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 <dbrownell@users.sourceforge.net>
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David Brownell
parent
22aff82cae
commit
40c9668b70
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@ -892,7 +892,15 @@ static bool jtag_examine_chain_check(uint8_t *idcodes, unsigned count)
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}
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/* if there wasn't a single non-zero bit or if all bits were one,
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* the scan is not valid */
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* the scan is not valid. We wrote a mix of both values; either
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*
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* - There's a hardware issue (almost certainly):
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* + all-zeroes can mean a target stuck in JTAG reset
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* + all-ones tends to mean no target
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* - The scan chain is WAY longer than we can handle, *AND* either
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* + there are several hundreds of TAPs in bypass, or
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* + at least a few dozen TAPs all have an all-ones IDCODE
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*/
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if (zero_check == 0x00 || one_check == 0xff)
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{
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LOG_ERROR("JTAG scan chain interrogation failed: all %s",
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@ -988,11 +996,14 @@ static int jtag_examine_chain(void)
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{
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uint8_t idcode_buffer[JTAG_MAX_CHAIN_SIZE * 4];
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unsigned bit_count;
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int retval;
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/* DR scan to collect BYPASS or IDCODE register contents.
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* Then make sure the scan data has both ones and zeroes.
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*/
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jtag_examine_chain_execute(idcode_buffer, JTAG_MAX_CHAIN_SIZE);
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retval = jtag_examine_chain_execute(idcode_buffer, JTAG_MAX_CHAIN_SIZE);
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if (retval != ERROR_OK)
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return retval;
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if (!jtag_examine_chain_check(idcode_buffer, JTAG_MAX_CHAIN_SIZE))
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return ERROR_JTAG_INIT_FAILED;
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@ -1012,7 +1023,7 @@ static int jtag_examine_chain(void)
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if ((idcode & 1) == 0)
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{
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/* LSB must not be 0, this indicates a device in bypass */
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/* Zero for LSB indicates a device in bypass */
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LOG_WARNING("TAP %s does not have IDCODE",
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tap->dotted_name);
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idcode = 0;
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@ -1024,7 +1035,8 @@ static int jtag_examine_chain(void)
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{
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/* Friendly devices support IDCODE */
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tap->hasidcode = true;
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jtag_examine_chain_display(LOG_LVL_INFO, "tap/device found",
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jtag_examine_chain_display(LOG_LVL_INFO,
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"tap/device found",
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tap->dotted_name, idcode);
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bit_count += 32;
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@ -1033,7 +1045,7 @@ static int jtag_examine_chain(void)
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/* ensure the TAP ID matches what was expected */
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if (!jtag_examine_chain_match_tap(tap))
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return ERROR_JTAG_INIT_FAILED;
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retval = ERROR_JTAG_INIT_SOFT_FAIL;
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}
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/* Fail if too many TAPs were enabled for us to verify them all. */
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@ -1049,11 +1061,14 @@ static int jtag_examine_chain(void)
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if (jtag_examine_chain_end(idcode_buffer, bit_count,
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8 * sizeof(idcode_buffer))) {
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LOG_ERROR("double-check your JTAG setup (interface, "
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"speed, TAPs, ...)");
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"speed, missing TAPs, ...)");
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return ERROR_JTAG_INIT_FAILED;
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}
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return ERROR_OK;
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/* Return success or, for backwards compatibility if only
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* some IDCODE values mismatched, a soft/continuable fault.
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*/
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return retval;
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}
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/*
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@ -1255,18 +1270,37 @@ int jtag_init_inner(struct command_context_s *cmd_ctx)
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if ((retval = jtag_execute_queue()) != ERROR_OK)
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return retval;
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/* examine chain first, as this could discover the real chain layout */
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if (jtag_examine_chain() != ERROR_OK)
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{
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/* Examine DR values first. This discovers problems which will
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* prevent communication ... hardware issues like TDO stuck, or
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* configuring the wrong number of (enabled) TAPs.
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*/
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retval = jtag_examine_chain();
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switch (retval) {
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case ERROR_OK:
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/* complete success */
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break;
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case ERROR_JTAG_INIT_SOFT_FAIL:
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/* For backward compatibility reasons, try coping with
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* configuration errors involving only ID mismatches.
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* We might be able to talk to the devices.
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*/
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LOG_ERROR("Trying to use configured scan chain anyway...");
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issue_setup = false;
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break;
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default:
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/* some hard error; already issued diagnostics */
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return retval;
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}
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if (jtag_validate_ircapture() != ERROR_OK)
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{
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LOG_WARNING("Errors during IR capture, continuing anyway...");
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issue_setup = false;
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}
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/* Now look at IR values. Problems here will prevent real
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* communication. They mostly mean that the IR length is
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* wrong ... or that the IR capture value is wrong. (The
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* latter is uncommon, but easily worked around: provide
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* ircapture/irmask values during TAP setup.)
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*/
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retval = jtag_validate_ircapture();
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if (retval != ERROR_OK)
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return retval;
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if (issue_setup)
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jtag_notify_event(JTAG_TAP_EVENT_SETUP);
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@ -689,6 +689,7 @@ extern void jtag_sleep(uint32_t us);
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#define ERROR_JTAG_DEVICE_ERROR (-107)
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#define ERROR_JTAG_STATE_INVALID (-108)
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#define ERROR_JTAG_TRANSITION_INVALID (-109)
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#define ERROR_JTAG_INIT_SOFT_FAIL (-110)
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/**
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* jtag_add_dr_out() is a version of jtag_add_dr_scan() which
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