Error in AXI4 Xbar with unused fields

[tymcauley]

Type of issue: bug report

Impact: no functional change

Development Phase: proposal

Other information

When constructing an AXI4 Xbar where some master/slave ports have extra fields (such as AMBACorrupt), but others don't, the new :<>= connectable operators throw the following errors:

[error] generators/rocket-chip/src/main/scala/amba/axi4/Xbar.scala:88:24: unconnected consumer field AXI4Xbar.in[1].w.bits.user.corrupt: Wire[Bool]
[error]       in(i).squeezeAll :<>= io_in(i).squeezeAll
[error]                        ^
[error] generators/rocket-chip/src/main/scala/amba/axi4/Xbar.scala:171:28: dangling producer field AXI4Xbar.out[1].w.bits.user.corrupt: Wire[Bool]
[error]       io_out(i).squeezeAll :<>= out(i).squeezeAll
[error]                            ^
[error] There were 2 error(s) during hardware elaboration.

It looks like this was resolved in the TileLink Xbar by adding .waiveAll to these operators, and I can confirm that this resolves the hardware elaboration error for me.

If the current behavior is a bug, please provide the steps to reproduce the problem:

This change will reproduce the error:

--- a/src/main/scala/amba/axi4/Xbar.scala
+++ b/src/main/scala/amba/axi4/Xbar.scala
@@ -319,7 +319,7 @@ class AXI4XbarFuzzTest(name: String, txns: Int, nMasters: Int, nSlaves: Int)(imp
   masters.zipWithIndex.foreach { case (m, i) => (xbar
     := AXI4Delayer(0.25)
     := AXI4Deinterleaver(4096)
-    := TLToAXI4()
+    := TLToAXI4(wcorrupt = (if (i == 0) false else true))
     := TLFilter(filter(i))
     := TLRAMModel(s"${name} Master $i")
     := m.node) }

Then try to emit FIRRTL for the AMBAUnitTestConfig.

Please tell us about your environment:

• Version: current HEAD on master: 74d65ca
• OS: macOS 14.2.1

What is the use case for changing the behavior?

If you have an AXI4 crossbar that is driven by two masters, one with the AMBACorruptField, and one without, then you'll get this elaboration error.

[tymcauley]

Resolved by #3549.