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JTAG: simple autoprobing

This patch adds basic autoprobing support for the JTAG scan chains
which cooperate.  To use, you can invoke OpenOCD with just:

 - interface spec: "-f interface/...cfg"
 - possibly with "-c 'reset_config ...'" for SRST/TRST
 - possibly with "-c 'jtag_khz ...'" for the JTAG clock

Then set up config files matching the reported TAPs.  It doesn't
declare targets ... just TAPs.  So facilities above the JTAG and
SVF/XSVF levels won't be available without a real config; this is
almost purely a way to generate diagnostics.

Autoprobe was successful with most boards I tested, except ones
incorporating C55x DSPs (which don't cooperate with this scheme
for IR length autodetection).  Here's what one multi-TAP chip
reported, with the "Warn:" prefixes removed:

 clock speed 500 kHz
 There are no enabled taps.  AUTO PROBING MIGHT NOT WORK!!
 AUTO auto0.tap - use "jtag newtap auto0 tap -expected-id 0x2b900f0f ..."
 AUTO auto1.tap - use "jtag newtap auto1 tap -expected-id 0x07926001 ..."
 AUTO auto2.tap - use "jtag newtap auto2 tap -expected-id 0x0b73b02f ..."
 AUTO auto0.tap - use "... -irlen 4"
 AUTO auto1.tap - use "... -irlen 4"
 AUTO auto2.tap - use "... -irlen 6"
 no gdb ports allocated as no target has been specified

The patch tweaks IR setup a bit, so we can represent TAPs with
undeclared IR length.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
tags/v0.3.0-rc0
David Brownell 12 years ago
parent
commit
6cb1d10cda
2 changed files with 109 additions and 14 deletions
  1. +7
    -2
      TODO
  2. +102
    -12
      src/jtag/core.c

+ 7
- 2
TODO View File

@@ -55,8 +55,10 @@ directly in minidriver API for better embedded host performance.

The following tasks have been suggested for adding new core JTAG support:

- autodetect devices present on the scan chain
- implement 'discover_taps' command
- Improve autodetection of TAPs by supporting tcl escape procedures that
can configure discovered TAPs based on IDCODE value ... they could:
- Remove guessing for irlen
- Allow non-default irmask/ircapture values
- SPI/UART emulation:
- (ab)use bit-banging JTAG interfaces to emulate SPI/UART
- allow SPI to program flash, MCUs, etc.
@@ -94,6 +96,8 @@ interface support:
- FT2232 (libftdi):
- make performance comparable to alternatives (on Win32, D2XX is faster)
- make usability comparable to alternatives
- Autodetect USB based adapters; this should be easy on Linux. If there's
more than one, list the options; otherwise, just select that one.

The following tasks have been suggested for adding new JTAG interfaces:

@@ -133,6 +137,7 @@ Once the above are completed:

@section thelisttargets Target Support

- Many common ARM cores could be autodetected using IDCODE
- general layer cleanup: @par
https://lists.berlios.de/pipermail/openocd-development/2009-May/006590.html
- regression: "reset halt" between 729(works) and 788(fails): @par


+ 102
- 12
src/jtag/core.c View File

@@ -890,6 +890,9 @@ void jtag_sleep(uint32_t us)
*/
#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 = {
@@ -1027,6 +1030,8 @@ static int jtag_examine_chain(void)
uint8_t idcode_buffer[JTAG_MAX_CHAIN_SIZE * 4];
unsigned bit_count;
int retval;
int tapcount = 0;
bool autoprobe = false;

/* DR scan to collect BYPASS or IDCODE register contents.
* Then make sure the scan data has both ones and zeroes.
@@ -1040,11 +1045,9 @@ static int jtag_examine_chain(void)

/* 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;
}

if (!tap)
autoprobe = true;

for (bit_count = 0;
tap && bit_count < (JTAG_MAX_CHAIN_SIZE * 32) - 31;
@@ -1086,6 +1089,59 @@ static int jtag_examine_chain(void)
return ERROR_JTAG_INIT_FAILED;
}

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

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

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

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

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

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

tap->enabled = true;

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

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

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

jtag_tap_init(tap);
}

/* After those IDCODE or BYPASS register values should be
* only the data we fed into the scan chain.
*/
@@ -1120,10 +1176,13 @@ static int jtag_validate_ircapture(void)
int chain_pos = 0;
int retval;

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

/* increase length to add 2 bit sentinel after scan */
total_ir_length += 2;
@@ -1156,6 +1215,25 @@ static int jtag_validate_ircapture(void)
break;
}

/* If we're autoprobing, guess IR lengths. They must be at
* least two bits. Guessing will fail if (a) any TAP does
* not conform to the JTAG spec; or (b) when the upper bits
* captured from some conforming TAP are nonzero.
*
* REVISIT alternative approach: escape to some tcl code
* which could provide more knowledge, based on IDCODE; and
* only guess when that has no success.
*/
if (tap->ir_length == 0) {
tap->ir_length = 2;
while ((val = buf_get_u32(ir_test, chain_pos,
tap->ir_length + 1)) == 1) {
tap->ir_length++;
}
LOG_WARNING("AUTO %s - use \"... -irlen %d\"",
jtag_tap_name(tap), tap->ir_length);
}

/* Validate the two LSBs, which must be 01 per JTAG spec.
*
* Or ... more bits could be provided by TAP declaration.
@@ -1207,9 +1285,8 @@ void jtag_tap_init(jtag_tap_t *tap)
unsigned ir_len_bits;
unsigned ir_len_bytes;

assert(0 != tap->ir_length);

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

tap->expected = calloc(1, ir_len_bytes);
@@ -1302,8 +1379,21 @@ int jtag_init_inner(struct command_context_s *cmd_ctx)

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

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

jtag_add_tlr();


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