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samd: Don't rely on RTC interrupt #6202

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Apr 5, 2022
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samd: Don't rely on RTC interrupt #6202

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46 changes: 17 additions & 29 deletions ports/atmel-samd/supervisor/port.c
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Original file line number Diff line number Diff line change
Expand Up @@ -247,7 +247,6 @@ static void rtc_init(void) {
RTC_MODE0_CTRLA_COUNTSYNC;
#endif

RTC->MODE0.INTENSET.reg = RTC_MODE0_INTENSET_OVF;

// Set all peripheral interrupt priorities to the lowest priority by default.
for (uint16_t i = 0; i < PERIPH_COUNT_IRQn; i++) {
Expand Down Expand Up @@ -501,45 +500,34 @@ uint32_t port_get_saved_word(void) {
// TODO: Move this to an RTC backup register so we can preserve it when only the BACKUP power domain
// is enabled.
static volatile uint64_t overflowed_ticks = 0;
static uint32_t rtc_old_count;

static uint32_t _get_count(uint64_t *overflow_count) {
while (1) {
// Disable interrupts so we can grab the count and the overflow atomically.
common_hal_mcu_disable_interrupts();

#ifdef SAM_D5X_E5X
while ((RTC->MODE0.SYNCBUSY.reg & (RTC_MODE0_SYNCBUSY_COUNTSYNC | RTC_MODE0_SYNCBUSY_COUNT)) != 0) {
}
#endif
// SAMD21 does continuous sync so we don't need to wait here.

uint32_t count = RTC->MODE0.COUNT.reg;
if (overflow_count != NULL) {
*overflow_count = overflowed_ticks;
}

bool overflow_pending = RTC->MODE0.INTFLAG.bit.OVF;

common_hal_mcu_enable_interrupts();
#ifdef SAM_D5X_E5X
while ((RTC->MODE0.SYNCBUSY.reg & (RTC_MODE0_SYNCBUSY_COUNTSYNC | RTC_MODE0_SYNCBUSY_COUNT)) != 0) {
}
#endif
// SAMD21 does continuous sync so we don't need to wait here.

if (!overflow_pending) {
return count;
}
uint32_t count = RTC->MODE0.COUNT.reg;
if (count < rtc_old_count) {
// Our RTC is 32 bits and we're clocking it at 16.384khz which is 16 (2 ** 4) subticks per
// tick.
overflowed_ticks += (1L << (32 - 4));
}
rtc_old_count = count;

// Try again if overflow hasn't been processed yet.
if (overflow_count != NULL) {
*overflow_count = overflowed_ticks;
}

return count;
}

volatile bool _woken_up;

void RTC_Handler(void) {
uint32_t intflag = RTC->MODE0.INTFLAG.reg;
if (intflag & RTC_MODE0_INTFLAG_OVF) {
RTC->MODE0.INTFLAG.reg = RTC_MODE0_INTFLAG_OVF;
// Our RTC is 32 bits and we're clocking it at 16.384khz which is 16 (2 ** 4) subticks per
// tick.
overflowed_ticks += (1L << (32 - 4));
}
#ifdef SAM_D5X_E5X
if (intflag & RTC_MODE0_INTFLAG_PER2) {
RTC->MODE0.INTFLAG.reg = RTC_MODE0_INTFLAG_PER2;
Expand Down