From: Jack Koenig <koenig@sifive.com>
Date: Fri, 31 Mar 2017 02:12:15 +0000 (-0700)
Subject: "Fix" false combinational loop through SPIArbiter
X-Git-Url: https://git.libre-soc.org/?p=sifive-blocks.git;a=commitdiff_plain;h=6a3b5e1a31f0fa317d9ede581545ba27952ab1a4;hp=e2073feef87f080ac3e354774c3a0cbb0a55be3d

"Fix" false combinational loop through SPIArbiter

Mux1H converts aggregates to UInt, muxes, then converts back which can
look like a cominational loop.
---

diff --git a/src/main/scala/devices/spi/SPIArbiter.scala b/src/main/scala/devices/spi/SPIArbiter.scala
index 56c484e..df87d95 100644
--- a/src/main/scala/devices/spi/SPIArbiter.scala
+++ b/src/main/scala/devices/spi/SPIArbiter.scala
@@ -20,7 +20,9 @@ class SPIArbiter(c: SPIParamsBase, n: Int) extends Module {
   io.outer.tx.bits := Mux1H(sel, io.inner.map(_.tx.bits))
   io.outer.cnt := Mux1H(sel, io.inner.map(_.cnt))
   io.outer.fmt := Mux1H(sel, io.inner.map(_.fmt))
-  io.outer.cs := Mux1H(sel, io.inner.map(_.cs))
+  // Workaround for overzealous combinational loop detection
+  io.outer.cs := Mux(sel(1), io.inner(0).cs, io.inner(1).cs)
+  require(n == 2, "SPIArbiter currently only supports 2 clients")
 
   (io.inner zip sel).foreach { case (inner, s) =>
     inner.tx.ready := io.outer.tx.ready && s