target/cortex_m: try to re-examine under reset in cortex_m_assert_reset()

An application often idling in real sleep mode may make a Cortex-M target
hard to access as CPU clock are gated and debug requests are responded
by WAIT ack.

Try to examine the target under reset as the last resort.

Change-Id: Ife875a966a838c37dde987bc584ad0a1f4d020d6
Signed-off-by: Tomas Vanek <vanekt@fbl.cz>
Reviewed-on: https://review.openocd.org/c/openocd/+/7228
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 94c75a1d4946dde0c71928dcb2f6202677dee04b..1863441674ef3ba34f6b7f76909cbc4cb548f183 100644 (file)
--- a/src/target/cortex_m.c
+++ b/src/target/cortex_m.c
@@ -1437,6 +1437,14 @@ static int cortex_m_assert_reset(struct target *target)
                srst_asserted = true;
        }
 
+       /* TODO: replace the hack calling target_examine_one()
+        * as soon as a better reset framework is available */
+       if (!target_was_examined(target) && !target->defer_examine
+               && srst_asserted && (jtag_reset_config & RESET_SRST_NO_GATING)) {
+               LOG_TARGET_DEBUG(target, "Trying to re-examine under reset");
+               target_examine_one(target);
+       }
+
        /* We need at least debug_ap to go further.
         * Inform user and bail out if we don't have one. */
        if (!armv7m->debug_ap) {
@@ -1578,7 +1586,7 @@ static int cortex_m_deassert_reset(struct target *target)
        enum reset_types jtag_reset_config = jtag_get_reset_config();
 
        if ((jtag_reset_config & RESET_HAS_SRST) &&
-           !(jtag_reset_config & RESET_SRST_NO_GATING) &&
+               !(jtag_reset_config & RESET_SRST_NO_GATING) &&
                armv7m->debug_ap) {
 
                int retval = dap_dp_init_or_reconnect(armv7m->debug_ap->dap);