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[core] Add permalink to BDK sctrl_dpll_delay200us in WDT interval comment

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So future readers can verify the errata claim without chasing the PR.
This commit is contained in:
J. Nick Koston
2026-04-23 04:47:52 -05:00
parent 72d4efb681
commit 3b212b9944
1 changed files with 31 additions and 6 deletions
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esphome/core/application.h
+31 -6
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@@ -226,11 +226,13 @@ class Application {
/// - BK72xx HW WDT (10 s): ~5x <-- platform override below
#ifdef USE_BK72XX
/// BK72xx silicon requires a ~200 µs busy-wait between two watchdog register
/// key writes on every reload (sctrl_dpll_delay200us() in BDK wdt.c), making
/// each arch_feed_wdt() ~300 µs. LibreTiny initialises the HW WDT at 10 s,
/// so 2000 ms keeps a 5x safety margin — matching the ESP8266 ratio that
/// motivated the generic 300 ms value — while cutting feed frequency ~6x
/// and recovering ~50 ms/min of main-loop overhead on typical configs.
/// key writes on every reload, making each arch_feed_wdt() ~300 µs. The
/// sctrl_dpll_delay200us() call lives in BDK's wdt_ctrl (WCMD_RELOAD_PERIOD):
/// https://github.com/libretiny-eu/framework-beken-bdk/blob/44800e7451ea30fbcbd3bb6e905315de59349fee/beken378/driver/wdt/wdt.c#L75-L87
/// LibreTiny initialises the HW WDT at 10 s, so 2000 ms keeps a 5x safety
/// margin — matching the ESP8266 ratio that motivated the generic 300 ms
/// value — while cutting feed frequency ~6x and recovering ~50 ms/min of
/// main-loop overhead on typical configs.
static constexpr uint32_t WDT_FEED_INTERVAL_MS = 2000;
#else
static constexpr uint32_t WDT_FEED_INTERVAL_MS = 300;
@@ -474,6 +476,11 @@ class Application {
// millis() of most recent status_led dispatch; rate-limits independently of last_wdt_feed_
uint32_t last_status_led_service_{0};
#endif
#ifdef USE_RUNTIME_STATS
// Count of feed_wdt_slow_() invocations since last runtime_stats log. Lets
// stats output report how often the slow path (arch_feed_wdt) actually runs.
uint32_t wdt_slow_count_{0};
#endif
// 2-byte members (grouped together for alignment)
uint16_t dump_config_at_{std::numeric_limits<uint16_t>::max()}; // Index into components_ for dump_config progress
@@ -572,6 +579,12 @@ inline void ESPHOME_ALWAYS_INLINE __attribute__((optimize("O2"))) Application::l
// so the gate check and WDT feed both reflect actual elapsed time after
// scheduler dispatch, without an extra millis() call.
uint32_t now = this->scheduler_tick_(MillisInternal::get());
#ifdef USE_RUNTIME_STATS
// Capture immediately after scheduler_tick_ returns so the post-scheduler
// feed_wdt_with_time slice can be separated from the scheduler slice in
// the `before` bucket.
uint32_t loop_after_sched_us = micros();
#endif
// Guarantee one WDT feed per tick even when the scheduler had nothing to
// dispatch and the component phase is gated out — covers configs with no
// looping components and no scheduler work (setup() has its own
@@ -643,10 +656,22 @@ inline void ESPHOME_ALWAYS_INLINE __attribute__((optimize("O2"))) Application::l
uint32_t loop_before_overhead_us = loop_before_wall_us > loop_before_scheduled_us
? loop_before_wall_us - static_cast<uint32_t>(loop_before_scheduled_us)
: 0;
// Sub-split of the `before` bucket. `sched_us` covers MillisInternal::get()
// plus scheduler_tick_ (everything before the post-scheduler feed_wdt_with_time),
// with scheduled-component time subtracted out so it reflects scheduler
// infrastructure overhead only. `wdt_us` covers the post-scheduler
// feed_wdt_with_time() call (including any status_led dispatch when the
// STATUS_LED_DISPATCH_INTERVAL_MS gate also elapses on the same call).
uint32_t loop_before_sched_wall_us = loop_after_sched_us - loop_active_start_us;
uint32_t loop_before_sched_us = loop_before_sched_wall_us > loop_before_scheduled_us
? loop_before_sched_wall_us - static_cast<uint32_t>(loop_before_scheduled_us)
: 0;
uint32_t loop_before_wdt_us = loop_before_end_us - loop_after_sched_us;
// tail_us is only defined when Phase B ran; 0 on Phase A-only ticks so the
// stats bucket keeps its "component-phase trailing overhead" meaning.
uint32_t loop_tail_us = do_component_phase ? (loop_now_us - loop_tail_start_us) : 0;
global_runtime_stats->record_loop_active(loop_now_us - loop_active_start_us, loop_before_overhead_us, loop_tail_us);
global_runtime_stats->record_loop_active(loop_now_us - loop_active_start_us, loop_before_overhead_us,
loop_before_sched_us, loop_before_wdt_us, loop_tail_us);
global_runtime_stats->process_pending_stats(now);
}
#endif