Add 'riscv set_ir' command to set IR value for JTAG registers.

This allows using different TAP addresses, for example, if using
BSCANE2 primitives on a Xilinx FPGA.

doc/openocd.texi

@@ -9145,6 +9145,17 @@ When on, prefer to use System Bus Access to access memory.  When off, prefer to
 use the Program Buffer to access memory.
 @end deffn
 
+@deffn Command {riscv set_ir} (@option{idcode}|@option{dtmcs}|@option{dmi}) [value]
+Set the IR value for the specified JTAG register.  This is useful, for
+example, when using the existing JTAG interface on a Xilinx FPGA by
+way of BSCANE2 primitives that only permit a limited selection of IR
+values.
+
+When utilizing version 0.11 of the RISC-V Debug Specification,
+@option{dtmcs} and @option{dmi} set the IR values for the DTMCONTROL
+and DBUS registers, respectively.
+@end deffn
+
 @subsection RISC-V Authentication Commands
 
 The following commands can be used to authenticate to a RISC-V system. Eg.  a

src/target/riscv/riscv-013.c

@@ -396,16 +396,7 @@ static void dump_field(int idle, const struct scan_field *field)
 
 static void select_dmi(struct target *target)
 {
-	static uint8_t ir_dmi[1] = {DTM_DMI};
-	struct scan_field field = {
-		.num_bits = target->tap->ir_length,
-		.out_value = ir_dmi,
-		.in_value = NULL,
-		.check_value = NULL,
-		.check_mask = NULL
-	};
-
-	jtag_add_ir_scan(target->tap, &field, TAP_IDLE);
+	jtag_add_ir_scan(target->tap, &select_dbus, TAP_IDLE);
 }
 
 static uint32_t dtmcontrol_scan(struct target *target, uint32_t out)

src/target/riscv/riscv.c

@@ -154,17 +154,17 @@ typedef enum slot {
 #define MAX_HWBPS			16
 #define DRAM_CACHE_SIZE		16
 
-uint8_t ir_dtmcontrol[1] = {DTMCONTROL};
+uint8_t ir_dtmcontrol[4] = {DTMCONTROL};
 struct scan_field select_dtmcontrol = {
 	.in_value = NULL,
 	.out_value = ir_dtmcontrol
 };
-uint8_t ir_dbus[1] = {DBUS};
+uint8_t ir_dbus[4] = {DBUS};
 struct scan_field select_dbus = {
 	.in_value = NULL,
 	.out_value = ir_dbus
 };
-uint8_t ir_idcode[1] = {0x1};
+uint8_t ir_idcode[4] = {0x1};
 struct scan_field select_idcode = {
 	.in_value = NULL,
 	.out_value = ir_idcode
@@ -1626,6 +1626,30 @@ COMMAND_HANDLER(riscv_reset_delays)
 	return ERROR_OK;
 }
 
+COMMAND_HANDLER(riscv_set_ir)
+{
+	if (CMD_ARGC != 2) {
+		LOG_ERROR("Command takes exactly 2 arguments");
+		return ERROR_COMMAND_SYNTAX_ERROR;
+	}
+
+	uint32_t value;
+	COMMAND_PARSE_NUMBER(u32, CMD_ARGV[1], value);
+
+	if (!strcmp(CMD_ARGV[0], "idcode")) {
+		buf_set_u32(ir_idcode, 0, 32, value);
+		return ERROR_OK;
+	} else if (!strcmp(CMD_ARGV[0], "dtmcs")) {
+		buf_set_u32(ir_dtmcontrol, 0, 32, value);
+		return ERROR_OK;
+	} else if (!strcmp(CMD_ARGV[0], "dmi")) {
+		buf_set_u32(ir_dbus, 0, 32, value);
+		return ERROR_OK;
+	} else {
+		return ERROR_FAIL;
+	}
+}
+
 static const struct command_registration riscv_exec_command_handlers[] = {
 	{
 		.name = "test_compliance",
@@ -1725,6 +1749,13 @@ static const struct command_registration riscv_exec_command_handlers[] = {
 			"command resets those learned values after `wait` scans. It's only "
 			"useful for testing OpenOCD itself."
 	},
+	{
+		.name = "set_ir",
+		.handler = riscv_set_ir,
+		.mode = COMMAND_ANY,
+		.usage = "riscv set_ir_idcode [idcode|dtmcs|dmi] value",
+		.help = "Set IR value for specified JTAG register."
+	},
 	COMMAND_REGISTRATION_DONE
 };
 

src/target/riscv/riscv.h

@@ -151,11 +151,11 @@ static inline riscv_info_t *riscv_info(const struct target *target)
 { return target->arch_info; }
 #define RISCV_INFO(R) riscv_info_t *R = riscv_info(target);
 
-extern uint8_t ir_dtmcontrol[1];
+extern uint8_t ir_dtmcontrol[4];
 extern struct scan_field select_dtmcontrol;
-extern uint8_t ir_dbus[1];
+extern uint8_t ir_dbus[4];
 extern struct scan_field select_dbus;
-extern uint8_t ir_idcode[1];
+extern uint8_t ir_idcode[4];
 extern struct scan_field select_idcode;
 
 /*** OpenOCD Interface */