interface: define TMS sequence command

For support of SWD we need to be able to clock out special bit
sequences over TMS or SWDIO.  Create this as a generic operation,
not yet called by anything, which is split as usual into:

 - upper level abstraction ... here, jtag_add_tms_seq();
 - midlayer implementation logic hooking that to the lowlevel code;
 - lowlevel minidriver operation ... here, interface_add_tms_seq();
 - message type for request queue, here JTAG_TMS.

This is done slightly differently than other operations: there's a flag
saying whether the interface driver supports this request.  (In fact a
flag *word* so upper layers can learn about other capabilities too ...
for example, supporting SWD operations.)

That approach (flag) lets this method *eventually* be used to eliminate
pathmove() and statemove() support from most adapter drivers, by moving
all that logic into the mid-layer and increasing uniformity between the
various drivers.  (Which will in turn reduce subtle bugginess.)

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

src/jtag/commands.h

@@ -98,19 +98,39 @@ struct sleep_command {
 	uint32_t us;
 };
 
+/**
+ * Encapsulates a series of bits to be clocked out, affecting state
+ * and mode of the interface.
+ *
+ * In JTAG mode these are clocked out on TMS, using TCK.  They may be
+ * used for link resets, transitioning between JTAG and SWD modes, or
+ * to implement JTAG state machine transitions (implementing pathmove
+ * or statemove operations).
+ *
+ * In SWD mode these are clocked out on SWDIO, using SWCLK, and are
+ * used for link resets and transitioning between SWD and JTAG modes.
+ */
+struct tms_command {
+	/** How many bits should be clocked out. */
+	unsigned	num_bits;
+	/** The bits to clock out; the LSB is bit 0 of bits[0].  */
+	const uint8_t		*bits;
+};
+
 /**
  * Defines a container type that hold a pointer to a JTAG command
  * structure of any defined type.
  */
 union jtag_command_container {
-	struct scan_command*         scan;
-	struct statemove_command*    statemove;
-	struct pathmove_command*     pathmove;
-	struct runtest_command*      runtest;
-	struct stableclocks_command* stableclocks;
-	struct reset_command*        reset;
-	struct end_state_command*    end_state;
-	struct sleep_command* sleep;
+	struct scan_command		*scan;
+	struct statemove_command	*statemove;
+	struct pathmove_command		*pathmove;
+	struct runtest_command		*runtest;
+	struct stableclocks_command	*stableclocks;
+	struct reset_command		*reset;
+	struct end_state_command	*end_state;
+	struct sleep_command		*sleep;
+	struct tms_command		*tms;
 };
 
 /**
@@ -124,7 +144,8 @@ enum jtag_command_type {
 	JTAG_RESET        = 4,
 	JTAG_PATHMOVE     = 6,
 	JTAG_SLEEP        = 7,
-	JTAG_STABLECLOCKS = 8
+	JTAG_STABLECLOCKS = 8,
+	JTAG_TMS          = 9,
 };
 
 struct jtag_command {

src/jtag/core.c

@@ -488,6 +488,35 @@ void jtag_add_tlr(void)
 	jtag_notify_event(JTAG_TRST_ASSERTED);
 }
 
+/**
+ * If supported by the underlying adapter, this clocks a raw bit sequence
+ * onto TMS for switching betwen JTAG and SWD modes.
+ *
+ * DO NOT use this to bypass the integrity checks and logging provided
+ * by the jtag_add_pathmove() and jtag_add_statemove() calls.
+ *
+ * @param nbits How many bits to clock out.
+ * @param seq The bit sequence.  The LSB is bit 0 of seq[0].
+ * @param state The JTAG tap state to record on completion.  Use
+ *	TAP_INVALID to represent being in in SWD mode.
+ *
+ * @todo Update naming conventions to stop assuming everything is JTAG.
+ */
+int jtag_add_tms_seq(unsigned nbits, const uint8_t *seq, enum tap_state state)
+{
+	int retval;
+
+	if (!(jtag->supported & DEBUG_CAP_TMS_SEQ))
+		return ERROR_JTAG_NOT_IMPLEMENTED;
+
+	jtag_checks();
+	cmd_queue_cur_state = state;
+
+	retval = interface_add_tms_seq(nbits, seq);
+	jtag_set_error(retval);
+	return retval;
+}
+
 void jtag_add_pathmove(int num_states, const tap_state_t *path)
 {
 	tap_state_t cur_state = cmd_queue_cur_state;

src/jtag/drivers/driver.c

@@ -388,6 +388,31 @@ int interface_jtag_add_tlr(void)
 	return ERROR_OK;
 }
 
+int interface_add_tms_seq(unsigned num_bits, const uint8_t *seq)
+{
+	struct jtag_command *cmd;
+
+	cmd = cmd_queue_alloc(sizeof(struct jtag_command));
+	if (cmd == NULL)
+		return ERROR_FAIL;
+
+	cmd->type = JTAG_TMS;
+	cmd->cmd.tms = cmd_queue_alloc(sizeof(*cmd->cmd.tms));
+	if (!cmd->cmd.tms)
+		return ERROR_FAIL;
+
+	/* copy the bits; our caller doesn't guarantee they'll persist */
+	cmd->cmd.tms->num_bits = num_bits;
+	cmd->cmd.tms->bits = buf_cpy(seq,
+			cmd_queue_alloc(DIV_ROUND_UP(num_bits, 8)), num_bits);
+	if (!cmd->cmd.tms->bits)
+		return ERROR_FAIL;
+
+	jtag_queue_command(cmd);
+
+	return ERROR_OK;
+}
+
 int interface_jtag_add_pathmove(int num_states, const tap_state_t *path)
 {
 	/* allocate memory for a new list member */

src/jtag/interface.h

@@ -184,10 +184,28 @@ static inline tap_state_t jtag_debug_state_machine(const void *tms_buf,
 }
 #endif // _DEBUG_JTAG_IO_
 
+/**
+ * Represents a driver for a debugging interface.
+ *
+ * @todo Rename; perhaps "debug_driver".  This isn't an interface,
+ * it's a driver!  Also, not all drivers support JTAG.
+ *
+ * @todo We need a per-instance structure too, and changes to pass
+ * that structure to the driver.  Instances can for example be in
+ * either SWD or JTAG modes.  This will help remove globals, and
+ * eventually to cope with systems which have more than one such
+ * debugging interface.
+ */
 struct jtag_interface {
 	/// The name of the JTAG interface driver.
 	char* name;
 
+	/**
+	 * Bit vector listing capabilities exposed by this driver.
+	 */
+	unsigned supported;
+#define DEBUG_CAP_TMS_SEQ	(1 << 0)
+
 	/**
 	 * Execute queued commands.
 	 * @returns ERROR_OK on success, or an error code on failure.

src/jtag/jtag.h

@@ -575,6 +575,8 @@ tap_state_t jtag_get_end_state(void);
 
 void jtag_add_sleep(uint32_t us);
 
+int jtag_add_tms_seq(unsigned nbits, const uint8_t *seq, enum tap_state t);
+
 /**
  * Function jtag_add_clocks
  * first checks that the state in which the clocks are to be issued is
@@ -693,7 +695,7 @@ int jtag_error_clear(void);
 /**
  * Return true if it's safe for a background polling task to access the
  * JTAG scan chain.  Polling may be explicitly disallowed, and is also
- * unsafe while nTRST is active or the JTAG clock is gated off.,
+ * unsafe while nTRST is active or the JTAG clock is gated off.
  */
 bool is_jtag_poll_safe(void);
 

src/jtag/minidriver.h

@@ -67,6 +67,8 @@ int interface_jtag_add_tlr(void);
 int interface_jtag_add_pathmove(int num_states, const tap_state_t* path);
 int interface_jtag_add_runtest(int num_cycles, tap_state_t endstate);
 
+int interface_add_tms_seq(unsigned num_bits, const uint8_t *bits);
+
 /**
  * This drives the actual srst and trst pins. srst will always be 0
  * if jtag_reset_config & RESET_SRST_PULLS_TRST != 0 and ditto for

src/jtag/minidummy/minidummy.c

@@ -147,6 +147,13 @@ int interface_jtag_add_pathmove(int num_states, const tap_state_t *path)
 	return ERROR_OK;
 }
 
+int interface_add_tms_seq(unsigned num_bits, const uint8_t *seq)
+{
+	/* synchronously do the operation here */
+
+	return ERROR_OK;
+}
+
 void embeddedice_write_dcc(struct jtag_tap *tap, int reg_addr, uint8_t *buffer, int little, int count)
 {
 	int i;

src/jtag/zy1000/zy1000.c

@@ -804,7 +804,16 @@ int interface_jtag_add_pathmove(int num_states, const tap_state_t *path)
 	return ERROR_OK;
 }
 
-
+int interface_add_tms_seq(unsigned num_bits, const uint8_t *seq)
+{
+	/* FIXME just implement this, like pathmove but without
+	 * JTAG-specific state transition checking.  Then update
+	 * zy1000_interface to report that it's supported.
+	 *
+	 * Eventually interface_jtag_add_pathmove() could vanish.
+	 */
+	return ERROR_JTAG_NOT_IMPLEMENTED;
+}
 
 void embeddedice_write_dcc(struct jtag_tap *tap, int reg_addr, uint8_t *buffer, int little, int count)
 {