Make minimum RTI behavior more realistic. (#375)

* Make minimum RTI behavior more realistic.

Now DMI will return busy when you'd expect it to, instead of a few scans
later. This only matters when testing OpenOCD. There is no other reason
to use --dmi-rti.

* dmireset only resets busy.

riscv/jtag_dtm.cc

@@ -20,9 +20,10 @@ enum {
 
 #define DTMCONTROL_VERSION      0xf
 #define DTMCONTROL_ABITS        (0x3f << 4)
-#define DTMCONTROL_DBUSSTAT     (3<<10)
+#define DTMCONTROL_DMISTAT      (3<<10)
 #define DTMCONTROL_IDLE         (7<<12)
-#define DTMCONTROL_DBUSRESET    (1<<16)
+#define DTMCONTROL_DMIRESET     (1<<16)
+#define DTMCONTROL_DMIHARDRESET (1<<17)
 
 #define DMI_OP                 3
 #define DMI_DATA               (0xffffffffLL<<2)
@@ -144,7 +145,12 @@ void jtag_dtm_t::capture_dr()
       dr_length = 32;
       break;
     case IR_DBUS:
+      if (rti_remaining > 0 || busy_stuck) {
+        dr = DMI_OP_STATUS_BUSY;
+        busy_stuck = true;
+      } else {
         dr = dmi;
+      }
       dr_length = abits + 34;
       break;
     default:
@@ -160,13 +166,11 @@ void jtag_dtm_t::update_dr()
   D(fprintf(stderr, "Update DR; IR=0x%x, DR=0x%lx (%d bits)\n",
         ir, dr, dr_length));
   if (ir == IR_DTMCONTROL) {
-    if (dr & DTMCONTROL_DBUSRESET)
+    if (dr & DTMCONTROL_DMIRESET)
+      busy_stuck = false;
+    if (dr & DTMCONTROL_DMIHARDRESET)
       reset();
-  } else if (ir == IR_DBUS) {
-    if (rti_remaining > 0 || busy_stuck) {
-        dmi = DMI_OP_STATUS_BUSY;
-        busy_stuck = true;
-    } else {
+  } else if (ir == IR_DBUS && !busy_stuck) {
     unsigned op = get_field(dr, DMI_OP);
     uint32_t data = get_field(dr, DMI_DATA);
     unsigned address = get_field(dr, DMI_ADDRESS);
@@ -194,5 +198,4 @@ void jtag_dtm_t::update_dr()
 
     rti_remaining = required_rti_cycles;
   }
-  }
 }