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fix: #4 systick timer reading 64b timer #88

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fix: #4 systick timer reading 64b timer #88

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14 changes: 11 additions & 3 deletions src/embassy/time_driver_systick.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -117,15 +117,24 @@ impl SystickDriver {
#[inline]
fn raw_cnt(&self) -> u64 {
let rb = crate::pac::SYSTICK;
rb.cnt().read()
// Typical implementation of reading 64-bit value from two 32-bit
// self-incrementing registers: H->L->H loop.
// See-also: https://github.com/ch32-rs/ch32-hal/issues/4
loop {
let cnt_high = rb.cnth().read();
let cnt_low = rb.cntl().read();
if rb.cnth().read() == cnt_high {
return (cnt_high as u64) << 32 | cnt_low as u64;
}
}
}
}

impl Driver for SystickDriver {
fn now(&self) -> u64 {
let rb = crate::pac::SYSTICK;
let period = self.period.load(Ordering::Relaxed) as u64;
rb.cnt().read() / period
self.raw_cnt() / period
}

unsafe fn allocate_alarm(&self) -> Option<AlarmHandle> {
Expand Down Expand Up @@ -162,7 +171,6 @@ impl Driver for SystickDriver {

let period = self.period.load(Ordering::Relaxed) as u64;

// See-also: https://github.com/ch32-rs/ch32-hal/issues/4
let t = self.raw_cnt();
let timestamp = timestamp * period;
if timestamp <= t {
Expand Down