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Tierney bq207 Presentation Transcript

  • 1. Experiences with SystemC Design Verification Using SystemC Greg Tierney Presented to DV Club, Boston March 5, 2007 DV Club, Boston
  • 2. Experiences with SystemC About Avid Invented digital video editing Headquartered in Tewksbury – http://www.avid.com/company/ Products – Film/Video Editing and Finishing – Audio – Broadcast – Animation – Storage & Workgroups – Digital Asset and Production Management Services – Support – Training – Consulting DV Club, Boston
  • 3. Experiences with SystemC Agenda What is SystemC? Why did Avid choose to use SystemC? DV problems solved by SystemC. Summary DV Club, Boston
  • 4. Experiences with SystemC What is SystemC? Provides hardware constructs and a simulation kernel for C++ It is a class library – And it is a language standard (IEEE 1666TM 2005) It has utilities and constructs – Data types, ports, channels, processes Adopted by different disciplines – Architectural Modeling (SoC, performance) – DV (RTL simulation, HW/SW co-verification) – Synthesis It is open source (OSCI) – http://www.systemc.org DV Club, Boston
  • 5. Experiences with SystemC Why Avid Chose SystemC Enhanced existing C++ DV code – Replaced an unreliable in-house framework • Signal encapsulation • Thread management • Random seed management – Smooth transition from C++ to SystemC Tool availability – Single kernel multi-language simulator Industry acceptance Low cost Came with built-in verification capabilities DV Club, Boston
  • 6. Experiences with SystemC Agenda What is SystemC? Why did Avid choose to use SystemC? DV problems solved by SystemC. Summary DV Club, Boston
  • 7. Experiences with SystemC Crossing Language Boundaries Connect an entire HDL module to the testbench. – Wrap the module with a SystemC class (sc_foreign_module). – Provide a string mapping for each port. Connect a foreign signal anywhere in the hierarchy. – Bind a sc_signal (observe_foreign_signal). – Provide a string of hierarchical path to wire or reg. DV Club, Boston
  • 8. Experiences with SystemC Code Examples class MyDUT : public sc_foreign_module { SC_MODULE(MyVTB) public: { sc_in<sc_logic> reset; public: sc_in<sc_logic> clock; sc_out<sc_lv<16> > AD; SC_CTOR(MyVTB) : MyDUTInst(“MyDUTInst”, “MyDUT”), MyDUT(sc_module_nam nm, const char* hdl_name) MyMonitorInst(“MyMonitorInst”, : sc_foreign_module(nm, hdl_name), “MyVTB.MyDUTInst.FooInst”) reset(“reset”), { clock(“clock”), AD(“AD”){} MyDUTInst.reset(tb_reset); }; MyDUTInst.clock(tb_clock); MyDUTInst.AD(tb_AD); class MyMonitor : public sc_module { } public: private: MyMonitor(sc_module_name, MyDUT MyDUTInst; const string& path2DUT){ MyMonitor MyMonitorInst; string path2sig = path2DUT + “.snoop”; snoopSig_.observe_foreign_signal(path2sig); sc_signal<sc_logic> tb_reset; SC_THREAD(threadT); sc_signal<sc_logic> tb_clock; sensitive << sc_signal<sc_lv<16> > tb_AD; snoopSig_.value_changed_event(); }; } private: sc_signal<sc_logic> snoopSig_; void threadT(); }; DV Club, Boston
  • 9. Experiences with SystemC Issues with Binding No clear standard for language boundary resolution. – Each vendor has its own implementation. – Implementation we use doesn’t map arrays or records (yet). Supporting foreign interface requires two pass compilation. – First pass creates object files. – Second pass builds a symbol library used in design elaboration. DV Club, Boston
  • 10. Experiences with SystemC SystemC Connections p start() p start() Call a public method Connect sc_port to a via pointer to object sc_export outp write() read() inp Connect sc_port to a channel DV Club, Boston
  • 11. Experiences with SystemC Code Examples struct start_stop_if : public sc_interface SC_MODULE(MyTest){ { public: virtual void start()=0; sc_port<start_stop_if> bfm_port; virtual void stop()=0; }; }; SC_MODULE(vtb){ public: class MyBFM : SC_CTOR(vtb); public sc_module, private: public virtual start_stop_if sc_signal<sc_logic> Clock; { sc_signal<sc_logic> Request; public: sc_signal<sc_lv<16> > AD; sc_in<sc_logic> Clock; tlm::tlm_fifo<MyX> MyXReceiveChan; sc_out<sc_logic> Request; MyTest MyTestInst; sc_in<sc_lv<16> > AD; MyBFM MyBFMInst; tlm::tlm_put_port<MyX> MyXReceivePort; }; sc_export<start_stop_if> StartStopExport; vtb:vtb(sc_module_name) : void start(); MyBFMInst(“MyBFMInst”), MyTestInst(“MyTestInst”) void stop(); { MyBFMInst.Clock(Clock); SC_CTOR(MyBFM){ MyBFMInst.Request(Request); StartStopExport(*this); MyBFMInst.AD(AD); } MyBFMInst.MyXReceivePort(MyXReceiveChan); }; MyTestInst.bfm_port(MyBFMInst.StartStopExport); } DV Club, Boston
  • 12. Experiences with SystemC Issues with Connections Construction and binding are separate steps. – Ports must be public. – Ports bound after modules and channels are constructed. Binding uses “strict type checking”. – Compilation will fail if type mismatch in the connection. – Splitting a vector across multiple ports is complicated. Binding errors detected at elaboration. – Simulation should abort at runtime if a port is not bound. – Need to assign attributes to port (e.g. # of connections). DV Club, Boston
  • 13. Experiences with SystemC Randomization Separate library dedicated to verification constructs (SCV). Robust, rich feature set for randomization. – Simple constraints (ranges and lists). – Complex constraint solver. – Thread-safe seeding. – Extendible to custom object types. DV Club, Boston
  • 14. Experiences with SystemC Randomization at Avid SCV more than we needed. – So, we use a subset of the features. Provide a Tcl interface to apply constraints. – Wrap scv_smart_ptr. – Define string representations for simple constraints. – Recompilation not required to change constraints. – Reapply constraints over course of simulation. DV Club, Boston
  • 15. Experiences with SystemC Processes Hardware is inherently parallel. DV must be multi-threaded. SystemC solves this with processes. – Macros: SC_THREAD and SC_METHOD. – Events, mutexes, semaphores. – Dynamic processes (sc_spawn). DV Club, Boston
  • 16. Experiences with SystemC Hierarchy SystemC defines an object hierarchy. – Relates objects (parent/child). – Familiar to HDL design. Avid DV defines a layer hierarchy. – Relates connections. – Familiar to communication stacks. Issue: SystemC is not a methodology. DV Club, Boston
  • 17. Experiences with SystemC Example Hierarchy VTOP VTEST Test Translator Reference Model Scoreboard VTB TLM Agent STIMGEN Analysis Agent Analysis Agent Commander_BFM TX_BFM Snooper_BFM RX_BFM Driver Monitor Driver Monitor Monitor Monitor DUT DV Club, Boston
  • 18. Experiences with SystemC Agenda What is SystemC? Why did Avid choose to use SystemC? DV problems solved by SystemC. Summary DV Club, Boston
  • 19. Experiences with SystemC Additional Issues Compile and link performance is disappointing. – Overuse of C++ templates in library. – Partially attributed to vendor implementation. Libraries are huge. Being a language standard has tool implications. C++ learning curve. – C++ code debug very different than HDL. • Segmentation faults, stack traces, code stepping Think like a HW engineer, code like a SW engineer. DV Club, Boston
  • 20. Experiences with SystemC Avid’s Experience Used reliably for nearly 3 years. Runtime performance very satisfactory. Provides opportunity to assist product development beyond DV. – Evaluate architectures and predict performance. – Create programmer’s view models for emulation and HW/SW co-verification. DV Club, Boston