[ci] Add CS registers TB to CI

Add a return code to TB which Verilator sims can check
Build and run TB, checking for failures

Signed-off-by: Tom Roberts <tomroberts@lowrisc.org>

azure-pipelines.yml

@@ -95,6 +95,11 @@ jobs:
       fi
     displayName: Lint Verilog source files with Verilator
 
+  - bash: |
+      # Build and run CSR testbench
+      fusesoc --cores-root=. run --target=sim --tool=verilator lowrisc:ibex:tb_cs_registers
+    displayName: Build and run CSR testbench with Verilator
+
   - bash: |
       cd build
       git clone https://github.com/riscv/riscv-compliance.git

dv/cs_registers/env/env_dpi.cc

@@ -35,7 +35,10 @@ void env_final() {
   delete reg_env;
 }
 
-void env_tick(svBit *stop_req) { reg_env->GetStopReq(stop_req); }
+void env_tick(svBit *stop_req, svBit *test_passed) {
+  reg_env->GetStopReq(stop_req);
+  reg_env->GetTestPass(test_passed);
+}
 
 #ifdef __cplusplus
 }

dv/cs_registers/env/env_dpi.sv

@@ -15,7 +15,8 @@ package env_dpi;
 
   import "DPI-C"
   function void env_tick(
-    output bit stop_req);
+    output bit stop_req,
+    output bit test_passed);
 
 endpackage
 

dv/cs_registers/env/register_environment.cc

@@ -29,3 +29,7 @@ void RegisterEnvironment::OnFinal() {
 void RegisterEnvironment::GetStopReq(unsigned char *stop_req) {
   *stop_req = simctrl_->StopRequested();
 }
+
+void RegisterEnvironment::GetTestPass(unsigned char *test_passed) {
+  *test_passed = simctrl_->TestPassed();
+}

dv/cs_registers/env/register_environment.h

@@ -23,6 +23,8 @@ class RegisterEnvironment {
 
   void GetStopReq(unsigned char *stop_req);
 
+  void GetTestPass(unsigned char *test_passed);
+
  private:
   CSRParams params_;
   SimCtrl *simctrl_;

dv/cs_registers/env/simctrl.cc

@@ -15,6 +15,8 @@ void SimCtrl::RequestStop(bool success) {
 
 bool SimCtrl::StopRequested() { return stop_requested_; }
 
+bool SimCtrl::TestPassed() { return success_; }
+
 void SimCtrl::OnFinal() {
   std::cout << std::endl
             << "//-------------//" << std::endl

dv/cs_registers/env/simctrl.h

@@ -10,6 +10,7 @@ class SimCtrl {
   SimCtrl();
   void RequestStop(bool success);
   bool StopRequested();
+  bool TestPassed();
   void OnFinal();
 
  private:

dv/cs_registers/tb/tb_cs_registers.cc

@@ -18,5 +18,12 @@ int main(int argc, char **argv) {
   simctrl.SetTop(&top, &top.clk_i, &top.in_rst_ni,
                  VerilatorSimCtrlFlags::ResetPolarityNegative);
 
-  return simctrl.Exec(argc, argv);
+
+  // Get pass / fail from Verilator
+  int retcode = simctrl.Exec(argc, argv);
+  if (!retcode) {
+    // Get pass / fail from testbench
+    retcode = !top.test_passed_o;
+  }
+  return retcode;
 }

dv/cs_registers/tb/tb_cs_registers.sv

@@ -13,7 +13,8 @@ module tb_cs_registers #(
 ) (
     // Clock and Reset
     inout  wire                 clk_i,
-    inout  wire                 in_rst_ni
+    inout  wire                 in_rst_ni,
+    output wire                 test_passed_o
 );
 
   logic                 dpi_rst_ni;
@@ -126,6 +127,7 @@ module tb_cs_registers #(
 
   // DPI calls
   bit stop_simulation;
+  bit test_passed;
   bit [31:0] seed;
 
   initial begin
@@ -140,13 +142,17 @@ module tb_cs_registers #(
   end
 
   always_ff @(posedge clk_i) begin
-    env_dpi::env_tick(stop_simulation);
+    env_dpi::env_tick(stop_simulation, test_passed);
     rst_dpi::rst_tick("rstn_driver", dpi_rst_ni);
     if (stop_simulation) begin
       $finish();
     end
   end
 
+  // Signal test pass / fail as an output (Verilator sims can pick this up and use it as a
+  // return code)
+  assign test_passed_o = test_passed;
+
   always_ff @(posedge clk_i or negedge rst_ni) begin
     reg_dpi::monitor_tick("reg_driver",
                           rst_ni,