rt-thread/libcpu/Kconfig

if ARCH_ARMV8 && ARCH_CPU_64BIT
    orsource "./aarch64/Kconfig"
endif

config ARCH_CPU_64BIT
    bool
    help
        Indicates that this architecture uses 64-bit addressing and data types.
        When enabled, pointers and registers are 64-bit wide, providing access
        to larger memory spaces (>4GB). This is automatically selected by 64-bit
        architectures like AArch64, RISC-V64, and MIPS64.
        
        Impact: Affects memory layout, data structure sizes, and ABI conventions.

config RT_USING_CACHE
    bool
    default n
    help
        Enable CPU cache support for data and instruction caches.
        
        When enabled, RT-Thread will provide cache management APIs (flush, invalidate)
        and properly handle cache coherency during DMA operations and memory management.
        This is essential for high-performance CPUs like Cortex-A and Cortex-M7.
        
        Typical use cases:
        - DMA transfers requiring cache synchronization
        - Memory-mapped I/O operations
        - Multi-core systems requiring cache coherency
        
        Note: Automatically selected by architectures with cache support (e.g., Cortex-M7,
        Cortex-A series, ARMv8). Improper cache management can lead to data corruption.

config RT_USING_HW_ATOMIC
    bool
    default n
    help
        Enable hardware atomic operations support using CPU-specific instructions.
        
        When enabled, RT-Thread uses hardware atomic instructions (e.g., LDREX/STREX on ARM,
        atomic instructions on RISC-V) for lock-free synchronization primitives, improving
        performance and reducing interrupt latency compared to software implementations.
        
        Automatically selected by CPUs with atomic instruction support:
        - ARM Cortex-M3 and above (LDREX/STREX)
        - ARM Cortex-A series
        - ARM Cortex-R series
        - RISC-V with 'A' extension
        
        Benefits: Better performance for spinlocks, reference counting, and concurrent data structures.
        No action required - this is automatically configured based on CPU architecture.

config ARCH_CPU_BIG_ENDIAN
    bool
    help
        Indicates that this CPU uses big-endian byte ordering.
        
        In big-endian systems, the most significant byte is stored at the lowest memory address.
        This affects how multi-byte data (integers, floats) are stored and accessed in memory.
        
        Most ARM, RISC-V, and x86 systems use little-endian. Big-endian is common in:
        - Some PowerPC configurations
        - MIPS systems (configurable)
        - Network protocols (network byte order)
        
        Note: This must match your hardware configuration. Incorrect setting will cause
        data corruption when accessing multi-byte values.

config ARCH_ARM_BOOTWITH_FLUSH_CACHE
    bool
    default n
    help
        Flush and disable caches during system boot on ARM platforms.
        
        When enabled, the bootloader will flush and disable instruction and data caches
        before jumping to RT-Thread kernel. This ensures clean cache state during initialization.
        
        Enable this when:
        - Bootloader leaves caches in inconsistent state
        - Transitioning from another OS or bootloader
        - Debugging cache-related boot issues
        
        Note: Not needed for most configurations. Only enable if experiencing boot failures
        related to stale cache data.

config ARCH_CPU_STACK_GROWS_UPWARD
    bool
    default n
    help
        Indicates that the stack grows toward higher memory addresses (upward).
        
        Most architectures (ARM, RISC-V, x86, MIPS) use downward-growing stacks where
        the stack pointer decreases as items are pushed. However, some architectures
        like TI DSP C28x use upward-growing stacks.
        
        This setting affects:
        - Stack pointer initialization and overflow detection
        - Context switching and exception handling
        - Stack boundary checking
        
        Note: This is architecture-specific and automatically configured. Do not change
        unless porting to a new architecture with upward-growing stack.

config RT_USING_CPU_FFS
    bool
    default n
    help
        Enable optimized Find First Set (FFS) implementation using CPU instructions.
        
        FFS finds the position of the first (least significant) bit set in a word. When enabled,
        RT-Thread uses hardware instructions like CLZ (Count Leading Zeros) on ARM or equivalent
        on other architectures for fast bit scanning operations.
        
        Used internally by:
        - Scheduler for finding highest-priority ready thread
        - Bitmap operations
        - IPC mechanisms
        
        Automatically selected by CPUs with FFS support:
        - ARM Cortex-M3 and above (CLZ instruction)
        - ARM Cortex-A series
        - ARM Cortex-R series
        
        Benefits: Significantly faster scheduler operation (O(1) vs O(n) thread selection).
        No configuration needed - automatically enabled for supported CPUs.

config ARCH_MM_MMU
    bool
    help
        Enable Memory Management Unit (MMU) support for virtual memory.
        
        MMU provides hardware-based virtual memory management, enabling:
        - Virtual to physical address translation
        - Memory protection between processes
        - Demand paging and memory mapping
        - Separate address spaces for different processes
        
        Required for:
        - RT-Smart mode (user-space applications)
        - Process isolation and protection
        - Dynamic memory mapping (mmap)
        - Copy-on-write mechanisms
        
        Automatically selected by MMU-capable architectures:
        - ARM Cortex-A series
        - AArch64 (ARMv8)
        - RISC-V with Sv39/Sv48 paging
        
        Note: MMU requires proper page table setup and increases system complexity.
        Only available on CPUs with hardware MMU support.

config ARCH_MM_MPU
    bool
    help
        Enable Memory Protection Unit (MPU) support.
        
        MPU provides hardware-based memory protection without full virtual memory capabilities.
        Unlike MMU, MPU works with physical addresses and has limited number of regions (typically 8-16).
        
        Features:
        - Protect memory regions from unauthorized access
        - Define region permissions (read, write, execute)
        - Prevent stack overflow and buffer overruns
        - Isolate kernel from user code
        
        Common use cases:
        - Thread stack protection
        - Peripheral register protection
        - Code/data separation
        - Safety-critical applications
        
        Available on:
        - ARM Cortex-M0+/M3/M4/M7/M23/M33/M85 (with MPU option)
        - ARM Cortex-R series
        
        Note: Less flexible than MMU but lower overhead. Suitable for microcontrollers
        without MMU. Enable RT_USING_HW_STACK_GUARD for automatic stack protection.

config ARCH_ARM
    bool
    help
        Select ARM architecture family support.
        
        ARM is a widely-used RISC architecture family for embedded systems and mobile devices.
        This is automatically selected when choosing a specific ARM CPU variant.
        
        Supported ARM variants in RT-Thread:
        - ARM9/ARM11: Legacy 32-bit ARM cores
        - Cortex-M: Microcontroller profile (M0/M0+/M3/M4/M7/M23/M33/M85)
        - Cortex-R: Real-time profile (R4/R52)
        - Cortex-A: Application profile (A5/A7/A8/A9/A55)
        - ARMv8: 64-bit architecture (Cortex-A53/A57/A72/A73)
        
        No direct configuration needed - select specific CPU type instead.

config ARCH_ARM_CORTEX_M
    bool
    select ARCH_ARM
    help
        ARM Cortex-M microcontroller profile.
        
        Cortex-M is ARM's microcontroller-optimized architecture designed for low-power,
        cost-sensitive embedded applications with deterministic interrupt handling.
        
        Features:
        - Nested Vectored Interrupt Controller (NVIC)
        - Low interrupt latency (typically 12-15 cycles)
        - Thumb-2 instruction set for code density
        - Optional MPU for memory protection
        - Optional FPU (M4F/M7F variants)
        
        Variants: M0/M0+/M3/M4/M7/M23/M33/M85
        
        Automatically selected when choosing specific Cortex-M CPU variant.

config ARCH_ARM_CORTEX_R
    bool
    select ARCH_ARM
    help
        ARM Cortex-R real-time profile.
        
        Cortex-R is designed for high-performance real-time applications requiring
        deterministic behavior and fault tolerance.
        
        Features:
        - Tightly-coupled memory (TCM) for deterministic access
        - Error detection and correction (ECC)
        - Dual-core lockstep for safety-critical applications
        - Low and deterministic interrupt latency
        - Optional MPU or MMU
        
        Common applications:
        - Automotive (ADAS, engine control)
        - Industrial control systems
        - Medical devices
        - Hard real-time systems
        
        Variants: R4/R5/R52
        Automatically selected when choosing specific Cortex-R CPU variant.

config ARCH_ARM_CORTEX_FPU
    bool
    help
        Enable Floating Point Unit (FPU) support for ARM Cortex processors.
        
        When enabled, RT-Thread will:
        - Save/restore FPU registers during context switch
        - Enable FPU coprocessor access
        - Support hardware floating-point operations
        
        FPU variants:
        - Cortex-M4F/M7F: Single-precision FPv4-SP
        - Cortex-M7: Optional double-precision FPv5
        - Cortex-A: VFPv3/VFPv4/NEON
        
        Benefits: 10-100x performance improvement for floating-point math
        Cost: Increased context switch time, larger stack frames
        
        Enable if your application requires:
        - DSP operations
        - Audio/video processing
        - Scientific computations
        - Graphics operations
        
        Note: Hardware must have FPU. Check your MCU datasheet.

config ARCH_ARM_CORTEX_SECURE
    bool
    help
        Enable ARM TrustZone security extension support.
        
        TrustZone provides hardware-based isolation between secure and non-secure worlds,
        enabling trusted execution environments (TEE).
        
        Features:
        - Secure and non-secure memory regions
        - Secure and non-secure peripheral access
        - Secure state transitions
        - Protection of cryptographic keys and sensitive data
        
        Available on:
        - Cortex-M23/M33/M35P/M55/M85 (ARMv8-M)
        - Cortex-A with Security Extensions
        
        Use cases:
        - Secure boot
        - Cryptographic operations
        - Key storage
        - Secure firmware updates
        - Payment and DRM systems
        
        Note: Requires secure firmware and proper secure/non-secure memory partitioning.

config ARCH_ARM_CORTEX_M0
    bool
    select ARCH_ARM_CORTEX_M
    help
        ARM Cortex-M0 ultra-low-power microcontroller core.
        
        Smallest and most energy-efficient ARM processor, ideal for simple control applications.
        
        Features:
        - ARMv6-M architecture
        - 32-bit processor with Thumb instruction set (subset)
        - Minimal interrupt latency
        - No MPU, no FPU, no cache
        - Very low gate count and power consumption
        
        Performance: ~0.9 DMIPS/MHz
        Typical applications: Sensors, simple controllers, battery-powered devices
        
        Choose this for your BSP if using Cortex-M0 based MCU.

config ARCH_ARM_CORTEX_M3
    bool
    select ARCH_ARM_CORTEX_M
    select RT_USING_CPU_FFS
    select RT_USING_HW_ATOMIC
    help
        ARM Cortex-M3 mainstream microcontroller core.
        
        Balanced processor for general-purpose embedded applications with good performance
        and energy efficiency.
        
        Features:
        - ARMv7-M architecture
        - Thumb-2 instruction set (full)
        - Hardware divide instructions
        - Optional MPU (8 regions)
        - Atomic operations (LDREX/STREX)
        - No FPU, no cache
        
        Performance: ~1.25 DMIPS/MHz
        
        Common use cases:
        - Industrial control
        - Consumer electronics
        - Motor control
        - IoT devices
        
        Examples: STM32F1xx, LPC17xx, EFM32
        Choose this for your BSP if using Cortex-M3 based MCU.

config ARCH_ARM_MPU
    bool
    depends on ARCH_ARM
    select ARCH_MM_MPU
    help
        Enable Memory Protection Unit for ARM Cortex-M/R processors.
        
        Select this to enable MPU support on compatible ARM cores. The MPU provides
        hardware-based memory protection with configurable regions.
        
        When enabled, you can:
        - Protect thread stacks from overflow
        - Restrict access to peripheral registers
        - Enforce execute-never (XN) permissions
        - Separate privileged and unprivileged memory
        
        Configuration:
        - Number of regions: Typically 8 (Cortex-M3/M4) or 16 (Cortex-M7/M33)
        - Region size: Must be power of 2, minimum 32 bytes (Cortex-M3/M4) or 256 bytes (ARMv8-M)
        - Permissions: Read, write, execute, privileged/unprivileged
        
        Enable this along with RT_USING_HW_STACK_GUARD for automatic stack protection.
        See components/mprotect/Kconfig for detailed MPU configuration.

config ARCH_ARM_CORTEX_M4
    bool
    select ARCH_ARM_CORTEX_M
    select RT_USING_CPU_FFS
    select RT_USING_HW_ATOMIC
    help
        ARM Cortex-M4 DSP-oriented microcontroller core.
        
        Enhanced version of M3 with DSP extensions and optional FPU, designed for
        digital signal processing and motor control applications.
        
        Features:
        - ARMv7E-M architecture
        - DSP instructions (SIMD, saturating arithmetic, MAC)
        - Optional single-precision FPU (FPv4-SP)
        - Optional MPU (8 regions)
        - Hardware divide and atomic operations
        - No cache
        
        Performance: ~1.25 DMIPS/MHz (CPU), 10x faster for DSP operations with FPU
        
        Ideal for:
        - Audio processing
        - Motor control (FOC algorithms)
        - Sensor fusion
        - Real-time control loops
        
        Examples: STM32F4xx, K64F, nRF52, TM4C
        Choose this for your BSP if using Cortex-M4 or M4F based MCU.

config ARCH_ARM_CORTEX_M7
    bool
    select ARCH_ARM_CORTEX_M
    select RT_USING_CPU_FFS
    select RT_USING_CACHE
    select RT_USING_HW_ATOMIC
    help
        ARM Cortex-M7 high-performance microcontroller core.
        
        Most powerful Cortex-M processor with superscalar architecture, cache, and
        advanced features for demanding embedded applications.
        
        Features:
        - ARMv7E-M architecture with 6-stage superscalar pipeline
        - L1 instruction and data cache (configurable 0-64KB each)
        - Optional single/double-precision FPU (FPv5)
        - Tightly-coupled memory (TCM) for deterministic access
        - Optional MPU (8 or 16 regions)
        - DSP instructions and atomic operations
        
        Performance: ~2.14 DMIPS/MHz (up to 600MHz), 5 CoreMark/MHz
        
        Critical for cache management:
        - Must flush cache before DMA reads from memory
        - Must invalidate cache after DMA writes to memory
        - Cache coherency APIs automatically enabled
        
        Ideal for:
        - High-performance embedded systems
        - Vision and image processing
        - Advanced motor control
        - Real-time communication protocols
        
        Examples: STM32F7xx/H7xx, i.MX RT, SAM V71
        Choose this for your BSP if using Cortex-M7 based MCU.

config ARCH_ARM_CORTEX_M85
    bool
    select ARCH_ARM_CORTEX_M
    select RT_USING_CPU_FFS
    select RT_USING_HW_ATOMIC
    help
        ARM Cortex-M85 next-generation high-performance microcontroller core.
        
        Latest and most powerful Cortex-M processor with AI/ML acceleration and
        advanced security features (ARMv8.1-M architecture).
        
        Features:
        - ARMv8.1-M architecture with Helium (M-Profile Vector Extension)
        - TrustZone security
        - L1 cache (optional)
        - Optional single/double-precision FPU
        - Optional MPU (8 or 16 regions)
        - Pointer authentication and branch target identification
        - DSP and atomic operations
        
        Performance: Up to 6.2 CoreMark/MHz
        
        Helium benefits:
        - 5-15x performance for ML inference
        - Enhanced DSP for signal processing
        - Vector operations for parallel data processing
        
        Ideal for:
        - Edge AI/ML applications
        - Advanced image/audio processing
        - Security-critical applications
        - Next-generation IoT devices
        
        Examples: Future MCUs with Cortex-M85
        Choose this for your BSP if using Cortex-M85 based MCU.

config ARCH_ARM_CORTEX_M23
    bool
    select ARCH_ARM_CORTEX_M
    select RT_USING_HW_ATOMIC
    help
        ARM Cortex-M23 ultra-low-power core with TrustZone.
        
        Energy-efficient processor with security features, successor to Cortex-M0+.
        
        Features:
        - ARMv8-M Baseline architecture
        - TrustZone security extension
        - Optional MPU (8 or 16 regions)
        - Atomic operations (LDREX/STREX)
        - Low power consumption
        - No FPU, no cache
        
        Performance: ~1.0 DMIPS/MHz
        
        Key advantage: Hardware security with minimal area/power overhead
        
        Ideal for:
        - Secure IoT devices
        - Battery-powered secure sensors
        - Payment terminals
        - Smart cards
        
        Examples: Future secure IoT MCUs
        Choose this for your BSP if using Cortex-M23 based MCU.

config ARCH_ARM_CORTEX_M33
    bool
    select ARCH_ARM_CORTEX_M
    select RT_USING_CPU_FFS
    select RT_USING_HW_ATOMIC
    help
        ARM Cortex-M33 mainstream core with TrustZone.
        
        Balanced processor combining Cortex-M4 performance with TrustZone security,
        ideal for secure IoT and connected devices.
        
        Features:
        - ARMv8-M Mainline architecture
        - TrustZone security extension
        - Optional single-precision FPU (FPv5)
        - Optional MPU (8 or 16 regions)
        - DSP instructions
        - Atomic operations
        - Optional cache (Cortex-M33 derivatives)
        
        Performance: ~1.5 DMIPS/MHz
        
        Security features:
        - Secure/non-secure memory partitioning
        - Secure function calls
        - Stack limit checking
        - Co-processor isolation
        
        Ideal for:
        - Secure IoT gateways
        - Industrial automation with security
        - Connected consumer devices
        - Secure bootloaders
        
        Examples: nRF91, LPC55xx, STM32L5xx
        Choose this for your BSP if using Cortex-M33 based MCU.

config ARCH_ARM_CORTEX_R
    bool
    select ARCH_ARM
    select RT_USING_HW_ATOMIC
    help
        ARM Cortex-R real-time processor family.
        
        High-performance real-time processors with deterministic behavior for
        safety-critical and real-time systems.
        
        Common features across Cortex-R family:
        - Low and deterministic interrupt latency
        - Tightly-coupled memory (TCM)
        - Error correction code (ECC)
        - Optional MPU or MMU
        - VFP floating-point
        
        Automatically selected when choosing specific Cortex-R variant (R4/R52).
        See individual Cortex-R variant options for detailed specifications.

config ARCH_ARM_CORTEX_R52
    bool
    select ARCH_ARM_CORTEX_R
    help
        ARM Cortex-R52 safety-critical real-time core.
        
        Latest Cortex-R processor designed for ASIL-D automotive and IEC 61508 SIL-3
        industrial safety applications.
        
        Features:
        - ARMv8-R architecture (32-bit)
        - Dual-core lockstep for fault detection
        - ECC on caches and TCM
        - Optional MPU or MMU
        - Virtualization extensions
        - Single/double precision FPU
        - NEON SIMD
        
        Performance: Up to 1.6 DMIPS/MHz per core
        
        Safety features:
        - Redundant execution for error detection
        - Memory protection and ECC
        - Built-in self-test (BIST)
        
        Ideal for:
        - Automotive ADAS and autonomous driving
        - Industrial safety controllers (SIL-3)
        - Medical devices
        - Aerospace applications
        
        Choose this for your BSP if using Cortex-R52 based SoC.

config ARCH_ARM_MMU
    bool
    select RT_USING_CACHE
    select ARCH_MM_MMU
    depends on ARCH_ARM
    help
        Enable MMU support for ARM Cortex-A processors.
        
        Provides full virtual memory management with page-based address translation.
        Automatically selected by Cortex-A variants.
        
        Features:
        - 4KB/16KB/64KB page sizes
        - Two-level (LPAE: three-level) page tables
        - Virtual memory for multiple processes
        - Memory attributes (cacheable, bufferable, shareable)
        - Access permissions (privileged, user, read-only, execute-never)
        
        Enables:
        - RT-Smart user-space applications
        - Memory protection between processes
        - Demand paging and swapping
        - Memory-mapped files (mmap)
        - Shared memory between processes
        
        Performance impact:
        - TLB (Translation Lookaside Buffer) misses add latency
        - Page table walks on TLB miss
        - Requires proper cache and TLB management
        
        Note: Automatically enabled for Cortex-A. Required for RT-Smart mode.

if RT_USING_SMART
    config KERNEL_VADDR_START
        hex "The virtural address of kernel start"
        default 0xffff000000000000 if ARCH_ARMV8
        default 0xc0000000 if ARCH_ARM
        default 0xffffffc000000000 if ARCH_RISCV && ARCH_REMAP_KERNEL
        default 0x80000000 if ARCH_RISCV
        depends on ARCH_MM_MMU
        help
            Starting virtual address for kernel space in RT-Smart mode.
            
            This defines where the kernel is mapped in the virtual address space.
            The kernel typically resides in the upper half of the address space to
            separate it from user-space applications.
            
            Default values:
            - ARMv8 (64-bit): 0xffff000000000000 (upper 256TB)
            - ARM (32-bit): 0xc0000000 (upper 1GB, Linux-compatible)
            - RISC-V with remap: 0xffffffc000000000
            - RISC-V standard: 0x80000000 (2GB mark)
            
            User-space applications use addresses below this value.
            
            Note: Must be aligned to architecture's virtual memory requirements.
            Changing this requires recompiling all kernel and user-space code.

    config RT_IOREMAP_LATE
        bool "Support to create IO mapping in the kernel address space after system initlalization."
        default n
        depends on ARCH_ARM_CORTEX_A
        depends on ARCH_MM_MMU
        help
            Enable dynamic I/O memory remapping after system initialization.
            
            When enabled, allows mapping device I/O memory into kernel virtual address
            space at runtime using rt_ioremap(). This is useful for:
            - Hot-pluggable devices
            - Runtime device discovery (device tree)
            - Drivers loaded after boot
            - Flexible peripheral address mapping
            
            Without this option, all I/O mappings must be established during early boot.
            
            Impact:
            - Slightly increased memory overhead for dynamic mapping tables
            - Additional TLB entries for I/O regions
            
            Enable if you need runtime flexibility for device driver loading or
            working with device tree-based systems.
endif

config ARCH_ARM_ARM9
    bool
    select ARCH_ARM
    help
        ARM9 processor family (legacy ARMv4T/ARMv5 architecture).
        
        Classic ARM architecture used in many embedded systems from the 2000s.
        Now largely superseded by Cortex-A for application processors.
        
        Features:
        - 5-stage pipeline
        - MMU for virtual memory
        - Separate instruction and data caches
        - ARM and Thumb instruction sets
        
        Performance: ~1.1 DMIPS/MHz
        
        Examples: ARM926EJ-S (NXP i.MX, Atmel AT91SAM9)
        Choose this if your BSP uses ARM9-based SoC.

config ARCH_ARM_ARM11
    bool
    select ARCH_ARM
    help
        ARM11 processor family (ARMv6 architecture).
        
        Enhanced ARM architecture with improved performance and SIMD extensions.
        Bridges the gap between ARM9 and Cortex-A.
        
        Features:
        - 8-stage pipeline
        - MMU with improved TLB
        - SIMD instructions
        - Unaligned access support
        - Hardware divide (some variants)
        
        Performance: ~1.25 DMIPS/MHz
        
        Examples: ARM1176JZF-S (Raspberry Pi 1, BCM2835)
        Choose this if your BSP uses ARM11-based SoC.

config ARCH_ARM_CORTEX_A
    bool
    select ARCH_ARM
    select ARCH_ARM_MMU
    select RT_USING_CPU_FFS
    select RT_USING_HW_ATOMIC
    help
        ARM Cortex-A application processor family.
        
        High-performance processors designed for complex operating systems and
        rich applications (Linux, Android, RT-Smart).
        
        Common features:
        - MMU for virtual memory (required)
        - Multi-level caches (L1/L2/L3)
        - VFP floating-point and NEON SIMD
        - TrustZone security extensions
        - Multi-core configurations (SMP)
        - GIC (Generic Interrupt Controller)
        
        Typical applications:
        - Industrial HMI and gateways
        - Multimedia devices
        - Automotive infotainment
        - Edge computing
        - RT-Smart mixed-criticality systems
        
        Variants: A5/A7/A8/A9/A15/A17/A35/A53/A55/A57/A72/A73
        
        Automatically selected when choosing specific Cortex-A variant.

    if ARCH_ARM_CORTEX_A
        config RT_SMP_AUTO_BOOT
            bool
            default n
            help
                Automatically boot secondary CPU cores at system startup.
                
                When enabled, RT-Thread will start all available CPU cores during
                initialization for symmetric multiprocessing (SMP).
                
                If disabled, secondary cores remain in reset/low-power state until
                explicitly started by application code.
                
                Enable for:
                - Multi-core load distribution
                - Parallel task execution
                - Maximum system performance
                
                Disable for:
                - Power-sensitive applications
                - Asymmetric multiprocessing (AMP)
                - Single-core debugging
                
                Note: Requires RT_USING_SMP to be enabled.

        config RT_USING_GIC_V2
            bool
            default n
            help
                Use ARM Generic Interrupt Controller version 2 (GICv2).
                
                GICv2 is the interrupt controller for Cortex-A processors, providing:
                - Up to 1020 interrupt sources
                - Interrupt priority and masking
                - CPU interface for each core
                - Distributor for routing interrupts to cores
                - Software-generated interrupts (SGI) for inter-core communication
                
                Used in:
                - Cortex-A5/A7/A8/A9/A15/A17
                - Single and multi-core SMP systems
                
                Mutually exclusive with GICv3. Select based on your SoC hardware.

        config RT_USING_GIC_V3
            bool
            default n
            help
                Use ARM Generic Interrupt Controller version 3/4 (GICv3/GICv4).
                
                GICv3 is the enhanced interrupt controller for newer ARM processors:
                - Improved scalability (supports more cores)
                - System register access (no memory-mapped CPU interface)
                - Locality-specific peripheral interrupts (LPI)
                - Message-based interrupts
                - GICv4: Direct injection of virtual interrupts
                
                Used in:
                - Cortex-A55/A57/A72/A73 and newer
                - ARMv8 (AArch64) systems
                - Large SMP systems (>8 cores)
                
                Mutually exclusive with GICv2. Select based on your SoC hardware.

        config RT_NO_USING_GIC
            bool
            default y if !RT_USING_GIC_V2 && !RT_USING_GIC_V3
            help
                No GIC interrupt controller in use.
                
                Automatically set when neither GICv2 nor GICv3 is selected.
                This may indicate:
                - Custom interrupt controller
                - Legacy interrupt controller
                - Configuration error
                
                Most Cortex-A systems require either GICv2 or GICv3.
    endif

config ARCH_ARM_CORTEX_A5
    bool
    select ARCH_ARM_CORTEX_A
    help
        ARM Cortex-A5 energy-efficient application processor.
        
        Entry-level Cortex-A processor offering lower cost and power than A9
        while maintaining application-class capabilities.
        
        Features:
        - ARMv7-A architecture
        - 1-4 cores, in-order execution
        - Optional NEON SIMD and VFPv4
        - TrustZone security
        - L1 cache, optional L2
        - GICv2
        
        Performance: ~1.57 DMIPS/MHz
        
        Ideal for: Cost-sensitive IoT gateways, industrial HMI
        Examples: Vybrid VF6xx (Cortex-A5 + Cortex-M4)
        Choose this if your BSP uses Cortex-A5 based SoC.

config ARCH_ARM_CORTEX_A7
    bool
    select ARCH_ARM_CORTEX_A
    help
        ARM Cortex-A7 power-efficient application processor.
        
        Most power-efficient ARMv7-A processor, often paired with A15 in big.LITTLE
        configurations or used standalone for cost-effective systems.
        
        Features:
        - ARMv7-A architecture with hardware virtualization
        - 1-4 cores, in-order execution
        - VFPv4 and NEON standard
        - TrustZone security
        - L1 and L2 cache
        - GICv2
        
        Performance: ~1.9 DMIPS/MHz
        Power: 40% lower than Cortex-A9 at same performance
        
        Ideal for: IoT gateways, set-top boxes, entry-level tablets
        Examples: BCM2836 (Raspberry Pi 2), i.MX6UL, Allwinner A33
        Choose this if your BSP uses Cortex-A7 based SoC.

config ARCH_ARM_CORTEX_A8
    bool
    select ARCH_ARM_CORTEX_A
    help
        ARM Cortex-A8 general-purpose application processor.
        
        First Cortex-A processor, designed for multimedia and mobile applications.
        
        Features:
        - ARMv7-A architecture
        - Single core, 13-stage superscalar pipeline
        - VFPv3 and NEON
        - TrustZone security
        - L1 and L2 cache
        
        Performance: ~2.0 DMIPS/MHz
        
        Ideal for: Industrial automation, multimedia systems
        Examples: TI AM335x (BeagleBone), OMAP3
        Choose this if your BSP uses Cortex-A8 based SoC.

config ARCH_ARM_CORTEX_A9
    bool
    select ARCH_ARM_CORTEX_A
    help
        ARM Cortex-A9 high-performance application processor.
        
        Popular multi-core processor balancing performance and power efficiency.
        
        Features:
        - ARMv7-A architecture
        - 1-4 cores, out-of-order execution
        - VFPv3 and NEON
        - TrustZone security
        - L1 cache per core, shared L2
        - GICv2
        
        Performance: ~2.5 DMIPS/MHz per core
        
        Ideal for: Industrial gateways, automotive, network equipment
        Examples: Zynq-7000 (A9 + FPGA), i.MX6, NVIDIA Tegra 2/3
        Choose this if your BSP uses Cortex-A9 based SoC.

config ARCH_ARM_CORTEX_A55
    bool
    select ARCH_ARM_CORTEX_A
    help
        ARM Cortex-A55 ultra-efficient 64-bit processor (ARMv8.2-A).
        
        DynamIQ-enabled processor for modern SMP and big.LITTLE configurations,
        designed for power efficiency and AI/ML workloads.
        
        Features:
        - ARMv8.2-A architecture (64-bit)
        - 1-8 cores in DynamIQ cluster
        - Dot product instructions for ML
        - TrustZone and pointer authentication
        - L1 and L2 cache, optional L3
        - GICv3
        
        Performance: ~1.8 DMIPS/MHz (better IPC than A53)
        
        Ideal for: Mobile, automotive ADAS, edge AI
        Examples: MediaTek Helio, Qualcomm Snapdragon 7xx/6xx
        Choose this if your BSP uses Cortex-A55 based SoC.

config ARCH_ARM_SECURE_MODE
    bool "Running in secure mode [ARM Cortex-A]"
    default n
    depends on ARCH_ARM_CORTEX_A
    help
        Run RT-Thread in ARM secure mode (TrustZone secure world).
        
        TrustZone divides the system into two execution environments:
        - Secure world: Access to all resources, runs trusted code
        - Non-secure world: Restricted access, runs normal applications
        
        Enable this when:
        - RT-Thread acts as secure monitor or trusted OS
        - Implementing secure boot chain
        - Running in EL3 (ARMv8) or secure state (ARMv7)
        - Providing secure services to non-secure OS
        
        Disable when:
        - Running as normal OS in non-secure world
        - No TrustZone partitioning needed
        - Booting directly without secure monitor
        
        Impact:
        - Changes memory access permissions
        - Affects SCR (Secure Configuration Register) settings
        - Influences interrupt routing
        
        Note: Most applications run in non-secure mode. Only enable if you're
        implementing secure firmware or trusted execution environment.

config RT_BACKTRACE_FUNCTION_NAME
    bool "To show function name when backtrace."
    default n
    depends on ARCH_ARM_CORTEX_A
    help
        Display function names in backtrace/call stack dumps.
        
        When enabled, exception handlers and assertion failures will show
        symbolic function names in addition to addresses, making debugging easier.
        
        Requires:
        - Debug symbols in the binary
        - Symbol table in memory or accessible
        - Additional processing during backtrace
        
        Benefits:
        - Easier identification of crash location
        - Better error reports
        - Faster debugging
        
        Costs:
        - Slightly larger binary (symbol information)
        - Increased backtrace processing time
        
        Recommended for development builds. May be disabled for production
        to save space and improve backtrace speed.

config ARCH_ARMV8
    bool
    select ARCH_ARM
    select ARCH_ARM_MMU
    select RT_USING_CPU_FFS
    select ARCH_USING_ASID
    select ARCH_USING_IRQ_CTX_LIST
    help
        ARM 64-bit architecture (ARMv8-A / AArch64).
        
        Modern 64-bit ARM architecture for high-performance application processors.
        Represents major architectural evolution from ARMv7 with enhanced features.
        
        Key features:
        - 64-bit addressing and registers (can also run 32-bit code in AArch32 mode)
        - Exception levels (EL0-EL3) for privilege separation
        - Enhanced virtual memory (48-bit addressing, up to 256TB)
        - ASID (Address Space ID) for efficient context switching
        - Improved SIMD (Advanced SIMD / NEON)
        - Hardware virtualization support
        - Scalable Vector Extension (SVE) on some variants
        
        Advantages over ARMv7:
        - More registers (31 general-purpose 64-bit registers)
        - Larger addressable memory (>4GB)
        - Better performance and efficiency
        - Enhanced security features
        
        Processors: Cortex-A53/A57/A72/A73/A75/A76, Neoverse, Apple M-series
        
        Automatically selected by AArch64 BSP configurations.
        Required for RT-Smart on 64-bit ARM platforms.

config ARCH_MIPS
    bool
    help
        MIPS (Microprocessor without Interlocked Pipeline Stages) architecture.
        
        Classic RISC architecture used in embedded systems, networking equipment,
        and consumer electronics.
        
        Features:
        - Simple load/store RISC design
        - Configurable endianness (big or little)
        - Optional FPU and DSP extensions
        - Hardware multithreading (MIPS MT)
        
        Common applications:
        - Network routers and switches
        - Set-top boxes
        - Gaming consoles
        - Embedded Linux systems
        
        Variants: MIPS32, MIPS64, microMIPS
        Choose this if your BSP uses MIPS-based SoC.

config ARCH_MIPS64
    bool
    select ARCH_CPU_64BIT
    help
        MIPS 64-bit architecture.
        
        64-bit extension of MIPS architecture providing:
        - 64-bit addressing and registers
        - Backward compatible with MIPS32 code
        - Enhanced performance for 64-bit operations
        - Access to larger memory spaces
        
        Applications: High-end networking equipment, servers
        Examples: Cavium OCTEON, Loongson processors
        Choose this if your BSP uses MIPS64-based SoC.

config ARCH_MIPS_XBURST
    bool
    select ARCH_MIPS
    help
        Ingenic XBurst MIPS-based processor family.
        
        Customized MIPS architecture optimized for mobile and multimedia applications
        by Ingenic Semiconductor.
        
        Features:
        - MIPS32-compatible core with enhancements
        - Low power consumption
        - Integrated multimedia accelerators
        
        Common applications: Handheld devices, e-readers, IoT
        Examples: JZ47xx series SoCs
        Choose this if your BSP uses Ingenic XBurst processor.

config ARCH_ANDES
    bool
    help
        Andes RISC-V based architecture.
        
        Custom RISC-V implementation by Andes Technology with proprietary extensions
        for enhanced performance and features.
        
        Features:
        - RISC-V ISA with Andes-specific extensions
        - CoDense (16-bit instruction compression)
        - StackSafe for stack protection
        - PowerBrake for power management
        
        Applications: AIoT, storage controllers, automotive
        Choose this if your BSP uses Andes processor core.

config ARCH_CSKY
    bool
    help
        C-SKY CPU architecture.
        
        Chinese-designed processor architecture (now part of Alibaba's T-Head).
        
        Features:
        - 16/32-bit RISC architecture
        - Low power and small code size
        - DSP extensions
        
        Applications: IoT devices, consumer electronics
        Choose this if your BSP uses C-SKY based processor.

config ARCH_POWERPC
    bool
    help
        PowerPC architecture.
        
        High-performance RISC architecture traditionally used in embedded and
        server applications.
        
        Features:
        - Big-endian (configurable to little-endian on some models)
        - AltiVec SIMD on some variants
        - Strong memory consistency model
        
        Applications: Networking equipment, aerospace, industrial control
        Examples: MPC5xxx, QorIQ series
        Choose this if your BSP uses PowerPC processor.

config ARCH_RISCV
    bool
    help
        RISC-V open standard instruction set architecture.
        
        Modern, modular, open-source ISA designed for efficiency and extensibility.
        Gaining rapid adoption in embedded systems, IoT, and AI/ML applications.
        
        Key advantages:
        - Open standard (no licensing fees)
        - Modular design (choose only needed extensions)
        - Simple and clean architecture
        - Growing ecosystem and vendor support
        
        Base ISAs: RV32I (32-bit), RV64I (64-bit)
        Common extensions:
        - M: Integer multiplication/division
        - A: Atomic instructions
        - F: Single-precision floating-point
        - D: Double-precision floating-point
        - C: Compressed 16-bit instructions
        - V: Vector operations
        
        Examples: SiFive, Allwinner D1, ESP32-C3/C6, GigaDevice GD32V
        
        Automatically selected when choosing RV32 or RV64 variant.

config ARCH_RISCV_FPU
    bool
    help
        RISC-V floating-point unit support.
        
        Enable hardware floating-point operations using RISC-V F and/or D extensions.
        Automatically selected by ARCH_RISCV_FPU_S or ARCH_RISCV_FPU_D.
        
        When enabled:
        - FPU registers (f0-f31) saved/restored during context switch
        - Hardware FP instructions used by compiler
        - Significant performance improvement for floating-point math
        
        Note: CPU must have F and/or D extension support.

config ARCH_RISCV_VECTOR
    bool
    help
        RISC-V Vector Extension (RVV) support.
        
        Enable RISC-V Vector Extension for SIMD operations, ideal for data-parallel
        workloads like DSP, image processing, and AI/ML inference.
        
        Features:
        - Vector registers with configurable length (VLEN)
        - Vector arithmetic, logic, and memory operations
        - Predication and masking
        - Auto-vectorization by compiler
        
        Benefits:
        - 4-10x performance for vectorizable workloads
        - Efficient memory access patterns
        - Scalable across different vector lengths
        
        Applications: Signal processing, multimedia, ML inference
        
        Note: Requires CPU with V extension (ratified v1.0).
        Select VLEN based on your hardware specification.

    if ARCH_RISCV_VECTOR
        choice ARCH_VECTOR_VLEN
            prompt "RISCV Vector Vlen"
            default ARCH_VECTOR_VLEN_128
            help
                Select the vector register length (VLEN) for RISC-V Vector Extension.
                
                VLEN defines the width of vector registers in bits. This must match
                your hardware's vector implementation.
                
                Common VLEN values:
                - 128-bit: Entry-level vector implementations, good balance
                - 256-bit: Higher throughput, more aggressive vectorization
                
                Larger VLEN:
                + More data processed per instruction
                + Better performance for vector operations
                - Larger context switch overhead
                - More silicon area required
                
                Check your CPU documentation for supported VLEN.

            config ARCH_VECTOR_VLEN_128
                bool "128"
                help
                    128-bit vector register length.
                    
                    Standard choice for embedded RISC-V processors with vector support.
                    Provides good performance/area balance.
                    
                    Choose this for most RISC-V vector implementations.

            config ARCH_VECTOR_VLEN_256
                bool "256"
                help
                    256-bit vector register length.
                    
                    Wider vector registers for higher throughput in data-parallel workloads.
                    Requires more silicon area and increases context switch time.
                    
                    Choose this only if your CPU supports 256-bit VLEN.
        endchoice
    endif

config ARCH_RISCV_FPU_S
    select ARCH_RISCV_FPU
    bool
    help
        RISC-V single-precision floating-point (F extension).
        
        Enable support for 32-bit (float) floating-point operations in hardware.
        
        Features:
        - 32 single-precision FP registers (f0-f31)
        - IEEE 754 single-precision arithmetic
        - FP load/store, arithmetic, conversion instructions
        
        Sufficient for many embedded applications requiring FP without the
        overhead of double-precision.
        
        Automatically selected by BSP when CPU has F extension.

config ARCH_RISCV_FPU_D
    select ARCH_RISCV_FPU
    bool
    help
        RISC-V double-precision floating-point (D extension).
        
        Enable support for 64-bit (double) floating-point operations in hardware.
        Includes F extension functionality.
        
        Features:
        - 32 double-precision FP registers (f0-f31, 64-bit wide)
        - IEEE 754 double-precision arithmetic
        - Both single and double-precision operations
        
        Required for:
        - High-precision scientific computations
        - Financial calculations
        - Applications requiring >7 significant digits
        
        Note: D extension requires F extension as prerequisite.
        Automatically selected by BSP when CPU has D extension.

config ARCH_RISCV32
    select ARCH_RISCV
    bool
    help
        RISC-V 32-bit architecture (RV32).
        
        32-bit RISC-V implementation optimized for resource-constrained
        embedded systems and microcontrollers.
        
        Features:
        - 32-bit addressing (4GB address space)
        - 32 general-purpose 32-bit registers
        - Compact code size with C extension
        - Lower power consumption
        
        Ideal for:
        - Microcontrollers and IoT devices
        - Cost-sensitive applications
        - Battery-powered systems
        
        Common variants: RV32IMAC, RV32IMAFC
        Examples: ESP32-C3, GigaDevice GD32VF103, Nuclei Bumblebee
        
        Choose this if your BSP uses 32-bit RISC-V processor.

config ARCH_RISCV64
    select ARCH_RISCV
    select ARCH_CPU_64BIT
    bool
    help
        RISC-V 64-bit architecture (RV64).
        
        64-bit RISC-V implementation for high-performance embedded systems
        and application processors.
        
        Features:
        - 64-bit addressing (16 exabyte address space)
        - 32 general-purpose 64-bit registers
        - Backward compatible with RV32 software (with proper toolchain)
        - Better performance for 64-bit arithmetic
        
        Ideal for:
        - Application processors
        - RT-Smart user-space applications
        - Systems requiring >4GB memory
        - High-performance embedded Linux
        
        Common variants: RV64IMAC, RV64GC
        Examples: SiFive U74, Allwinner D1 (C906), Kendryte K210
        
        Choose this if your BSP uses 64-bit RISC-V processor.

if ARCH_RISCV64
    config ARCH_USING_NEW_CTX_SWITCH
        bool
        default y
        help
            Use optimized context switch implementation for RISC-V 64-bit.
            
            Enables improved context switching with better performance and
            smaller code size. This is the recommended implementation for RV64.
            
            Automatically enabled for RISC-V 64-bit. No manual configuration needed.

    config ARCH_USING_RISCV_COMMON64
        bool
        depends on ARCH_RISCV64
        select RT_USING_CPUTIME
        select ARCH_USING_NEW_CTX_SWITCH
        help
            Use common 64-bit RISC-V implementation under ./libcpu/risc-v/common64.
            
            Provides unified, optimized implementation for 64-bit RISC-V cores:
            - Standard context switch routines
            - Exception and interrupt handling
            - MMU/PMP management
            - CPU time measurement
            
            Benefits:
            - Code reuse across different RV64 cores
            - Well-tested implementation
            - Consistent behavior
            
            Enable this for standard RV64 cores (SiFive U74, T-Head C906, etc.)
            unless you have specific custom requirements.
endif

config ARCH_REMAP_KERNEL
    bool
    depends on RT_USING_SMART
    help
        Remap kernel image to high virtual address region.
        
        In RT-Smart mode, move kernel to upper virtual memory region to separate
        it from user-space, similar to Linux kernel layout.
        
        Benefits:
        - Clear separation between kernel and user address spaces
        - User applications can use lower addresses (0x0 upward)
        - Prevents accidental user access to kernel memory
        - Compatible with standard executable loaders
        
        Memory layout with remapping:
        - User space: 0x00000000 - KERNEL_VADDR_START
        - Kernel space: KERNEL_VADDR_START - 0xFFFFFFFF...
        
        Required for: Full RT-Smart user-space isolation
        Note: Increases boot time slightly due to remapping overhead.

config ARCH_USING_ASID
    bool
    depends on RT_USING_SMART
    help
        Enable Address Space ID (ASID) support from architecture.
        
        ASID is a hardware feature that tags TLB (Translation Lookaside Buffer)
        entries with process identifiers, avoiding TLB flushes on context switch.
        
        Benefits:
        - Faster context switches between processes
        - Better TLB utilization (multiple processes' translations cached)
        - Reduced MMU overhead
        
        Without ASID: TLB must be flushed on every context switch (expensive)
        With ASID: TLB entries for multiple processes coexist (efficient)
        
        Performance impact: Can reduce context switch time by 50-70%
        
        Automatically enabled for:
        - ARMv8 (8-bit or 16-bit ASID)
        - Some ARMv7-A implementations
        - RISC-V with ASID support
        
        Note: Requires MMU with ASID support. Automatically selected by
        compatible architectures.

config ARCH_IA32
    bool
    help
        Intel IA-32 (x86 32-bit) architecture.
        
        32-bit x86 architecture for PC-compatible systems and embedded x86 platforms.
        
        Features:
        - CISC architecture
        - Segmented memory model (legacy) or flat model
        - x87 FPU, MMX, SSE extensions
        - Paging and segmentation
        
        Applications: Industrial PCs, legacy embedded systems, virtualization hosts
        Examples: Intel Atom, AMD Geode
        
        Choose this if your BSP uses x86 32-bit processor.

config ARCH_TIDSP
    bool
    help
        Texas Instruments DSP architecture family.
        
        Specialized processors for digital signal processing applications.
        
        Features:
        - Optimized for real-time signal processing
        - Harvard architecture (separate program/data memory)
        - Hardware multipliers and MAC units
        - Low-latency interrupt handling
        
        Applications: Motor control, audio processing, power electronics
        
        Automatically selected by specific TI DSP variant (e.g., C28x).

config ARCH_TIDSP_C28X
    bool
    select ARCH_TIDSP
    select ARCH_CPU_STACK_GROWS_UPWARD
    help
        Texas Instruments C28x DSP architecture.
        
        Fixed-point DSP optimized for real-time control applications,
        especially motor control and power conversion.
        
        Features:
        - 32-bit fixed-point architecture
        - Upward-growing stack (unusual characteristic)
        - Single-cycle MAC operations
        - Fast interrupt response (<50ns)
        - Floating-point unit (C28x+FPU variants)
        
        Ideal for:
        - Digital motor control (FOC, vector control)
        - Power inverters and converters
        - Solar inverters
        - Industrial drives
        
        Examples: TMS320F28xxx series
        
        Note: Stack grows upward unlike most architectures.
        Choose this if your BSP uses TI C28x DSP.

config ARCH_HOST_SIMULATOR
    bool
    help
        Host machine simulator (running RT-Thread on development PC).
        
        Allows running RT-Thread as a user-space application on Linux, Windows,
        or macOS for development, testing, and debugging without physical hardware.
        
        Features:
        - Rapid prototyping and testing
        - Debugger-friendly (use GDB, Visual Studio debugger)
        - File system access to host files
        - Network simulation
        
        Use cases:
        - Algorithm development and testing
        - Application logic verification
        - CI/CD automated testing
        - Learning RT-Thread without hardware
        
        Note: Timing behavior differs from real hardware. Not suitable for
        real-time performance validation.
        
        Choose this for simulator-based BSP (e.g., qemu-vexpress-a9, simulator).

config ARCH_USING_HW_THREAD_SELF
    bool
    default n
    help
        Use hardware register to identify current thread (thread self-identification).
        
        Some architectures provide dedicated registers or instructions to identify
        the currently executing thread without memory access.
        
        Benefits:
        - Faster rt_thread_self() operation (single register read)
        - Reduced memory bandwidth
        - Better performance in multi-core systems
        
        Examples:
        - ARM: TPIDRURO/TPIDR_EL0 register
        - x86: FS/GS segment registers
        - RISC-V: Some implementations use tp register
        
        Automatically enabled by architectures supporting this feature.
        No manual configuration needed.

config ARCH_USING_IRQ_CTX_LIST
    bool
    default n
    help
        Use interrupt context list for nested interrupt handling.
        
        Maintains a list of interrupt contexts for proper nested interrupt
        management, especially important for complex interrupt scenarios.
        
        Benefits:
        - Correct handling of deeply nested interrupts
        - Proper context tracking in multi-level interrupt systems
        - Better debugging of interrupt-related issues
        
        Overhead:
        - Slight increase in interrupt entry/exit time
        - Small memory overhead for context list
        
        Automatically enabled by architectures requiring it (e.g., ARMv8).
        No manual configuration needed.