[otbn] Fix ALU flag enables
`flags_en` should only be asserted where there is a valid executing
instruction.
Fixes #5655
Signed-off-by: Greg Chadwick <gac@lowrisc.org>
diff --git a/hw/ip/otbn/rtl/otbn_controller.sv b/hw/ip/otbn/rtl/otbn_controller.sv
index c67c6e2..c0465c6 100644
--- a/hw/ip/otbn/rtl/otbn_controller.sv
+++ b/hw/ip/otbn/rtl/otbn_controller.sv
@@ -468,8 +468,8 @@
assign alu_bignum_operation_o.shift_amt = insn_dec_bignum_i.alu_shift_amt;
assign alu_bignum_operation_o.flag_group = insn_dec_bignum_i.alu_flag_group;
assign alu_bignum_operation_o.sel_flag = insn_dec_bignum_i.alu_sel_flag;
- assign alu_bignum_operation_o.alu_flag_en = insn_dec_bignum_i.alu_flag_en;
- assign alu_bignum_operation_o.mac_flag_en = insn_dec_bignum_i.mac_flag_en;
+ assign alu_bignum_operation_o.alu_flag_en = insn_dec_bignum_i.alu_flag_en & insn_executing;
+ assign alu_bignum_operation_o.mac_flag_en = insn_dec_bignum_i.mac_flag_en & insn_executing;
assign mac_bignum_operation_o.operand_a = rf_bignum_rd_data_a_i;
assign mac_bignum_operation_o.operand_b = rf_bignum_rd_data_b_i;
