ARM64 GCC Doubleword Alignment for .rodata Strings When working with ARM64 architectures, particularly on platforms like the Raspberry Pi running a 64-bit OS, developers often encounter specific alignment requirements for different sections of their code. One such section is the .rodata segment, which stores read-only data, including string literals. The alignment of these segments can…
ARM Cortex-R5 System Reset Register Inquiry The ARM Cortex-R5 processor, a member of the Cortex-R series, is designed for real-time and safety-critical applications. Unlike the Cortex-M series, which features a straightforward System Control Block (SCB) with an Application Interrupt and Reset Control Register (AIRCR) for system resets, the Cortex-R5 does not have an equivalent register….
LPC1857 On-Chip RAM Fragmentation and Keil IDE Limitations The LPC1857 microcontroller, based on the ARM Cortex-M3 architecture, features 136KB of on-chip RAM distributed across three non-contiguous memory blocks. These blocks are located at specific address ranges: Block 1 (0x10000000 to 0x10007FFF, 32KB), Block 2 (0x10080000 to 0x10089FFF, 40KB), and Block 3 (0x20000000 to 0x2000FFFF, 64KB)….
Cortex-A715 Power State Characteristics and Measurement Requirements The Cortex-A715 processor, like many modern ARM cores, incorporates advanced power management features to optimize energy efficiency across various operational and sleep states. These states include active-idle, standby, dormant, and shut down, each with distinct dynamic and static power consumption profiles. Dynamic power refers to the power consumed…
ARMv8 NEON SIMD UQRSHRN Rounding-to-Nearest Behavior and Limitations The ARMv8 NEON SIMD instruction set includes the UQRSHRN (Unsigned Saturating Rounded Shift Right Narrow) and its variant vqrshrn_n_u16, which are designed to perform bit-shifting operations with rounding. These instructions are particularly useful in scenarios where data precision needs to be reduced while maintaining as much accuracy…
ARM Cortex-A Cache Coherency and Memory Access Latency in EL3 vs NS.EL1 The performance discrepancy of memcpy() between EL3 (ARM Trusted Firmware BL31) and NS.EL1 (Linux kernel module) is primarily rooted in the differences in cache coherency models, memory access latencies, and privilege level overheads. In NS.EL1, the Linux kernel operates in a non-secure state…
ARM FVP SMMU Peripheral Emulation and Testing Challenges The ARM Fixed Virtual Platform (FVP) is a powerful tool for simulating ARM-based systems, enabling developers to test software and hardware interactions without requiring physical hardware. However, when it comes to testing peripherals connected through the System Memory Management Unit (SMMU), particularly in the context of emulating…
ARM TrustZone Peripheral Access Mechanisms and Security Models The ARM TrustZone architecture introduces a hardware-based security model that partitions the system into Secure World (SW) and Non-Secure World (NW). This partitioning extends to peripherals, which can be accessed by either world depending on their configuration and the security requirements of the system. The core issue…
Cortex-A53 BUS_ACCESS Event Underreporting and Read Allocate Mode Writes The Cortex-A53 Performance Monitoring Unit (PMU) provides a suite of events that allow developers to profile and analyze system performance. One such event, BUS_ACCESS (event ID 0x19), is designed to count all bus accesses, including cacheable traffic, non-cacheable traffic, and write streaming. However, as noted in…
L2 Cache Stalls Due to Indefinite Memory Read Issues The ARM Cortex-A series processors are widely used in embedded systems due to their high performance and efficiency. However, certain architectural nuances can lead to unexpected behavior, particularly in the memory subsystem. One such issue is the indefinite stalling of memory reads in the L2 cache,…