stm32: add low power for g4

1 files changed, 162 insertions, 0 deletions

diff --git a/embassy-stm32/src/rtc/mod.rs b/embassy-stm32/src/rtc/mod.rs
index e94a58575..3f03d83a4 100644
--- a/embassy-stm32/src/rtc/mod.rs
+++ b/embassy-stm32/src/rtc/mod.rs
@@ -33,6 +33,60 @@ use embassy_hal_internal::Peripheral;
 use crate::peripherals::RTC;
 use crate::rtc::sealed::Instance;
 
+#[repr(u8)]
+#[derive(Clone, Copy, Debug)]
+pub(crate) enum WakeupPrescaler {
+    Div2 = 2,
+    Div4 = 4,
+    Div8 = 8,
+    Div16 = 16,
+}
+
+#[cfg(any(stm32wb, stm32f4, stm32l0, stm32g4))]
+impl From<WakeupPrescaler> for crate::pac::rtc::vals::Wucksel {
+    fn from(val: WakeupPrescaler) -> Self {
+        use crate::pac::rtc::vals::Wucksel;
+
+        match val {
+            WakeupPrescaler::Div2 => Wucksel::DIV2,
+            WakeupPrescaler::Div4 => Wucksel::DIV4,
+            WakeupPrescaler::Div8 => Wucksel::DIV8,
+            WakeupPrescaler::Div16 => Wucksel::DIV16,
+        }
+    }
+}
+
+#[cfg(any(stm32wb, stm32f4, stm32l0, stm32g4))]
+impl From<crate::pac::rtc::vals::Wucksel> for WakeupPrescaler {
+    fn from(val: crate::pac::rtc::vals::Wucksel) -> Self {
+        use crate::pac::rtc::vals::Wucksel;
+
+        match val {
+            Wucksel::DIV2 => WakeupPrescaler::Div2,
+            Wucksel::DIV4 => WakeupPrescaler::Div4,
+            Wucksel::DIV8 => WakeupPrescaler::Div8,
+            Wucksel::DIV16 => WakeupPrescaler::Div16,
+            _ => unreachable!(),
+        }
+    }
+}
+
+#[cfg(feature = "low-power")]
+impl WakeupPrescaler {
+    pub fn compute_min(val: u32) -> Self {
+        *[
+            WakeupPrescaler::Div2,
+            WakeupPrescaler::Div4,
+            WakeupPrescaler::Div8,
+            WakeupPrescaler::Div16,
+        ]
+        .iter()
+        .skip_while(|psc| **psc as u32 <= val)
+        .next()
+        .unwrap_or(&WakeupPrescaler::Div16)
+    }
+}
+
 /// Errors that can occur on methods on [RtcClock]
 #[non_exhaustive]
 #[derive(Clone, Debug, PartialEq, Eq)]
@@ -277,6 +331,114 @@ impl Rtc {
     pub fn write_backup_register(&self, register: usize, value: u32) {
         RTC::write_backup_register(&RTC::regs(), register, value)
     }
+
+    #[cfg(feature = "low-power")]
+    /// start the wakeup alarm and wtih a duration that is as close to but less than
+    /// the requested duration, and record the instant the wakeup alarm was started
+    pub(crate) fn start_wakeup_alarm(
+        &self,
+        requested_duration: embassy_time::Duration,
+        cs: critical_section::CriticalSection,
+    ) {
+        use embassy_time::{Duration, TICK_HZ};
+
+        #[cfg(any(rtc_v3, rtc_v3u5))]
+        use crate::pac::rtc::vals::Calrf;
+
+        // Panic if the rcc mod knows we're not using low-power rtc
+        #[cfg(any(rcc_wb, rcc_f4, rcc_f410))]
+        unsafe { crate::rcc::get_freqs() }.rtc.unwrap();
+
+        let requested_duration = requested_duration.as_ticks().clamp(0, u32::MAX as u64);
+        let rtc_hz = Self::frequency().0 as u64;
+        let rtc_ticks = requested_duration * rtc_hz / TICK_HZ;
+        let prescaler = WakeupPrescaler::compute_min((rtc_ticks / u16::MAX as u64) as u32);
+
+        // adjust the rtc ticks to the prescaler and subtract one rtc tick
+        let rtc_ticks = rtc_ticks / prescaler as u64;
+        let rtc_ticks = rtc_ticks.clamp(0, (u16::MAX - 1) as u64).saturating_sub(1) as u16;
+
+        self.write(false, |regs| {
+            regs.cr().modify(|w| w.set_wute(false));
+
+            #[cfg(any(
+                rtc_v2f0, rtc_v2f2, rtc_v2f3, rtc_v2f4, rtc_v2f7, rtc_v2h7, rtc_v2l0, rtc_v2l1, rtc_v2l4, rtc_v2wb
+            ))]
+            {
+                regs.isr().modify(|w| w.set_wutf(false));
+                while !regs.isr().read().wutwf() {}
+            }
+
+            #[cfg(any(rtc_v3, rtc_v3u5))]
+            {
+                regs.scr().write(|w| w.set_cwutf(Calrf::CLEAR));
+                while !regs.icsr().read().wutwf() {}
+            }
+
+            regs.cr().modify(|w| w.set_wucksel(prescaler.into()));
+            regs.wutr().write(|w| w.set_wut(rtc_ticks));
+            regs.cr().modify(|w| w.set_wute(true));
+            regs.cr().modify(|w| w.set_wutie(true));
+        });
+
+        let instant = self.instant().unwrap();
+        trace!(
+            "rtc: start wakeup alarm for {} ms (psc: {}, ticks: {}) at {}",
+            Duration::from_ticks(rtc_ticks as u64 * TICK_HZ * prescaler as u64 / rtc_hz).as_millis(),
+            prescaler as u32,
+            rtc_ticks,
+            instant,
+        );
+
+        assert!(self.stop_time.borrow(cs).replace(Some(instant)).is_none())
+    }
+
+    #[cfg(feature = "low-power")]
+    /// stop the wakeup alarm and return the time elapsed since `start_wakeup_alarm`
+    /// was called, otherwise none
+    pub(crate) fn stop_wakeup_alarm(&self, cs: critical_section::CriticalSection) -> Option<embassy_time::Duration> {
+        use crate::interrupt::typelevel::Interrupt;
+        #[cfg(any(rtc_v3, rtc_v3u5))]
+        use crate::pac::rtc::vals::Calrf;
+
+        let instant = self.instant().unwrap();
+        if RTC::regs().cr().read().wute() {
+            trace!("rtc: stop wakeup alarm at {}", instant);
+
+            self.write(false, |regs| {
+                regs.cr().modify(|w| w.set_wutie(false));
+                regs.cr().modify(|w| w.set_wute(false));
+
+                #[cfg(any(
+                    rtc_v2f0, rtc_v2f2, rtc_v2f3, rtc_v2f4, rtc_v2f7, rtc_v2h7, rtc_v2l0, rtc_v2l1, rtc_v2l4, rtc_v2wb
+                ))]
+                regs.isr().modify(|w| w.set_wutf(false));
+
+                #[cfg(any(rtc_v3, rtc_v3u5))]
+                regs.scr().write(|w| w.set_cwutf(Calrf::CLEAR));
+
+                crate::pac::EXTI
+                    .pr(0)
+                    .modify(|w| w.set_line(RTC::EXTI_WAKEUP_LINE, true));
+
+                <RTC as crate::rtc::sealed::Instance>::WakeupInterrupt::unpend();
+            });
+        }
+
+        self.stop_time.borrow(cs).take().map(|stop_time| instant - stop_time)
+    }
+
+    #[cfg(feature = "low-power")]
+    pub(crate) fn enable_wakeup_line(&self) {
+        use crate::interrupt::typelevel::Interrupt;
+        use crate::pac::EXTI;
+
+        <RTC as crate::rtc::sealed::Instance>::WakeupInterrupt::unpend();
+        unsafe { <RTC as crate::rtc::sealed::Instance>::WakeupInterrupt::enable() };
+
+        EXTI.rtsr(0).modify(|w| w.set_line(RTC::EXTI_WAKEUP_LINE, true));
+        EXTI.imr(0).modify(|w| w.set_line(RTC::EXTI_WAKEUP_LINE, true));
+    }
 }
 
 pub(crate) fn byte_to_bcd2(byte: u8) -> (u8, u8) {