uvm_send is blocked even after driver executes item_done

[ninad.pachpute]

Hi All,

 

I have a sequence sending a created and randomized item using `uvm_send.

 

The driver receives an item using try_next_item. Upon receiving, it drives the item and calls item_done.

Using debug message after item_done, I can clearly see that item_done is called and returned but `uvm_send in sequence is still blocked and not doing forward to send next item (it implements a loop).

 

Can anyone help me with possible reasons why `uvm_send would not return even when driver has called item_done and come out of item_done.

 

Thanks in advance!

Ninad

[tudor.timi]

Just off the top of my head, make sure that what you are sending is what actually ends up in the driver. Put a print before `uvm_send and one after try_next_item() and see if the handles match.

[ninad.pachpute]

Just off the top of my head, make sure that what you are sending is what actually ends up in the driver. Put a print before `uvm_send and one after try_next_item() and see if the handles match.

 

Hi Tudor,

 

Let me provide pseudo code for details.

 

my_trans_item item;

 

for (n_trans = 0; n_trans < 4; n_trans++) begin

  `uvm_create_on(item, p_sequencer.sequencer_for_item);

  dp.randomize();

  `uvm_send(item);

  /* Later replaced `uvm_send with following:

  start_item(item);

  finish_item(item);

  */

end

 

For 2 out of 4 iterations, the code runs absolutely fine (and data is driven on the DUT interface as expected).

(This probably would answer your question).

For 3rd iteration, `uvm_send is blocked.

In waveforms, I see that complete transaction is driven on DUT interface but `uvm_send does not return.

 

Then I broke `uvm_send in start_item(item) and finish_item(item).

In this case, I see start_item returning but finish_item does not return.

 

Ninad

[tudor.timi]

What would also be helpful would be to post some code from the driver.

[ninad.pachpute]

What would also be helpful would be to post some code from the driver.

 

Yes. Should have done that earlier

 

* driver

forever begin

  seq_item_port.try_next_item(item); 

  if (item == null) begin

    // Drive junk without valid

  end else begin

    fork

      reset_detect();

      begin

      uvm_test_done.raise_objection(this, tID);

      send_to_dut(item);

      seq_item_port.item_done();

      uvm_test_done.drop_objection(this, tID);

      end

    join_any

    disable fork;

  end // if (item == null)

end // forever

[tudor.timi]

I see there that reset_detect() has the potential to kill the thread that calls item_done() (the one between begin ... end). Have a look if this is the case for you.

 

If you want to interrupt driving on reset, then you should make sure to call item_done() to signal to the sequencer that the item is finished (either driven or discarded in your case) and that a new item can start.

[ninad.pachpute]

I see there that reset_detect() has the potential to kill the thread that calls item_done() (the one between begin ... end). Have a look if this is the case for you.

 

If you want to interrupt driving on reset, then you should make sure to call item_done() to signal to the sequencer that the item is finished (either driven or discarded in your case) and that a new item can start.

 

You are correct. It is been taken care of. This is code for reset_detect(). And in waveforms I dont see reset triggering either.

 

    task reset_detect();

 

      wait(vif.rst_n === 1'b1);

      wait(vif.rst_n === 1'b0);

 

      if(uvm_test_done.get_objection_total(this) > 0)

        uvm_test_done.drop_objection(this, tID, uvm_test_done.get_objection_total(this));

      seq_item_port.item_done();

 

    endtask

[tudor.timi]

Are you sure it isn't hanging somewhere in send_to_dut(...) then?

[avinash123]

Hi,

I got a similar issue but i have checked the sending item and driver ending item, both are similar. Below is the description of my problem. If you guys have any solution please share.

 

I have a task in virtual sequencer which actually randomizes the sequence item and then uses execute_item to send the randomized sequence item to the driver.

The driver receives an item using get_next_item. Upon receiving, it drives the item and calls item_done.
Using debug message after item_done, I can clearly see that item_done is called and returned but execute_item in sequencer is still blocked and not going forward to send next item (it implements a loop).

Can anyone help me with possible reasons why execute_item would not return even when driver has called item_done and come out of item_done.

Below is the code of task in sequencer:
assert(item.randomize());
dc_seqr.execute_item(item);

Below is the code in driver:

forever begin
seq_item_port.get_next_item(item);
$cast(m_transfer,item);
void'(this.begin_tr(m_transfer));
drive_data(m_transfer);
this.end_tr(m_transfer);
seq_item_port.item_done(m_transfer);
end

PS:
execute_item has finish_item() and kept display statements below and above of it and i can find that its hanging at finish_item.
The task is called multiple times and the issue is coming for only recent call and is there are no more calls are happening because its hanging at finish_item.

Thanks in advance!
Avinash.