stlink: add armv7m stlink handling

This enables us to better handle some of the low level functions that the
stlink does not support. It also enables us to share a few more of the
standard cortex_m3 functions if necessary.

Change-Id: I7a2c57450122012ec189245d8879d8967913e00e
Signed-off-by: Spencer Oliver <spen@spen-soft.co.uk>
Reviewed-on: http://openocd.zylin.com/637
Tested-by: jenkins

src/target/arm_adi_v5.c

@@ -1096,14 +1096,6 @@ int ahbap_debugport_init(struct adiv5_dap *dap)
 
 	LOG_DEBUG(" ");
 
-	/* test for initialized low level jtag hardware
-	 * this always fails for stlink hardware
-	 */
-	if (!dap->jtag_info) {
-		LOG_DEBUG("No low level jtag hardware found");
-		return ERROR_OK;
-	}
-
 	/* JTAG-DP or SWJ-DP, in JTAG mode
 	 * ... for SWD mode this is patched as part
 	 * of link switchover

src/target/armv7m.h

@@ -171,9 +171,11 @@ struct armv7m_common {
 	struct adiv5_dap dap;
 
 	int fp_feature;
-
 	uint32_t demcr;
 
+	/* stlink is a high level adapter, does not support all functions */
+	bool stlink;
+
 	/* Direct processor core register read and writes */
 	int (*load_core_reg_u32)(struct target *target,
 		enum armv7m_regtype type, uint32_t num, uint32_t *value);

src/target/cortex_m.c

@@ -1780,9 +1780,13 @@ int cortex_m3_examine(struct target *target)
 	struct adiv5_dap *swjdp = &cortex_m3->armv7m.dap;
 	struct armv7m_common *armv7m = target_to_armv7m(target);
 
-	retval = ahbap_debugport_init(swjdp);
-	if (retval != ERROR_OK)
-		return retval;
+	/* stlink shares the examine handler but does not support
+	 * all its calls */
+	if (!armv7m->stlink) {
+		retval = ahbap_debugport_init(swjdp);
+		if (retval != ERROR_OK)
+			return retval;
+	}
 
 	if (!target_was_examined(target)) {
 		target_set_examined(target);

src/target/stm32_stlink.c

@@ -278,6 +278,7 @@ static int stm32_stlink_init_arch_info(struct target *target,
 	armv7m->store_core_reg_u32 = stm32_stlink_store_core_reg_u32;
 
 	armv7m->examine_debug_reason = stm32_stlink_examine_debug_reason;
+	armv7m->stlink = true;
 
 	return ERROR_OK;
 }