rp/timer: add

embassy-rp/Cargo.toml

@@ -22,6 +22,6 @@ cortex-m-rt = "0.6.13"
 cortex-m = "0.7.1"
 critical-section = "0.2.1"
 
-rp2040-pac2 = { git = "https://github.com/embassy-rs/rp2040-pac2", rev="91fa122b4923fdc02462a39ec109b161aedb29b4", features = ["rt"] }
-#rp2040-pac2 = { path = "../../rp/rp2040-pac2" }
+rp2040-pac2 = { git = "https://github.com/embassy-rs/rp2040-pac2", rev="2ce29ba58ad904d3995ce65bb46807e853f1fbf9", features = ["rt"] }
+#rp2040-pac2 = { path = "../../rp/rp2040-pac2", features = ["rt"] }
 embedded-hal = { version = "0.2.4", features = [ "unproven" ] }

embassy-rp/src/clocks.rs

@@ -4,6 +4,7 @@ use crate::{pac, reset};
 
 const XOSC_MHZ: u32 = 12;
 
+/// safety: must be called exactly once at bootup
 pub unsafe fn init() {
     // Reset everything except:
     // - QSPI (we're using it to run this code!)

embassy-rp/src/lib.rs

@@ -11,10 +11,12 @@ pub use rp2040_pac2 as pac;
 pub(crate) mod fmt;
 
 pub mod interrupt;
+pub use embassy_macros::interrupt;
 
 pub mod dma;
 pub mod gpio;
 pub mod spi;
+pub mod timer;
 pub mod uart;
 
 mod clocks;
@@ -64,6 +66,11 @@ embassy_extras::peripherals! {
     SPI0,
     SPI1,
 
+    TIMER_ALARM0,
+    TIMER_ALARM1,
+    TIMER_ALARM2,
+    TIMER_ALARM3,
+
     DMA_CH0,
     DMA_CH1,
     DMA_CH2,
@@ -100,6 +107,7 @@ pub fn init(_config: config::Config) -> Peripherals {
 
     unsafe {
         clocks::init();
+        timer::init();
     }
 
     peripherals

embassy-rp/src/timer.rs

@@ -0,0 +1,187 @@
+use core::cell::Cell;
+use critical_section::CriticalSection;
+use embassy::interrupt::{Interrupt, InterruptExt};
+use embassy::util::CriticalSectionMutex as Mutex;
+
+use crate::{interrupt, pac};
+
+struct AlarmState {
+    timestamp: Cell<u64>,
+    callback: Cell<Option<(fn(*mut ()), *mut ())>>,
+}
+unsafe impl Send for AlarmState {}
+
+const ALARM_COUNT: usize = 4;
+const DUMMY_ALARM: AlarmState = AlarmState {
+    timestamp: Cell::new(0),
+    callback: Cell::new(None),
+};
+
+static ALARMS: Mutex<[AlarmState; ALARM_COUNT]> = Mutex::new([DUMMY_ALARM; ALARM_COUNT]);
+
+fn now() -> u64 {
+    loop {
+        unsafe {
+            let hi = pac::TIMER.timerawh().read();
+            let lo = pac::TIMER.timerawl().read();
+            let hi2 = pac::TIMER.timerawh().read();
+            if hi == hi2 {
+                return (hi as u64) << 32 | (lo as u64);
+            }
+        }
+    }
+}
+
+struct Timer;
+impl embassy::time::Clock for Timer {
+    fn now(&self) -> u64 {
+        now()
+    }
+}
+
+pub trait AlarmInstance {
+    fn alarm_num(&self) -> usize;
+}
+
+impl AlarmInstance for crate::peripherals::TIMER_ALARM0 {
+    fn alarm_num(&self) -> usize {
+        0
+    }
+}
+impl AlarmInstance for crate::peripherals::TIMER_ALARM1 {
+    fn alarm_num(&self) -> usize {
+        1
+    }
+}
+impl AlarmInstance for crate::peripherals::TIMER_ALARM2 {
+    fn alarm_num(&self) -> usize {
+        2
+    }
+}
+impl AlarmInstance for crate::peripherals::TIMER_ALARM3 {
+    fn alarm_num(&self) -> usize {
+        3
+    }
+}
+
+pub struct Alarm<T: AlarmInstance> {
+    inner: T,
+}
+
+impl<T: AlarmInstance> Alarm<T> {
+    pub fn new(inner: T) -> Self {
+        Self { inner }
+    }
+}
+
+impl<T: AlarmInstance> embassy::time::Alarm for Alarm<T> {
+    fn set_callback(&self, callback: fn(*mut ()), ctx: *mut ()) {
+        let n = self.inner.alarm_num();
+        critical_section::with(|cs| {
+            let alarm = &ALARMS.borrow(cs)[n];
+            alarm.callback.set(Some((callback, ctx)));
+        })
+    }
+
+    fn set(&self, timestamp: u64) {
+        let n = self.inner.alarm_num();
+
+        critical_section::with(|cs| {
+            let alarm = &ALARMS.borrow(cs)[n];
+            alarm.timestamp.set(timestamp);
+
+            // Arm it.
+            // Note that we're not checking the high bits at all. This means the irq may fire early
+            // if the alarm is more than 72 minutes (2^32 us) in the future. This is OK, since on irq fire
+            // it is checked if the alarm time has passed.
+            unsafe { pac::TIMER.alarm(n).write_value(timestamp as u32) };
+
+            let now = now();
+
+            // If alarm timestamp has passed, trigger it instantly.
+            // This disarms it.
+            if timestamp <= now {
+                trigger_alarm(n, cs);
+            }
+        })
+    }
+
+    fn clear(&self) {
+        self.set(u64::MAX);
+    }
+}
+
+fn check_alarm(n: usize) {
+    critical_section::with(|cs| {
+        let alarm = &ALARMS.borrow(cs)[n];
+        let timestamp = alarm.timestamp.get();
+        if timestamp <= now() {
+            trigger_alarm(n, cs)
+        } else {
+            // Not elapsed, arm it again.
+            // This can happen if it was set more than 2^32 us in the future.
+            unsafe { pac::TIMER.alarm(n).write_value(timestamp as u32) };
+        }
+    });
+
+    // clear the irq
+    unsafe { pac::TIMER.intr().write(|w| w.set_alarm(n, true)) }
+}
+
+fn trigger_alarm(n: usize, cs: CriticalSection) {
+    // disarm
+    unsafe { pac::TIMER.armed().write(|w| w.set_armed(1 << n)) }
+
+    let alarm = &ALARMS.borrow(cs)[n];
+    alarm.timestamp.set(u64::MAX);
+
+    // Call after clearing alarm, so the callback can set another alarm.
+    if let Some((f, ctx)) = alarm.callback.get() {
+        f(ctx);
+    }
+}
+
+/// safety: must be called exactly once at bootup
+pub unsafe fn init() {
+    // init alarms
+    critical_section::with(|cs| {
+        let alarms = ALARMS.borrow(cs);
+        for a in alarms {
+            a.timestamp.set(u64::MAX);
+        }
+    });
+
+    // enable all irqs
+    pac::TIMER.inte().write(|w| {
+        w.set_alarm(0, true);
+        w.set_alarm(1, true);
+        w.set_alarm(2, true);
+        w.set_alarm(3, true);
+    });
+    interrupt::TIMER_IRQ_0::steal().enable();
+    interrupt::TIMER_IRQ_1::steal().enable();
+    interrupt::TIMER_IRQ_2::steal().enable();
+    interrupt::TIMER_IRQ_3::steal().enable();
+
+    embassy::time::set_clock(&Timer);
+}
+
+#[interrupt]
+unsafe fn TIMER_IRQ_0() {
+    check_alarm(0)
+}
+
+#[interrupt]
+unsafe fn TIMER_IRQ_1() {
+    check_alarm(1)
+}
+
+#[interrupt]
+unsafe fn TIMER_IRQ_2() {
+    check_alarm(2)
+}
+
+#[interrupt]
+unsafe fn TIMER_IRQ_3() {
+    check_alarm(3)
+}