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[uvm_phase] on-the-fly reset example and discuss


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Hi UVM Experts,

I am trying to organize a guideline to achieve the on-the-fly reset discussed in the Cypress' paper.

http://events.dvcon.org/events/proceedings.aspx?id=131-2

The steps:

1. component: reset valuables, queue in pre_reset_phase.

2. sequence: release all resources such as semaphores in do_kill()

3. execute the on-the-fly reset in uvm_test as the example below.

virtual task main_phase(uvm_phase phase);
  // after some events or random 
  phase.jump(uvm_pre_reset_phase::get());
  phase.phase_done.clear(); // Question 1
  foreach (sqr[i]) sqr[i].stop_sequences(); // Question 2
endtask: main_pahse

Question 0: It already works in my simple example, however, I am not sure is there anything that I did not take into consideration? please give me some hints and thanks!

Question 1: do you suggest to use "phase.phase_done.clear(); directly to end the main_phase? is there any risk or there exists better alternative.

Question 2: to make sequence::do_kill() invoked by all sequences, is there better way than finding all sequencer handles and perform stop_sequences()?

thanks in advanced!

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The uvm_phase::jump() clears the phase done objection, so you don't really need the explicit clear afterwards. You could find all the sequencer handles and call stop_sequences() just before the jump. If you have multiple domains, make sure you check the domain of the sequencer matches what you are jumping. The stop_sequences() resolves problems in the sequencer-sequence interaction. You may also have to consider problems in the sequencer-driver interaction -- if your driver calls get_next_item() and then due to reset the sequence is killed, a subsequent item_done() from the driver will cause an error.

An alternative we are using is to replace using jump with setting a notification flag in the config_db and then clearing the phase_done manually. That will cause all components in the domain to get a phase_ready_to_end() callback, which we use in the sequencer to kill sequences (when the notification flag is present).

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Thanks for mastrick's sharing,

In my understand, uvm_phase::jump only set the next phase to go, and it will really go to the phase when all drop. that's why I need to clear it explicitly.

About the driver's problem, for example, the driver:

1. set jump from main_phase to pre_reset_phase

2. get the item at 1ns and plan to invoke item_done in 3ns

3. phase.done.clear in 2ns

4. I originally think the driver stops executing main_phase and to pre_reset_phase() at this monent, and will not execute item_done, so the probelm stated before will not happen, am I correct?

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