uvm callback and reg backdoor access callback
2022/8/31 6:24:33
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uvm callback and reg backdoor access callback
using uvm_callback class
Linux上写的,没有中文输入法,也不翻译了,留个档。
there are 4 main steps to using uvm_callback class to implement callback function.
- extend callback class from uvm_callback class, and defined user callback class.
- add register message(marcos) to the class who call the callback class method.
- place the callback hook in the place you want to call.
- In the test envrionment, create the callback class and add the callback information to the UVM.
here's the details.
extend user callback class from uvm_callback
class driver_callback extends uvm_callback; `uvm_object_utils(driver_callback) function new (string name = "driver_callback"); super.new(name); endfunction virtual task user_drive_pre_cb; endtask virtual task user_drive_post_cb; endtask endclass class user_driver_callback extends driver_callback; `uvm_object_utils(user_driver_callback) function new (string name = "user_driver_callback"); super.new(name); endfunction task user_drive_pre_cb; `uvm_info("callback", "here is the pre_cb called", UVM_LOW) endtask task user_drive_post_cb; `uvm_info("callback", "here is the post_cb called", UVM_LOW) endtask endclass
place the callback hook in the place you want to call
class user_driver extends uvm_driver #(uvm_sequence_item); ... `uvm_components_utils(user_driver) `uvm_register_cb(user_driver, driver_callback) endclass
add the callback marcos to the place you want to call
class user_driver extends uvm_driver #(uvm_sequence_item); ... `uvm_components_utils(user_driver) `uvm_register_cb(user_driver, driver_callback) task run_phase(uvm_phase); `uvm_do_callbacks(user_driver, driver_callback, user_drive_pre_cb); do_run_phase_task(); `uvm_do_callbacks(user_driver, driver_callback, user_drive_post_cb); endtask endclass
create callback class in test environment, and add to uvm environment
class base_test extends uvm_test; user_driver_callback user_cb; ... function build_phase (uvm_phase phase); user_cb = user_driver_callback::create("user_cb"); uvm_callbacks#(user_driver, driver_callback)::add(env.mst_agent.driver, user_cb); endfunction endclass
when have more than 1 callback class
when there are more than 1 callback class extends from driver_callback, the call marcos could call the callback methods multi times, the callback method execute order depends on the which object is using uvm_callbacks#(driver,driver_callback)::add
add to envrionment first.
uvm register model backdoor access callback
background
I have a verification project which need to collect coverage of register value, so I create frontdoor_access uvm_event and backdoor_access uvm_event to sample data(actually, it could using the reg coverage of uvm register model, here is talking about another method). The front door event is easy to triggered, only triggering in the monitor getting the item on uvm_analysis_port. The backdoor_access event is hard to triggered, because such write()/read()/update()/mirror()
methods, all of them could use backdoor path, so it is not possible to use pre_write()/pre_read()
to trigger the backdoor_access event.
and here is the solution of using uvm_reg_cbs
about uvm_reg_cbs
uvm_reg_cbs
derives from uvm_callback
, so the major opeartion is same like part1, the first half of the article. here is the virtual method of uvm_callback.
- pre_write()
- post_write()
- pre_read()
- post_read()
- post_predict()
- encode()
- decode()
we will use post_predict()
to triggered the backdoor_access event.
why we use the post_predict()
post_predict
will be called after a successful UVM_PREDICT_READ or UVM_PREDICT_WRITE prediction. And when we update the register model mirrored value by update()/read()/write()
, it will call predict()
method automatically, so we can use post_predict()
to trigger backdoor_access event.
here's the details.
trig_reg_bd_access_cbs
define
class trig_reg_bd_access_cbs extends uvm_reg_cbs; `uvm_object_utils(trig_reg_bd_access_cbs) uvm_event bd_access_e; function new(string name = "trigger_reg_field_cbs"); super.new(name); endfunction: new function void post_predict(input uvm_reg_field fld, input uvm_reg_data_t previous, inout uvm_reg_data_t value, input uvm_predict_e kind, input uvm_path_e path, input uvm_reg_map map); bd_access_e = uvm_event_pool::get_global("backdoor_access_event"); bd_access_e.trigger(fld); endfunction endclass
instantiate callback class
class test_base extends uvm_test; ... register_model rgm; trig_reg_bd_access_cbs reg_cbs; uvm_reg_field all_fields[$]; function build_phase(uvm_phase); reg_cbs = trig_reg_bd_access_cbs::type_id::create("reg_cbs"); rgm.get_fields(all_fields); foreach(all_fields[i]) uvm_reg_filed_cb::add(all_fields, reg_cbs); endfunction endclass
get triggered data
the backdoor access can be successfully triggered, then you can set uvm_event to get the triggered data.
class cov_model extends uvm_component; uvm_event bd_access_e; uvm_reg_field r; uvm_object tmp; task run_phase(); forever begin bd_access_e = uvm_event_pool::get_global("backdoor_access_event"); bd_access_e.wait_trigger(tmp); void'($cast(r, tmp)); ... end endtask endclass
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