Floating-Point Exception Handling and FMADD Performance Anomaly The core issue revolves around the observed performance difference in the FMADD (Fused Multiply-Add) instruction on ARM processors when the FPSCR.IXC (Inexact Cumulative Exception) flag is set versus when it is not set. Specifically, the FMADD instruction executes faster when FPSCR.IXC is set to 1, compared to when…
ARM Cortex-A53 Bootloader Segfault During Baremetal Initialization When implementing a baremetal bootloader for the ARM Cortex-A53 processor on the NXP i.MX8qm Evaluation Kit (EVK), a segmentation fault (segfault) can occur during the initialization phase. This issue is particularly common when transitioning from vendor-provided bootloader packages (such as those from NXP’s Yocto BSP) to a minimalistic,…
ARM Cortex-A Multi-Core Boot Failure in Linux Kernel The issue described involves the Linux kernel hanging during the boot process when attempting to bring up secondary CPUs in a multi-core ARM Cortex-A processor cluster. Specifically, the kernel fails to boot CPU1, resulting in a system hang. This problem only occurs when there are multiple cores…
ARM DynamIQ Shared Unit Cache Partitioning Mechanics The ARM DynamIQ Shared Unit (DSU) is a critical component in modern ARM-based systems, particularly in multi-core processors. It manages the shared L3 cache and provides advanced features such as cache partitioning, which allows for the allocation of specific cache ways to individual cores. This partitioning mechanism is…
Off-Chip Memory Integration at 0x00000000 on Cortex-M0 The Cortex-M0 processor, being a highly efficient and cost-effective ARM core, is often used in resource-constrained embedded systems. One common requirement in such systems is the integration of off-chip memory, particularly when the on-chip memory is insufficient for the application’s needs. A critical question arises: Can off-chip memory…
Core 1 Execution Start Address Ambiguity in Dual-Core Bare-Metal Systems In a dual-core ARM Cortex-A9 system running bare-metal programs, one of the most critical challenges is ensuring that Core 1 begins execution at the correct memory address after being released from reset. The Cortex-A9 cores, by default, start executing instructions from address 0x00000000 or 0xFFFF0000…
Cortex-M7 TCMWAIT Signal Behavior and System Hang The Cortex-M7 processor, known for its high performance and efficiency, utilizes Tightly Coupled Memory (TCM) for low-latency access to critical data and instructions. The TCM interface includes the TCMWAIT signal, which is used to handle multi-cycle memory accesses. When the TCMWAIT signal is asserted, the processor stalls, waiting…
NVIC_EnableIRQ Functionality and ISER Register Behavior The NVIC_EnableIRQ function is a commonly used utility in ARM Cortex-M processors to enable specific interrupts via the Nested Vectored Interrupt Controller (NVIC). The function operates by setting a bit in the Interrupt Set Enable Register (ISER), which is part of the NVIC. The ISER is a memory-mapped register…
ARM Cortex-A9 Processor Halting During __libc_init_array Execution The issue at hand involves an ARM Cortex-A9 processor halting during the execution of the __libc_init_array function, specifically when attempting to execute a function pointer from the .init_array section. This behavior is observed on two out of three identical hardware setups, while the third operates as expected. The…
Undefined Instruction Error on ICC_HSRE Access in AArch32 EL2 The core issue revolves around an undefined instruction error when attempting to access the ICC_HSRE (Interrupt Controller Hyp System Register Enable) register in AArch32 EL2 mode on a Cortex-A53 processor with a GICv3 (Generic Interrupt Controller version 3) implementation. The specific instruction causing the error is:…