数字IC验证 - Portable Stimulus Standard(PSS) 子系统级测试用例

本文链接：https://blog.youkuaiyun.com/small_process/article/details/141864022

测试用例简介：

uart ip来自于openc910项目的uart源代码，本测试用例通过配置uart寄存器来实现uart的组件的发送和接收以及数据的检查，使用dsl语言抽象描述uart组件和vip_uart组件，并通过PSS的action infer feature来推断生成各种合法的配置场景。此测试用例在数字IC验证 - Portable Stimulus Standard(PSS) Uart IP级测试用例的基础之上，进一步在子系统上对uart ip进行的测试。uart_c组件以及vip_uart_c组件可以复用Uart IP级测试用例，需要修改的部分仅仅是将apb_sv_binding_pkg部分对apb写接口xpss_scalar_write32和读接口xpss_scalar_read32的实现，替换成axi_sv_binding_pkg部分对axi写接口xpss_scalar_write32和读接口xpss_scalar_read32的实现，vip_uart_sv_binding_pkg.pss无需修改。

task automatic axi_write8(input axi_master_agent master, longint unsigned addr, input byte unsigned data);
  axi_write_byte_sequence byte_seq;
  byte_seq = axi_write_byte_sequence::type_id::create("byte_seq");
  byte_seq.addr = addr[39:0];
  byte_seq.data = data[7:0];
  byte_seq.start(master.sequencer);
endtask;

task automatic axi_write16(input axi_master_agent master, longint unsigned addr, input shortint unsigned data);
  axi_write_hword_sequence hword_seq;
  hword_seq = axi_write_hword_sequence::type_id::create("hword_seq");
  hword_seq.addr = addr[39:0];
  hword_seq.data = data[15:0];
  hword_seq.start(master.sequencer);
endtask;

task automatic axi_write32(input axi_master_agent master, longint unsigned addr, input int unsigned data);
  axi_write_word_sequence word_seq;
  word_seq = axi_write_wrod_sequence::type_id::create("word_seq");
  word_seq.addr = addr[39:0];
  word_seq.data = data[31:0];
  word_seq.start(master.sequencer);
endtask;

task automatic axi_write64(input axi_master_agent master, longint unsigned addr, input longint unsigned data);
  axi_dwrite_word_sequence word_seq;
  dword_seq = axi_write_dwrod_sequence::type_id::create("dword_seq");
  dword_seq.addr = addr[39:0];
  dword_seq.data = data[63:0];
  dword_seq.start(master.sequencer);
endtask;

task automatic axi_read8(input axi_master_agent master, longint unsigned addr, output byte unsigned data);
  axi_read_byte_sequence byte_seq;
  byte_seq = axi_read_byte_sequence::type_id::create("byte_seq");
  byte_seq.addr = addr[39:0];
  byte_seq.start(master.sequencer);
  data = byte_seq.data[7:0];
endtask;

task automatic axi_read16(input axi_master_agent master, longint unsigned addr, output shortint unsigned data);
  axi_read_hword_sequence hword_seq;
  hword_seq = axi_read_hword_sequence::type_id::create("hword_seq");
  hword_seq.addr = addr[39:0];
  hword_seq.start(master.sequencer);
  data = hword_seq.data[15:0];
endtask;

task automatic axi_read32(input axi_master_agent master, longint unsigned addr, output int unsigned data);
  axi_read_word_sequence hword_seq;
  word_seq = axi_read_word_sequence::type_id::create("word_seq");
  word_seq.addr = addr[39:0];
  word_seq.start(master.sequencer);
  data = word_seq.data[31:0];
endtask;

task automatic axi_read64(input axi_master_agent master, longint unsigned addr, output longint unsigned data);
  axi_read_dword_sequence dword_seq;
  dword_seq = axi_read_dword_sequence::type_id::create("dword_seq");
  dword_seq.addr = addr[39:0];
  dword_seq.start(master.sequencer);
  data = dword_seq.data[63:0];
endtask;

export "DPI-C" task xpss_scalar_write8;
task xpss_scalar_write8(input longint unsigned addr, input byte unsigned data);
  static string axi_master = {"*.", inst_name, ".master"};
  axi_master_agent master;
  master = find_axi_master_agent(axi_master);
  axi_write8(master, addr, data);
endtask;

export "DPI-C" task xpss_scalar_write16;
task xpss_scalar_write16(input longint unsigned addr, input shortint unsigned data);
  static string axi_master = {"*.", inst_name, ".master"};
  axi_master_agent master;
  master = find_axi_master_agent(axi_master);
  axi_write16(master, addr, data);
endtask;
 
export "DPI-C" task xpss_scalar_write32;
task xpss_scalar_write32(input longint unsigned addr, input int unsigned data);
  static string axi_master = {"*.", inst_name, ".master"};
  axi_master_agent master;
  master = find_axi_master_agent(axi_master);
  axi_write32(master, addr, data); 
endtask;

export "DPI-C" task xpss_scalar_write64;
task xpss_scalar_write64(input longint unsigned addr, input longint unsigned data);
  static string axi_master = {"*.", inst_name, ".master"};
  axi_master_agent master;
  master = find_axi_master_agent(axi_master);
  axi_write64(master, addr, data); 
endtask;
 
export "DPI-C" task xpss_scalar_read8;
task xpss_scalar_read8(input longint unsigned addr, output byte unsigned data);
  static string axi_master = {"*.", inst_name, ".master"};
  axi_master_agent master;
  master = find_axi_master_agent(axi_master);
  apb_read8(master, addr, data);
endtask;

export "DPI-C" task xpss_scalar_read16;
task xpss_scalar_read16(input longint unsigned addr, output shortint unsigned data);
  static string axi_master = {"*.", inst_name, ".master"};
  axi_master_agent master;
  master = find_axi_master_agent(axi_master);
  apb_read16(master, addr, data);
endtask;
 
export "DPI-C" task xpss_scalar_read32;
task xpss_scalar_read32(input longint unsigned addr, output int unsigned data);
  static string axi_master = {"*.", inst_name, ".master"};
  axi_master_agent master;
  master = find_axi_master_agent(axi_master);
  axi_write32(master, addr, data); 
endtask;

export "DPI-C" task xpss_scalar_read64;
task xpss_scalar_read64(input longint unsigned addr, output longint unsigned data);
  static string axi_master = {"*.", inst_name, ".master"};
  axi_master_agent master;
  master = find_axi_master_agent(axi_master);
  axi_write64(master, addr, data); 
endtask;

将pss_top component中insts.inst[0].tag的"apb0"修改成"axi0_agent"，根据这个字符串匹配查找axi agent，将axi agent绑定到线程0执行。

component pss_top {

  exec init_down {
    // bind threads to exectors
    insts.inst[0].tag = "axi0_agent";
    insts.inst[0].agent_context_type = UVM_TYPE;
  };
}；

从Uart IP级测试用例到子系统级测试用例model部分就修改完成了，主要是两部分：

1. 实现AXI写接口xpss_scalar_write32和读接口xpss_scalar_read32；

2. 实现AXI agent与excutor线程绑定；

下面介绍如何将PSS生成的文件集成到testbench。由于是测试用例是子系统测试用例，因此我们把openc910的核部分代码给去掉，连接AXI信号到module soc，如下图所示。

1. 在module tb_top中例化module lib_entry_top;

2. 在pss_sequence_test类的run_phase，启动C main同步；

module tb_top;
  ......
 
  // instance pss entry module
  lib_entry_top entry_top();
 
  // instance uart interface and apb interface
  uart_if uart_if_0(...);
  axi_if apb_if[2](...);

  soc x_soc(
    .i_pad_rst_b            (rst_b),
    .i_pad_clk              (sys_clk),
    ...
    // axi signals
    .pad_biu_core0_arready  (axi_if[0].arready),
    ...
    .biu_pad_core1_wvalid   (axi_if[1].wvalid),
    .i_pad_uart0_sin        (uart_if_0.txd),
    .o_pad_uart0_sout       (uart_if_0.rxd)
  );

  initial begin
    ......
    run_test();
  end
  
  ......
endmodule

class pss_sequence_test extends pss_base_test;
  `uvm_component_utils(pss_sequence_test);

  function new(string name = "pss_sequence_test", uvm_component parent=null);
    super.new(name, parent);
  endfunction

  function void build_phase(uvm_phase phase);
    super.build_phase(phase);
  endfunction

  task run_phase(uvm_phase phase);
    phase.raise_objection(this);

    // entry the PSS C test main scenario 
    lib_startup_pkg::xpss_sync_entry_main();

    phase.drop_objection(this);
  endtask;
endclass;

使用PSS工具生成测试用例，下面是在vcs下的仿真结果：