【UVM COOKBOOK】Sequences||Virtual Sequencers

// Virtual sequencer class:
class virtual_sequencer extends uvm_sequencer #(uvm_sequence_item);
 `uvm_component_utils(virtual_sequencer)
// Note that the handles are in terms that the test writer understands
 bus_master_sequencer bus; 
 gpio_sequencer gpio;
    function new(string name = "virtual_sequencer", uvm_component parent = null);
  super.new(name, parent);
    endfunction
endclass: virtual_sequencer
class env extends uvm_env;
// Relevant parts of the env which combines the
// virtual_sequencer and the bus and gpio agents
//
// Build:
 function void build_phase( uvm_phase phase );
  m_bus_agent = bus_master_agent::type_id::create("m_bus_agent", this);
        m_gpio_agent = gpio_agent::type_id::create("m_gpio_agent", this); 
        m_v_sqr = virtual_sequencer::type_id::create("m_v_sqr", this);
 endfunction: build_phase
// Connect - where the virtual_sequencer is hooked up:
// Note that these references are constant in the context of this env
 function void connect_phase( uvm_phase phase ); 
       m_v_sqr.bus = m_bus_agent.m_sequencer; 
        m_v_sqr.gpio = m_gpio_agent.m_sequencer;
 endfunction: connect_phase
endclass:env
// Virtual sequence base class:
//
class virtual_sequence_base extends uvm_sequence #(uvm_sequence_item);
 `uvm_object_utils(virtual_sequence_base)
// This is needed to get to the sub-sequencers in the
// m_sequencer
 virtual_sequencer v_sqr;
// Local sub-sequencer handles 
 bus_master_sequencer bus; 
    gpio_sequencer gpio;
 function new(string name = "virtual_sequence_base");
  super.new(name); 
 endfunction
// Assign pointers to the sub-sequences in the base body method:
 task body();
  if(!$cast(v_sqr, m_sequencer)) begin
            `uvm_error(get_full_name(), "Virtual sequencer pointer cast failed");
  end
  bus = v_sqr.bus; 
        gpio = v_sqr.gpio;
 endtask: body
endclass: virtual_sequence_base
// Virtual sequence class:
//
class example_virtual_seq extends virtual_sequence_base;
 random_bus_seq bus_seq; 
 random_gpio_chunk_seq gpio_seq;
 `uvm_object_utils(example_virtual_seq)
 function new(string name = "example_virtual_seq");
  super.new(name); 
 endfunction
 task body();
  super.body; // Sets up the sub-sequencer pointers
  gpio_seq = random_gpio_chunk_seq::type_id::create("gpio_seq"); 
        bus_seq = random_bus_seq::type_id::create("bus_seq");
  repeat(20) begin 
   bus_seq.start(bus); 
   gpio_seq.start(gpio);
  end 
    endtask: body
endclass: example_virtual_seq
// Inside the test class:
//
task run;
 example_virtual_sequence test_seq = 
 example_virtual_sequencer::type_id::create("test_seq");
//...
 test_seq.start(m_env.m_v_sqr);
//...
endtask: run

// Virtual sequencer from the UART env
class uart_env_virtual_sqr extends uvm_sequencer #(uvm_sequence_item);
// ..
 uart_sequencer uart; 
 bus_sequencer bus;
// ..
endclass: uart_env_virtual_sqr
// Virtual sequencer from the GPIO env
class gpio_env_virtual_sqr extends uvm_sequencer #(uvm_sequence_item);
// ..
 gpio_sequencer gpio; 
 bus_sequencer bus;
// ..
endclass: gpio_env_virtual_sqr
// Virtual sequencer from the SoC env
class soc_env_virtual_sqr extends uvm_sequencer #(uvm_sequence_item);
//..
// Low level sequencers to support virtual sequences running across
// TB hierarchical boundaries 
 uart_sequencer uart; 
 bus_sequencer uart_bus; 
 gpio_sequencer gpio; 
 bus_sequencer gpio_bus;
// Virtual sequencers to support existing virtual sequences
//
 uart_env_virtual_sqr uart_v_sqr; 
 gpio_env_virtual_sqr gpio_v_sqr;
// Low level sequencer pointer assignment:
// This has to be after connect because these connections are
// one down in the hierarchy
 function void end_of_elaboration(); 
  uart = uart_v_sqr.uart;
  uart_bus = uart_v_sqr.bus; 
  gpio = gpio_v_sqr.gpio; 
  gpio_bus = gpio_v_sqr.bus;
 endfunction: end_of_elaboration
endclass: soc_env_virtual_sqr

// Either inside the virtual sequence base class or in
// an extension of it that will use specific sequencers:
task body();
 if(!$cast(v_sqr, m_sequencer)) begin
        `uvm_error(get_full_name(), "Virtual sequencer pointer cast failed")
 end
 if(v_sqr.gpio == null) begin
  `uvm_fatal(get_full_name(), "GPIO sub-sequencer null pointer: this test case will fail, check config or virtual sequence")
 end
 else begin
  gpio = v_sqr.gpio;
 end
 if(v_sqr.gpio_bus == null) begin
  `uvm_fatal(get_full_name(), "BUS sub-sequencer null pointer: this test case will fail, check config or virtual sequence")
    end
 else begin
  gpio_bus = v_sqr.gpio_bus;
 end 
endtask: body