stlink: support connecting under reset

Some targets support connecting while the target's srst is asserted.
Tested on stm32 family.

Change-Id: I1197dd721a1e1cbf95ee77dfd8e1082b165b22a9
Signed-off-by: Spencer Oliver <spen@spen-soft.co.uk>
Reviewed-on: http://openocd.zylin.com/607
Tested-by: jenkins

diff --git a/src/target/stm32_stlink.c b/src/target/stm32_stlink.c
index f9daa014a0de3851093b19b4dec497c2e839169a..4044654cfe37c49b2d940d831889dd4234cde4b9 100644 (file)
--- a/src/target/stm32_stlink.c
+++ b/src/target/stm32_stlink.c
@@ -406,7 +406,7 @@ static int stm32_stlink_poll(struct target *target)
 
 static int stm32_stlink_assert_reset(struct target *target)
 {
-       int res;
+       int res = ERROR_OK;
        struct stlink_interface_s *stlink_if = target_to_stlink(target);
        struct armv7m_common *armv7m = target_to_armv7m(target);
        bool use_srst_fallback = true;
@@ -415,12 +415,22 @@ static int stm32_stlink_assert_reset(struct target *target)
 
        enum reset_types jtag_reset_config = jtag_get_reset_config();
 
+       bool srst_asserted = false;
+
+       if (jtag_reset_config & RESET_SRST_NO_GATING) {
+               jtag_add_reset(0, 1);
+               res = stlink_if->layout->api->assert_srst(stlink_if->fd, 0);
+               srst_asserted = true;
+       }
+
        stlink_if->layout->api->write_debug_reg(stlink_if->fd, DCB_DHCSR, DBGKEY|C_DEBUGEN);
        stlink_if->layout->api->write_debug_reg(stlink_if->fd, DCB_DEMCR, VC_CORERESET);
 
        if (jtag_reset_config & RESET_HAS_SRST) {
-               jtag_add_reset(0, 1);
-               res = stlink_if->layout->api->assert_srst(stlink_if->fd, 0);
+               if (!srst_asserted) {
+                       jtag_add_reset(0, 1);
+                       res = stlink_if->layout->api->assert_srst(stlink_if->fd, 0);
+               }
                if (res == ERROR_COMMAND_NOTFOUND)
                        LOG_ERROR("Hardware srst not supported, falling back to software reset");
                else if (res == ERROR_OK) {