Using portable-atomic always

Author: romancardenas

.cargo/config.toml

@@ -0,0 +1,7 @@
+[target.'cfg(all(target_arch = "riscv32", target_os = "none"))']
+rustflags = [
+    "--cfg", "portable_atomic_target_feature=\"zaamo\"",
+]
+
+[build]
+target = "riscv32imc-unknown-none-elf"

.github/workflows/e310x-hal.yaml

@@ -13,9 +13,6 @@ jobs:
       matrix:
         # All generated code should be running on stable now, MRSV is 1.65.0
         toolchain: [ stable, nightly, 1.65.0 ]
-        target:
-          - riscv32imc-unknown-none-elf
-          - riscv32imac-unknown-none-elf # TODO e310x is not a purely IMAC core
         include:
           # Nightly is only for reference and allowed to fail
           - toolchain: nightly
@@ -27,11 +24,11 @@ jobs:
     - name: Update Rust toolchain
       run: rustup update ${{ matrix.toolchain }} && rustup default ${{ matrix.toolchain }}
     - name: Install Rust target
-      run: rustup target install ${{ matrix.target }}
+      run: rustup target install riscv32imc-unknown-none-elf
     - name: Build (no features)
-      run: cargo build --package e310x-hal --target ${{ matrix.target }}
+      run: cargo build --package e310x-hal --target riscv32imc-unknown-none-elf
     - name: Build (all features)
-      run: cargo build --package e310x-hal --target ${{ matrix.target }} --all-features
+      run: cargo build --package e310x-hal --target riscv32imc-unknown-none-elf --all-features
 
   # On MacOS and Ubuntu, we at least make sure that the crate builds and links.
   # On Windows, linking fails when the rt feature is enabled.
@@ -44,6 +41,8 @@ jobs:
       - uses: actions/checkout@v4
       - name: Update Rust toolchain
         run: rustup update stable && rustup default stable
+      - name: Rename .cargo/config to .cargo/config.bak to ignore it
+        run: mv .cargo/config.toml .cargo/config.bak
       - name: Build (no features)
         run: cargo test --package e310x-hal
       - name: Build (all features)

.github/workflows/e310x.yaml

@@ -44,6 +44,8 @@ jobs:
       - uses: actions/checkout@v4
       - name: Update Rust toolchain
         run: rustup update stable && rustup default stable
+      - name: Rename .cargo/config to .cargo/config.bak to ignore it
+        run: mv .cargo/config.toml .cargo/config.bak
       - name: Build (no features)
         run: cargo test --package e310x
       - name: Build (all features)

e310x-hal/CHANGELOG.md

@@ -8,9 +8,10 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 ## [Unreleased]
 
 ### Changed
+- Use `portable-atomic` with `zaamo` feature to use native `amo*` operations.
+- Official target is now `riscv32imc-unknown-none-elf`, as it does not fully support the A extension.
 - Update `e310x` dependency and adapt code
 - Bump MSRV to 1.65.0 (check Cargo.toml)
-- Use `portable-atomic` to allow builds on `riscv32imc-unknown-none-elf`` targets when needed.
 
 ## [v0.10.0] - 2023-03-28
 

e310x-hal/Cargo.toml

@@ -15,9 +15,7 @@ embedded-hal = { version = "0.2.6", features = ["unproven"] }
 nb = "1.0.0"
 riscv = { version = "0.10.1", features = ["critical-section-single-hart"] }
 e310x = { path = "../e310x", version = "0.11.0", features = ["rt", "critical-section"] }
-
-[target.'cfg(not(target_has_atomic = "32"))'.dependencies]
-portable-atomic = { version = "1.4", default-features = false, features = ["unsafe-assume-single-core"] }
+portable-atomic = { version = "1.9", default-features = false}
 
 [features]
 g002 = ["e310x/g002"]

e310x-hal/src/gpio.rs

@@ -2,9 +2,6 @@
 
 use core::marker::PhantomData;
 
-#[cfg(target_has_atomic = "32")]
-use core::sync::atomic::{AtomicU32, Ordering};
-#[cfg(not(target_has_atomic = "32"))]
 use portable_atomic::{AtomicU32, Ordering};
 
 /// GpioExt trait extends the GPIO0 peripheral.

e310x-hal/src/lib.rs

@@ -2,6 +2,42 @@
 //!
 //! This is an implementation of the [`embedded-hal`] traits for the E310x
 //! family of microcontrollers.
+//!
+//! # Building an application for the E310x chips
+//!
+//! The E310x chips implement the [Zaamo](https://github.com/riscv/riscv-zaamo-zalrsc/blob/main/zaamo-zalrsc.adoc)
+//! extension for atomic instructions. This means that it *partially* supports the `A`
+//! extension for atomic. Specifically, it supports the `amo*` instructions, but not the
+//! `lr*` and `sc*` instructions.
+//!
+//! It is discouraged to use the `riscv32imac-unknown-none-elf` target for E310x chips, as it
+//! will potentially generate code that uses the `lr*` and `sc*` instructions, which are not
+//! supported by the E310x chips. Thus, it is recommended to use `riscv32imc-unknown-none-elf`.
+//!
+//! # Working with atomic operations
+//!
+//! If you are using the `riscv32imc-unknown-none-elf` target, you will notice that
+//! `core::sync::atomic` is not available. To work around this, you can use the
+//! [`portable-atomic`](https://docs.rs/portable-atomic/1.8.0/portable_atomic/) crate.
+//! This crate allows us to use native `amo*` instructions on the E310x chips without requiring
+//! the `A` extension. Furthermore, you can emulate the `lr*` and `sc*` instructions if needed.
+//!
+//! Thus, the recommended way to work with E310x chips is:
+//!
+//! 1. Compile your code against the `riscv32imc-unknown-none-elf` target.
+//! 2. Add the following configuration to your `.cargo/config.toml`:
+//!
+//! ```toml
+//! [target.'cfg(all(target_arch = "riscv32", target_os = "none"))']
+//! rustflags = [
+//!    "--cfg", "portable_atomic_target_feature=\"zaamo\"",
+//! ]
+//!
+//! [build]
+//! target = "riscv32imc-unknown-none-elf"
+//! ```
+//!
+//! This will ensure that the `portable-atomic` crate is correctly configured to work with the E310x chips.
 
 #![deny(missing_docs)]
 #![no_std]