Determine the hart count dynamically

This assumes that v0.11 targets have one hart, and that v0.13 targets
have harts IDs that start at 0 and are concecutive.

src/target/riscv/riscv-011.c

@@ -1810,6 +1810,9 @@ static int examine(struct target *target)
 		return ERROR_FAIL;
 	}
 
+	RISCV_INFO(r);
+	r->hart_count = 1;
+
 	riscv011_info_t *info = get_info(target);
 	info->addrbits = get_field(dtmcontrol, DTMCONTROL_ADDRBITS);
 	info->dtmcontrol_idle = get_field(dtmcontrol, DTMCONTROL_IDLE);

src/target/riscv/riscv-013.c

@@ -1220,6 +1220,20 @@ static int examine(struct target *target)
 	info->datacount = get_field(abstractcs, DMI_ABSTRACTCS_DATACOUNT);
 	info->progsize = get_field(abstractcs, DMI_ABSTRACTCS_PROGSIZE);
 
+	/* Before doing anything else we must first enumerate the harts. */
+	RISCV_INFO(r);
+	for (int i = 0; i < RISCV_MAX_HARTS; ++i) {
+		riscv_set_current_hartid(target, i);
+		uint32_t s = dmi_read(target, DMI_DMSTATUS);
+		if (get_field(s, DMI_DMSTATUS_ANYNONEXISTENT))
+			break;
+		r->hart_count = i + 1;
+	}
+
+	/* FIXME: This is broken. */
+	LOG_ERROR("Enumerated %d harts, but there's an off-by-one error in the hardware", r->hart_count);
+	r->hart_count--;
+
 	/* Halt every hart so we can probe them. */
 	riscv_halt_all_harts(target);
 

src/target/riscv/riscv.c

@@ -963,7 +963,10 @@ void riscv_set_rtos_hartid(struct target *target, int hartid)
 
 int riscv_count_harts(struct target *target)
 {
-	return 3;
+	if (target == NULL) return 1;
+	RISCV_INFO(r);
+	if (r == NULL) return 1;
+	return r->hart_count;
 }
 
 bool riscv_has_register(struct target *target, int hartid, int regid)

src/target/riscv/riscv.h

@@ -33,6 +33,9 @@ typedef struct {
 	struct command_context *cmd_ctx;
 	void *version_specific;
 
+	/* The number of harts on this system. */
+	int hart_count;
+
 	/* When the RTOS is enabled this target is expected to handle all the
 	 * harts in the system.  When it's disabled this just uses the regular
 	 * multi-target mode.  */