Merge #1435

1435: Added example for multi priority executors rp2040 r=Dirbaio a=fakusb

I added an example for multiple priorities of tasks on rp2040 by adjusting [examples/nrf52840/src/bin/multiprio.rs](https://github.com/embassy-rs/embassy/blob/master/examples/nrf52840/src/bin/multiprio.rs) .

This needs https://github.com/embassy-rs/rp-pac/pull/2 , and this commit also adds the 6 new interrupt handlers for software interrupts to embassy-rs.

We might need to change the git path for rp-pac in [embassy-rp/Cargo.toml](https://github.com/embassy-rs/embassy/compare/master...fakusb:rp2040-multiprio-executor?expand=1#diff-47463ea358745927ecdb686f52feab816fde5d402a9628a136c116f34a802ab0)

Closes #1413

Co-authored-by: Fabian Kunze <fkunze@fkunze.de>

embassy-rp/Cargo.toml

@@ -61,7 +61,7 @@ embedded-storage = { version = "0.3" }
 rand_core = "0.6.4"
 fixed = "1.23.1"
 
-rp-pac = { version = "2", features = ["rt"] }
+rp-pac = { version = "3", features = ["rt"] }
 
 embedded-hal-02 = { package = "embedded-hal", version = "0.2.6", features = ["unproven"] }
 embedded-hal-1 = { package = "embedded-hal", version = "=1.0.0-alpha.10", optional = true}

embassy-rp/src/interrupt.rs

@@ -34,3 +34,9 @@ declare!(ADC_IRQ_FIFO);
 declare!(I2C0_IRQ);
 declare!(I2C1_IRQ);
 declare!(RTC_IRQ);
+declare!(SWI_IRQ_0);
+declare!(SWI_IRQ_1);
+declare!(SWI_IRQ_2);
+declare!(SWI_IRQ_3);
+declare!(SWI_IRQ_4);
+declare!(SWI_IRQ_5);

examples/rp/Cargo.toml

@@ -8,7 +8,7 @@ license = "MIT OR Apache-2.0"
 [dependencies]
 embassy-embedded-hal = { version = "0.1.0", path = "../../embassy-embedded-hal", features = ["defmt"] }
 embassy-sync = { version = "0.2.0", path = "../../embassy-sync", features = ["defmt"] }
-embassy-executor = { version = "0.2.0", path = "../../embassy-executor", features = ["arch-cortex-m", "executor-thread", "defmt", "integrated-timers"] }
+embassy-executor = { version = "0.2.0", path = "../../embassy-executor", features = ["arch-cortex-m", "executor-thread", "executor-interrupt", "defmt", "integrated-timers"] }
 embassy-time = { version = "0.1.0", path = "../../embassy-time", features = ["nightly", "unstable-traits", "defmt", "defmt-timestamp-uptime"] }
 embassy-rp = { version = "0.1.0", path = "../../embassy-rp", features = ["defmt", "unstable-traits", "nightly", "unstable-pac", "time-driver", "critical-section-impl"] }
 embassy-usb = { version = "0.1.0", path = "../../embassy-usb", features = ["defmt"] }

examples/rp/src/bin/multiprio.rs

@@ -0,0 +1,152 @@
+//! This example showcases how to create multiple Executor instances to run tasks at
+//! different priority levels.
+//!
+//! Low priority executor runs in thread mode (not interrupt), and uses `sev` for signaling
+//! there's work in the queue, and `wfe` for waiting for work.
+//!
+//! Medium and high priority executors run in two interrupts with different priorities.
+//! Signaling work is done by pending the interrupt. No "waiting" needs to be done explicitly, since
+//! when there's work the interrupt will trigger and run the executor.
+//!
+//! Sample output below. Note that high priority ticks can interrupt everything else, and
+//! medium priority computations can interrupt low priority computations, making them to appear
+//! to take significantly longer time.
+//!
+//! ```not_rust
+//!     [med] Starting long computation
+//!     [med] done in 992 ms
+//!         [high] tick!
+//! [low] Starting long computation
+//!     [med] Starting long computation
+//!         [high] tick!
+//!         [high] tick!
+//!     [med] done in 993 ms
+//!     [med] Starting long computation
+//!         [high] tick!
+//!         [high] tick!
+//!     [med] done in 993 ms
+//! [low] done in 3972 ms
+//!     [med] Starting long computation
+//!         [high] tick!
+//!         [high] tick!
+//!     [med] done in 993 ms
+//! ```
+//!
+//! For comparison, try changing the code so all 3 tasks get spawned on the low priority executor.
+//! You will get an output like the following. Note that no computation is ever interrupted.
+//!
+//! ```not_rust
+//!         [high] tick!
+//!     [med] Starting long computation
+//!     [med] done in 496 ms
+//! [low] Starting long computation
+//! [low] done in 992 ms
+//!     [med] Starting long computation
+//!     [med] done in 496 ms
+//!         [high] tick!
+//! [low] Starting long computation
+//! [low] done in 992 ms
+//!         [high] tick!
+//!     [med] Starting long computation
+//!     [med] done in 496 ms
+//!         [high] tick!
+//! ```
+//!
+
+#![no_std]
+#![no_main]
+#![feature(type_alias_impl_trait)]
+
+use core::mem;
+
+use cortex_m::peripheral::NVIC;
+use cortex_m_rt::entry;
+use defmt::{info, unwrap};
+use embassy_rp::executor::{Executor, InterruptExecutor};
+use embassy_rp::interrupt;
+use embassy_rp::pac::Interrupt;
+use embassy_time::{Duration, Instant, Timer, TICK_HZ};
+use static_cell::StaticCell;
+use {defmt_rtt as _, panic_probe as _};
+
+#[embassy_executor::task]
+async fn run_high() {
+    loop {
+        info!("        [high] tick!");
+        Timer::after(Duration::from_ticks(673740)).await;
+    }
+}
+
+#[embassy_executor::task]
+async fn run_med() {
+    loop {
+        let start = Instant::now();
+        info!("    [med] Starting long computation");
+
+        // Spin-wait to simulate a long CPU computation
+        cortex_m::asm::delay(125_000_000); // ~1 second
+
+        let end = Instant::now();
+        let ms = end.duration_since(start).as_ticks() * 1000 / TICK_HZ;
+        info!("    [med] done in {} ms", ms);
+
+        Timer::after(Duration::from_ticks(53421)).await;
+    }
+}
+
+#[embassy_executor::task]
+async fn run_low() {
+    loop {
+        let start = Instant::now();
+        info!("[low] Starting long computation");
+
+        // Spin-wait to simulate a long CPU computation
+        cortex_m::asm::delay(250_000_000); // ~2 seconds
+
+        let end = Instant::now();
+        let ms = end.duration_since(start).as_ticks() * 1000 / TICK_HZ;
+        info!("[low] done in {} ms", ms);
+
+        Timer::after(Duration::from_ticks(82983)).await;
+    }
+}
+
+static EXECUTOR_HIGH: InterruptExecutor = InterruptExecutor::new();
+static EXECUTOR_MED: InterruptExecutor = InterruptExecutor::new();
+static EXECUTOR_LOW: StaticCell<Executor> = StaticCell::new();
+
+#[interrupt]
+unsafe fn SWI_IRQ_1() {
+    EXECUTOR_HIGH.on_interrupt()
+}
+
+#[interrupt]
+unsafe fn SWI_IRQ_0() {
+    EXECUTOR_MED.on_interrupt()
+}
+
+#[entry]
+fn main() -> ! {
+    info!("Hello World!");
+
+    let _p = embassy_rp::init(Default::default());
+    let mut nvic: NVIC = unsafe { mem::transmute(()) };
+
+    // High-priority executor: SWI_IRQ_1, priority level 2
+    unsafe { nvic.set_priority(Interrupt::SWI_IRQ_1, 2 << 6) };
+    info!("bla: {}", NVIC::get_priority(Interrupt::SWI_IRQ_1));
+    let spawner = EXECUTOR_HIGH.start(Interrupt::SWI_IRQ_1);
+    unwrap!(spawner.spawn(run_high()));
+
+    // Medium-priority executor: SWI_IRQ_0, priority level 3
+    unsafe { nvic.set_priority(Interrupt::SWI_IRQ_0, 3 << 6) };
+    info!("bla: {}", NVIC::get_priority(Interrupt::SWI_IRQ_0));
+    let spawner = EXECUTOR_MED.start(Interrupt::SWI_IRQ_0);
+    unwrap!(spawner.spawn(run_med()));
+
+    // Low priority executor: runs in thread mode, using WFE/SEV
+    let executor = EXECUTOR_LOW.init(Executor::new());
+    executor.run(|spawner| {
+        unwrap!(spawner.spawn(run_low()));
+    });
+}