Modify noncombin memory to follow new good policy

src/main/scala/components/memory/memory-noncombin-ports.scala

@@ -24,7 +24,7 @@ class OutstandingReq extends Bundle {
 class INonCombinMemPort extends ICombinMemPort {
   // To fake combinational writes
   // TODO: It may be a good idea to move this into a custom utility module
-  val imemBusy  = Reg (new Bool)
+  val imemBusy  = RegInit (false.B)
   imemBusy := DontCare
 
   when (io.pipeline.valid) {
@@ -33,7 +33,9 @@ class INonCombinMemPort extends ICombinMemPort {
     imemBusy := false.B
   }
 
-  io.pipeline.good := (~ imemBusy || io.bus.response.valid)
+  val ready = !imemBusy || io.bus.response.valid
+
+  io.pipeline.good := ready
 }
 
 /**
@@ -42,19 +44,6 @@ class INonCombinMemPort extends ICombinMemPort {
  * The I/O for this module is defined in [[DMemPortIO]].
  */
 class DNonCombinMemPort extends BaseDMemPort {
-  // To fake combinational writes
-  // TODO: It may be a good idea to move this into a custom utility module
-  val dmemBusy  = Reg (new Bool)
-  dmemBusy := DontCare
-
-  io.pipeline.good := (! dmemBusy || io.bus.response.valid)
-
-  when (io.pipeline.valid && io.pipeline.memread && !io.pipeline.memwrite) {
-    dmemBusy := true.B
-  } .elsewhen (io.bus.response.valid) {
-    dmemBusy := false.B
-  }
-
   // A register to hold intermediate data (e.g., write data, mask mode) while the request
   // is outstanding to memory.
   val outstandingReq = RegInit(0.U.asTypeOf(Valid(new OutstandingReq)))
@@ -68,7 +57,11 @@ class DNonCombinMemPort extends BaseDMemPort {
   // Ready if either we don't have an outstanding request or the outstanding request is a read and
   // it has been satisfied this cycle. Note: we cannot send a read until one cycle after the write has
   // been sent.
-  val ready = !outstandingReq.valid || (io.bus.response.valid && (outstandingReq.valid && outstandingReq.bits.operation === MemoryOperation.Read))
+  val wasRequestARead = outstandingReq.valid && outstandingReq.bits.operation === MemoryOperation.Read
+  val ready = !outstandingReq.valid || (io.bus.response.valid && wasRequestARead)
+
+  io.pipeline.good := ready
+
   when (io.pipeline.valid && (io.pipeline.memread || io.pipeline.memwrite) && ready) {
     // Check if we aren't issuing both a read and write at the same time
     assert (! (io.pipeline.memread && io.pipeline.memwrite))

src/test/scala/components/NonCombinMemoryUnitTest.scala

@@ -115,7 +115,9 @@ class AsyncMemoryUnitTester$IMemRead(m: NonCombinMemoryTestHarness, size: Int, l
 }
 // Test data port writes and instruction port reads
 class AsyncMemoryUnitTester$IMemWrite(m: NonCombinMemoryTestHarness, size: Int, latency: Int) extends PeekPokeTester(m) {
+  println ("First expect\n")
   expect(m.io.dmem_good, 1)
+  println ("Done\n")
   // write ascending data to memory 
   for (i <- 0 until size/8) {
     poke(m.io.dmem_address, i*4)
@@ -129,20 +131,25 @@ class AsyncMemoryUnitTester$IMemWrite(m: NonCombinMemoryTestHarness, size: Int,
     poke(m.io.dmem_valid, 0)
 
     if (latency > 1) {
-      // Data memory does not stall on writes
-      expect(m.io.dmem_good, 1)
+      expect(m.io.dmem_good, 0)
       step(latency - 1)
     }
+    // We expect not good from the dmemport, as this is the cycle used to perform a writeback
+    expect(m.io.dmem_good, 0)
     // We wait 1 extra cycle for the data memory to send the write back
     step(1)
 
-    // Memory should be outputting high on good
+    // Memory should now be good
     expect(m.io.dmem_good, 1)
   }
-
   poke (m.io.dmem_memwrite, 0)
   poke (m.io.dmem_valid, 0)
 
+  // Check that data memory remains good after performing an operation
+  for (i <- 0 until 4) {
+    step(1)
+    expect(m.io.dmem_good, 1)
+  }
   expect (m.io.imem_good, 1)
 
   // expect ascending bytes, the first size/8 of them being incremented by 100, on instruction port
@@ -164,6 +171,12 @@ class AsyncMemoryUnitTester$IMemWrite(m: NonCombinMemoryTestHarness, size: Int,
     }
     expect(m.io.imem_good, 1)
   }
+
+  // Check that memory remains good after performing operations (idling)
+  for (i <- 0 until 4) {
+    step (1)
+    expect (m.io.imem_good, 1)
+  }
 }
 
 // Test data port reading a zeroed memory file
@@ -242,10 +255,11 @@ class AsyncMemoryUnitTester$DMemWrite(m: NonCombinMemoryTestHarness, size: Int,
     poke(m.io.dmem_valid, 0)
     if (latency > 1) {
       // Data memory does not stall on writes
-      expect(m.io.dmem_good, 1)
+      expect(m.io.dmem_good, 0)
       step(latency - 1)
     }
-    // We wait 1 extra cycle for the data memory to send the write back
+    // Memory should not be outputting high since this is the cycle used for the writeback
+    expect(m.io.dmem_good, 0)
     step(1)
 
     expect(m.io.dmem_good, 1)
@@ -300,7 +314,6 @@ class AsyncMemoryUnitTester$DMemWrite(m: NonCombinMemoryTestHarness, size: Int,
   */
 class NonCombinMemoryTester extends ChiselFlatSpec {
   val latency = new Random().nextInt (4) + 3
-
   // imem side
   "DualPortedNonCombinMemory" should s"have all zeros in instruction port (with treadle and $latency latency cycles)"  in {
     Driver(() => new NonCombinMemoryTestHarness(2048, "src/test/resources/raw/zero.hex", latency), "treadle") {
@@ -311,20 +324,18 @@ class NonCombinMemoryTester extends ChiselFlatSpec {
     Driver(() => new NonCombinMemoryTestHarness(2048, "src/test/resources/raw/ascending.hex", latency), "treadle") {
       m => new AsyncMemoryUnitTester$IMemRead(m, 2048, latency)
     } should be (true)
-  } 
+  }
   "DualPortedNonCombinMemory" should s"store words with data port and load with instruction port (with treadle and $latency latency cycles)" in {
     Driver(() => new NonCombinMemoryTestHarness(2048, "src/test/resources/raw/ascending.hex", latency), "treadle") {
       m => new AsyncMemoryUnitTester$IMemWrite(m, 2048, latency)
     } should be (true)
   }
-
   // dmem side
   "DualPortedNonCombinMemory" should s"have all zeros in data port (with treadle and $latency latency cycles)"  in {
     Driver(() => new NonCombinMemoryTestHarness(2048, "src/test/resources/raw/zero.hex", latency), "treadle") {
       m => new AsyncMemoryUnitTester$DMemZero(m, 2048, latency)
     } should be (true)
   }
-
   "DualPortedNonCombinMemory" should s"have increasing words in data port (with treadle and $latency latency cycles)" in {
     Driver(() => new NonCombinMemoryTestHarness(2048, "src/test/resources/raw/ascending.hex", latency), "treadle") {
       m => new AsyncMemoryUnitTester$DMemRead(m, 2048, latency)