Use a timer instead of systick for Nordic clock (#929)

Author: ia0

crates/runner-nordic/src/board.rs

@@ -19,7 +19,7 @@ use crate::{Board, with_state};
 
 pub mod applet;
 pub mod button;
-mod clock;
+pub mod clock;
 #[cfg(feature = "_crypto")]
 mod crypto;
 mod debug;

crates/runner-nordic/src/board/clock.rs

@@ -12,13 +12,49 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+use nrf52840_hal::Timer;
+use nrf52840_hal::pac::TIMER1;
+use nrf52840_hal::timer::Periodic;
 use wasefire_board_api::Error;
 use wasefire_board_api::clock::Api;
 
+use crate::with_state;
+
 pub enum Impl {}
 
 impl Api for Impl {
     fn uptime_us() -> Result<u64, Error> {
-        Ok(crate::systick::uptime_us())
+        with_state(|state| Ok(state.clock.uptime_us()))
     }
 }
+
+pub struct Clock {
+    timer: Timer<TIMER1, Periodic>,
+    base: u64,
+}
+
+impl Clock {
+    pub fn new(timer: TIMER1) -> Self {
+        let mut timer = Timer::periodic(timer);
+        timer.enable_interrupt();
+        timer.start((PERIOD - 1) as u32);
+        Clock { timer, base: 0 }
+    }
+
+    pub fn tick(&mut self) {
+        self.timer.reset_event();
+        self.base += PERIOD;
+    }
+
+    fn uptime_us(&self) -> u64 {
+        let mut counter = self.timer.read() as u64;
+        // We assume the timer can't wrap around twice without self.base being updated (this would
+        // mean not processing interrupts for more than 1 hour).
+        if self.timer.event_compare_cc0().read().events_compare().bit() {
+            counter = self.timer.read() as u64 + PERIOD;
+        }
+        self.base + counter
+    }
+}
+
+const PERIOD: u64 = u32::MAX as u64 + 1;

crates/runner-nordic/src/board/timer.rs

@@ -17,7 +17,7 @@ use alloc::boxed::Box;
 use cortex_m::prelude::_embedded_hal_timer_CountDown;
 use embedded_hal_02::timer::Cancel;
 use nrf52840_hal::Timer;
-use nrf52840_hal::pac::{TIMER1, TIMER2, TIMER3, TIMER4};
+use nrf52840_hal::pac::{TIMER2, TIMER3, TIMER4};
 use nrf52840_hal::timer::{Instance, OneShot, Periodic};
 use wasefire_board_api::timer::{Api, Command};
 use wasefire_board_api::{Error, Id, Support};
@@ -28,7 +28,7 @@ use crate::with_state;
 pub enum Impl {}
 
 impl Support<usize> for Impl {
-    const SUPPORT: usize = 4;
+    const SUPPORT: usize = 3;
 }
 
 impl Api for Impl {
@@ -57,13 +57,8 @@ impl Api for Impl {
 pub struct Timers([ErasedTimer; <Impl as Support<usize>>::SUPPORT]);
 
 impl Timers {
-    pub fn new(t1: TIMER1, t2: TIMER2, t3: TIMER3, t4: TIMER4) -> Self {
-        Timers([
-            ErasedTimer::new(t1),
-            ErasedTimer::new(t2),
-            ErasedTimer::new(t3),
-            ErasedTimer::new(t4),
-        ])
+    pub fn new(t2: TIMER2, t3: TIMER3, t4: TIMER4) -> Self {
+        Timers([ErasedTimer::new(t2), ErasedTimer::new(t3), ErasedTimer::new(t4)])
     }
 
     pub fn tick(&mut self, index: usize) {

crates/runner-nordic/src/main.rs

@@ -23,6 +23,7 @@ extern crate alloc;
 mod allocator;
 mod board;
 mod storage;
+#[cfg(feature = "debug")]
 mod systick;
 
 use core::cell::RefCell;
@@ -69,6 +70,7 @@ use wasefire_one_of::{at_most_one_of, exactly_one_of};
 use wasefire_scheduler::Scheduler;
 
 use crate::board::button::{Button, Channels};
+use crate::board::clock::Clock;
 #[cfg(feature = "gpio")]
 use crate::board::gpio::Gpio;
 use crate::board::timer::Timers;
@@ -103,6 +105,7 @@ struct State {
     ctap: Ctap<'static, Usb>,
     #[cfg(feature = "usb-serial")]
     serial: Serial<'static, Usb>,
+    clock: Clock,
     timers: Timers,
     #[cfg(feature = "ble-adv")]
     ble: Ble,
@@ -134,7 +137,9 @@ fn main() -> ! {
     static mut USB_BUS: MaybeUninit<UsbBusAllocator<Usb>> = MaybeUninit::uninit();
 
     allocator::init();
+    #[cfg(feature = "debug")]
     let c = nrf52840_hal::pac::CorePeripherals::take().unwrap();
+    #[cfg(feature = "debug")]
     systick::init(c.SYST);
     log::debug!("Runner starts.");
     let p = nrf52840_hal::pac::Peripherals::take().unwrap();
@@ -183,7 +188,8 @@ fn main() -> ! {
         Gpio::new(port0.p0_30.degrade(), 0, 30),
         Gpio::new(port0.p0_31.degrade(), 0, 31),
     ];
-    let timers = Timers::new(p.TIMER1, p.TIMER2, p.TIMER3, p.TIMER4);
+    let clock = Clock::new(p.TIMER1);
+    let timers = Timers::new(p.TIMER2, p.TIMER3, p.TIMER4);
     let gpiote = Gpiote::new(p.GPIOTE);
     #[cfg_attr(not(feature = "fpc2534"), allow(unused_mut))]
     let mut channels = Channels::default();
@@ -255,6 +261,7 @@ fn main() -> ! {
         ctap,
         #[cfg(feature = "usb-serial")]
         serial,
+        clock,
         timers,
         #[cfg(feature = "ble-adv")]
         ble,
@@ -300,10 +307,10 @@ interrupts! {
     RADIO = radio(),
     #[cfg(feature = "ble-adv")]
     TIMER0 = radio_timer(),
-    TIMER1 = timer(0),
-    TIMER2 = timer(1),
-    TIMER3 = timer(2),
-    TIMER4 = timer(3),
+    TIMER1 = clock(),
+    TIMER2 = timer(0),
+    TIMER3 = timer(1),
+    TIMER4 = timer(2),
     #[cfg(feature = "uart")]
     UARTE0_UART0 = uarte(0),
     #[cfg(feature = "uart")]
@@ -345,6 +352,10 @@ fn radio_timer() {
     with_state(|state| state.ble.tick_timer())
 }
 
+fn clock() {
+    with_state(|state| state.clock.tick())
+}
+
 fn timer(timer: usize) {
     let timer = Id::new(timer).unwrap();
     with_state(|state| {