pw_kernel/config/lib.rs

// Copyright 2025 The Pigweed Authors
//
// Licensed under the Apache License, Version 2.0 (the "License"); you may not
// use this file except in compliance with the License. You may obtain a copy of
// the License at
//
//     https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
// License for the specific language governing permissions and limitations under
// the License.
#![no_std]
use memory_config::MemoryRegion;

/// Kernel configuration common to all architectures.
pub trait KernelConfigInterface {
    /// Rate of the scheduler monotonic tick.
    const SCHEDULER_TICK_HZ: u32 = 100;

    /// The number of bytes allocated for each kernel stack.
    const KERNEL_STACK_SIZE_BYTES: usize = 2048;

    /// The native rate at which the system clock advances.
    const SYSTEM_CLOCK_HZ: u64;
}

/// Cortex-M specific configuration.
// TODO: davidroth - Once Arch is out of tree, move this configuration also.
pub trait CortexMKernelConfigInterface {
    /// Rate of the Cortex-M systick system timer.
    const SYS_TICK_HZ: u32;

    /// Number of supported MPU regions
    const NUM_MPU_REGIONS: usize;
}

/// NVIC configuration.
pub trait NvicConfigInterface {
    /// The maximum number of interrupts the NVIC supports.
    const MAX_IRQS: u32 = 480;
}

/// RISC-V specific configuration.
// TODO: davidroth - Once Arch is out of tree, move this configuration also.
pub trait RiscVKernelConfigInterface {
    /// Rate of the machine time.
    const MTIME_HZ: u64;

    /// Machine time configuration.
    type Timer: Sized;

    /// Number of PMP entries.  Per the architecture spec this may be 0, 16
    /// or 64.
    const PMP_ENTRIES: usize;

    /// A range of PMP entries the kernel will use to configure memory access
    /// for userspace.
    const PMP_USERSPACE_ENTRIES: core::ops::Range<usize>;

    /// RISC-V PMP Granularity.  This defines the minimum size of PMP protection
    /// regions, which is 2**(G+2) bytes (That is, when G=0, the minimum size is 4 bytes).
    const PMP_GRANULARITY: usize;

    /// Non-locked memory regions to configure during kernel execution.
    const KERNEL_MEMORY_REGIONS: &'static [MemoryRegion];

    /// mtvec exception mode. When in direct mode, base address will be set
    /// to the `_start_trap` address.
    /// When in vectored mode, the address of the vector table is passed
    /// as a usize.
    /// This isn't const, as rust doesn't allow an address only know at
    /// link time to be const.
    /// https://users.rust-lang.org/t/using-linker-defined-symbols-in-const-context-as-integers/120081
    fn get_exception_mode() -> ExceptionMode;
}

/// mtvec exception mode.
pub enum ExceptionMode {
    Direct,
    Vectored(usize),
}

/// PLIC configuration.
pub trait PlicConfigInterface {
    /// The PLIC base address.
    const PLIC_BASE_ADDRESS: usize;

    /// The maximum number of interrupts the
    /// PLIC supports per context.
    const MAX_IRQS: u32 = 1023;
}

/// VeeR PIC configuration.
pub trait VeerPicConfigInterface {
    /// The PIC base address.
    const PIC_BASE_ADDRESS: usize;

    /// The maximum number of interrupts the
    /// PIC supports per context.
    const MAX_IRQS: u32 = 256;
}

/// CLINT timer config.
pub trait ClintTimerConfigInterface {
    /// Address of mtime register.
    const MTIME_REGISTER: usize;

    /// Address of mtime compare register.
    const MTIMECMP_REGISTER: usize;
}

/// mtime timer config.
pub trait MTimeTimerConfigInterface {
    /// Address of mtime register.
    const MTIME_REGISTER: usize;

    /// Address of mtime compare register.
    const MTIMECMP_REGISTER: usize;

    /// Address of timer control register.
    const TIMER_CTRL_REGISTER: usize;

    /// Address of interrupt enable register.
    const TIMER_INTR_ENABLE_REGISTER: usize;

    /// Address of interrupt state register.
    const TIMER_INTR_STATE_REGISTER: usize;
}