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.
--
I merged this along with the patches adding that call and
implementing it for FT2232 based hardware. Øyvind and I
have had a bit of off-list discussion on that ... he thinks
those are at least a good enough start, and that (as like
with other Free Software projects) we can fix goofage later.
If we start seeing JTAG/SWD adapter hardware which needs
a different kind of primitive for mode switching we can
change how we do this. But this approach can clearly work
on FT2232 and bitbangers (parport and friends). It's also
very similar to what Simon sent around for Versaloon late
last year. (And ZY1000 looks like it bitbangs TMS too.)
--- 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;
+}
--- a/src/target/arm_adi_v5.h
+++ b/src/target/arm_adi_v5.h
@@ -235,4 +235,12 @@ DAP_COMMAND_HANDLER(dap_memaccess_comman
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
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