8_t *idcodes, unsigned count, unsigned max)
+static bool jtag_examine_chain_end(uint8_t *idcodes, unsigned count, unsigned max)
 {
        bool triggered = false;
        for (; count < max - 31; count += 32)
@@ -895,35 +935,25 @@ static void jtag_examine_chain_end(uint8_t *idcodes, unsigned count, unsigned ma
                                        count, (unsigned int)idcode);
                triggered = true;
        }
+       return triggered;
 }
 
 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
+       /* 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 */
        uint8_t ii;
        for (ii = 0; ii < tap->expected_ids_cnt; ii++)
        {
                if (tap->idcode == tap->expected_ids[ii])
-                       break;
+                       return true;
        }
 
        /* 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",
+       jtag_examine_chain_display(LOG_LVL_ERROR, "UNEXPECTED",
                        tap->dotted_name, tap->idcode);
        for (ii = 0; ii < tap->expected_ids_cnt; ii++)
        {
@@ -937,14 +967,17 @@ static bool jtag_examine_chain_match_tap(const struct jtag_tap_s *tap)
 }
 
 /* Try to examine chain layout according to IEEE 1149.1 §12
+ * This is called a "blind interrogation" of the scan chain.
  */
-int jtag_examine_chain(void)
+static int jtag_examine_chain(void)
 {
        uint8_t idcode_buffer[JTAG_MAX_CHAIN_SIZE * 4];
-       unsigned device_count = 0;
+       unsigned bit_count;
 
+       /* DR scan to collect BYPASS or IDCODE register contents.
+        * Then make sure the scan data has both ones and zeroes.
+        */
        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;
 
@@ -956,65 +989,64 @@ int jtag_examine_chain(void)
                return ERROR_JTAG_INIT_FAILED;
        }
 
-       for (unsigned bit_count = 0; bit_count < (JTAG_MAX_CHAIN_SIZE * 32) - 31;)
+       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)
                {
                        /* LSB must not be 0, this indicates a device in bypass */
-                       LOG_WARNING("Tap/Device does not have IDCODE");
+                       LOG_WARNING("TAP %s does not have IDCODE",
+                                       tap->dotted_name);
                        idcode = 0;
+                       tap->hasidcode = false;
 
                        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;
-                       }
-
+                       /* Friendly devices support IDCODE */
+                       tap->hasidcode = true;
                        jtag_examine_chain_display(LOG_LVL_INFO, "tap/device found",
-                                       tap ? tap->dotted_name : "(not-named)",
-                                       idcode);
+                                       tap->dotted_name, 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))
+               if (!jtag_examine_chain_match_tap(tap))
                        return ERROR_JTAG_INIT_FAILED;
+       }
 
-               tap = jtag_tap_next_enabled(tap);
+       /* 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;
        }
 
-       /* 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, ...)");
+       /* 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, TAPs, ...)");
                return ERROR_JTAG_INIT_FAILED;
        }
 
        return ERROR_OK;
 }
 
-int jtag_validate_chain(void)
+/*
+ * 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.
+ */
+static int jtag_validate_ircapture(void)
 {
        jtag_tap_t *tap;
        int total_ir_length = 0;
@@ -1033,7 +1065,11 @@ int jtag_validate_chain(void)
        }
 
        total_ir_length += 2;
+
        ir_test = malloc(CEIL(total_ir_length, 8));
+       if (ir_test == NULL)
+               return ERROR_FAIL;
+
        buf_set_ones(ir_test, total_ir_length);
 
        field.tap = NULL;
@@ -1042,8 +1078,13 @@ int jtag_validate_chain(void)
        field.in_value = ir_test;
 
 
-       jtag_add_plain_ir_scan(1, &field, TAP_RESET);
-       jtag_execute_queue();
+       jtag_add_plain_ir_scan(1, &field, TAP_IRPAUSE);
+       jtag_add_tlr();
+
+       int retval;
+       retval = jtag_execute_queue();
+       if (retval != ERROR_OK)
+               return retval;
 
        tap = NULL;
        chain_pos = 0;
@@ -1054,23 +1095,37 @@ int jtag_validate_chain(void)
                        break;
                }
 
+               /* Validate the two LSBs, which must be 01 per JTAG spec.
+                * REVISIT we might be able to verify some MSBs too, using
+                * ircapture/irmask attributes.
+                */
                val = buf_get_u32(ir_test, chain_pos, 2);
-               if (val != 0x1)
-               {
+               if (val != 1) {
                        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;
+
+                       LOG_ERROR("%s: IR capture error; saw 0x%s not 0x..1",
+                                       jtag_tap_name(tap), cbuf);
+
+                       /* Fail only if we have IDCODE for this device.
+                        * REVISIT -- why not fail-always?
+                        */
+                       if (tap->hasidcode) {
+                               free(cbuf);
+                               free(ir_test);
+                               return ERROR_JTAG_INIT_FAILED;
+                       }
                }
                chain_pos += tap->ir_length;
        }
 
+       /* verify the '11' sentinel we wrote is returned at the end */
        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);
+
+               LOG_ERROR("IR capture error at bit %d, saw 0x%s not 0x...3",
+                               chain_pos, cbuf);
                free(cbuf);
                free(ir_test);
                return ERROR_JTAG_INIT_FAILED;
@@ -1086,6 +1141,7 @@ void jtag_tap_init(jtag_tap_t *tap)
 {
        assert(0 != tap->ir_length);
 
+       /// @todo fix, this allocates one byte per bit for all three fields!
        tap->expected = malloc(tap->ir_length);
        tap->expected_mask = malloc(tap->ir_length);
        tap->cur_instr = malloc(tap->ir_length);
@@ -1103,7 +1159,8 @@ void jtag_tap_init(jtag_tap_t *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 int)(tap->ir_capture_value), (unsigned int)(tap->ir_capture_mask));
+                               (unsigned) tap->ir_capture_value,
+                               (unsigned) tap->ir_capture_mask);
        jtag_tap_add(tap);
 }
 
@@ -1111,7 +1168,8 @@ void jtag_tap_free(jtag_tap_t *tap)
 {
        jtag_unregister_event_callback(&jtag_reset_callback, tap);
 
-       /// @todo is anything missing? no memory leaks please 
+       /// @todo is anything missing? no memory leaks please
+       free((void *)tap->expected);
        free((void *)tap->expected_ids);
        free((void *)tap->chip);
        free((void *)tap->tapname);
@@ -1130,16 +1188,33 @@ int jtag_interface_init(struct command_context_s *cmd_ctx)
                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;
-       }
 
+       jtag = jtag_interface;
        if (jtag_interface->init() != ERROR_OK)
+       {
+               jtag = NULL;
                return ERROR_JTAG_INIT_FAILED;
+       }
+
+       int requested_khz = jtag_get_speed_khz();
+       int actual_khz = requested_khz;
+       int retval = jtag_get_speed_readable(&actual_khz);
+       if (ERROR_OK != retval)
+               LOG_INFO("interface specific clock speed value %d", jtag_get_speed());
+       else if (actual_khz)
+       {
+               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)");
 
-       jtag = jtag_interface;
        return ERROR_OK;
 }
 
@@ -1166,9 +1241,9 @@ static int jtag_init_inner(struct command_context_s *cmd_ctx)
                LOG_ERROR("trying to validate configured JTAG chain anyway...");
        }
 
-       if (jtag_validate_chain() != ERROR_OK)
+       if (jtag_validate_ircapture() != ERROR_OK)
        {
-               LOG_WARNING("Could not validate JTAG chain, continuing anyway...");
+               LOG_WARNING("Errors during IR capture, continuing anyway...");
        }
 
        return ERROR_OK;
@@ -1195,11 +1270,11 @@ int jtag_init_reset(struct command_context_s *cmd_ctx)
        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");
+       LOG_DEBUG("Trying to bring the JTAG controller to life by asserting TRST / TLR");
 
        /* Reset can happen after a power cycle.
         *
-        * Ideally we would only assert TRST or run RESET before the target reset.
+        * Ideally we would only assert TRST or run TLR before the target reset.
         *
         * However w/srst_pulls_trst, trst is asserted together with the target
         * reset whether we want it or not.
@@ -1212,7 +1287,7 @@ int jtag_init_reset(struct command_context_s *cmd_ctx)
         * NB! order matters!!!! srst *can* disconnect JTAG circuitry
         *
         */
-       jtag_add_reset(1, 0); /* RESET or TRST */
+       jtag_add_reset(1, 0); /* TAP_RESET, using TMS+TCK or TRST */
        if (jtag_reset_config & RESET_HAS_SRST)
        {
                jtag_add_reset(1, 1);
@@ -1245,20 +1320,15 @@ int jtag_init(struct command_context_s *cmd_ctx)
        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;
+static int jtag_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");
@@ -1266,33 +1336,84 @@ int jtag_config_khz(unsigned khz)
                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;
+               *speed = speed_div1;
        }
-       return jtag_set_speed(cur_speed);
+       return ERROR_OK;
 }
 
-int jtag_get_speed(void)
+static int jtag_rclk_to_speed(unsigned fallback_speed_khz, int* speed)
 {
-       return jtag_speed;
+       int retval = jtag_khz_to_speed(0, speed);
+       if ((ERROR_OK != retval) && fallback_speed_khz)
+       {
+               LOG_DEBUG("trying fallback speed...");
+               retval = jtag_khz_to_speed(fallback_speed_khz, speed);
+       }
+       return retval;
 }
 
-int jtag_set_speed(int speed)
+static 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)
+int jtag_config_speed(int speed)
+{
+       LOG_DEBUG("handle jtag speed");
+       clock_mode = CLOCK_MODE_SPEED;
+       return jtag_set_speed(speed);
+}
+
+int jtag_config_khz(unsigned khz)
+{
+       LOG_DEBUG("handle jtag khz");
+       clock_mode = CLOCK_MODE_KHZ;
+       int speed = 0;
+       int retval = jtag_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(void)
 {
-       return jtag ? jtag->speed_div(jtag_get_speed(), speed) : ERROR_OK;
+       int speed;
+       switch(clock_mode)
+       {
+               case CLOCK_MODE_SPEED:
+                       speed = jtag_speed;
+                       break;
+               case CLOCK_MODE_KHZ:
+                       jtag_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");
+                       speed = 0;
+                       break;
+       }
+       return speed;
 }
 
+int jtag_get_speed_readable(int *khz)
+{
+       return jtag ? jtag->speed_div(jtag_get_speed(), khz) : ERROR_OK;
+}
 
 void jtag_set_verify(bool enable)
 {