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RP2040: Fix 64-bit uptime being wrapped as a 32-bit value whenever a timer event happens #38

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RP2040: Fix 64-bit uptime being wrapped as a 32-bit value whenever a timer event happens #38

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e67b7f8
RP2040: us_ticker: use API to force a timer event and get an interrupt
nomis May 19, 2025
2ec6917
RP2040: us_ticker: don't modify the system uptime
nomis May 19, 2025
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41 changes: 22 additions & 19 deletions targets/TARGET_RASPBERRYPI/TARGET_RP2040/us_ticker.c
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Original file line number Diff line number Diff line change
Expand Up @@ -54,6 +54,7 @@ const ticker_info_t* us_ticker_get_info()
}

static const uint8_t alarm_num = 0;
static uint64_t last_read_u64 = 0;

static void us_ticker_irq_handler_internal(uint alarm_src) {
if (alarm_num == alarm_src) {
Expand All @@ -69,37 +70,39 @@ void us_ticker_init(void)

uint32_t us_ticker_read()
{
return time_us_32();
uint64_t now_u64 = time_us_64();

core_util_critical_section_enter();
last_read_u64 = now_u64;
core_util_critical_section_exit();

return now_u64;
}

void us_ticker_set_interrupt(timestamp_t timestamp)
void us_ticker_set_interrupt(timestamp_t timestamp_u32)
{
core_util_critical_section_enter();

uint64_t _timestamp = (uint64_t)timestamp;

if (timestamp < time_us_32()) {
//32 bit timestamp has been wrapped
//We need to provide a 64 bit timestamp able to fire the irq for this round
_timestamp = (((time_us_64() >> 32) + 1) << 32) + timestamp;
} else {
//Then, at the next round, wrap the 64 bit timer to follow the 32 bit one
if ((time_us_64() >> 32) > 0) {
uint64_t current_time = time_us_64();
uint64_t wrapped_time = current_time - 0xFFFFFFFF;
timer_hw->timelw = (uint32_t)wrapped_time;
timer_hw->timehw = 0;
}
uint32_t last_read_u32 = (uint32_t)last_read_u64;
uint64_t timestamp_u64 = (uint64_t)timestamp_u32 | (last_read_u64 & 0xFFFFFFFF00000000ULL);

if (timestamp_u32 < last_read_u32) {
timestamp_u64 += 1ULL << 32;
}

absolute_time_t target = { timestamp_u64 };
bool missed = hardware_alarm_set_target(alarm_num, target);

if (missed) {
us_ticker_fire_interrupt();
}
absolute_time_t target = { _timestamp };
hardware_alarm_set_target(alarm_num, target);

core_util_critical_section_exit();
}

void us_ticker_fire_interrupt(void)
{
us_ticker_irq_handler();
hardware_alarm_force_irq(alarm_num);
}

void us_ticker_disable_interrupt(void)
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