From ec70e5fb02bbdabc1118057c93553412b20b0af4 Mon Sep 17 00:00:00 2001
From: "Wesley W. Terpstra" <wesley@sifive.com>
Date: Mon, 30 Oct 2017 14:00:53 -0700
Subject: [PATCH] apb: inject fuzzy errors

---
 src/main/scala/amba/apb/SRAM.scala | 8 +++++---
 src/main/scala/amba/apb/Test.scala | 3 ++-
 2 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/src/main/scala/amba/apb/SRAM.scala b/src/main/scala/amba/apb/SRAM.scala
index 91e1f210..b9063195 100644
--- a/src/main/scala/amba/apb/SRAM.scala
+++ b/src/main/scala/amba/apb/SRAM.scala
@@ -12,7 +12,9 @@ class APBRAM(
     executable: Boolean = true,
     beatBytes: Int = 4,
     devName: Option[String] = None,
-    errors: Seq[AddressSet] = Nil)
+    errors: Seq[AddressSet] = Nil,
+    fuzzReady: Boolean = false,
+    fuzzError: Boolean = false)
   (implicit p: Parameters) extends DiplomaticSRAM(address, beatBytes, devName)
 {
   val node = APBSlaveNode(Seq(APBSlavePortParameters(
@@ -37,8 +39,8 @@ class APBRAM(
       mem.write(paddr, Vec.tabulate(beatBytes) { i => in.pwdata(8*(i+1)-1, 8*i) }, in.pstrb.toBools)
     }
 
-    in.pready  := Bool(true)
-    in.pslverr := RegNext(!legal)
+    in.pready  := Bool(!fuzzReady) || LFSR16(!in.penable)(0)
+    in.pslverr := RegEnable(!legal, !in.penable) || (Bool(fuzzError) && LFSR16(Bool(true))(0))
     in.prdata  := mem.readAndHold(paddr, read).asUInt
   }
 }
diff --git a/src/main/scala/amba/apb/Test.scala b/src/main/scala/amba/apb/Test.scala
index 2d88c031..5c57191a 100644
--- a/src/main/scala/amba/apb/Test.scala
+++ b/src/main/scala/amba/apb/Test.scala
@@ -21,7 +21,7 @@ class APBFuzzBridge(aFlow: Boolean, txns: Int)(implicit p: Parameters) extends L
   val fuzz  = LazyModule(new TLFuzzer(txns))
   val model = LazyModule(new TLRAMModel("APBFuzzMaster"))
   val xbar  = LazyModule(new APBFanout)
-  val ram   = LazyModule(new APBRAM(AddressSet(0x0, 0xff)))
+  val ram   = LazyModule(new APBRAM(AddressSet(0x0, 0xff), fuzzReady = true, fuzzError = true))
   val gpio  = LazyModule(new RRTest0(0x100))
 
   ram.node  := xbar.node
@@ -31,6 +31,7 @@ class APBFuzzBridge(aFlow: Boolean, txns: Int)(implicit p: Parameters) extends L
     := TLDelayer(0.2)
     := TLBuffer(BufferParams.flow)
     := TLDelayer(0.2)
+    := TLFragmenter(4, 8)
     := model.node
     := fuzz.node)