csrng_agent_cov.sv

// Copyright lowRISC contributors (OpenTitan project).
// Licensed under the Apache License, Version 2.0, see LICENSE for details.
// SPDX-License-Identifier: Apache-2.0

`define CSRNG_GLEN_COVBIN \
    csrng_glen: coverpoint item.glen { \
      // TODO: EDN testbench currently sends a max of 64 endpoints, which is 64/4 genbits. \
      bins glens[4] = {[1:16]}; \
    }

`define CSRNG_STS_COVBIN \
    csrng_sts: coverpoint sts { \
    bins pass =  {CMD_STS_SUCCESS}; \
    bins fail = {CMD_STS_INVALID_ACMD, CMD_STS_INVALID_GEN_CMD, \
                 CMD_STS_INVALID_CMD_SEQ, CMD_STS_RESEED_CNT_EXCEEDED}; \
    }

// covergroups
// Depends on whether the agent is device or host mode, the "csrng_cmd_cp" are slightly different:
// In device mode: acmd INV, GENB, GENU are in the illegal bin.
covergroup device_cmd_cg with function sample(csrng_item item, csrng_cmd_sts_e sts);
  option.name         = "csrng_device_cmd_cg";
  option.per_instance = 1;

  csrng_cmd_cp: coverpoint item.acmd {
    bins ins = {INS};
    bins res = {RES};
    bins gen = {GEN};
    bins uni = {UNI};
    bins upd = {UPD};
    illegal_bins il = default;
  }
  csrng_clen_cp: coverpoint item.clen {
    bins zero = {0};
    bins non_zero_bins[2] = {[1:15]};
  }
  // TODO: do not use enum to sample non-true/false data
  csrng_flag_cp: coverpoint item.flags {
    bins mubi_true = {MuBi4True};
    bins mubi_false = {MuBi4False};
  }
  csrng_sts: coverpoint sts {
    bins pass = {CMD_STS_SUCCESS};
    bins fail = {CMD_STS_INVALID_ACMD, CMD_STS_INVALID_GEN_CMD,
                 CMD_STS_INVALID_CMD_SEQ, CMD_STS_RESEED_CNT_EXCEEDED};
  }

  csrng_cmd_cross: cross csrng_cmd_cp, csrng_clen_cp, csrng_sts, csrng_flag_cp {
    // Only a value of zero should be used for clen when UNI command is used.
    ignore_bins uni_clen = binsof(csrng_cmd_cp.uni) && binsof(csrng_clen_cp.non_zero_bins);
  }
endgroup

covergroup host_cmd_cg with function sample(csrng_item item, csrng_cmd_sts_e sts);
  option.name         = "csrng_host_cmd_cg";
  option.per_instance = 1;

  csrng_cmd_cp: coverpoint item.acmd {
    bins inv = {INV};
    bins ins = {INS};
    bins res = {RES};
    bins gen = {GEN};
    bins upd = {UPD};
    bins uni = {UNI};
    bins genb = {GENB};
    bins genu = {GENU};
    illegal_bins il = default;
  }
  csrng_clen_cp: coverpoint item.clen {
    bins zero = {0};
    bins other_bins[2] = {[1:15]};
  }
  // TODO: do not use enum to sample non-true/false data
  csrng_flag_cp: coverpoint item.flags {
    bins mubi_true = {MuBi4True};
    bins mubi_false = {MuBi4False};
  }
  csrng_sts: coverpoint sts {
    bins pass = {CMD_STS_SUCCESS};
    bins fail = {CMD_STS_INVALID_ACMD, CMD_STS_INVALID_GEN_CMD,
                 CMD_STS_INVALID_CMD_SEQ, CMD_STS_RESEED_CNT_EXCEEDED};
  }

  csrng_cmd_clen_flag_cross: cross csrng_cmd_cp, csrng_clen_cp, csrng_flag_cp;

  csrng_cmd_clen_flag_sts_cross: cross csrng_cmd_cp, csrng_clen_cp, csrng_flag_cp, csrng_sts {
    // Illegal commands (INV, GENB, GENU) don't get a response, thus don't have a status.
    ignore_bins illegal_cmds = binsof(csrng_cmd_cp) intersect {INV, GENB, GENU};
    // Ignore status error responses for legal commands.
    ignore_bins legal_cmds_with_error_sts = !binsof(csrng_cmd_cp) intersect {INV, GENB, GENU} &&
                                            !binsof(csrng_sts) intersect {CMD_STS_SUCCESS};
  }

endgroup

// Depends on whether the agent is device or host mode, the "csrng_genbits_cross" are slightly
// different:
// In device mode: csrng agent can drive `sts` to pass or fail randomly.
// In host mode: DUT will also return pass for genbits data.
covergroup device_genbits_cg with function sample(csrng_item item, csrng_cmd_sts_e sts);
  option.name         = "csrng_device_genbits_cg";
  option.per_instance = 1;

  `CSRNG_GLEN_COVBIN
  `CSRNG_STS_COVBIN

  csrng_genbits_cross: cross csrng_glen, csrng_sts;
endgroup

covergroup host_genbits_cg with function sample(csrng_item item, csrng_cmd_sts_e sts);
  option.name         = "csrng_host_genbits_cg";
  option.per_instance = 1;

  `CSRNG_GLEN_COVBIN
  `CSRNG_STS_COVBIN

  csrng_genbits_cross: cross csrng_glen, csrng_sts {
    // Generate may not return fail as status.
    ignore_bins sts_fail = binsof(csrng_sts.fail);
  }
endgroup

class csrng_agent_cov extends dv_base_agent_cov#(csrng_agent_cfg);
  host_cmd_cg       m_host_cmd_cg;
  device_cmd_cg     m_device_cmd_cg;
  host_genbits_cg   m_host_genbits_cg;
  device_genbits_cg m_device_genbits_cg;

  `uvm_component_utils(csrng_agent_cov)
  `uvm_component_new

  function void build_phase(uvm_phase phase);
    super.build_phase(phase);

    if (cfg.if_mode == dv_utils_pkg::Device) begin
      m_device_cmd_cg = new();
      m_device_genbits_cg = new();
    end else begin
      m_host_cmd_cg = new();
      m_host_genbits_cg = new();
    end
  endfunction

  function void sample_csrng_cmds(csrng_item item, csrng_cmd_sts_e sts);
    if (cfg.if_mode == dv_utils_pkg::Device) begin
      m_device_cmd_cg.sample(item, cfg.vif.cmd_rsp.csrng_rsp_sts);
      if (item.acmd == csrng_pkg::GEN) begin
        m_device_genbits_cg.sample(item, cfg.vif.cmd_rsp.csrng_rsp_sts);
      end
    end else begin
      m_host_cmd_cg.sample(item, cfg.vif.cmd_rsp.csrng_rsp_sts);
      if (item.acmd == csrng_pkg::GEN) begin
        m_host_genbits_cg.sample(item, cfg.vif.cmd_rsp.csrng_rsp_sts);
      end
    end
  endfunction

endclass