Synchronous Exceptions at EL0 During User Program Execution When transitioning from EL1 (kernel mode) to EL0 (user mode) on an ARM Cortex-A processor, synchronous exceptions can occur unexpectedly during the execution of user-space instructions. These exceptions are often accompanied by an Exception Syndrome Register (ESR) value of 0x2000000, indicating an "Unknown reason" with an instruction…
ARM Cortex-M4 LDR Instruction Execution Failure Leading to BusFault The core issue revolves around an ARM Cortex-M4 processor experiencing a BusFault during USB communications, specifically when executing an LDR (Load Register) instruction. The fault occurs at address 0x0040 0008, which is derived from the value in register R2 (0x0040 0000) with an offset of 8….
ARM Cortex-M4 Cache Coherency Problems During DMA Transfers The ARM architecture provides a set of synchronization primitives known as Load-Exclusive (LDREX) and Store-Exclusive (STREX) instructions. These instructions are crucial for implementing atomic operations in multi-threaded environments or when dealing with shared resources. However, the ARM Architecture Reference Manual for ARMv7-A and ARMv7-R explicitly states that…
ARM Cortex-A72 L2 Cache Disabling Procedure and Timing Observations The ARM Cortex-A72 is a high-performance processor core designed for applications requiring significant computational power, such as mobile devices, networking equipment, and embedded systems. One of its key features is the inclusion of Level 1 (L1) and Level 2 (L2) caches, which are critical for reducing…
Cache Coherency Behavior in ARM Cortex-A15 During Multi-Core Cache Flush and Invalidate Operations In ARM Cortex-A15-based systems, cache coherency is a critical aspect of ensuring data integrity and consistency across multiple cores. When two cores, such as Core 0 and Core 1, operate within the same inner shareable domain and access the same cache line,…
PL230 DMA Controller Arbitration Cycle Consumption and Timing Analysis The PL230 DMA controller is a critical component in many ARM-based embedded systems, responsible for managing data transfers between peripherals and memory without CPU intervention. One of the key aspects of its operation is the arbitration process, which determines how the DMA controller allocates its resources…
Cortex-R52 SPI Interrupt Routing to PEs Not Functioning GIC Configuration and Affinity Routing Issues The core issue revolves around the inability to route Shared Peripheral Interrupts (SPIs) to Processing Elements (PEs) other than core 0 in a Cortex-R52 multicore setup. The Generic Interrupt Controller (GIC) is configured to use affinity routing, as indicated by the…
ARMv8-A Secure vs Non-Secure State Detection in EL1 Kernel Code The ARMv8-A architecture introduces a robust security model that partitions the system into Secure and Non-Secure states. This separation is crucial for implementing TrustZone technology, which provides a secure environment for sensitive operations. However, when developing a Linux kernel that operates at Exception Level 1…
SPI4 Pin Configuration and DMA Initialization Failures on STM32 F411RE The STM32 F411RE microcontroller, based on the ARM Cortex-M4 architecture, is a powerful device widely used in embedded systems for its robust peripheral support, including multiple SPI interfaces. However, when transitioning from SPI1 to SPI4 on the STM32 F411RE Nucleo board, users often encounter issues…
ARM TrustZone Isolation and Secure Boot Limitations in Raspberry Pi ARM TrustZone is a hardware-based security feature embedded in ARM processors, designed to create isolated execution environments for secure and non-secure worlds. This isolation ensures that sensitive operations, such as cryptographic key management or secure boot processes, are protected from potential attacks. However, not all…