UVM in UVM_ config_ Setting and obtaining DB non-linear

In the figure 3-4 Shown UVM In the tree ,driver The path of is uvm_test_top.env.i_agt.drv. stay uvm_test_top,env perhaps i_agt in , Yes driver Some of the variables in
adopt config_db Set the mechanism , It is called the setting of straight line . But if in other component, Such as scoreboard in , Yes driver Some variables of use config_db Mechanism
Set it up , It is called non-linear setting .
stay my_driver Use in config_db::get Get any other component Set to my_driver Parameters of , It is called the acquisition of straight lines . If you want to be in other component, If in reference model Get other from component Set to my_driver The value of the parameter , It is called non-linear acquisition .
Set non-linear , It needs to be set carefully set The first and second arguments of the function . In the scoreboard Set in driver Medium pre_num For example ：
file ：src/ch3/section3.5/3.5.6/set/my_scoreboard.sv

18 function void my_scoreboard::build_phase(uvm_phase phase);
…
22 uvm_config_db#(int)::set(this.m_parent, "i_agt.drv", "pre_num", 200);
26 `uvm_info("my_scoreboard", "in my_scoreboard, uvm_test_top.env.i_agt.drv.pre_num is set to 200", UVM_LOW)
27 endfunction

perhaps ：

function void my_scoreboard::build_phase(uvm_phase phase);
super.build_phase(phase);
uvm_config_db#(int)::set(uvm_root::get(), "uvm_test_top.env.i_agt.drv", "pre_num", 200);
endfunction

Either way , Has brought a new problem . stay UVM In the tree ,build_phase It's top-down , But for graphs 3-4 Shown UVM For trees ,scb And i_agt At the same level ,UVM The same level of build_phase Execution order of . So when my_driver When getting the parameter value ,my_scoreboard Of build_phase It may have been implemented , It may not be implemented . therefore , This non-linear setting , There will be some risks , This should be avoided .
For the acquisition of non-linear lines, only the first and second parameters need to be set . If you want to be in reference model In order to get driver Of pre_num Value ：

 file ：src/ch3/section3.5/3.5.6/get/my_model.sv
21 function void my_model::build_phase(uvm_phase phase);
22 super.build_phase(phase);
23 port = new("port", this);
24 ap = new("ap", this);
25 `uvm_info("my_model", $sformatf("before get, the pre_num is %0d", drv_pre_num), UVM_LOW)
26 void'(uvm_config_db#(int)::get(this.m_parent, "i_agt.drv", "pre_num", drv_pre_num));
27 `uvm_info("my_model", $sformatf("after get, the pre_num is %0d", drv_pre_num), UVM_LOW)
28 endfunction

perhaps ：

void'(uvm_config_db#(int)::get(uvm_root::get(), "uvm_test_top.env.i_agt.drv",
"pre_num", drv_pre_num));

Both of these methods can be set correctly pre_num Value .
The acquisition of non-linear lines can be avoided in some cases config_db::set Redundancy of . The above example is in reference model In order to get driver Of pre_num Value , If
Don't do this , The method of straight line acquisition , Then you need to pass in the test case cofig_db::set Give to separately reference model and driver Set up pre_num Value .
The same parameter value setting appears in two different statements , This greatly increases the likelihood of mistakes . therefore , The non-linear acquisition can be performed on multiple components in the verification platform
（UVM Tree nodes ） When the same parameter is required , Reduce config_db：：set Redundancy of .