tilelink: more verbose requires

src/main/scala/tilelink/Fragmenter.scala

@@ -66,8 +66,7 @@ class TLFragmenter(val minSize: Int, val maxSize: Int, val alwaysMin: Boolean =
       require (fifoId.isDefined && managers.map(_.fifoId == fifoId).reduce(_ && _))
       require (manager.endSinkId <= 1)
 
-      // We don't support fragmenting to sub-beat accesses
-      require (minSize >= beatBytes)
+      require (minSize >= beatBytes, s"We don't support fragmenting ($minSize) to sub-beat ($beatBytes) accesses")
       // We can't support devices which are cached on both sides of us
       require (!edgeOut.manager.anySupportAcquireB || !edgeIn.client.anySupportProbe)