embassy/embassy-stm32/src/rtc.rs

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2021-05-23 04:58:40 +02:00
use core::cell::Cell;
use core::convert::TryInto;
use core::sync::atomic::{compiler_fence, AtomicU32, Ordering};
use embassy::interrupt::InterruptExt;
use embassy::time::{Clock, TICKS_PER_SECOND};
use embassy::util::AtomicWaker;
use crate::interrupt::{CriticalSection, Interrupt, Mutex};
use crate::pac::timer::TimGp16;
use crate::time::Hertz;
// RTC timekeeping works with something we call "periods", which are time intervals
// of 2^15 ticks. The RTC counter value is 16 bits, so one "overflow cycle" is 2 periods.
//
// A `period` count is maintained in parallel to the RTC hardware `counter`, like this:
// - `period` and `counter` start at 0
// - `period` is incremented on overflow (at counter value 0)
// - `period` is incremented "midway" between overflows (at counter value 0x8000)
//
// Therefore, when `period` is even, counter is in 0..0x7FFF. When odd, counter is in 0x8000..0xFFFF
// This allows for now() to return the correct value even if it races an overflow.
//
// To get `now()`, `period` is read first, then `counter` is read. If the counter value matches
// the expected range for the `period` parity, we're done. If it doesn't, this means that
// a new period start has raced us between reading `period` and `counter`, so we assume the `counter` value
// corresponds to the next period.
//
// `period` is a 32bit integer, so It overflows on 2^32 * 2^15 / 32768 seconds of uptime, which is 136 years.
fn calc_now(period: u32, counter: u16) -> u64 {
((period as u64) << 15) + ((counter as u32 ^ ((period & 1) << 15)) as u64)
}
struct AlarmState {
timestamp: Cell<u64>,
#[allow(clippy::type_complexity)]
callback: Cell<Option<(fn(*mut ()), *mut ())>>,
}
impl AlarmState {
fn new() -> Self {
Self {
timestamp: Cell::new(u64::MAX),
callback: Cell::new(None),
}
}
}
// TODO: This is sometimes wasteful, try to find a better way
const ALARM_COUNT: usize = 3;
/// RTC timer that can be used by the executor and to set alarms.
///
/// It can work with Timers 2, 3, 4, 5, 9 and 12. Timers 9 and 12 only have one alarm available,
/// while the others have three each.
/// This timer works internally with a unit of 2^15 ticks, which means that if a call to
/// [`embassy::time::Clock::now`] is blocked for that amount of ticks the returned value will be
/// wrong (an old value). The current default tick rate is 32768 ticks per second.
pub struct RTC<T: Instance> {
_inner: T,
irq: T::Interrupt,
/// Number of 2^23 periods elapsed since boot.
period: AtomicU32,
/// Timestamp at which to fire alarm. u64::MAX if no alarm is scheduled.
alarms: Mutex<[AlarmState; ALARM_COUNT]>,
}
impl<T: Instance> RTC<T> {
pub fn new(peripheral: T, irq: T::Interrupt) -> Self {
Self {
_inner: peripheral,
irq,
period: AtomicU32::new(0),
alarms: Mutex::new([AlarmState::new(), AlarmState::new(), AlarmState::new()]),
}
}
pub fn start(&'static self, pfreq: Hertz, ppre: u8) {
let inner = T::inner();
// NOTE(unsafe) Critical section to use the unsafe methods
critical_section::with(|_| {
unsafe {
inner.prepare(pfreq, ppre);
}
self.irq.set_handler_context(self as *const _ as *mut _);
self.irq.set_handler(|ptr| unsafe {
let this = &*(ptr as *const () as *const Self);
this.on_interrupt();
});
self.irq.unpend();
self.irq.enable();
unsafe {
inner.start_counter();
}
})
}
fn on_interrupt(&self) {
let inner = T::inner();
// NOTE(unsafe) Use critical section to access the methods
// XXX: reduce the size of this critical section ?
critical_section::with(|cs| unsafe {
if inner.overflow_interrupt_status() {
inner.overflow_clear_flag();
self.next_period();
}
// Half overflow
if inner.compare_interrupt_status(0) {
inner.compare_clear_flag(0);
self.next_period();
}
for n in 1..=ALARM_COUNT {
if inner.compare_interrupt_status(n) {
inner.compare_clear_flag(n);
self.trigger_alarm(n, cs);
}
}
})
}
fn next_period(&self) {
let inner = T::inner();
let period = self.period.fetch_add(1, Ordering::Relaxed) + 1;
let t = (period as u64) << 15;
critical_section::with(move |cs| {
for n in 1..=ALARM_COUNT {
let alarm = &self.alarms.borrow(cs)[n - 1];
let at = alarm.timestamp.get();
let diff = at - t;
if diff < 0xc000 {
inner.set_compare(n, at as u16);
// NOTE(unsafe) We're in a critical section
unsafe {
inner.set_compare_interrupt(n, true);
}
}
}
})
}
fn trigger_alarm(&self, n: usize, cs: CriticalSection) {
let inner = T::inner();
// NOTE(unsafe) We have a critical section
unsafe {
inner.set_compare_interrupt(n, false);
}
let alarm = &self.alarms.borrow(cs)[n - 1];
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);
}
}
fn set_alarm_callback(&self, n: usize, callback: fn(*mut ()), ctx: *mut ()) {
critical_section::with(|cs| {
let alarm = &self.alarms.borrow(cs)[n - 1];
alarm.callback.set(Some((callback, ctx)));
})
}
fn set_alarm(&self, n: usize, timestamp: u64) {
critical_section::with(|cs| {
let inner = T::inner();
let alarm = &self.alarms.borrow(cs)[n - 1];
alarm.timestamp.set(timestamp);
let t = self.now();
if timestamp <= t {
self.trigger_alarm(n, cs);
return;
}
let diff = timestamp - t;
if diff < 0xc000 {
let safe_timestamp = timestamp.max(t + 3);
inner.set_compare(n, safe_timestamp as u16);
// NOTE(unsafe) We're in a critical section
unsafe {
inner.set_compare_interrupt(n, true);
}
} else {
unsafe {
inner.set_compare_interrupt(n, false);
}
}
})
}
pub fn alarm1(&'static self) -> Alarm<T> {
Alarm { n: 1, rtc: self }
}
pub fn alarm2(&'static self) -> Alarm<T> {
Alarm { n: 2, rtc: self }
}
pub fn alarm3(&'static self) -> Alarm<T> {
Alarm { n: 3, rtc: self }
}
}
impl<T: Instance> embassy::time::Clock for RTC<T> {
fn now(&self) -> u64 {
let inner = T::inner();
let period = self.period.load(Ordering::Relaxed);
compiler_fence(Ordering::Acquire);
let counter = inner.counter();
calc_now(period, counter)
}
}
pub struct Alarm<T: Instance> {
n: usize,
rtc: &'static RTC<T>,
}
impl<T: Instance> embassy::time::Alarm for Alarm<T> {
fn set_callback(&self, callback: fn(*mut ()), ctx: *mut ()) {
self.rtc.set_alarm_callback(self.n, callback, ctx);
}
fn set(&self, timestamp: u64) {
self.rtc.set_alarm(self.n, timestamp);
}
fn clear(&self) {
self.rtc.set_alarm(self.n, u64::MAX);
}
}
pub struct TimerInner(pub(crate) TimGp16);
impl TimerInner {
unsafe fn prepare(&self, pfreq: Hertz, ppre: u8) {
self.stop_and_reset();
let multiplier = if ppre == 1 { 1 } else { 2 };
let freq = pfreq.0 * multiplier;
let psc = freq / TICKS_PER_SECOND as u32 - 1;
let psc: u16 = psc.try_into().unwrap();
self.set_psc_arr(psc, u16::MAX);
// Mid-way point
self.set_compare(0, 0x8000);
self.set_compare_interrupt(0, true);
}
unsafe fn start_counter(&self) {
self.0.cr1().modify(|w| w.set_cen(true));
}
unsafe fn stop_and_reset(&self) {
let regs = self.0;
regs.cr1().modify(|w| w.set_cen(false));
regs.cnt().write(|w| w.set_cnt(0));
}
fn overflow_interrupt_status(&self) -> bool {
// NOTE(unsafe) Atomic read with no side-effects
unsafe { self.0.sr().read().uif() }
}
unsafe fn overflow_clear_flag(&self) {
self.0.sr().modify(|w| w.set_uif(false));
}
unsafe fn set_psc_arr(&self, psc: u16, arr: u16) {
use crate::pac::timer::vals::Urs;
let regs = self.0;
regs.psc().write(|w| w.set_psc(psc));
regs.arr().write(|w| w.set_arr(arr));
// Set URS, generate update and clear URS
regs.cr1().modify(|w| w.set_urs(Urs::COUNTERONLY));
regs.egr().write(|w| w.set_ug(true));
regs.cr1().modify(|w| w.set_urs(Urs::ANYEVENT));
}
fn compare_interrupt_status(&self, n: usize) -> bool {
if n > 3 {
false
} else {
// NOTE(unsafe) Atomic read with no side-effects
unsafe { self.0.sr().read().ccif(n) }
}
}
unsafe fn compare_clear_flag(&self, n: usize) {
if n > 3 {
return;
}
self.0.sr().modify(|w| w.set_ccif(n, false));
}
fn set_compare(&self, n: usize, value: u16) {
if n > 3 {
return;
}
// NOTE(unsafe) Atomic write
unsafe {
self.0.ccr(n).write(|w| w.set_ccr(value));
}
}
unsafe fn set_compare_interrupt(&self, n: usize, enable: bool) {
if n > 3 {
return;
}
self.0.dier().modify(|w| w.set_ccie(n, enable));
}
fn counter(&self) -> u16 {
// NOTE(unsafe) Atomic read with no side-effects
unsafe { self.0.cnt().read().cnt() }
}
}
// ------------------------------------------------------
pub(crate) mod sealed {
use super::*;
pub trait Instance {
type Interrupt: Interrupt;
fn inner() -> TimerInner;
fn state() -> &'static AtomicWaker;
}
}
pub trait Instance: sealed::Instance + Sized + 'static {}
/*
#[allow(unused_macros)]
macro_rules! impl_timer {
($module:ident: ($TYPE:ident, $INT:ident, $apbenr:ident, $enrbit:expr, $apbrstr:ident, $rstrbit:expr, $ppre:ident, $pclk: ident), 3) => {
mod $module {
use super::*;
impl sealed::Instance for $TYPE {}
impl Instance for $TYPE {
type Interrupt = interrupt::$INT;
fn set_compare(&self, n: usize, value: u16) {
// NOTE(unsafe) these registers accept all the range of u16 values
match n {
0 => self.ccr1.write(|w| unsafe { w.bits(value.into()) }),
1 => self.ccr2.write(|w| unsafe { w.bits(value.into()) }),
2 => self.ccr3.write(|w| unsafe { w.bits(value.into()) }),
3 => self.ccr4.write(|w| unsafe { w.bits(value.into()) }),
_ => {}
}
}
fn set_compare_interrupt(&self, n: usize, enable: bool) {
if n > 3 {
return;
}
let bit = n as u8 + 1;
unsafe {
if enable {
bb::set(&self.dier, bit);
} else {
bb::clear(&self.dier, bit);
}
}
}
fn compare_interrupt_status(&self, n: usize) -> bool {
let status = self.sr.read();
match n {
0 => status.cc1if().bit_is_set(),
1 => status.cc2if().bit_is_set(),
2 => status.cc3if().bit_is_set(),
3 => status.cc4if().bit_is_set(),
_ => false,
}
}
fn compare_clear_flag(&self, n: usize) {
if n > 3 {
return;
}
let bit = n as u8 + 1;
unsafe {
bb::clear(&self.sr, bit);
}
}
fn overflow_interrupt_status(&self) -> bool {
self.sr.read().uif().bit_is_set()
}
fn overflow_clear_flag(&self) {
unsafe {
bb::clear(&self.sr, 0);
}
}
fn set_psc_arr(&self, psc: u16, arr: u16) {
// NOTE(unsafe) All u16 values are valid
self.psc.write(|w| unsafe { w.bits(psc.into()) });
self.arr.write(|w| unsafe { w.bits(arr.into()) });
unsafe {
// Set URS, generate update, clear URS
bb::set(&self.cr1, 2);
self.egr.write(|w| w.ug().set_bit());
bb::clear(&self.cr1, 2);
}
}
fn stop_and_reset(&self) {
unsafe {
bb::clear(&self.cr1, 0);
}
self.cnt.reset();
}
fn start(&self) {
unsafe { bb::set(&self.cr1, 0) }
}
fn counter(&self) -> u16 {
self.cnt.read().bits() as u16
}
fn ppre(clocks: &Clocks) -> u8 {
clocks.$ppre()
}
fn pclk(clocks: &Clocks) -> u32 {
clocks.$pclk().0
}
}
}
};
($module:ident: ($TYPE:ident, $INT:ident, $apbenr:ident, $enrbit:expr, $apbrstr:ident, $rstrbit:expr, $ppre:ident, $pclk: ident), 1) => {
mod $module {
use super::*;
use crate::hal::pac::{$TYPE, RCC};
impl sealed::Sealed for $TYPE {}
impl Instance for $TYPE {
type Interrupt = interrupt::$INT;
const REAL_ALARM_COUNT: usize = 1;
fn enable_clock(&self) {
// NOTE(unsafe) It will only be used for atomic operations
unsafe {
let rcc = &*RCC::ptr();
bb::set(&rcc.$apbenr, $enrbit);
bb::set(&rcc.$apbrstr, $rstrbit);
bb::clear(&rcc.$apbrstr, $rstrbit);
}
}
fn set_compare(&self, n: usize, value: u16) {
// NOTE(unsafe) these registers accept all the range of u16 values
match n {
0 => self.ccr1.write(|w| unsafe { w.bits(value.into()) }),
1 => self.ccr2.write(|w| unsafe { w.bits(value.into()) }),
_ => {}
}
}
fn set_compare_interrupt(&self, n: usize, enable: bool) {
if n > 1 {
return;
}
let bit = n as u8 + 1;
unsafe {
if enable {
bb::set(&self.dier, bit);
} else {
bb::clear(&self.dier, bit);
}
}
}
fn compare_interrupt_status(&self, n: usize) -> bool {
let status = self.sr.read();
match n {
0 => status.cc1if().bit_is_set(),
1 => status.cc2if().bit_is_set(),
_ => false,
}
}
fn compare_clear_flag(&self, n: usize) {
if n > 1 {
return;
}
let bit = n as u8 + 1;
unsafe {
bb::clear(&self.sr, bit);
}
}
fn overflow_interrupt_status(&self) -> bool {
self.sr.read().uif().bit_is_set()
}
fn overflow_clear_flag(&self) {
unsafe {
bb::clear(&self.sr, 0);
}
}
fn set_psc_arr(&self, psc: u16, arr: u16) {
// NOTE(unsafe) All u16 values are valid
self.psc.write(|w| unsafe { w.bits(psc.into()) });
self.arr.write(|w| unsafe { w.bits(arr.into()) });
unsafe {
// Set URS, generate update, clear URS
bb::set(&self.cr1, 2);
self.egr.write(|w| w.ug().set_bit());
bb::clear(&self.cr1, 2);
}
}
fn stop_and_reset(&self) {
unsafe {
bb::clear(&self.cr1, 0);
}
self.cnt.reset();
}
fn start(&self) {
unsafe { bb::set(&self.cr1, 0) }
}
fn counter(&self) -> u16 {
self.cnt.read().bits() as u16
}
fn ppre(clocks: &Clocks) -> u8 {
clocks.$ppre()
}
fn pclk(clocks: &Clocks) -> u32 {
clocks.$pclk().0
}
}
}
};
}
*/
/*
impl_timer!(tim2: (TIM2, TIM2, apb1enr, 0, apb1rstr, 0, ppre1, pclk1), 3);
impl_timer!(tim3: (TIM3, TIM3, apb1enr, 1, apb1rstr, 1, ppre1, pclk1), 3);
impl_timer!(tim4: (TIM4, TIM4, apb1enr, 2, apb1rstr, 2, ppre1, pclk1), 3);
impl_timer!(tim5: (TIM5, TIM5, apb1enr, 3, apb1rstr, 3, ppre1, pclk1), 3);
impl_timer!(tim9: (TIM9, TIM1_BRK_TIM9, apb2enr, 16, apb2rstr, 16, ppre2, pclk2), 1);
#[cfg(not(any(feature = "stm32f401", feature = "stm32f410", feature = "stm32f411")))]
impl_timer!(tim12: (TIM12, TIM8_BRK_TIM12, apb1enr, 6, apb1rstr, 6, ppre1, pclk1), 1);
*/