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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>
This commit is contained in:
David Brownell 2009-10-08 09:16:01 -07:00
parent 22aff82cae
commit 40c9668b70
2 changed files with 50 additions and 15 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

64
src/jtag/core.c
View File

@ -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);

1
src/jtag/jtag.h
View File

@ -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