Add RISC-V support.

This supports both 0.11 and 0.13 versions of the debug spec.

Support for `-rtos riscv` will come in a separate commit since it was
easy to separate out, and is likely to be more controversial.

Flash support for the SiFive boards will also come in a later commit.

Change-Id: I1d38fe669c2041b4e21a5c54a091594aac3e2190
Signed-off-by: Tim Newsome <tim@sifive.com>
Reviewed-on: http://openocd.zylin.com/4578
Tested-by: jenkins
Reviewed-by: Liviu Ionescu <ilg@livius.net>
Reviewed-by: Matthias Welwarsky <matthias@welwarsky.de>

src/target/riscv/batch.h

@@ -0,0 +1,64 @@
+#ifndef TARGET__RISCV__SCANS_H
+#define TARGET__RISCV__SCANS_H
+
+#include "target/target.h"
+#include "jtag/jtag.h"
+
+enum riscv_scan_type {
+	RISCV_SCAN_TYPE_INVALID,
+	RISCV_SCAN_TYPE_NOP,
+	RISCV_SCAN_TYPE_READ,
+	RISCV_SCAN_TYPE_WRITE,
+};
+
+/* A batch of multiple JTAG scans, which are grouped together to avoid the
+ * overhead of some JTAG adapters when sending single commands.  This is
+ * designed to support block copies, as that's what we actually need to go
+ * fast. */
+struct riscv_batch {
+	struct target *target;
+
+	size_t allocated_scans;
+	size_t used_scans;
+
+	size_t idle_count;
+
+	uint8_t *data_out;
+	uint8_t *data_in;
+	struct scan_field *fields;
+
+	/* In JTAG we scan out the previous value's output when performing a
+	 * scan.  This is a pain for users, so we just provide them the
+	 * illusion of not having to do this by eliding all but the last NOP.
+	 * */
+	enum riscv_scan_type last_scan;
+
+	/* The read keys. */
+	size_t *read_keys;
+	size_t read_keys_used;
+};
+
+/* Allocates (or frees) a new scan set.  "scans" is the maximum number of JTAG
+ * scans that can be issued to this object, and idle is the number of JTAG idle
+ * cycles between every real scan. */
+struct riscv_batch *riscv_batch_alloc(struct target *target, size_t scans, size_t idle);
+void riscv_batch_free(struct riscv_batch *batch);
+
+/* Checks to see if this batch is full. */
+bool riscv_batch_full(struct riscv_batch *batch);
+
+/* Executes this scan batch. */
+int riscv_batch_run(struct riscv_batch *batch);
+
+/* Adds a DMI write to this batch. */
+void riscv_batch_add_dmi_write(struct riscv_batch *batch, unsigned address, uint64_t data);
+
+/* DMI reads must be handled in two parts: the first one schedules a read and
+ * provides a key, the second one actually obtains the value of that read .*/
+size_t riscv_batch_add_dmi_read(struct riscv_batch *batch, unsigned address);
+uint64_t riscv_batch_get_dmi_read(struct riscv_batch *batch, size_t key);
+
+/* Scans in a NOP. */
+void riscv_batch_add_nop(struct riscv_batch *batch);
+
+#endif