target/cortex_m: make reset robust again

After merging [1] 'reset halt' does not work on not responding Cortex-M.

Relax the examined tests and try to set vector catch VC_CORERESET
if debug_ap is available.

While on it add an info about examination state to debug logs.

Fixes: [1] commit 98d9f1168cbd ("target: reset target examined flag if target::examine() fails")
Change-Id: Ie2e018610026180af5997d70231061a275f05c76
Signed-off-by: Tomas Vanek <vanekt@fbl.cz>
Reviewed-on: https://review.openocd.org/c/openocd/+/6745
Tested-by: jenkins
Reviewed-by: Antonio Borneo <borneo.antonio@gmail.com>

diff --git a/src/target/cortex_m.c b/src/target/cortex_m.c
index 23d9065e2a7e09ccb36fa8b56e7e66260cbc8719..94c75a1d4946dde0c71928dcb2f6202677dee04b 100644 (file)
--- a/src/target/cortex_m.c
+++ b/src/target/cortex_m.c
@@ -1408,8 +1408,9 @@ static int cortex_m_assert_reset(struct target *target)
        struct armv7m_common *armv7m = &cortex_m->armv7m;
        enum cortex_m_soft_reset_config reset_config = cortex_m->soft_reset_config;
 
-       LOG_TARGET_DEBUG(target, "target->state: %s",
-               target_state_name(target));
+       LOG_TARGET_DEBUG(target, "target->state: %s,%s examined",
+               target_state_name(target),
+               target_was_examined(target) ? "" : " not");
 
        enum reset_types jtag_reset_config = jtag_get_reset_config();
 
@@ -1428,24 +1429,32 @@ static int cortex_m_assert_reset(struct target *target)
 
        bool srst_asserted = false;
 
-       if (!target_was_examined(target)) {
-               if (jtag_reset_config & RESET_HAS_SRST) {
-                       adapter_assert_reset();
+       if ((jtag_reset_config & RESET_HAS_SRST) &&
+               ((jtag_reset_config & RESET_SRST_NO_GATING) || !armv7m->debug_ap)) {
+               /* If we have no debug_ap, asserting SRST is the only thing
+                * we can do now */
+               adapter_assert_reset();
+               srst_asserted = true;
+       }
+
+       /* We need at least debug_ap to go further.
+        * Inform user and bail out if we don't have one. */
+       if (!armv7m->debug_ap) {
+               if (srst_asserted) {
                        if (target->reset_halt)
-                               LOG_TARGET_ERROR(target, "Target not examined, will not halt after reset!");
+                               LOG_TARGET_ERROR(target, "Debug AP not available, will not halt after reset!");
+
+                       /* Do not propagate error: reset was asserted, proceed to deassert! */
+                       target->state = TARGET_RESET;
+                       register_cache_invalidate(cortex_m->armv7m.arm.core_cache);
                        return ERROR_OK;
+
                } else {
-                       LOG_TARGET_ERROR(target, "Target not examined, reset NOT asserted!");
+                       LOG_TARGET_ERROR(target, "Debug AP not available, reset NOT asserted!");
                        return ERROR_FAIL;
                }
        }
 
-       if ((jtag_reset_config & RESET_HAS_SRST) &&
-           (jtag_reset_config & RESET_SRST_NO_GATING)) {
-               adapter_assert_reset();
-               srst_asserted = true;
-       }
-
        /* Enable debug requests */
        int retval = cortex_m_read_dhcsr_atomic_sticky(target);
 
@@ -1546,7 +1555,7 @@ static int cortex_m_assert_reset(struct target *target)
        if (retval != ERROR_OK)
                return retval;
 
-       if (target->reset_halt) {
+       if (target->reset_halt && target_was_examined(target)) {
                retval = target_halt(target);
                if (retval != ERROR_OK)
                        return retval;
@@ -1559,8 +1568,9 @@ static int cortex_m_deassert_reset(struct target *target)
 {
        struct armv7m_common *armv7m = &target_to_cm(target)->armv7m;
 
-       LOG_TARGET_DEBUG(target, "target->state: %s",
-               target_state_name(target));
+       LOG_TARGET_DEBUG(target, "target->state: %s,%s examined",
+               target_state_name(target),
+               target_was_examined(target) ? "" : " not");
 
        /* deassert reset lines */
        adapter_deassert_reset();
@@ -1569,7 +1579,7 @@ static int cortex_m_deassert_reset(struct target *target)
 
        if ((jtag_reset_config & RESET_HAS_SRST) &&
            !(jtag_reset_config & RESET_SRST_NO_GATING) &&
-               target_was_examined(target)) {
+               armv7m->debug_ap) {
 
                int retval = dap_dp_init_or_reconnect(armv7m->debug_ap->dap);
                if (retval != ERROR_OK) {