stm32: fix stop

ci.sh

@@ -196,8 +196,6 @@ cargo batch  \
     --- build --release --manifest-path tests/riscv32/Cargo.toml --target riscv32imac-unknown-none-elf \
     $BUILD_EXTRA
 
-# temporarily disabled: broken by nightly update and/or clock settings update.
-rm out/tests/stm32f429zi/stop
 
 if [[ -z "${TELEPROBE_TOKEN-}" ]]; then
     echo No teleprobe token found, skipping running HIL tests

embassy-stm32/src/low_power.rs

@@ -1,6 +1,7 @@
 use core::arch::asm;
 use core::marker::PhantomData;
 
+use atomic_polyfill::{compiler_fence, Ordering};
 use cortex_m::peripheral::SCB;
 use embassy_executor::*;
 
@@ -67,10 +68,8 @@ impl Executor {
     }
 
     unsafe fn on_wakeup_irq(&mut self) {
-        trace!("low power: on wakeup irq");
-
         self.time_driver.resume_time();
-        trace!("low power: resume time");
+        trace!("low power: resume");
     }
 
     pub(self) fn stop_with_rtc(&mut self, rtc: &'static Rtc) {
@@ -82,22 +81,19 @@ impl Executor {
     }
 
     fn configure_pwr(&mut self) {
-        trace!("low power: configure_pwr");
-
         self.scb.clear_sleepdeep();
+
+        compiler_fence(Ordering::SeqCst);
+
         if !low_power_ready() {
-            trace!("low power: configure_pwr: low power not ready");
-            return;
-        }
-
-        if self.time_driver.pause_time().is_err() {
-            trace!("low power: configure_pwr: time driver failed to pause");
-            return;
-        }
-
-        trace!("low power: enter stop...");
+            trace!("low power: not ready to stop");
+        } else if self.time_driver.pause_time().is_err() {
+            trace!("low power: failed to pause time");
+        } else {
+            trace!("low power: stop");
             self.scb.set_sleepdeep();
         }
+    }
 
     /// Run the executor.
     ///

embassy-stm32/src/rcc/mod.rs

@@ -111,8 +111,7 @@ static CLOCK_REFCOUNT: AtomicU32 = AtomicU32::new(0);
 
 #[cfg(feature = "low-power")]
 pub fn low_power_ready() -> bool {
-    trace!("clock refcount: {}", CLOCK_REFCOUNT.load(Ordering::SeqCst));
-
+    // trace!("clock refcount: {}", CLOCK_REFCOUNT.load(Ordering::SeqCst));
     CLOCK_REFCOUNT.load(Ordering::SeqCst) == 0
 }
 

embassy-stm32/src/rtc/v2.rs

@@ -112,6 +112,7 @@ impl super::Rtc {
     pub(crate) fn stop_wakeup_alarm(&self, cs: critical_section::CriticalSection) -> Option<embassy_time::Duration> {
         use crate::interrupt::typelevel::Interrupt;
 
+        if RTC::regs().cr().read().wute() {
             trace!("rtc: stop wakeup alarm at {}", self.instant());
 
             self.write(false, |regs| {
@@ -125,12 +126,12 @@ impl super::Rtc {
 
                 <RTC as crate::rtc::sealed::Instance>::WakeupInterrupt::unpend();
             });
-
-        if let Some(stop_time) = self.stop_time.borrow(cs).take() {
-            Some(self.instant() - stop_time)
-        } else {
-            None
         }
+
+        self.stop_time
+            .borrow(cs)
+            .take()
+            .map(|stop_time| self.instant() - stop_time)
     }
 
     #[cfg(feature = "low-power")]

embassy-stm32/src/time_driver.rs

@@ -340,7 +340,11 @@ impl RtcDriver {
     #[cfg(feature = "low-power")]
     /// Set the rtc but panic if it's already been set
     pub(crate) fn set_rtc(&self, rtc: &'static Rtc) {
-        critical_section::with(|cs| assert!(self.rtc.borrow(cs).replace(Some(rtc)).is_none()));
+        critical_section::with(|cs| {
+            rtc.stop_wakeup_alarm(cs);
+
+            assert!(self.rtc.borrow(cs).replace(Some(rtc)).is_none())
+        });
     }
 
     #[cfg(feature = "low-power")]