October 2025: Cross-repo platform improvements focused on ARM MPS4 stability, deployment reliability, and code quality for Zephyr and Trusted Firmware-M. Key features include aligning flash layout with MCUBoot recommendations and cleanup of compiler warnings in TF-M for maintainability. Major fixes addressed build warnings and test reliability, notably the TF-M upgrade to resolve MPS4 warnings and the arch.arm.user.stack/QEMU stack stability improvements. Overall, these changes reduce flash deployment variability, stabilize builds, and enhance test reliability, strengthening the platform for ARM-based devices and accelerating delivery cycles. Technologies demonstrated include MCUBoot memory partitioning, Kconfig/DTS updates, west tool integration, TF-M integration, QEMU-based testing, and C hygiene improved through warning cleanup.

September 2025 monthly summary for zephyrproject-rtos/zephyr. Focused on ARM privileged stack startup for K_USER threads. Delivered a fix that ensures K_USER threads start on a privileged stack by refactoring thread creation and user-mode entry logic, adjusting stack guards and FPU offsets, and updating z_arm_userspace_enter to accept a flag indicating whether the stack pointer is on the privileged stack. Commit 0438b9f29e4f4f696115d42c696f0573e7d7a994. Outcome: improved stability and security of user-space thread startup, enabling reliable user-space threading on ARM. This reduces the risk of privilege boundary violations and stack-related crashes, benefiting downstream features and system reliability.

August 2025 monthly summary: Delivered security, reliability, and documentation improvements across three Zephyr-related repositories, with a focus on ARM architecture and build governance. Key features delivered include PACBTI security enhancements for unprivileged mode in the nrfconnect/sdk-zephyr, with tests validating PAC keys during context switches and under pseudo RNG scenarios; ARM stack protection enhancements in zephyr-testing, including switching to a privileged stack in SVC handling and resilience tests for stack frame manipulation; and a documentation-focused update in zephyr (TF-M dependency management and board support), expanding supported boards and clarifying requirements. Major build stability improvement was achieved by fixing a dependency issue in the mps2/an521/cpu1 configuration to ensure empty_cpu0 is built before the app. These changes collectively reduce security risk, minimize build-time failures, and ease downstream integration and testing for TF-M and board variants.

July 2025 performance: Delivered security hardening and memory-region reliability improvements across two core Zephyr repos. Implemented ARM PACBTI security hardening with per-thread PAC keys, BTI enforcement, and consolidated PACBTI configuration for ARM/ARM64, complemented by tests to verify BTI enforcement. Fixed DDR4 memory region generation for the MPS4 board by splitting/redefining DDR4 DT nodes per-board, enabling correct memory sections and aligning sample addresses for secure variants. The work enhances security posture, memory-mapping reliability, and cross-variant build consistency.

June 2025 performance-oriented update: Stabilized CI for AmbiqZephyr by updating the CMSIS revision to align with the latest toolchain, resolving build errors and the missing pac_armv81.h header. Enabled non-secure TF-M builds for MPS4 with Corstone-315/320 support in Zephyr, including TF-M configuration changes, binary image format, and load address setups. These changes broaden hardware coverage, strengthen security deployment options, and improve CI reliability across two major repositories.

May 2025 monthly summary for AmbiqMicro/ambiqzephyr: Delivered CMSIS 6 migration and compatibility to broaden Cortex-M ecosystem support, expanded platform coverage with MPS4 Corstone-320, and improved CI reliability for MPS3 tests. These changes enable CMSIS_6 adoption, enable Corstone-320 with Ethos-U integration, and reduce CI flakiness, accelerating customer onboarding and release confidence. Key achievements included: 1) CMSIS 6 migration and compatibility across Cortex-M platforms with build/documentation alignment and copyright cleanup; 2) Full MPS4 Corstone-320 support including Cortex-M85 with Ethos-U85 in simulation, pinctrl for UART/SPI/I2C, and default Ethos-U NPU configuration; 3) CI stability improvements for MPS3 test runs to address intermittent failures on FVP/QEMU; 4) Documentation updates on CMSIS_6 transition and MPS4 integration.

April 2025 (AmbiqMicro/ambiqzephyr): Delivered security and build reliability improvements with ARMv8.1-M PACBTI support, TF-M integration refinements, and non-secure variant handling fixes. Key outcomes include PACBTI support for Armv8.1-M Mainline CPUs with build flags and updated documentation; TF-M build configuration now references CMSIS_6 as a Zephyr module (west.yml updated); ARMFVP_FLAGS bug in cmake fixed to correctly detect non-secure variants. Documentation updated to reflect Cortex-M85 PACBTI and PXN/PACBTI details. These changes enhance security posture, reduce build-time regressions, and improve maintainability and alignment with Zephyr TF-M requirements.

Monthly work summary for 2024-10 focusing on features delivered, key impact, and technical achievements for kholia/zephyr. This period concentrated on standardizing ARM timing configuration via CMSIS SystemCoreClock to centralize and simplify timing-related code across architecture layers, supported by a targeted refactor to reduce SOC-flag fragmentation. Commit traceability is preserved in the accompanying change set.