Add support for Cortex-A/R

ci-nightly.sh

@@ -21,5 +21,6 @@ cargo batch  \
     --- build --release --manifest-path embassy-executor/Cargo.toml --target riscv32imac-unknown-none-elf --features nightly,arch-riscv32 \
     --- build --release --manifest-path embassy-executor/Cargo.toml --target riscv32imac-unknown-none-elf --features nightly,arch-riscv32,executor-thread \
     --- build --release --manifest-path examples/nrf52840-rtic/Cargo.toml --target thumbv7em-none-eabi --artifact-dir out/examples/nrf52840-rtic \
+    --- build --release --manifest-path embassy-executor/Cargo.toml --target armv7a-none-eabi --features nightly,arch-cortex-ar,executor-thread \
 
 RUSTFLAGS="$RUSTFLAGS -C target-cpu=atmega328p" cargo build --release --manifest-path embassy-executor/Cargo.toml --target avr-none -Z build-std=core,alloc --features nightly,arch-avr,avr-device/atmega328p

ci.sh

@@ -35,6 +35,9 @@ cargo batch \
     --- build --release --manifest-path embassy-executor/Cargo.toml --target thumbv7em-none-eabi --features arch-cortex-m,executor-thread \
     --- build --release --manifest-path embassy-executor/Cargo.toml --target thumbv7em-none-eabi --features arch-cortex-m,executor-interrupt \
     --- build --release --manifest-path embassy-executor/Cargo.toml --target thumbv7em-none-eabi --features arch-cortex-m,executor-thread,executor-interrupt \
+    --- build --release --manifest-path embassy-executor/Cargo.toml --target armv7a-none-eabi --features arch-cortex-ar,executor-thread \
+    --- build --release --manifest-path embassy-executor/Cargo.toml --target armv7r-none-eabi --features arch-cortex-ar,executor-thread \
+    --- build --release --manifest-path embassy-executor/Cargo.toml --target armv7r-none-eabihf --features arch-cortex-ar,executor-thread \
     --- build --release --manifest-path embassy-executor/Cargo.toml --target riscv32imac-unknown-none-elf --features arch-riscv32 \
     --- build --release --manifest-path embassy-executor/Cargo.toml --target riscv32imac-unknown-none-elf --features arch-riscv32,executor-thread \
     --- build --release --manifest-path embassy-sync/Cargo.toml --target thumbv6m-none-eabi --features defmt \

embassy-executor-macros/src/lib.rs

@@ -70,6 +70,31 @@ pub fn main_cortex_m(args: TokenStream, item: TokenStream) -> TokenStream {
     main::run(args.into(), item.into(), &main::ARCH_CORTEX_M).into()
 }
 
+/// Creates a new `executor` instance and declares an application entry point for Cortex-A/R
+/// spawning the corresponding function body as an async task.
+///
+/// The following restrictions apply:
+///
+/// * The function must accept exactly 1 parameter, an `embassy_executor::Spawner` handle that it
+///   can use to spawn additional tasks.
+/// * The function must be declared `async`.
+/// * The function must not use generics.
+/// * Only a single `main` task may be declared.
+///
+/// ## Examples
+/// Spawning a task:
+///
+/// ``` rust
+/// #[embassy_executor::main]
+/// async fn main(_s: embassy_executor::Spawner) {
+///     // Function body
+/// }
+/// ```
+#[proc_macro_attribute]
+pub fn main_cortex_ar(args: TokenStream, item: TokenStream) -> TokenStream {
+    main::run(args.into(), item.into(), &main::ARCH_CORTEX_AR).into()
+}
+
 /// Creates a new `executor` instance and declares an architecture agnostic application entry point spawning
 /// the corresponding function body as an async task.
 ///

embassy-executor-macros/src/macros/main.rs

@@ -37,6 +37,12 @@ pub static ARCH_CORTEX_M: Arch = Arch {
     executor_required: false,
 };
 
+pub static ARCH_CORTEX_AR: Arch = Arch {
+    default_entry: None,
+    flavor: Flavor::Standard,
+    executor_required: false,
+};
+
 pub static ARCH_SPIN: Arch = Arch {
     default_entry: None,
     flavor: Flavor::Standard,

embassy-executor/CHANGELOG.md

@@ -5,6 +5,10 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## unreleased
+
+- Added support for Cortex-A and Cortex-R
+
 ## 0.7.0 - 2025-01-02
 
 - Performance optimizations.

embassy-executor/Cargo.toml

@@ -45,6 +45,9 @@ portable-atomic = { version = "1.5", optional = true }
 # arch-cortex-m dependencies
 cortex-m = { version = "0.7.6", optional = true }
 
+# arch-cortex-ar dependencies
+cortex-ar = { version = "0.2", optional = true }
+
 # arch-wasm dependencies
 wasm-bindgen = { version = "0.2.82", optional = true }
 js-sys = { version = "0.3", optional = true }
@@ -73,6 +76,8 @@ _arch = [] # some arch was picked
 arch-std = ["_arch"]
 ## Cortex-M
 arch-cortex-m = ["_arch", "dep:cortex-m"]
+## Cortex-A/R
+arch-cortex-ar = ["_arch", "dep:cortex-ar"]
 ## RISC-V 32
 arch-riscv32 = ["_arch"]
 ## WASM

embassy-executor/src/arch/cortex_ar.rs

@@ -0,0 +1,84 @@
+#[cfg(feature = "executor-interrupt")]
+compile_error!("`executor-interrupt` is not supported with `arch-cortex-ar`.");
+
+#[export_name = "__pender"]
+#[cfg(any(feature = "executor-thread", feature = "executor-interrupt"))]
+fn __pender(context: *mut ()) {
+    // `context` is always `usize::MAX` created by `Executor::run`.
+    let context = context as usize;
+
+    #[cfg(feature = "executor-thread")]
+    // Try to make Rust optimize the branching away if we only use thread mode.
+    if !cfg!(feature = "executor-interrupt") || context == THREAD_PENDER {
+        cortex_ar::asm::sev();
+        return;
+    }
+}
+
+#[cfg(feature = "executor-thread")]
+pub use thread::*;
+#[cfg(feature = "executor-thread")]
+mod thread {
+    pub(super) const THREAD_PENDER: usize = usize::MAX;
+
+    use core::marker::PhantomData;
+
+    use cortex_ar::asm::wfe;
+    pub use embassy_executor_macros::main_cortex_ar as main;
+
+    use crate::{raw, Spawner};
+
+    /// Thread mode executor, using WFE/SEV.
+    ///
+    /// This is the simplest and most common kind of executor. It runs on
+    /// thread mode (at the lowest priority level), and uses the `WFE` ARM instruction
+    /// to sleep when it has no more work to do. When a task is woken, a `SEV` instruction
+    /// is executed, to make the `WFE` exit from sleep and poll the task.
+    ///
+    /// This executor allows for ultra low power consumption for chips where `WFE`
+    /// triggers low-power sleep without extra steps. If your chip requires extra steps,
+    /// you may use [`raw::Executor`] directly to program custom behavior.
+    pub struct Executor {
+        inner: raw::Executor,
+        not_send: PhantomData<*mut ()>,
+    }
+
+    impl Executor {
+        /// Create a new Executor.
+        pub fn new() -> Self {
+            Self {
+                inner: raw::Executor::new(THREAD_PENDER as *mut ()),
+                not_send: PhantomData,
+            }
+        }
+
+        /// Run the executor.
+        ///
+        /// The `init` closure is called with a [`Spawner`] that spawns tasks on
+        /// this executor. Use it to spawn the initial task(s). After `init` returns,
+        /// the executor starts running the tasks.
+        ///
+        /// To spawn more tasks later, you may keep copies of the [`Spawner`] (it is `Copy`),
+        /// for example by passing it as an argument to the initial tasks.
+        ///
+        /// This function requires `&'static mut self`. This means you have to store the
+        /// Executor instance in a place where it'll live forever and grants you mutable
+        /// access. There's a few ways to do this:
+        ///
+        /// - a [StaticCell](https://docs.rs/static_cell/latest/static_cell/) (safe)
+        /// - a `static mut` (unsafe)
+        /// - a local variable in a function you know never returns (like `fn main() -> !`), upgrading its lifetime with `transmute`. (unsafe)
+        ///
+        /// This function never returns.
+        pub fn run(&'static mut self, init: impl FnOnce(Spawner)) -> ! {
+            init(self.inner.spawner());
+
+            loop {
+                unsafe {
+                    self.inner.poll();
+                }
+                wfe();
+            }
+        }
+    }
+}

embassy-executor/src/lib.rs

@@ -26,6 +26,7 @@ macro_rules! check_at_most_one {
 check_at_most_one!(
     "arch-avr",
     "arch-cortex-m",
+    "arch-cortex-ar",
     "arch-riscv32",
     "arch-std",
     "arch-wasm",
@@ -35,6 +36,7 @@ check_at_most_one!(
 #[cfg(feature = "_arch")]
 #[cfg_attr(feature = "arch-avr", path = "arch/avr.rs")]
 #[cfg_attr(feature = "arch-cortex-m", path = "arch/cortex_m.rs")]
+#[cfg_attr(feature = "arch-cortex-ar", path = "arch/cortex_ar.rs")]
 #[cfg_attr(feature = "arch-riscv32", path = "arch/riscv32.rs")]
 #[cfg_attr(feature = "arch-std", path = "arch/std.rs")]
 #[cfg_attr(feature = "arch-wasm", path = "arch/wasm.rs")]

rust-toolchain-nightly.toml

@@ -9,4 +9,5 @@ targets = [
     "thumbv8m.main-none-eabihf",
     "riscv32imac-unknown-none-elf",
     "wasm32-unknown-unknown",
+    "armv7a-none-eabi",
 ]

rust-toolchain.toml

@@ -9,4 +9,7 @@ targets = [
     "thumbv8m.main-none-eabihf",
     "riscv32imac-unknown-none-elf",
     "wasm32-unknown-unknown",
+    "armv7a-none-eabi",
+    "armv7r-none-eabi",
+    "armv7r-none-eabihf",
 ]