[aes,dv] Fix coverage definition of AES operation (enc/dec)

[Alfaisal57]

During regression i found that dec bin never got hit. because missing bit width definition.

covergroup aes_ctrl_cg with function sample(
bit aes_op, //here is the error
bit [aes_pkg::AES_MODE_WIDTH-1:0] aes_mode,
bit [aes_pkg::AES_KEYLEN_WIDTH-1:0] aes_keylen,
bit aes_man_op,
bit aes_sideload,
bit [aes_pkg::AES_PRNGRESEEDRATE_WIDTH-1:0] aes_prng_reseed_rate
);
option.per_instance = 1;
option.name = "aes_ctrl_cg";

cp_operation: coverpoint aes_op
  {
   bins enc     = {AES_ENC};
   bins dec     = {AES_DEC};
   bins illegal = { [0:$] } with ($countones(item) != 1);
  }

Solution :
covergroup aes_ctrl_cg with function sample(
bit [aes_pkg::AES_OP_WIDTH-1:0] aes_op, //Modification
bit [aes_pkg::AES_MODE_WIDTH-1:0] aes_mode,
bit [aes_pkg::AES_KEYLEN_WIDTH-1:0] aes_keylen,
bit aes_man_op,
bit aes_sideload,
bit [aes_pkg::AES_PRNGRESEEDRATE_WIDTH-1:0] aes_prng_reseed_rate
);

Thanks a lot to all contributor !

Edit by @vogelpi :
the file to change is: https://github.com/lowRISC/opentitan/blob/master/hw/ip/aes/dv/cov/aes_cov_if.sv

[rswarbrick]

Oops, that looks like a silly error that we made! Thanks for noticing it. Would you be happy to open a PR with the fix?

At a glance, I think the declaration of cg_ctrl_sample also needs sorting out to match.

[vogelpi]

Thanks for reporting this issue @Alfaisal57 . I've now filed a PR to fix the sample function declaration.

This bug masked a little coverage hole that we should fix at some point. I am not worried about this as the logic is very similar to other register fields but we should do it. I've opened #20941 to track this.