parameter not find in freechips.rocketchip.config

**when i build verilog, i got the error as follows:**
rocket-chip/src/main/scala/amba/axi4/Credited.scala:12:64: not found: type Parameters
[error] class AXI4CreditedBuffer(delay: AXI4CreditedDelay)(implicit p: Parameters) extends LazyModule

I open the Credited.scala file, and found that `import freechips.rocketchip.config.Parameters`. But i can't find the config directory. Hope someone can tell me what i should do to resolve the error.

Start with rocket-chip/src/main/scala/amba/axi4/Credited.scala and inspect how the build resolves the freechips.rocketchip.config.Parameters import. Run the Verilog build that produces the error and check whether the config source is present in the expected source tree. Done means the build can resolve Parameters without the reported error.

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