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[esp32] Document why millis_64() uses a different clock than millis()

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millis() uses xTaskGetTickCount (tick clock) while millis_64() uses
esp_timer_get_time (hardware timer). Safe because they are never
cross-compared: Scheduler::millis_64_from_() on ESP32 discards the
32-bit millis parameter and calls millis_64() directly, keeping all
64-bit scheduling on the esp_timer clock.
This commit is contained in:
J. Nick Koston
2026-04-12 09:48:23 -10:00
parent b5a2d58b80
commit 0249c30cbf
1 changed files with 6 additions and 0 deletions
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esphome/components/esp32/core.cpp
+6
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@@ -37,6 +37,12 @@ uint32_t IRAM_ATTR HOT millis() {
return micros_to_millis(static_cast<uint64_t>(esp_timer_get_time()));
#endif
}
// millis_64() stays on esp_timer — a different clock from xTaskGetTickCount(). This is
// safe because the two are never cross-compared: millis() values are only used for
// millis()-vs-millis() deltas (feed_wdt, warn_blocking, component start time), while
// millis_64() is used by the Scheduler and uptime sensors. On ESP32 (USE_NATIVE_64BIT_TIME),
// Scheduler::millis_64_from_(now) discards the 32-bit now and calls millis_64() directly,
// so the Scheduler is internally consistent on the esp_timer clock.
uint64_t HOT millis_64() { return micros_to_millis<uint64_t>(static_cast<uint64_t>(esp_timer_get_time())); }
void HOT delay(uint32_t ms) { vTaskDelay(ms / portTICK_PERIOD_MS); }
uint32_t IRAM_ATTR HOT micros() { return (uint32_t) esp_timer_get_time(); }