wip, async_systic2

examples/async_systick2.rs

@@ -0,0 +1,264 @@
+//! examples/async_task2
+#![no_main]
+#![no_std]
+#![feature(const_fn)]
+#![feature(type_alias_impl_trait)]
+
+// use core::cell::Cell;
+// use core::cell::UnsafeCell;
+use core::future::Future;
+use core::mem;
+// use core::mem::MaybeUninit;
+use core::pin::Pin;
+// use core::ptr;
+// use core::ptr::NonNull;
+// use core::sync::atomic::{AtomicPtr, AtomicU32, Ordering};
+use core::task::{Context, Poll, RawWaker, RawWakerVTable, Waker};
+
+use cortex_m_semihosting::{debug, hprintln};
+use panic_semihosting as _;
+use rtic::Mutex;
+
+#[rtic::app(device = lm3s6965, dispatchers = [SSI0])]
+mod app {
+    use crate::Timer;
+    use crate::*;
+
+    #[resources]
+    struct Resources {
+        systick: Systick,
+    }
+
+    #[init]
+    fn init(cx: init::Context) -> init::LateResources {
+        hprintln!("init").unwrap();
+        foo::spawn().unwrap();
+        init::LateResources {
+            systick: Systick {
+                syst: cx.core.SYST,
+                state: State::Done,
+                queue: BinaryHeap::new(),
+                waker: None,
+            },
+        }
+    }
+
+    #[idle]
+    fn idle(_: idle::Context) -> ! {
+        // debug::exit(debug::EXIT_SUCCESS);
+        loop {
+            hprintln!("idle");
+            cortex_m::asm::wfi(); // put the MCU in sleep mode until interrupt occurs
+        }
+    }
+
+    #[task(resources = [systick])]
+    fn foo(mut cx: foo::Context) {
+        // BEGIN BOILERPLATE
+        type F = impl Future + 'static;
+        fn create(cx: foo::Context<'static>) -> F {
+            task(cx)
+        }
+
+        static mut TASK: Task<F> = Task::new();
+
+        hprintln!("foo trampoline").ok();
+        unsafe {
+            match TASK {
+                Task::Idle | Task::Done(_) => {
+                    hprintln!("foo spawn task").ok();
+                    TASK.spawn(|| create(mem::transmute(cx)));
+                }
+                _ => {}
+            };
+
+            hprintln!("foo trampoline poll").ok();
+            TASK.poll(|| {
+                let _ = foo::spawn();
+            });
+
+            match TASK {
+                Task::Done(ref r) => {
+                    hprintln!("foo trampoline done").ok();
+                    // hprintln!("r = {:?}", mem::transmute::<_, &u32>(r)).ok();
+                }
+                _ => {
+                    hprintln!("foo trampoline running").ok();
+                }
+            }
+        }
+        // END BOILERPLATE
+
+        async fn task(mut cx: foo::Context<'static>) {
+            hprintln!("foo task").ok();
+
+            hprintln!("delay long time").ok();
+            timer_delay(&mut cx.resources.systick, 5000000).await;
+            hprintln!("foo task resumed").ok();
+
+            hprintln!("delay short time").ok();
+            timer_delay(&mut cx.resources.systick, 1000000).await;
+            hprintln!("foo task resumed").ok();
+        }
+    }
+
+    // This the actual RTIC task, binds to systic.
+    #[task(binds = SysTick, resources = [systick], priority = 2)]
+    fn systic(mut cx: systic::Context) {
+        hprintln!("systic interrupt").ok();
+        cx.resources.systick.lock(|s| {
+            s.syst.disable_interrupt();
+            s.state = State::Done;
+            s.waker.take().map(|w| w.wake());
+        });
+    }
+}
+
+//=============
+// Waker
+
+static WAKER_VTABLE: RawWakerVTable =
+    RawWakerVTable::new(waker_clone, waker_wake, waker_wake, waker_drop);
+
+unsafe fn waker_clone(p: *const ()) -> RawWaker {
+    RawWaker::new(p, &WAKER_VTABLE)
+}
+
+unsafe fn waker_wake(p: *const ()) {
+    let f: fn() = mem::transmute(p);
+    f();
+}
+
+unsafe fn waker_drop(_: *const ()) {
+    // nop
+}
+
+//============
+// Task
+
+enum Task<F: Future + 'static> {
+    Idle,
+    Running(F),
+    Done(F::Output),
+}
+
+impl<F: Future + 'static> Task<F> {
+    const fn new() -> Self {
+        Self::Idle
+    }
+
+    fn spawn(&mut self, future: impl FnOnce() -> F) {
+        *self = Task::Running(future());
+    }
+
+    unsafe fn poll(&mut self, wake: fn()) {
+        match self {
+            Task::Idle => {}
+            Task::Running(future) => {
+                let future = Pin::new_unchecked(future);
+                let waker_data: *const () = mem::transmute(wake);
+                let waker = Waker::from_raw(RawWaker::new(waker_data, &WAKER_VTABLE));
+                let mut cx = Context::from_waker(&waker);
+
+                match future.poll(&mut cx) {
+                    Poll::Ready(r) => *self = Task::Done(r),
+                    Poll::Pending => {}
+                };
+            }
+            Task::Done(_) => {}
+        }
+    }
+}
+
+//=============
+// Timer
+// Later we want a proper queue
+
+//use core::cmp::{Ord, Ordering, PartialOrd};
+use core::cmp::Ordering;
+use heapless::binary_heap::{BinaryHeap, Max};
+use heapless::consts::*;
+
+pub enum State {
+    Started,
+    Done,
+}
+
+struct Timeout {
+    time: u32,
+    waker: Option<Waker>,
+}
+
+impl Ord for Timeout {
+    fn cmp(&self, other: &Self) -> Ordering {
+        self.time.cmp(&other.time)
+    }
+}
+
+impl PartialOrd for Timeout {
+    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
+        Some(self.cmp(&other))
+    }
+}
+
+impl PartialEq for Timeout {
+    fn eq(&self, other: &Self) -> bool {
+        self.time == other.time
+    }
+}
+
+impl Eq for Timeout {}
+
+pub struct Systick {
+    syst: cortex_m::peripheral::SYST,
+    state: State,
+    queue: BinaryHeap<Timeout, U8, Max>,
+    waker: Option<Waker>,
+}
+
+//=============
+// Timer
+// Later we want a proper queue
+
+pub struct Timer<'a, T: Mutex<T = Systick>> {
+    started: bool,
+    t: u32,
+    systick: &'a mut T,
+}
+
+impl<'a, T: Mutex<T = Systick>> Future for Timer<'a, T> {
+    type Output = ();
+    fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
+        let Self {
+            started,
+            t,
+            systick,
+        } = &mut *self;
+        systick.lock(|s| {
+            if !*started {
+                s.syst.set_reload(*t);
+                s.syst.enable_counter();
+                s.syst.enable_interrupt();
+                s.state = State::Started;
+                *started = true;
+            }
+
+            match s.state {
+                State::Done => Poll::Ready(()),
+                State::Started => {
+                    s.waker = Some(cx.waker().clone());
+                    Poll::Pending
+                }
+            }
+        })
+    }
+}
+
+fn timer_delay<'a, T: Mutex<T = Systick>>(systick: &'a mut T, t: u32) -> Timer<'a, T> {
+    hprintln!("timer_delay {}", t);
+    Timer {
+        started: false,
+        t,
+        systick,
+    }
+}