Add restart input to ProgrammableMaster

* while high, won't execute any actions, but reset its step counter

src/main/scala/axi4lite/ProgrammableMaster.scala

@@ -35,6 +35,7 @@ final case class MasterWrite(address: Int, v: BigInt) extends MasterAction {
     val w_resp   = Decoupled(new chisel.axi.Axi4Lite.WriteResponse)
     val finished = Output(Bool())
     val start    = Input(UInt(if (startable) 1.W else 0.W))
+    val restart  = Input(Bool())
   })
 
   val cnt = RegInit(UInt(log2Ceil(action.length + 1).W), init = 0.U)
@@ -77,20 +78,26 @@ final case class MasterWrite(address: Int, v: BigInt) extends MasterAction {
   when (io.maxi.writeData.fire) { wd_valid := false.B }
   when (io.maxi.writeResp.fire) { wr_ready := false.B }
 
-  when ((if (startable) RegNext(io.start(0), init = false.B) else true.B)) {
-    when (!signals.reduce(_ || _)) {
-      for (i <- 0 until action.length) {
-        when (i.U === cnt) {
-          //info(s"Starting action #$i: ${action(i)}")
-          ra := action(i).address.U
-          wa := action(i).address.U
-          wd := action(i).value.getOrElse(BigInt(0)).U
-          ra_valid := action(i).isRead.B
-          rd_ready := action(i).isRead.B
-          wa_valid := (!action(i).isRead).B
-          wd_valid := (!action(i).isRead).B
-          wr_ready := (!action(i).isRead).B
-          cnt := cnt + 1.U
+  when (RegNext(io.restart)) {
+    info("restarting action sequence ...")
+    cnt := 0.U
+  }
+  .otherwise {
+    when ((if (startable) RegNext(io.start(0), init = false.B) else true.B)) {
+      when (!signals.reduce(_ || _)) {
+        for (i <- 0 until action.length) {
+          when (i.U === cnt) {
+            //info(s"Starting action #$i: ${action(i)}")
+            ra := action(i).address.U
+            wa := action(i).address.U
+            wd := action(i).value.getOrElse(BigInt(0)).U
+            ra_valid := action(i).isRead.B
+            rd_ready := action(i).isRead.B
+            wa_valid := (!action(i).isRead).B
+            wd_valid := (!action(i).isRead).B
+            wr_ready := (!action(i).isRead).B
+            cnt := cnt + 1.U
+          }
         }
       }
     }