stlink: support srst reset

This adds the ability to support srst reset for the stlink/v2.
stlink/v1 will fallback to using SYSRESETREQ which is a full reset - including peripherals.

To enable the use of the srst add the following to your cfg:
reset_config srst_only

Change-Id: I570de607c5f370fd6a4abf47360686c9be07bcdd
Signed-off-by: Spencer Oliver <spen@spen-soft.co.uk>
Reviewed-on: http://openocd.zylin.com/581
Tested-by: jenkins
Reviewed-by: Mathias Küster <kesmtp@freenet.de>
Reviewed-by: Freddie Chopin <freddie.chopin@gmail.com>

diff --git a/src/target/stm32_stlink.c b/src/target/stm32_stlink.c
index c9ab81068f7bbea69535286610c5010be287eb34..f9daa014a0de3851093b19b4dec497c2e839169a 100644 (file)
--- a/src/target/stm32_stlink.c
+++ b/src/target/stm32_stlink.c
@@ -409,19 +409,36 @@ static int stm32_stlink_assert_reset(struct target *target)
        int res;
        struct stlink_interface_s *stlink_if = target_to_stlink(target);
        struct armv7m_common *armv7m = target_to_armv7m(target);
+       bool use_srst_fallback = true;
 
        LOG_DEBUG("%s", __func__);
 
+       enum reset_types jtag_reset_config = jtag_get_reset_config();
+
+       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 (res == ERROR_COMMAND_NOTFOUND)
+                       LOG_ERROR("Hardware srst not supported, falling back to software reset");
+               else if (res == ERROR_OK) {
+                       /* hardware srst supported */
+                       use_srst_fallback = false;
+               }
+       }
+
+       if (use_srst_fallback) {
+               /* stlink v1 api does support hardware srst, so we use a software reset fallback */
+               stlink_if->layout->api->write_debug_reg(stlink_if->fd, NVIC_AIRCR, AIRCR_VECTKEY | AIRCR_SYSRESETREQ);
+       }
+
        res = stlink_if->layout->api->reset(stlink_if->fd);
 
        if (res != ERROR_OK)
                return res;
 
-       /* virtual assert reset, we need it for the internal
-        * jtag state machine
-        */
-       jtag_add_reset(1, 1);
-
        /* registers are now invalid */
        register_cache_invalidate(armv7m->core_cache);
 
@@ -438,9 +455,15 @@ static int stm32_stlink_assert_reset(struct target *target)
 static int stm32_stlink_deassert_reset(struct target *target)
 {
        int res;
+       struct stlink_interface_s *stlink_if = target_to_stlink(target);
+
+       enum reset_types jtag_reset_config = jtag_get_reset_config();
 
        LOG_DEBUG("%s", __func__);
 
+       if (jtag_reset_config & RESET_HAS_SRST)
+               stlink_if->layout->api->assert_srst(stlink_if->fd, 1);
+
        /* virtual deassert reset, we need it for the internal
         * jtag state machine
         */