Possible optimization: tlbcamline.sv

[rosethompson]

Return key on the same cycle as write to save one cycle of latency. Check if this increases the critical path.

 // On a write, set the valid bit high and update the stored key.
  // On a flush, zero the valid bit and leave the key unchanged.
  // *** Might we want to update stored key right away to output match on the
  // write cycle? (using a mux)
  flopenr #(1) validbitflop(clk, reset, WriteEnable | TLBFlush, ~TLBFlush, Valid);
  flopenr #(KEY_BITS) keyflop(clk, reset, WriteEnable, {SATP_ASID, VPN}, Key);