Overview

Introduction

The Arm Zena CSS introduces the concept of a high-performance Arm® Cortex®-A720AE Application Processor (Primary Compute) system augmented with an Arm® Cortex®-R82AE based Safety Island and real-time domain for scenarios where additional system safety monitoring and real-time services are required. The system additionally includes a Runtime Security Engine (RSE) used for the secure boot of the system elements and the runtime Secure Services.

Throughout the following documentation, the names “CSS-Aspen” and “RD-Aspen” are used in place of Arm Zena CSS due to historical reasons. For more information, visit Arm Zena Compute Subsystem (CSS) on arm.com.

A Fixed Virtual Platform (FVP) is available as part of the Arm Zena CSS Reference Design Package. Further information on FVPs, including expected runtime performance and other capabilities, can be found at Arm Ecosystem FVPs.

This documentation, together with the FVP, allows for the exploration of baremetal and virtualization hosted Linux instances. The Primary Compute firmware stack of Trusted Firmware-A, U-Boot, and systemd-boot aims to align with the technologies and goals of the Arm SystemReady Devicetree program.

Arm Automotive Solutions overview

The CSS-Aspen is composed of multiple Open Source components, including:

The platform consists of the following CPU cores IP:

Table 1 Arm Automotive Solutions platform

Component

CSS-Aspen

Primary Compute

Cortex-A720AE Armv9.2-A

Safety Island

Cortex-R82AE Armv8-R AArch64

RSE

Cortex-M55 Armv8.1-M

The remaining software in the Primary Compute subsystem, based on the EWAOL distribution, is available in two main architectures: baremetal and virtualization. EWAOL provides Bluechi as a service controller for containerized workload orchestration.

Baremetal Architecture

The Primary Compute boots a single rich operating system (real-time Linux with PREEMPT_RT patches).

Arm Automotive Solutions High-Level Diagram - Pre Platform Architecture

Fig. 1 Arm Automotive Solutions High-Level Diagram - Pre Platform Architecture


Virtualization Architecture

The Primary Compute boots into a type-1 hypervisor (Xen) using Arm’s hardware virtualization support. There are three isolated, resource-managed virtual machines: Dom0 (privileged domain) and DomU1 and DomU2 (unprivileged domains).

Virtualization Architecture Diagram

Fig. 2 Virtualization Architecture Diagram


Use cases

Arm Automotive Solutions demonstrates how the following features can be used to enhance the overall functional safety level of a high-performance compute platform:

  • PSA APIs Tests in Primary Compute

  • Safety Status Unit (SSU) integration test

  • Fault Management Unit (FMU) integration test

  • Software Built-In Self-Test Controller (SBISTC) integration test

  • Platform Fault Detection Interface (PFDI) Integration

  • Reliability, Availability, and Serviceability (RAS) error processing validation

  • Arm Cryptographic Extension demo

  • Mission-based power profile demo

  • Virtualization demo

  • Linux Distribution Installation

  • Firmware aiming to align with Arm SystemReady Devicetree

The Reproduce section of the User Guide contains all the instructions necessary to fetch and build the source as well as to download the required FVP and launch the use cases.

Following are the main use cases implemented by the Reference Software Stack.

PSA APIs Tests in Primary Compute

Demonstrates implementation of the secure services on Application Processor.

Safety Status Unit (SSU) integration test

This test demonstrates the working of the Safety Status Unit.

Fault Management Unit (FMU) integration test

It validates that an FMU integrates and behaves correctly within the target system or simulation environment.

Software Built-In Self-Test Controller (SBISTC) integration test

It performs self-diagnostics of hardware blocks (like CPUs, memories, or logic clusters) under software control.

Platform Fault Detection Interface (PFDI) Integration

It is used to detect hardware faults by registering appropriate firmware test libraries.

Reliability, Availability, and Serviceability (RAS) error processing validation

Reliability, Availability, and Serviceability (RAS) aims to increase the robustness of a system by detecting hardware errors, recording them and correcting them where possible.

Arm Cryptographic Extension demo

The demo demonstrates how the Arm Cryptographic Extension can be used to offload cryptographic work to hardware instructions.

Mission-based power profile demo

This demo is used to demonstrate system power and performance settings for different mission modes.

Virtualization demo

Demonstrates Xen hypervisor boot with two guest domains.

Linux Distribution Installation

Demonstrates the installation of three unmodified generic UEFI distribution images, Debian, openSUSE and Fedora.

Firmware aiming to align with Arm SystemReady Devicetree

The Arm SystemReady Devicetree Firmware Build option just builds the Arm SystemReady Devicetree firmware.