ARMv7-M defines a "lockup" state that's entered in certain double
fault sequences which can't be recovered from without external help.
OpenOCD has previously ignored this.
Issue a diagnostic saying the chip has locked up, and force exit
from this state by halting the core. It's not clear this is the
best way to handle lockup; but there should now be less confusion.
---
I merged this ... minimally, the diagnostic will help, even if
there's some issue with clearing the lockup (awkeward to reproduce
for testing).
--- a/src/target/cortex_m3.c
+++ b/src/target/cortex_m3.c
@@ -416,6 +416,21 @@ static int cortex_m3_poll(struct target
return retval;
}
+ /* Recover from lockup. See ARMv7-M architecture spec,
+ * section B1.5.15 "Unrecoverable exception cases".
+ *
+ * REVISIT Is there a better way to report and handle this?
+ */
+ if (cortex_m3->dcb_dhcsr & S_LOCKUP) {
+ LOG_WARNING("%s -- clearing lockup after double fault",
+ target_name(target));
+ cortex_m3_write_debug_halt_mask(target, C_HALT, 0);
+ target->debug_reason = DBG_REASON_DBGRQ;
+
+ /* refresh status bits */
+ mem_ap_read_atomic_u32(swjdp, DCB_DHCSR, &cortex_m3->dcb_dhcsr);
+ }
+
if (cortex_m3->dcb_dhcsr & S_RESET_ST)
{
/* check if still in reset */
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