clk_reset_gen and Initial Value Problem

[kaanari]

Hello,
I tried to run tb_apb_regs.sv in QuestaSim andI encountered simulation errors.
1) The first error is parameter definition of clk_rst_gen in the common_verification does not match with the instantiation in tb_apb_regs.sv file.

To run without error, I need to change clk_rst_gen instantiation like below:

 clk_rst_gen #(
    .ClkPeriod    ( CyclTime ),
    .RstClkCycles( 5        )
  ) i_clk_gen (
    .clk_o (clk),
    .rst_no(rst_n)
  );
  

2) Second error is about register initialization values.
As I understand, the intention of the apb_regs is to set every read only registers to reg_init values (by connecting output of registers to reg_init directly) and non read only registers to zero.
Here are lines for that inference:

assign reg_q_o[i] = ReadOnly[i] ? reg_init_i[i] : reg_q[i];
 `FFLARN(reg_q[i], reg_d[i], reg_update[i], '0, pclk_i, preset_ni) // Initialization of non read only registers to 0

However, this behavior does not comply with the expected values in tb_apb_regs because golden model (reg_compare) is filled with random values for both read only and non-read only registers, which causes simulation errors when reading non read only registers.
Below you can find the problematic lines:

// initialize reset values and golden model
for (int unsigned i = 0; i < NoApbRegs; i++) begin
  init_val       = reg_data_t'($urandom()); // Initial value is 0 for non read only registers!
  reg_init[i]    = init_val;
  reg_compare[i] = init_val;
end
done <= 1'b0;

3) Write problem with strobe
When the strobe is not full set (e.g., 1100), corresponding bytes of zero indexes are set to corresponding value in reg_init_i in the line below. This is because has_reset_q is set to 0.

// default assignments
reg_d      = has_reset_q ? reg_q : reg_init_i;

I believe since reg_d is only meaningful for non read-only registers and it is only used to set value for them. It needs to be set to output of the register as default. Then, if there is a write request, it will overwrite the values with respect to strobe value and corresponding bytes would be stay unchanged when their strobe bit is set to 0.

I suggest couple of changes for fixing the issues that I mentioned in my pull request.

[kaanari]

I found out that first issue is related with versioning of Bender. If I set common_cells version to =1.16.2 (which is 1.16.2 right now), Bender also installs lower version for common verification, which has the aligned parameter definition with APB project.