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ac6 >> ac6-training >> Processors >> ARM Cores >> Cortex-A15 implementation Download as PDF Write us

RA3 Cortex-A15 implementation

This course covers Cortex-A15 high-end ARM CPU

  • his course is split into 3 important parts:
    • Cortex-A15 architecture
    • Cortex-A15 software implementation and debug
    • Cortex-A15 hardware implementation.
  • Introduction to Hypervisor new privilege mode is done at the beginning of this course.
  • The consequences on address translation is then explained, introducing the 2-stage translation.
  • Decoupling guest OS from hardware using traps to Hypervisor is studied.
  • The course also details the new features of the Generic Interrupt Controller v2, explaining how physical interrupt requests can be virtualized.
  • The course details the new approach regarding integrated timers / counters.
  • AXI v4 new capabilities are highlighted with regard to AXI v3.
  • Through sequences involving a Cortex-A15 and a Cortex-A7, the hardware coherency is studied, explaining how snoop requests can be forwarded by CCI-400 interconnect.
  • Implementation of I/O MMU-400 is also covered.
A more detailed course description is available on request at
  • Theoretical course
    • PDF course material (in English) supplemented by a printed version for face-to-face courses.
    • Online courses are dispensed using the Teams video-conferencing system.
    • The trainer answers trainees' questions during the training and provide technical and pedagogical assistance.
  • At the start of each session the trainer will interact with the trainees to ensure the course fits their expectations and correct if needed
  • Any embedded systems engineer or technician with the above prerequisites.
  • The prerequisites indicated above are assessed before the training by the technical supervision of the traineein his company, or by the trainee himself in the exceptional case of an individual trainee.
  • Trainee progress is assessed by quizzes offered at the end of various sections to verify that the trainees have assimilated the points presented
  • At the end of the training, each trainee receives a certificate attesting that they have successfully completed the course.
    • In the event of a problem, discovered during the course, due to a lack of prerequisites by the trainee a different or additional training is offered to them, generally to reinforce their prerequisites,in agreement with their company manager if applicable.

Course Outline

  • Cortex-A15 architecture
  • Organization of a SoC based on Cortex-A15MP
  • AMBA4 coherent interconnect capabilities
  • Inner Shareable vs Outer Shareable attribute
  • I/O MMU
  • 64-Byte cacheline size, integrated L2 cache
  • VFPv4 and SIMDv2
  • Highlighting differences between Cortex-A9 and Cortex-A15
  • Global organization, triple issue capability
  • Fetch / decode / rename / dispatch stages
  • Loop mode
  • Execution clusters
  • Out-of-order execution, 40-entry dispatch queue
  • Branch accelerators
  • Processor privilege levels state machine, user, guest OS, hypervisor
  • Detailing the various operation modes (Bare-Metal, Hypervisor kernel and user task, Hypervisor with Guest partition)
  • Asymmetric approach, no support for Virtualization of Secure state functionality
  • SVC, HVC and SMC instructions
  • Objective of the Hypervisor
  • Hypervisor related instructions and registers
  • List of registers that have to be saved / restored to be able to suspend / resume a guest partition
  • Accessing banked registers or any Non-Secure mode while running in Hypervisor mode
  • Hypervisor vector table
  • Utilization of Vector #5 to trap Guest partition events
  • System Call into Hypervisor mode
  • Asynchronous exceptions
  • Virtual Interrupt and Abort bits control, IRQ, FIQ, external abort routing control
  • Hypervisor exception return
  • Taking exceptions into Hypervisor mode
  • Integration in a SoC based on Cortex-A15MP and Cortex-A7MP
  • Highlighting the new features with regard to Cortex-A9MP
  • Steering interrupts to guest OS or Hypervisor
  • Virtual CPU interface
  • Split EOI functionality
  • Deactivating an interrupt source from the Virtual CPU interface
  • Front-end interface accessed by the Guest Kernel
  • Back-end interface accessed by the Hypervisor
  • New Intermediate Physical Address, 2-stage address translation
  • Memory translation system
  • Memory management when running in hypervisor mode
  • Virtual Machine Identification
  • Exposing the MMU to Other Masters, IO MMU
  • Emulation support, trapping load and store and executing them in Hypervisor state
  • Second-stage access permissions and attributes
  • Need to introduce support for a second stage of translation as part of the Virtualization Extensions
  • New 3-level translation
  • Level-1 table descriptor format
  • Level-2 table descriptor format
  • Attribute and Permission fields in the translation tables
  • Improving the caching of translation entries by providing contiguous hints
  • complete set of cache allocation hints
  • Handling of the ASID in the LPAE
  • New cache and TLB maintenance operations
  • TLB organization, L1-TLB, L2-TLB
  • TLB match process
  • Coherent table walk
  • Determining the exact cause of aborts through status registers
  • Behavior when MMU is disabled
  • Inter-Processor Interrupts
  • Barriers
  • Cluster ID
  • Exclusive access monitor, implementing Boolean semaphores
  • Global monitor
  • Spin-lock implementation
  • Using events
  • Indicating the effect of Multi Core on debug interfaces
  • Physically Indexed Physically Tagged caches
  • LRU replacement algorithm, implementation with a 2-way cache
  • Speculative accesses
  • Hit Under Miss, Miss under Miss
  • Write streaming threshold definition
  • Uploading the contents of L1 caches through dedicated CP15 registers
  • MESI data cacheline states
  • Cache organization
  • Strictly enforced inclusion property with L1 data caches, simplification of snooping
  • Optional ECC / parity protection
  • Impact of registers slices on performance
  • L2 prefetch engine
  • Table walk access prefetch
  • ACE master interface
  • ACP slave interface
  • By means of sequences involving a multi-core Cortex-A15 and external masters, understanding how snoop requests can be used to maintain coherency of data between caches and memory
  • ARM generic 64-bit timers for each processor
  • Virtual time vs Physical time
  • Effect of virtualization on these timers
  • Event stream purpose
  • Kernel event stream generation
  • Hypervisor event stream generation
  • Gray count timer distribution scheme
  • Hypervisor performance monitoring
  • Guest OS performance monitoring
  • Lazy switching of PMU state by a hypervisor
  • Reducing the number of counters available to a Guest OS
  • Fully virtualizing the PMU identity registers
  • AXI-4
    • Quality of Service signaling
    • Updated meaning of Read Allocate and Write Allocate
    • Transaction buffering
  • AXI-4 stream protocol
    • Byte types, data, position, null
    • Byte stream
    • Sparse stream
    • Data merging, packing, and width conversion
  • AXI-4 lite
    • Burst length of 1
    • No exclusive access support
  • AXI Coherency Extension (ACE)
    • Shareability domains
    • Coherency model, cache states
    • Additional channel signals
    • New channels, snoop address, snoop response, snoop data
    • Studying through sequences how a load request and a store request will be handled whenever they are marked as outer shareable requests
    • Using ReadUnique, CleanUnique and MakeUnique requests
    • Distributed Virtual Memory (DVM)
    • DVM synchronization message
    • Selecting the coherency state machine: MESI or MOESI according to the capabilities of the interconnect
    • Snoop filtering
  • Exported barriers
    • DMB / DSB inner shareable, outer shareable or system
  • Clock domains
  • Resets, power-on reset timing diagram
  • Valid reset combinations
  • Power domains
  • Power-on reset sequence, soft reset sequence
  • Power management
  • Maintaining coherency while CPUs are in standby state
  • Interface to the Power Management Unit
  • Powering down a CPU
  • External debug over power down
  • AMBA 4 snoop request transport
  • Snoop connectivity and control
  • By means of sequences involving a multi-core Cortex-A15 and external masters, understanding how snoop requests can be used to maintain coherency of data between caches and memory
  • Connecting 2 CPUs through CCI, managing coherency domains
  • Example of Cortex-A7 dual core and Cortex-A15 dual core
  • Program Trace Macrocell
  • Cross Trigger Interface and Criss Trigger Matrix for multi-processor debugging
  • Adding Virtual Machine ID in the criterion used to set a breakpoint / watchpoint
  • Tracking VMID change in trace output