uvm_hdl——DPI在UVM中的实现（四）

　　我们可以在uvm中实现HDL的后门访问，具体包括的function有uvm_hdl_check_path，uvm_hdl_deposit， uvm_hdl_force，uvm_hdl_release，uvm_hdl_read， task 有uvm_hdl_force_time。 这么做与直接用SV中force, release 有什么区别，有什么好处？这么做的话函数的输入是字符串而不是HDL（hardware description language, 硬件描述语言 ）的层次结构。有了字符串就可以模块化了(函数)，首先来看uvm_hdl.svh的源代码，当定义了UVM_HDL_NO_DPI，而用户由调用了HDL DPI相关的函数，这时会报错。

// TITLE: UVM HDL Backdoor Access support routines.
//
// These routines provide an interface to the DPI/PLI
// implementation of backdoor access used by registers.
//
// If you DON'T want to use the DPI HDL API, then compile your
// SystemVerilog code with the vlog switch
//:   vlog ... +define+UVM_HDL_NO_DPI ...
//


`ifndef UVM_HDL__SVH
`define UVM_HDL__SVH


`ifndef UVM_HDL_MAX_WIDTH
`define UVM_HDL_MAX_WIDTH 1024
`endif

/* 
 * VARIABLE: UVM_HDL_MAX_WIDTH
 * Sets the maximum size bit vector for backdoor access. 
 * This parameter will be looked up by the 
 * DPI-C code using:
 *   vpi_handle_by_name(
 *     "uvm_pkg::UVM_HDL_MAX_WIDTH", 0);
 */
parameter int UVM_HDL_MAX_WIDTH = `UVM_HDL_MAX_WIDTH;


typedef logic [UVM_HDL_MAX_WIDTH-1:0] uvm_hdl_data_t;

                            
`ifndef UVM_HDL_NO_DPI

  // Function: uvm_hdl_check_path
  //
  // Checks that the given HDL ~path~ exists. Returns 0 if NOT found, 1 otherwise.
  //
  import "DPI-C" context function int uvm_hdl_check_path(string path);


  // Function: uvm_hdl_deposit
  //
  // Sets the given HDL ~path~ to the specified ~value~.
  // Returns 1 if the call succeeded, 0 otherwise.
  //
  import "DPI-C" context function int uvm_hdl_deposit(string path, uvm_hdl_data_t value);


  // Function: uvm_hdl_force
  //
  // Forces the ~value~ on the given ~path~. Returns 1 if the call succeeded, 0 otherwise.
  //
  import "DPI-C" context function int uvm_hdl_force(string path, uvm_hdl_data_t value);


  // Function: uvm_hdl_force_time
  //
  // Forces the ~value~ on the given ~path~ for the specified amount of ~force_time~.
  // If ~force_time~ is 0, <uvm_hdl_deposit> is called.
  // Returns 1 if the call succeeded, 0 otherwise.
  //
  task uvm_hdl_force_time(string path, uvm_hdl_data_t value, time force_time = 0);
    if (force_time == 0) begin
      void'(uvm_hdl_deposit(path, value));
      return;
    end
    if (!uvm_hdl_force(path, value))
      return;
    #force_time;
    void'(uvm_hdl_release_and_read(path, value));
  endtask


  // Function: uvm_hdl_release_and_read
  //
  // Releases a value previously set with <uvm_hdl_force>.
  // Returns 1 if the call succeeded, 0 otherwise. ~value~ is set to
  // the HDL value after the release. For 'reg', the value will still be
  // the forced value until it has been procedurally reassigned. For 'wire',
  // the value will change immediately to the resolved value of its
  // continuous drivers, if any. If none, its value remains as forced until
  // the next direct assignment.
  //
  import "DPI-C" context function int uvm_hdl_release_and_read(string path, inout uvm_hdl_data_t value);


  // Function: uvm_hdl_release
  //
  // Releases a value previously set with <uvm_hdl_force>.
  // Returns 1 if the call succeeded, 0 otherwise.
  //
  import "DPI-C" context function int uvm_hdl_release(string path);


  // Function: uvm_hdl_read()
  //
  // Gets the value at the given ~path~.
  // Returns 1 if the call succeeded, 0 otherwise.
  //
  import "DPI-C" context function int uvm_hdl_read(string path, output uvm_hdl_data_t value);

`else

  function int uvm_hdl_check_path(string path);
    uvm_report_fatal("UVM_HDL_CHECK_PATH", 
      $sformatf("uvm_hdl DPI routines are compiled off. Recompile without +define+UVM_HDL_NO_DPI"));
    return 0;
  endfunction

  function int uvm_hdl_deposit(string path, uvm_hdl_data_t value);
    uvm_report_fatal("UVM_HDL_DEPOSIT", 
      $sformatf("uvm_hdl DPI routines are compiled off. Recompile without +define+UVM_HDL_NO_DPI"));
    return 0;
  endfunction

  function int uvm_hdl_force(string path, uvm_hdl_data_t value);
    uvm_report_fatal("UVM_HDL_FORCE", 
      $sformatf("uvm_hdl DPI routines are compiled off. Recompile without +define+UVM_HDL_NO_DPI"));
    return 0;
  endfunction

  task uvm_hdl_force_time(string path, uvm_hdl_data_t value, time force_time=0);
    uvm_report_fatal("UVM_HDL_FORCE_TIME", 
      $sformatf("uvm_hdl DPI routines are compiled off. Recompile without +define+UVM_HDL_NO_DPI"));
  endtask

  function int uvm_hdl_release(string path, output uvm_hdl_data_t value);
    uvm_report_fatal("UVM_HDL_RELEASE", 
      $sformatf("uvm_hdl DPI routines are compiled off. Recompile without +define+UVM_HDL_NO_DPI"));
    return 0;
  endfunction

  function int uvm_hdl_read(string path, output uvm_hdl_data_t value);
    uvm_report_fatal("UVM_HDL_READ", 
      $sformatf("uvm_hdl DPI routines are compiled off. Recompile without +define+UVM_HDL_NO_DPI"));
    return 0;
  endfunction

`endif


`endif

与之对应的uvm_hdl.c实现如下，由于每个EDA vendor 具体实现方式不同，所有分别包含在不同的文件中了。

// hdl vendor backends are defined for VCS,QUESTA,INCA
#if defined(VCS) || defined(VCSMX)
#include "uvm_hdl_vcs.c"
#else
#ifdef QUESTA
#include "uvm_hdl_questa.c"
#else
#if defined(INCA) || defined(NCSC)
#include "uvm_hdl_inca.c"
#else
#error "hdl vendor backend is missing"
#endif
#endif
#endif

首先来看Synopsy家的uvm_hdl_vcs.c：

#include "uvm_dpi.h"
#include <math.h>

#include "svdpi.h"
#include "vcsuser.h"

#ifdef VCSMX
#include "mhpi_user.h"
#include "vhpi_user.h"
#endif


/* 
 * UVM HDL access C code.
 *
 */

/*
 * This C code checks to see if there is PLI handle
 * with a value set to define the maximum bit width.
 *
 * If no such variable is found, then the default 
 * width of 1024 is used.
 *
 * This function should only get called once or twice,
 * its return value is cached in the caller.
 *
 */
static int uvm_hdl_max_width()
{
  vpiHandle ms;
  s_vpi_value value_s = { vpiIntVal, { 0 } };
  ms = vpi_handle_by_name((PLI_BYTE8*) "uvm_pkg::UVM_HDL_MAX_WIDTH", 0);
  if(ms == 0) 
    return 1024;  /* If nothing else is defined, 
                     this is the DEFAULT */
  vpi_get_value(ms, &value_s);
  return value_s.value.integer;
}


/*
 * Given a path, look the path name up using the PLI,
 * and set it to 'value'.
 */
static int uvm_hdl_set_vlog(char *path, p_vpi_vecval value, PLI_INT32 flag)
{
  static int maxsize = -1;
  vpiHandle r;
  s_vpi_value value_s = { vpiIntVal, { 0 } };
  s_vpi_time  time_s = { vpiSimTime, 0, 0, 0.0 };

  //vpi_printf("uvm_hdl_set_vlog(%s,%0x)\n",path,value[0].aval);

  r = vpi_handle_by_name(path, 0);

  if(r == 0)
  {
      const char * err_str = "set: unable to locate hdl path (%s)\n Either the name is incorrect, or you may not have PLI/ACC visibility to that name";
      char buffer[strlen(err_str) + strlen(path)];
      sprintf(buffer, err_str, path);
      m_uvm_report_dpi(M_UVM_ERROR,
                       (char*) "UVM/DPI/HDL_SET",
                       &buffer[0],
                       M_UVM_NONE,
                       (char*)__FILE__,
                       __LINE__);
    return 0;
  }
  else
  {
    if(maxsize == -1) 
        maxsize = uvm_hdl_max_width();

    if (flag == vpiReleaseFlag) {
      //size = vpi_get(vpiSize, r);
      //value_p = (p_vpi_vecval)(malloc(((size-1)/32+1)*8*sizeof(s_vpi_vecval)));
      //value = &value_p;
    }
    value_s.format = vpiVectorVal;
    value_s.value.vector = value;
    vpi_put_value(r, &value_s, &time_s, flag);  
    //if (value_p != NULL)
    //  free(value_p);
    if (value == NULL) {
      value = value_s.value.vector;
    }
  }
  return 1;
}


/*
 * Given a path, look the path name up using the PLI
 * and return its 'value'.
 */
static int uvm_hdl_get_vlog(char *path, p_vpi_vecval value, PLI_INT32 flag)
{
  static int maxsize = -1;
  int i, size, chunks;
  vpiHandle r;
  s_vpi_value value_s;

  r = vpi_handle_by_name(path, 0);

  if(r == 0)
  {
      const char * err_str = "get: unable to locate hdl path (%s)\n Either the name is incorrect, or you may not have PLI/ACC visibility to that name";
      char buffer[strlen(err_str) + strlen(path)];
      sprintf(buffer, err_str, path);
      m_uvm_report_dpi(M_UVM_ERROR,
              (char*)"UVM/DPI/HDL_GET",
                       &buffer[0],
                       M_UVM_NONE,
                       (char*)__FILE__,
                       __LINE__);
    // Exiting is too harsh. Just return instead.
    // tf_dofinish();
    return 0;
  }
  else
  {
    if(maxsize == -1) 
        maxsize = uvm_hdl_max_width();

    size = vpi_get(vpiSize, r);
    if(size > maxsize)
    {
      const char * err_str = "uvm_reg : hdl path '%s' is %0d bits, but the maximum size is %0d.  You can increase the maximum via a compile-time flag: +define+UVM_HDL_MAX_WIDTH=<value>";
      char buffer[strlen(err_str) + strlen(path) + (2*int_str_max(10))];
      sprintf(buffer, err_str, path, size, maxsize);
      m_uvm_report_dpi(M_UVM_ERROR,
              (char*)"UVM/DPI/HDL_SET",
                       &