Revert "[csrng] Temporarily hack-in disable handling"
The reverted commit was originally introduced as part of
lowRISC/OpenTitan#14410 to work around a temporary issue until
lowRISC/OpenTitan#14534 got merged. It seems we forgot to remove that
temporary workaround before merging the PR.
The workaround is critical because it weakens a security countermeasure
inside CSRNG: errors injected into the command stage FSMs are no longer
fatal. By disabling and re-enabling the module these FSMs can be made to
leave the "terminal" error state.
For this reason, we need to remove this workaround. This reverts commit
f4df12fa7e2bc1f4249ae21e94e258ad00aa9756.
Signed-off-by: Pirmin Vogel <vogelpi@lowrisc.org>
diff --git a/hw/ip/csrng/rtl/csrng_cmd_stage.sv b/hw/ip/csrng/rtl/csrng_cmd_stage.sv
index 9e00b00..afc5cb4 100644
--- a/hw/ip/csrng/rtl/csrng_cmd_stage.sv
+++ b/hw/ip/csrng/rtl/csrng_cmd_stage.sv
@@ -401,12 +401,6 @@
cmd_stage_sm_err_o = 1'b1;
end
endcase // unique case (state_q)
-
- // if disable, cycle back to Idle
- if (!cs_enable_i && state_q != Idle) begin
- state_d = Idle;
- end
-
end
//---------------------------------------------------------
