How can we invoke the stop task in ovm_component?

OVM
1

Dear all,
I saw a stop task in ovm_component.
How can we use this task?
Thank you!

2

Hi,

The stop task is called after a stop request if the component’s enable_stop_interrupt member has been set to 1.

Typically, you would wait within the stop task for some activity to complete - the simulation will continue until all of the stop tasks called have returned.

Here is a simple example that should give you the idea:

class dut_driver extends ovm_driver;
   ...  
   if_wrapper if_wr;

   function new(string name, ovm_component parent);
      super.new(name,parent);
      enable_stop_interrupt = 1;
   endfunction : new

   task stop(string ph_name);
      ovm_report_info("DRV","Waiting to stop");
      wait(if_wr.if1.driver.done == 1);
      ovm_report_info("DRV","Stopping now");
   endtask: stop

   task run();
     ...
   endtask: run
endclass: dut_driver

Regards,
Dave

3

Hi Dave,

How about this :

initial
begin
…
ovm_top.stop_timeout=16’h8;
…
run_test();
end
…
class dut_driver extends ovm_driver;
…
if_wrapper if_wr;
function new(string name, ovm_component parent);
super.new(name,parent);
enable_stop_interrupt = 1;
endfunction : new
task stop(string ph_name);

10000ns;

endtask: stop
task run();
ovm_top.stop_request();
endtask: run
endclass: dut_driver

Will the simulation stop after 8ns when run call ovm_top.stop_request?
Thank you!

4

Hi,

Will the simulation stop after 8ns when run call ovm_top.stop_request?

Yes. You should also get a message 8ns after the call to ovm_top.stop_request telling you that the stop-request timeout has expired.

Regards,
Dave

5

Hi Dave,
It seem my idea does not work well.
Enclosed is modified from your example.
Is there somethiing wrong when i use stop() task and stop_timeout?
Thank you!

6

Hi,

Is there somethiing wrong when i use stop() task and stop_timeout?

The problem with your example is that you have commented-out all of the statements in the driver’s run task so there is nothing else for it to do after stop_request is called!

If you restore the driver::run to its original state and call stop_request in the test’s run task then it should work as expected, e.g.

task run;
      tiny_transaction tx;
      tx = new;
      ovm_report_message("", "Called my_test::run");
      fork
         m_env.m_stimulus.generate_stimulus(tx, 10);
         #10 ovm_top.stop_request();
      join
    endtask: run

The output should be

...
# OVM_INFO @ 0: ovm_test_top [] Called my_test::run
# OVM_INFO @ 0: ovm_test_top.m_env [] Called my_env::run
# OVM_INFO @ 0: ovm_test_top.m_env.m_driver [] Called my_driver::run
# OVM_INFO @ 10: ovm_test_top.m_env.m_driver [] Driving cmd = R, addr =           2, data =           1}
# DUT received r0w1 = 0, addr =           2, data =           1 at 10
# OVM_WARNING @ 18 [STPTO] Stop-request timeout of 8 expired. Stopping phase 'run'
# OVM_INFO @ 18: ovm_test_top.m_env [] Called my_env::report
# ** Note: $finish    : /apps/questasim/linux/../verilog_src/ovm/base/ovm_root.svh(308)
#    Time: 18 ns  Iteration: 6  Instance: /ovm_pkg::ovm_root::run_test

Regards,
Dave

7

Hi Dave,
Could you share me the code and runscript in Questasim?
Thank you!

8

Hi,

The file is the same as the one you posted with the changes I described. I am including it anyway with a compile options file for Questa.

Regards,
Dave

P.S. you need to remember to use the +OVM_TESTNAME option to run it!

qverilog -f compile_questa.f -R +OVM_TESTNAME=my_test
9

Hi David long,
You are so kind!
Thanks for your great example and help!

But I still wonder why:

The problem with your example is that you have commented-out all of the statements in the driver’s run task so there is nothing else for it to do after stop_request is called!

why stop_timeout should can not work properly in my case?
why run should be running after stop_request is called?

virtual task run;
ovm_report_message("", "Called my_driver::run");
forever
begin
/*my_transaction tx;
#10
get_port.get(tx);
 
ovm_report_message("",$psprintf("Driving cmd = %s, addr = %d, data = %d}",
(tx.r0w1 ? "W" : "R"), tx.addr, tx.data));
m_dut_if.r0w1 = tx.r0w1;
m_dut_if.addr = tx.addr;
m_dut_if.data = tx.data;
*/
ovm_top.stop_request();
end
endtask: run
 
task stop(string ph_name);
#10000ns;
endtask
endclass: my_driver