ADIv5 DAP ops switching to JTAG or SWD modes

Define two new DAP operations which use the new jtag_add_tms_seq()
calls to put the DAP's transport into either SWD or JTAG mode, when
the hardware allows.

Tested with the Stellaris 'Recovering a "Locked" Device' procedure,
which loops five times over both of these.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>

diff --git a/src/target/arm_adi_v5.c b/src/target/arm_adi_v5.c
index 41f00ec0b7804b7f61e3005829bff5dbf8dc5253..6be60af3c49c94d46eceffaf12ce77fefc60d5b7 100644 (file)
--- a/src/target/arm_adi_v5.c
+++ b/src/target/arm_adi_v5.c
@@ -1716,3 +1716,116 @@ DAP_COMMAND_HANDLER(dap_apid_command)
 
        return retval;
 }
+
+/*
+ * This represents the bits which must be sent out on TMS/SWDIO to
+ * switch a DAP implemented using an SWJ-DP module into SWD mode.
+ * These bits are stored (and transmitted) LSB-first.
+ *
+ * See the DAP-Lite specification, section 2.2.5 for information
+ * about making the debug link select SWD or JTAG.  (Similar info
+ * is in a few other ARM documents.)
+ */
+static const uint8_t jtag2swd_bitseq[] = {
+       /* More than 50 TCK/SWCLK cycles with TMS/SWDIO high,
+        * putting both JTAG and SWD logic into reset state.
+        */
+       0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+       /* Switching sequence enables SWD and disables JTAG
+        * NOTE: bits in the DP's IDCODE may expose the need for
+        * an old/deprecated sequence (0xb6 0xed).
+        */
+       0x9e, 0xe7,
+       /* More than 50 TCK/SWCLK cycles with TMS/SWDIO high,
+        * putting both JTAG and SWD logic into reset state.
+        */
+       0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+};
+
+/**
+ * Put the debug link into SWD mode, if the target supports it.
+ * The link's initial mode may be either JTAG (for example,
+ * with SWJ-DP after reset) or SWD.
+ *
+ * @param target Enters SWD mode (if possible).
+ *
+ * Note that targets using the JTAG-DP do not support SWD, and that
+ * some targets which could otherwise support it may have have been
+ * configured to disable SWD signaling
+ *
+ * @return ERROR_OK or else a fault code.
+ */
+int dap_to_swd(struct target *target)
+{
+       int retval;
+
+       LOG_DEBUG("Enter SWD mode");
+
+       /* REVISIT it's nasty to need to make calls to a "jtag"
+        * subsystem if the link isn't in JTAG mode...
+        */
+
+       retval =  jtag_add_tms_seq(8 * sizeof(jtag2swd_bitseq),
+                       jtag2swd_bitseq, TAP_INVALID);
+       if (retval == ERROR_OK)
+               retval = jtag_execute_queue();
+
+       /* REVISIT set up the DAP's ops vector for SWD mode. */
+
+       return retval;
+}
+
+/**
+ * This represents the bits which must be sent out on TMS/SWDIO to
+ * switch a DAP implemented using an SWJ-DP module into JTAG mode.
+ * These bits are stored (and transmitted) LSB-first.
+ *
+ * These bits are stored (and transmitted) LSB-first.
+ */
+static const uint8_t swd2jtag_bitseq[] = {
+       /* More than 50 TCK/SWCLK cycles with TMS/SWDIO high,
+        * putting both JTAG and SWD logic into reset state.
+        */
+       0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+       /* Switching equence disables SWD and enables JTAG
+        * NOTE: bits in the DP's IDCODE can expose the need for
+        * the old/deprecated sequence (0xae 0xde).
+        */
+       0x3c, 0xe7,
+       /* At least 50 TCK/SWCLK cycles with TMS/SWDIO high,
+        * putting both JTAG and SWD logic into reset state.
+        * NOTE:  some docs say "at least 5".
+        */
+       0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+};
+
+/** Put the debug link into JTAG mode, if the target supports it.
+ * The link's initial mode may be either SWD or JTAG.
+ *
+ * @param target Enters JTAG mode (if possible).
+ *
+ * Note that targets implemented with SW-DP do not support JTAG, and
+ * that some targets which could otherwise support it may have been
+ * configured to disable JTAG signaling
+ *
+ * @return ERROR_OK or else a fault code.
+ */
+int dap_to_jtag(struct target *target)
+{
+       int retval;
+
+       LOG_DEBUG("Enter JTAG mode");
+
+       /* REVISIT it's nasty to need to make calls to a "jtag"
+        * subsystem if the link isn't in JTAG mode...
+        */
+
+       retval = jtag_add_tms_seq(8 * sizeof(swd2jtag_bitseq),
+                       swd2jtag_bitseq, TAP_RESET);
+       if (retval == ERROR_OK)
+               retval = jtag_execute_queue();
+
+       /* REVISIT set up the DAP's ops vector for JTAG mode. */
+
+       return retval;
+}

diff --git a/src/target/arm_adi_v5.h b/src/target/arm_adi_v5.h
index 316701e55e30c0c5b92c700c19e5b649aa7358c7..5c5ca4f041a1374b500b1ad27f94199c494f1f68 100644 (file)
--- a/src/target/arm_adi_v5.h
+++ b/src/target/arm_adi_v5.h
@@ -235,4 +235,12 @@ DAP_COMMAND_HANDLER(dap_memaccess_command);
 DAP_COMMAND_HANDLER(dap_apsel_command);
 DAP_COMMAND_HANDLER(dap_apid_command);
 
+struct target;
+
+/* Put debug link into SWD mode */
+int dap_to_swd(struct target *target);
+
+/* Put debug link into JTAG mode */
+int dap_to_jtag(struct target *target);
+
 #endif