Single Source Register Sequencing Toolkit and Methodology ...FW and verification teams commonly...

Single Source Register SequencingToolkit and Methodology for

FW and Verification Co-Development

Josh Loo, Anthony Cabrera, Kiel Boyle, Scott R. NelsonNon-Volatile Memory Solutions Group

Intel Corporation

Agenda

What is SSRS?

SSRS Infrastructure

Cross-Domain Register Access Handshaking

Results

Extended Verification Features

What is SSRS?

The Problem:

• Modern SoC productization requires FW for production releases and RAL sequences for pre-silicon verification

• FW and verification teams commonly access registers using different techniques and source languages (ex. C++ vs. SystemVerilog/UVM)

• This leads to effort duplication and discrepancies between sequences make it difficult to replicate exact behavior on different test platforms

What is SSRS?

The Solution:

• Single Source Register Sequencing (SSRS)

– A toolkit that includes a pair of support libraries with associated execution kernels, one in C++ and the other in SystemVerilog

– Enables FW C++ register sequences to be run against RTL simulations without needing a CPU simulation model

– C++ register sequences are executed on an x86 thread that runs parallel to the simulator

What is SSRS?

The Benefits:

• Earlier FW/HW integration testing against standalone IP modules• Faster simulations due to less RTL• Verbatim re-use of FW• Pre-silicon verification scoped to actual FW use cases• Accurate behavior replication on all test platforms

class ssrs_test extends uvm_test;...forkm_env.m_uvc.m_svek.run_c_sequence("path/to/cpp_collateral.so",

"function1");

m_uvm_sequence.start(m_sequencer);

m_env.m_uvc.m_svek.run_c_sequence("path/to/cpp_collateral.so","function2");

join...endclass

What is SSRS?

SSRS Infrastructure

BidirectionalCommunication

Channel

C++ Infrastructure

Firmware HAL

C++ Sequences

Drivers

Register Headers

Register Monitoring Classes

C++ Execution

Kernel(CEK)

SystemVerilog Infrastructure

SystemVerilog Execution Kernel

(SVEK)

Design Under Test (DUT)

RegisterInterface

Register Transaction

Adapter

DPIC++

Sequence Controller

UVM Testcase

Register Abstraction Layer (RAL)

SSRS Infrastructure

• C++ Sequences – orchestrate driver calls to perform a series of register accesses

Channel

C++ Infrastructure

Firmware HAL

Drivers

Register Headers

C++ Execution

Kernel(CEK)

(SVEK)

RegisterInterface

Adapter

DPIC++

Sequence Controller

UVM Testcase

C++ Sequences

SSRS Infrastructure

• Drivers – stateless FW modules that implement accessors to registers

Channel

C++ Infrastructure

Firmware HAL

Register Headers

C++ Execution

Kernel(CEK)

(SVEK)

RegisterInterface

Adapter

DPIC++

Sequence Controller

UVM Testcase

C++ Sequences

Drivers

SSRS Infrastructure

• Register Headers – contain data type definitions that describe the address map and access policies of registers

Channel

C++ Infrastructure

Firmware HAL

C++ Execution

Kernel(CEK)

(SVEK)

RegisterInterface

Adapter

DPIC++

Sequence Controller

UVM Testcase

C++ Sequences

Drivers

Register Headers

SSRS Infrastructure

• Register Monitoring Classes – class objects for registers are allocated in memory and operator overloading is used to monitor register accesses by drivers

Channel

C++ Infrastructure

Firmware HAL

C++ Execution

Kernel(CEK)

(SVEK)

RegisterInterface

Adapter

DPIC++

Sequence Controller

UVM Testcase

C++ Sequences

Drivers

Register Headers

SSRS Infrastructure

Channel

C++ Infrastructure

Firmware HAL

C++ Execution

Kernel(CEK)

(SVEK)

RegisterInterface

Adapter

DPIC++

Sequence Controller

UVM Testcase

C++ Sequences

Drivers

Register Headers

class ssrs_test extends uvm_test;...forkm_env.m_uvc.m_svek.run_c_sequence("path/to/cpp_collateral.so",

"function1");

m_uvm_sequence.start(m_sequencer);

m_env.m_uvc.m_svek.run_c_sequence("path/to/cpp_collateral.so","function2");

join...endclass

SSRS Infrastructure

SVEKCEKShared Object Library

(.so) 4. Control Returns to SVEK

2. Dynamically Load .so Library

4. Fork C++ Sequence

Execution on x86 Thread

1. Initiate C++ Sequence

C++ Domain

SystemVerilog Domain

3. Obtain Function Pointer to C++ Sequence

Cross-DomainRegister Access Handshaking

RUN BLOCKED RUN

Bidirectional Communication

Channel

C++ → SV Message Queue SV → C++ Message Queue

Register Access By Driver Observed

x86 Thread

SVEK Tries to Dequeue

New Message from CEK

Perform UVM

on DUT

SVEK Sends Completion Message to

@Posedge Clock

Get a Handle to Register from RAL

MessageReceived

Initiating a Register Access from C++

• Driver accesses to reg objects in memory are observed by reg monitoring classes

• Overloading read and write operators triggers the CEK to convert the memory address of a register being accessed to its equivalent address from the RAL

• Register Access Message (C++ → SV)

– RAL address of register being accessed

– Access type (e.g. read or write)

– Value to update DUT register with (writes only)

RUN BLOCKED RUN

Channel

x86 Thread

Perform UVM

on DUT

@Posedge Clock

MessageReceived

• Completion Message (SV → C++)

– Value to return to C++:

• Read accesses return the value read from the DUT

RUN BLOCKED RUN

Channel

x86 Thread

Perform UVM

on DUT

@Posedge Clock

MessageReceived

Bidirectional Communication Channel• Encapsulates two message queues: C++ → SV and SV → C++• Implemented in C++ and allocated in memory by CEK• Message queues hold entries of type message_t, a user-defined struct that is

identically defined in both language domains

Message Queue Accessor Function

Action Blocking? Accessible via DPI Import?

put() En-queues a message

No Yes

get() De-queues a message

Yes Yes

tryget() Attempts to de-queue a message

No Yes

Cross-Domain Register Access HandshakingDUT UVM Testbench SVEK C++ SequenceC++ -> SV Queue SV -> C++ Queue

Run C++ Sequence

Create x86 Thread to Run C++ Sequence (DPI call to CEK)

x86 Thread JoinedRun C++ Sequence (Return)

[C++ Sequence Executes a Register Access]

5. Get Register from RAL6. Register Access in DUT

7. Register Access in DUT(Return) 8. Get Register from RAL

(Return)

2. get() CompletionMessage

3. tryget() Register Access Message

4. tryget(): Received

10. get() CompletionMessage (Return)

1. put() Register Access Message

9. put() Completion Message

BLOCKED

Cross-Domain Register Access HandshakingDUT UVM Testbench SVEK C++ SequenceC++ -> SV Queue SV -> C++ Queue

Run C++ Sequence

Create x86 Thread to Run C++ Sequence (DPI call to CEK)

x86 Thread JoinedRun C++ Sequence (Return)

[C++ Sequence Executes Auxiliary Operations]

3. @(posedge clk)

1. tryget() Register Access Message

2. tryget(): Empty

Results

Portability

• SSRS is easily portable to existing UVM testbenches due to its RAL interface

Multi-Platform Code Re-use

• Scope of pre-silicon verification was focused on actual FW use cases as defined by the common sequences

• Sharing common FW drivers and sequences reduced code redundancy and ensured behavior replicability across different test platforms

Results

Flushing Out FW/HW Interaction Bugs Earlier

• Example:

– FW sequence appeared to be passing in post-silicon testing

– When re-running the FW sequence in an RTL simulation, we noticed IO glitches that could trigger undefined behavior on external components

Cross-Team Collaboration

• Verification experts should be able to easily notice errors in FW drivers or sequences since they are experts in SoC design specifications

Continuous Integration

• Changes to shared FW code triggered rigorous reviews across multiple disciplines resulting in higher quality code

• Modifications were automatically regressed against different test platforms

• Regressing FW in simulation provided prompt quality feedback to FW developers without requiring detailed knowledge about UVM environments

• SSRS provided greater debug visibility into FW interactions with the RTL by reproducing behavior in simulation

Results

Constrained Random Parameter Generation

• Existing constraint constructs within a UVM test environment can be used to generate constrained-random values for C++ Sequences

• Effectively reduces manual effort for test creation while increasing functional coverage of the DUT and FW source code

• Currently exploring how to share SystemVerilog generated parameters with other test platforms

Inter-Environment Communication

• Existing message passing mechanisms can also be used to trigger custom SystemVerilog or UVM functionality from C++

• Example use-cases:

– Converting assertion and print statements in C++ to UVM report macros

– Generating backdoor register accesses to accelerate run time

– Generating burst register accesses in simulation

Conclusion

Single Source Register Sequencing (SSRS)

• Enables FW execution against RTL simulations without a CPU model

• Portable to lower-level verification environments due to RAL interface

• Provides developers with greater debug visibility into FW/RTL interactions

• Verbatim reuse of FW enables trivial behavior replication in RTL simulation

• Allows for extension to trigger custom functionality between C++ and SystemVerilog

Questions?

Single Source Register Sequencing Toolkit and Methodology ...FW and verification teams commonly...

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