FPGA Partial Reconfiguration Presented by: Abelardo Jara-Berrocal HCS Research Laboratory College of Engineering University of Florida April 10 th, 2009

2 Outline Introduction Partial Reconfiguration (PR) Overview Proposed Design Methodologies Framework analysis F4: Virtual Architecture for Partial Reconfiguration and Design Automation for PR Design

3 General purpose I/O System controller FPGA Configuration lines Shared memory Battery Module A Module B Module A Module B Module A Module B Module C Introduction – Fully reconfigurable systems Bitstreams storage External I/O Design station Required design 1. Device too small for complex designs Module C Module B Module A Module B Module A Module C Module B Module A Module C 2. Big full bitstreams (long reconfiguration time) Config 1 Config 2 Config 3 Config 1 Request Config 2 Request 3. Complete system operation is halted prior to reconfiguration Does’nt fit Module C Module B disabled enabled disabled

4 Types of Modular Dynamic Reconfiguration:  Static Partial Reconfiguration: Reconfiguring a portion of the device (changing the functionality) when the device is inactive without affecting other areas of the device  Dynamic Partial Reconfiguration (PDR): Reconfiguring a portion of the device while the remaining design is still active and operating without affecting the remaining portion of the device. Virtex 4 and Virtex 5 devices support DPR Introduction – Modular Reconfiguration ) Reconfigurable region 1 Reconfigurable region 2

5 Partial Reconfiguration Partial Reconfiguration is useful for systems with multiple functions that can time-share the same FPGA resources. TERMINOLOGY Reconfigurable Region (PRR) Reconfigurable Module (PRM) Static Logic Bus Macro Partial Bitstream Merged Bitstream

6 Module A Module C Module B Introduction – A sample PR architecture FPGA Bitstreams storage Battery External I/O Module C 3. Smaller partial bitstreams Module A request 1. System controller does not need to be placed in an external device 2. Access to fast Internal Configuration Access Port (ICAP – 32 bits, 100 MHz) 4. No need to halt complete system when reconfiguring a module 5. Time multiplexing of FPGA resources, load and unload HW modules on demand Base system configuration JTAG Reconfigurable area disabled Controller (Microblaze) ICAP Flash controller Module C Module B enabled Module A enabled disabled Static area Module A Module B

7 Medium for Partial Reconfiguration External – JTAG, UART (RS232) Internal – ICAP ICAP (Internal Configuration Access Port)  Self-Reconfiguration controlled by soft-processor o Internal read and write access to configuration logic  Faster  HWICAP (provided by Xilinx) o Wraps the ICAP with additional logic to read and write frames to BRAM o Slave to PLB (Processor Peripheral Bus) o 100MHz, 32 bits

8 Additional considerations General benefits from PDR  Saves space on the FPGA  Less time to change only a part of design  Reduction of power dissipation by storing functionality to external memory  Smaller FPGAs can be used to run an application  Architecture adaptation Architecture adaptability  Main advantage, system can modify its internal modules based two schemes Data-Driven: Characteristics of input data changes at the runtime  Artificial intelligence, Evolutionary architectures, Adaptive Signal Processing Situation-Driven: System load/unload modules to adapt to environment conditions  Adaptive Fault tolerance, intelligent management of system resources

9 Bus Macros Bus Macros: Means of communication between PRMs and static design All connections between PRMs and static design must pass through a bus macro with the exception of a clock signal Type of Bus Macros  Tri-state buffer (TBUF) based bus macros  Slice-based (or LUT-based) bus macros Advantage of slice-based bus macros  No signals lines should cross the border in partial reconfiguration  TBUFs – will ignore the boundaries  Slice-based – signals not crossing boundaries

10 LUT-based Slice Macros

11 Controller (Microblaze) ICAP Flash controller Introduction – Current PR Design Flow Steps  Partition the system into modules  Define static modules and reconfigurable modules  Decide the number of PR regions (PRRs)  Decide PRR sizes, shapes and locations  Map modules to PRRs  Define PRR interfaces, instantiate slice macros for PRR interfaces Many manual steps  Design partitioning  Number of PRRs  PRR sizes, shapes and locations  Mapping PRMs to PRRs  Type and placement of PRR interfaces Module A Module C Module B Static modules Reconfigurable Modules (PRMs) 1 2 FPGA # of PRRs? PRR 1 PRR 2 Static region Static modules Modules: A and B Modules: C Design partitioning Design floorplanning and budgeting

12 Introduction – Early Access PR Design Flow Introduced by Xilinx in FPL’06 Major improvements: Automatic implementation scripts Rectangular regions (not full column reconfiguration) Static nets can cross reconfigurable regions Slice macros replace bus macros Partitioning and floorplanning steps are manually executed  Design guidelines for these steps are not provided (manual) Placement and PRRs constraints PRM Bitstreams Design partitioning Design floorplanning and budgeting Xilinx PR Implementation Flow Full Initial Bistream Reconfigurable design specifications (automatic) Potential for development of automatic CAD tools

13 Introduction – Current PR design tools limitations PR design is a very specialized task Only a physical level of support is provided  Architectural knowledge of the target device is a must  Not very flexible, many design constraints Partitioning and floorplanning steps are manually executed  No performance sensitive design guidelines are provided  No automatic heuristics based design flow is available too Lack of abstraction from low level details

14 PR Overview – Taxonomy of PR systems design flows PR Designs Multipurpose Special purpose Highly specialized systems design All PRMs that will exist on the system are known at design time Each PRR is independently optimized (size, shape, location, interface) based on the PRMs that will be mapped to it Output is: 1) Floorplan defining a static region and a set of optimized PRRs 2) The set of PRMs that can be placed in each PRR (PRMs to PRRs mapping) Not optimized for a specific application PRMs required by the application are not known when designing the base system Goal is to design a flexible and reusable base design that can be used for several different PR systems Base system designer defines a set of PRRs with fixed shapes, sizes, locations and interfaces Generated floorplan is used as input template for the PRMs implementation

15 PRR Geometries PR system design flows require:  Proper metrics for PRR performance analysis  Design guidelines for efficient PRR floorplanning Study of the effects of varying PRR shape over  Maximum Clock Frequency  Partial Bitstream Size Five separate test cores:  Beamforming (DSP/slice)  CFAR (slice/memory)  AES (register) Performed on V4SX55 thus far Aspect ratio = PRR Height / PRR Width

16 Framework analysis – Beamforming (~125 MHz, 40%) 5022 slices 16 DSP48s 17 RAMB16s Baseline, non-PR performance = 1614 kB, MHz Clock frequency (MHz)Bitstream size (kB) Aspect ratio

17 Framework analysis – CFAR (~100 MHz, 16%) 2610 slices 2 DSP48s 34 RAMB16s Baseline, non-PR performance = 1001 kB, MHz Clock frequency (MHz)Bitstream size (kB) Aspect ratio

18 Framework analysis – AES (~80 MHz, 13.75%) 3634 slices 3943 registers 4 RAMB16s Baseline, non-PR performance = 1393 kB, MHz Clock frequency (MHz) Bitstream size (kB) Aspect ratio

F4: Virtual Architecture and Design Automation for Partial Reconfiguration Abelardo Jara Shaon Yousuft Rohit Kumar Terence Frederick CHREC Students Dr. Ann Gordon-Ross Dr. Alan D. George UF ECE Faculty

20 Approach Task 1: VA for PR Adaptive Embedded Systems  SCORES Inter-module Communication Architecture  VAPRES Multipurpose Base Embedded Platform  Initial Research on fast algorithms for online PRMs placement and scheduling Task 2: PR Design Flow Automation  Framework to model and design PR systems  Identification of points in Xilinx PR Design Flow amenable for automation  Software tools (C/C++ programs/scripts) for automatable steps Task 3: Bitstream Relocation  Port Bit Reloc to Microblaze  Context save and restore for PRMs PR for Application Designers 20

21 Background – VA for Adaptive PR Embedded Systems Multi-purpose base system platform to build runtime-adaptive HW processing embedded systems  Architectural support for on-demand HW module loading/unloading HW modules can offer better performance than SW modules  Exploit increased parallelism  Main bottleneck: Inter-module communication flows through centralized controller Can be alleviated by adding custom inter-module communication architecture VA benefits:  Adaptive base system platform Response to environmental changes HW/SW partitioned applications  Time-shared virtual resources enable larger available area for system operations  Improved system resource utilization Case study application: PR for Mobile Agents SCORES Controller and peripherals External memory VAPRES Type A module Type B module Type A module Type B target Type A target Free slot e.g. Geographical area divided into 4 regions (one processing node per region) Adaptive embedded system at each processing node Target B Target A 21

22 VAPRES - (Virtual Architecture for Partially Reconfigurable Adaptive Embedded Systems) VAPRES Architectural Components Partially Reconfigurable Regions (PRRs)  Independently clocked using BUFRs  PR modules (PRMs) can span multiple PRRs Controlling agent (Microblaze):  Dynamic module placement and scheduling  Module control and context save/restore  Partial reconfiguration through ICAP  Communication with other VAPRES nodes VAPRES Motivations/Benefits  Embedded base architecture for multi-purpose PR systems  Facilitates dynamic HW modules placement and scheduling  Provides dynamic module frequency scaling  Computing power can be distributed among VAPRES-based nodes Microblaze PRR1PRR2PRR3PRR4 Network-on-chip (SCORES) Fast Simplex Link (FSL) PLB Bus ICAP Flash controller UART USB BUFR Switch Shared memory Interface Network Network (other VAPRES nodes) Network (other VAPRES nodes) PRM A

23 Central Controlling Agent ICAP Mem controller Background – Current Application PR Design Flow  Manual steps Partition the application into modules Define static modules and partially reconfigurable modules (PRMs) Determine the number of PR regions (PRRs) Determine PRR sizes, shapes, and locations (resource allocation) Map PRMs to PRRs Define PRR interfaces and instantiate slice macros for PRR interfaces  Automatiable points and optimization problems (design-time) Design partitioning Number of PRRs PRR sizes, shapes, and locations Mapping PRMs to PRRs Type and placement of PRR interfaces Reconfiguration schedule Module A Module C Module B Static modules Reconfigurable Modules (PRMs) 1 2 FPGA # of PRRs? PRR 1 PRR 2 Static region Static modules Modules: A and B Modules: C Design partitioning Design floorplanning and budgeting Potential for automation through C/C++ programs or scripts PR is a very powerful feature of Xilinx FPGAs, but requires specialized skills

24 Questions