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stm32/lp: clamp requested_duration to avoid overflow

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This commit is contained in:
xoviat 2023-09-22 15:35:20 -05:00
parent f1488864eb
commit c849620cd6
1 changed files with 13 additions and 7 deletions
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20
embassy-stm32/src/rtc/v2.rs
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@ -71,21 +71,27 @@ impl super::Rtc {
) {
use embassy_time::{Duration, TICK_HZ};
// 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();
/*
If the requested duration is u64::MAX, don't even set the alarm
Otherwise clamp the requested duration to u32::MAX so that we can do math
*/
if requested_duration.as_ticks() == u64::MAX {
return;
}
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.as_ticks() * rtc_hz / TICK_HZ;
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 = if rtc_ticks >= u16::MAX as u64 {
u16::MAX - 1
} else {
rtc_ticks as u16
}
.saturating_sub(1);
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));