1 files changed, 146 insertions, 69 deletions

diff --git a/embassy-stm32/src/rtc/mod.rs b/embassy-stm32/src/rtc/mod.rs
index a6102077a..73b78f253 100644
--- a/embassy-stm32/src/rtc/mod.rs
+++ b/embassy-stm32/src/rtc/mod.rs
@@ -1,7 +1,17 @@
 //! RTC peripheral abstraction
 mod datetime;
 
+#[cfg(feature = "low-power")]
+use core::cell::Cell;
+
+#[cfg(feature = "low-power")]
+use embassy_sync::blocking_mutex::raw::CriticalSectionRawMutex;
+#[cfg(feature = "low-power")]
+use embassy_sync::blocking_mutex::Mutex;
+
 pub use self::datetime::{DateTime, DayOfWeek, Error as DateTimeError};
+pub use crate::rcc::RtcClockSource;
+use crate::time::Hertz;
 
 /// refer to AN4759 to compare features of RTC2 and RTC3
 #[cfg_attr(any(rtc_v1), path = "v1.rs")]
@@ -30,60 +40,99 @@ pub enum RtcError {
     NotRunning,
 }
 
-/// RTC Abstraction
-pub struct Rtc {
-    rtc_config: RtcConfig,
+#[cfg(feature = "low-power")]
+/// Represents an instant in time that can be substracted to compute a duration
+struct RtcInstant {
+    second: u8,
+    subsecond: u16,
 }
 
-#[derive(Copy, Clone, Debug, PartialEq)]
-#[repr(u8)]
-pub enum RtcClockSource {
-    /// 00: No clock
-    NoClock = 0b00,
-    /// 01: LSE oscillator clock used as RTC clock
-    LSE = 0b01,
-    /// 10: LSI oscillator clock used as RTC clock
-    LSI = 0b10,
-    /// 11: HSE oscillator clock divided by 32 used as RTC clock
-    HSE = 0b11,
+#[cfg(all(feature = "low-power", feature = "defmt"))]
+impl defmt::Format for RtcInstant {
+    fn format(&self, fmt: defmt::Formatter) {
+        defmt::write!(
+            fmt,
+            "{}:{}",
+            self.second,
+            RTC::regs().prer().read().prediv_s() - self.subsecond,
+        )
+    }
+}
+
+#[cfg(feature = "low-power")]
+impl core::ops::Sub for RtcInstant {
+    type Output = embassy_time::Duration;
+
+    fn sub(self, rhs: Self) -> Self::Output {
+        use embassy_time::{Duration, TICK_HZ};
+
+        let second = if self.second < rhs.second {
+            self.second + 60
+        } else {
+            self.second
+        };
+
+        let psc = RTC::regs().prer().read().prediv_s() as u32;
+
+        let self_ticks = second as u32 * (psc + 1) + (psc - self.subsecond as u32);
+        let other_ticks = rhs.second as u32 * (psc + 1) + (psc - rhs.subsecond as u32);
+        let rtc_ticks = self_ticks - other_ticks;
+
+        Duration::from_ticks(((rtc_ticks * TICK_HZ as u32) / (psc + 1)) as u64)
+    }
+}
+
+pub struct RtcTimeProvider {
+    _private: (),
+}
+
+impl RtcTimeProvider {
+    /// Return the current datetime.
+    ///
+    /// # Errors
+    ///
+    /// Will return an `RtcError::InvalidDateTime` if the stored value in the system is not a valid [`DayOfWeek`].
+    pub fn now(&self) -> Result<DateTime, RtcError> {
+        let r = RTC::regs();
+        let tr = r.tr().read();
+        let second = bcd2_to_byte((tr.st(), tr.su()));
+        let minute = bcd2_to_byte((tr.mnt(), tr.mnu()));
+        let hour = bcd2_to_byte((tr.ht(), tr.hu()));
+        // Reading either RTC_SSR or RTC_TR locks the values in the higher-order
+        // calendar shadow registers until RTC_DR is read.
+        let dr = r.dr().read();
+
+        let weekday = dr.wdu();
+        let day = bcd2_to_byte((dr.dt(), dr.du()));
+        let month = bcd2_to_byte((dr.mt() as u8, dr.mu()));
+        let year = bcd2_to_byte((dr.yt(), dr.yu())) as u16 + 1970_u16;
+
+        self::datetime::datetime(year, month, day, weekday, hour, minute, second).map_err(RtcError::InvalidDateTime)
+    }
+}
+
+/// RTC Abstraction
+pub struct Rtc {
+    #[cfg(feature = "low-power")]
+    stop_time: Mutex<CriticalSectionRawMutex, Cell<Option<RtcInstant>>>,
+    #[cfg(not(feature = "low-power"))]
+    _private: (),
 }
 
+#[non_exhaustive]
 #[derive(Copy, Clone, PartialEq)]
 pub struct RtcConfig {
-    /// Asynchronous prescaler factor
-    /// This is the asynchronous division factor:
-    /// ck_apre frequency = RTCCLK frequency/(PREDIV_A+1)
-    /// ck_apre drives the subsecond register
-    async_prescaler: u8,
-    /// Synchronous prescaler factor
-    /// This is the synchronous division factor:
-    /// ck_spre frequency = ck_apre frequency/(PREDIV_S+1)
-    /// ck_spre must be 1Hz
-    sync_prescaler: u16,
+    /// The subsecond counter frequency; default is 256
+    ///
+    /// A high counter frequency may impact stop power consumption
+    pub frequency: Hertz,
 }
 
 impl Default for RtcConfig {
     /// LSI with prescalers assuming 32.768 kHz.
     /// Raw sub-seconds in 1/256.
     fn default() -> Self {
-        RtcConfig {
-            async_prescaler: 127,
-            sync_prescaler: 255,
-        }
-    }
-}
-
-impl RtcConfig {
-    /// Set the asynchronous prescaler of RTC config
-    pub fn async_prescaler(mut self, prescaler: u8) -> Self {
-        self.async_prescaler = prescaler;
-        self
-    }
-
-    /// Set the synchronous prescaler of RTC config
-    pub fn sync_prescaler(mut self, prescaler: u16) -> Self {
-        self.sync_prescaler = prescaler;
-        self
+        RtcConfig { frequency: Hertz(256) }
     }
 }
 
@@ -106,16 +155,44 @@ impl Default for RtcCalibrationCyclePeriod {
 
 impl Rtc {
     pub fn new(_rtc: impl Peripheral<P = RTC>, rtc_config: RtcConfig) -> Self {
-        RTC::enable_peripheral_clk();
+        #[cfg(any(rcc_wle, rcc_wl5, rcc_g4, rcc_g0, rtc_v2l4, rtc_v2wb))]
+        <RTC as crate::rcc::sealed::RccPeripheral>::enable();
+
+        let mut this = Self {
+            #[cfg(feature = "low-power")]
+            stop_time: Mutex::const_new(CriticalSectionRawMutex::new(), Cell::new(None)),
+            #[cfg(not(feature = "low-power"))]
+            _private: (),
+        };
+
+        let frequency = Self::frequency();
+        let async_psc = ((frequency.0 / rtc_config.frequency.0) - 1) as u8;
+        let sync_psc = (rtc_config.frequency.0 - 1) as u16;
 
-        let mut rtc_struct = Self { rtc_config };
+        this.configure(async_psc, sync_psc);
 
-        Self::enable();
+        this
+    }
+
+    fn frequency() -> Hertz {
+        #[cfg(any(rcc_wb, rcc_f4, rcc_f410))]
+        let freqs = unsafe { crate::rcc::get_freqs() };
+
+        // Load the clock frequency from the rcc mod, if supported
+        #[cfg(any(rcc_wb, rcc_f4, rcc_f410))]
+        match freqs.rtc {
+            Some(hertz) => hertz,
+            None => freqs.rtc_hse.unwrap(),
+        }
 
-        rtc_struct.configure(rtc_config);
-        rtc_struct.rtc_config = rtc_config;
+        // Assume the  default value, if not supported
+        #[cfg(not(any(rcc_wb, rcc_f4, rcc_f410)))]
+        Hertz(32_768)
+    }
 
-        rtc_struct
+    /// Acquire a [`RtcTimeProvider`] instance.
+    pub const fn time_provider(&self) -> RtcTimeProvider {
+        RtcTimeProvider { _private: () }
     }
 
     /// Set the datetime to a new value.
@@ -130,27 +207,27 @@ impl Rtc {
         Ok(())
     }
 
+    #[cfg(feature = "low-power")]
+    /// Return the current instant.
+    fn instant(&self) -> RtcInstant {
+        let r = RTC::regs();
+        let tr = r.tr().read();
+        let subsecond = r.ssr().read().ss();
+        let second = bcd2_to_byte((tr.st(), tr.su()));
+
+        // Unlock the registers
+        r.dr().read();
+
+        RtcInstant { second, subsecond }
+    }
+
     /// Return the current datetime.
     ///
     /// # Errors
     ///
     /// Will return an `RtcError::InvalidDateTime` if the stored value in the system is not a valid [`DayOfWeek`].
     pub fn now(&self) -> Result<DateTime, RtcError> {
-        let r = RTC::regs();
-        let tr = r.tr().read();
-        let second = bcd2_to_byte((tr.st(), tr.su()));
-        let minute = bcd2_to_byte((tr.mnt(), tr.mnu()));
-        let hour = bcd2_to_byte((tr.ht(), tr.hu()));
-        // Reading either RTC_SSR or RTC_TR locks the values in the higher-order
-        // calendar shadow registers until RTC_DR is read.
-        let dr = r.dr().read();
-
-        let weekday = dr.wdu();
-        let day = bcd2_to_byte((dr.dt(), dr.du()));
-        let month = bcd2_to_byte((dr.mt() as u8, dr.mu()));
-        let year = bcd2_to_byte((dr.yt(), dr.yu())) as u16 + 1970_u16;
-
-        self::datetime::datetime(year, month, day, weekday, hour, minute, second).map_err(RtcError::InvalidDateTime)
+        self.time_provider().now()
     }
 
     /// Check if daylight savings time is active.
@@ -166,10 +243,6 @@ impl Rtc {
         })
     }
 
-    pub fn get_config(&self) -> RtcConfig {
-        self.rtc_config
-    }
-
     pub const BACKUP_REGISTER_COUNT: usize = RTC::BACKUP_REGISTER_COUNT;
 
     /// Read content of the backup register.
@@ -215,12 +288,16 @@ pub(crate) mod sealed {
     pub trait Instance {
         const BACKUP_REGISTER_COUNT: usize;
 
+        #[cfg(feature = "low-power")]
+        const EXTI_WAKEUP_LINE: usize;
+
+        #[cfg(feature = "low-power")]
+        type WakeupInterrupt: crate::interrupt::typelevel::Interrupt;
+
         fn regs() -> Rtc {
             crate::pac::RTC
         }
 
-        fn enable_peripheral_clk() {}
-
         /// Read content of the backup register.
         ///
         /// The registers retain their values during wakes from standby mode or system resets. They also