Architectures and Processors

ARM Cortex-A FIQ Exception at EL3 Without External Interrupt Signal When working with ARM Cortex-A processors in AArch64 mode, encountering an unexpected Fast Interrupt Request (FIQ) can be a challenging issue to debug, especially when no external interrupt signal is asserted. In this scenario, the Program Counter (PC) jumps to the FIQ vector table entry…

RME-DA Support for On-Chip Devices and PCIe Integration The Realm Management Extension (RME) is a critical component of ARM’s security architecture, designed to provide hardware-enforced isolation between different software domains. RME-DA (Device Attribution) is a feature within RME that manages device access to memory, ensuring that devices can only access memory regions they are explicitly…

Virtual Interrupt Handling and GICv2 Behavior in AArch64 Hypervisors The issue at hand revolves around the failure of virtual interrupt deactivation in a system utilizing the Generic Interrupt Controller version 2 (GICv2) on an ARM AArch64 architecture. The system in question involves a hypervisor running at Exception Level 2 (EL2), managing a virtual machine that…

AXI4 Interconnect Behavior with Single Master and Multiple Slaves In an AXI4-based system with a single master and multiple slaves, the behavior of the interconnect plays a critical role in ensuring proper transaction ordering and response management. The AXI4 protocol mandates that responses to transactions initiated by a single master must be returned in the…

ARM Cortex-R5F CP14 Register Access Exception During Debug Setup The ARM Cortex-R5F processor, part of the ARMv7-R architecture, provides advanced debugging capabilities through its CP14 coprocessor interface. These capabilities include hardware breakpoints, watchpoints, and debug state control, which are essential for embedded systems development. However, accessing CP14 registers, such as DBGDSCR, DBGBVR, and DBGBCR, can…

ARM Cortex-M7 ITCMERR Event and Its Implications The ARM Cortex-M7 processor, known for its high performance and advanced features, includes Tightly Coupled Memory (TCM) for low-latency access. The Instruction Tightly Coupled Memory (ITCM) is a critical component for storing and executing code with minimal delay. However, when an ITCM error (ITCMERR) occurs, the processor must…

PMU Event Logging Overhead Impact on Cortex-R4 CPU Idle Time The Cortex-R4 processor, a member of ARM’s real-time processor family, is widely used in applications requiring high reliability and deterministic performance, such as automotive systems, storage controllers, and modems. One of its key features is the Performance Monitoring Unit (PMU), which allows developers to profile…

ARM Cortex-M55 Debugger Reconnection Issue After Warm Reset The Cortex-M55 is a highly capable processor designed for embedded systems, particularly in applications requiring machine learning and digital signal processing. However, during development and debugging, a critical issue arises where the debugger cannot reconnect to the Cortex-M55 after a warm reset (sysresetreq) without performing a hard…

ARM DSU Cluster Architecture and Linux Scheduling Constraints The scenario involves an ARM-based System-on-Chip (SoC) with two Dynamic Shared Unit (DSU) clusters: Cluster0, which consists of 4 Cortex-A76 cores and 4 Cortex-A55 cores, and Cluster2, which has 4 Cortex-A55 cores. Each cluster has its own L3 cache and connects to a Network-on-Chip (NoC). The SoC…

ARM Cortex-A53 Cache Coherency Breakdown During Warm Start The issue described revolves around the ARM Cortex-A53 cores experiencing cache coherency problems during a warm start sequence, specifically when transitioning between 64-bit and 32-bit execution modes. In a cold start scenario, all four A53 cores execute bare metal code in 64-bit mode before jumping to a…