From 40c9668b703389890d30ab5a410e39f6f1e5251e Mon Sep 17 00:00:00 2001 From: David Brownell Date: Thu, 8 Oct 2009 09:16:01 -0700 Subject: [PATCH] Stop ignoring most scan chain validation errors Among other things this causes startup errors to kick in the fallback "reset harder" logic during server startup. Comments are also updated a bit, explaining what the various error paths signify (in at least my observation). There's one class of validation error that we can still plausibly ignore: when wrong IDCODE values are observed. This change seems to have helped make an OMAP5912 behave much more reliably. There's still some post-reset flakiness, but it's unrelated to scan verification. Signed-off-by: David Brownell --- src/jtag/core.c | 64 +++++++++++++++++++++++++++++++++++++------------ src/jtag/jtag.h | 1 + 2 files changed, 50 insertions(+), 15 deletions(-) diff --git a/src/jtag/core.c b/src/jtag/core.c index f7d55b793..b8235eb1e 100644 --- a/src/jtag/core.c +++ b/src/jtag/core.c @@ -892,7 +892,15 @@ static bool jtag_examine_chain_check(uint8_t *idcodes, unsigned count) } /* if there wasn't a single non-zero bit or if all bits were one, - * the scan is not valid */ + * 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", @@ -988,11 +996,14 @@ static int jtag_examine_chain(void) { uint8_t idcode_buffer[JTAG_MAX_CHAIN_SIZE * 4]; unsigned bit_count; + int retval; /* 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); + retval = jtag_examine_chain_execute(idcode_buffer, JTAG_MAX_CHAIN_SIZE); + if (retval != ERROR_OK) + return retval; if (!jtag_examine_chain_check(idcode_buffer, JTAG_MAX_CHAIN_SIZE)) return ERROR_JTAG_INIT_FAILED; @@ -1012,7 +1023,7 @@ static int jtag_examine_chain(void) if ((idcode & 1) == 0) { - /* LSB must not be 0, this indicates a device in bypass */ + /* Zero for LSB indicates a device in bypass */ LOG_WARNING("TAP %s does not have IDCODE", tap->dotted_name); idcode = 0; @@ -1024,7 +1035,8 @@ static int jtag_examine_chain(void) { /* Friendly devices support IDCODE */ tap->hasidcode = true; - jtag_examine_chain_display(LOG_LVL_INFO, "tap/device found", + jtag_examine_chain_display(LOG_LVL_INFO, + "tap/device found", tap->dotted_name, idcode); bit_count += 32; @@ -1033,7 +1045,7 @@ static int jtag_examine_chain(void) /* ensure the TAP ID matches what was expected */ if (!jtag_examine_chain_match_tap(tap)) - return ERROR_JTAG_INIT_FAILED; + retval = ERROR_JTAG_INIT_SOFT_FAIL; } /* Fail if too many TAPs were enabled for us to verify them all. */ @@ -1049,11 +1061,14 @@ static int jtag_examine_chain(void) if (jtag_examine_chain_end(idcode_buffer, bit_count, 8 * sizeof(idcode_buffer))) { LOG_ERROR("double-check your JTAG setup (interface, " - "speed, TAPs, ...)"); + "speed, missing TAPs, ...)"); return ERROR_JTAG_INIT_FAILED; } - return ERROR_OK; + /* Return success or, for backwards compatibility if only + * some IDCODE values mismatched, a soft/continuable fault. + */ + return retval; } /* @@ -1255,18 +1270,37 @@ int jtag_init_inner(struct command_context_s *cmd_ctx) 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) - { + /* Examine DR values first. This discovers problems which will + * prevent communication ... hardware issues like TDO stuck, or + * configuring the wrong number of (enabled) TAPs. + */ + retval = jtag_examine_chain(); + switch (retval) { + case ERROR_OK: + /* complete success */ + break; + case ERROR_JTAG_INIT_SOFT_FAIL: + /* For backward compatibility reasons, try coping with + * configuration errors involving only ID mismatches. + * We might be able to talk to the devices. + */ LOG_ERROR("Trying to use configured scan chain anyway..."); issue_setup = false; + break; + default: + /* some hard error; already issued diagnostics */ + return retval; } - if (jtag_validate_ircapture() != ERROR_OK) - { - LOG_WARNING("Errors during IR capture, continuing anyway..."); - issue_setup = false; - } + /* Now look at IR values. Problems here will prevent real + * communication. They mostly mean that the IR length is + * wrong ... or that the IR capture value is wrong. (The + * latter is uncommon, but easily worked around: provide + * ircapture/irmask values during TAP setup.) + */ + retval = jtag_validate_ircapture(); + if (retval != ERROR_OK) + return retval; if (issue_setup) jtag_notify_event(JTAG_TAP_EVENT_SETUP); diff --git a/src/jtag/jtag.h b/src/jtag/jtag.h index 35635cd88..0126b3310 100644 --- a/src/jtag/jtag.h +++ b/src/jtag/jtag.h @@ -689,6 +689,7 @@ extern void jtag_sleep(uint32_t us); #define ERROR_JTAG_DEVICE_ERROR (-107) #define ERROR_JTAG_STATE_INVALID (-108) #define ERROR_JTAG_TRANSITION_INVALID (-109) +#define ERROR_JTAG_INIT_SOFT_FAIL (-110) /** * jtag_add_dr_out() is a version of jtag_add_dr_scan() which