diff --git a/src/jtag/core.c b/src/jtag/core.c
index bf4a9cc7f69a54c27a46d2d5d22e07c0977d8aea..f9ebb3fa6f50d9ed401fb66f11932832f9ae1901 100644
--- a/src/jtag/core.c
+++ b/src/jtag/core.c
@@ -837,13 +837,18 @@ 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)
+#define END_OF_CHAIN_FLAG 0x000000ff
+
static int jtag_examine_chain_execute(uint8_t *idcode_buffer, unsigned num_idcode)
{
scan_field_t field = {
@@ -855,7 +860,7 @@ 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_DRPAUSE);
jtag_add_tlr();
@@ -899,7 +904,12 @@ static void jtag_examine_chain_display(enum log_levels level, const char *msg,
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;
}
/**
@@ -907,8 +917,9 @@ 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)
@@ -921,19 +932,14 @@ 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;
@@ -944,7 +950,7 @@ static bool jtag_examine_chain_match_tap(const struct jtag_tap_s *tap)
}
/* If none of the expected ids matched, log an error */
- 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++)
{
@@ -962,10 +968,12 @@ static bool jtag_examine_chain_match_tap(const struct jtag_tap_s *tap)
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;
@@ -977,7 +985,7 @@ static int jtag_examine_chain(void)
return ERROR_JTAG_INIT_FAILED;
}
- for (unsigned bit_count = 0;
+ for (bit_count = 0;
tap && bit_count < (JTAG_MAX_CHAIN_SIZE * 32) - 31;
tap = jtag_tap_next_enabled(tap))
{
@@ -995,26 +1003,13 @@ static int jtag_examine_chain(void)
}
else
{
+ /* Friendly devices support IDCODE */
tap->hasidcode = true;
-
- /*
- * 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->dotted_name, idcode);
bit_count += 32;
}
- device_count++;
tap->idcode = idcode;
// ensure the TAP ID does matches what was expected
@@ -1022,14 +1017,20 @@ static int jtag_examine_chain(void)
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, ...)");
+ /* 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;
+ }
+
+ /* 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;
}