From 7277b04039c245cb5d6ab7b0a618e16f2f813cb5 Mon Sep 17 00:00:00 2001
From: Matthew Kennedy <matthewkennedy@outlook.com>
Date: Fri, 18 Dec 2020 05:21:18 -0800
Subject: [PATCH] force a pwm cycle start (skip cycles) if late (#2097)

* skip cycles if late

* fail at lower count

* start at -1
---
 .../system/timer/pwm_generator_logic.cpp           | 14 ++++++++++++--
 .../controllers/system/timer/pwm_generator_logic.h |  3 +++
 .../system/timer/single_timer_executor.cpp         | 13 +++++++++----
 3 files changed, 24 insertions(+), 6 deletions(-)

diff --git a/firmware/controllers/system/timer/pwm_generator_logic.cpp b/firmware/controllers/system/timer/pwm_generator_logic.cpp
index 19738e0f1e..b16e2f9e34 100644
--- a/firmware/controllers/system/timer/pwm_generator_logic.cpp
+++ b/firmware/controllers/system/timer/pwm_generator_logic.cpp
@@ -160,13 +160,15 @@ void PwmConfig::handleCycleStart() {
 
 		efiAssertVoid(CUSTOM_ERR_6580, periodNt != 0, "period not initialized");
 		efiAssertVoid(CUSTOM_ERR_6580, iterationLimit > 0, "iterationLimit invalid");
-		if (safe.periodNt != periodNt || safe.iteration == iterationLimit) {
+		if (forceCycleStart || safe.periodNt != periodNt || safe.iteration == iterationLimit) {
 			/**
 			 * period length has changed - we need to reset internal state
 			 */
 			safe.startNt = getTimeNowNt();
 			safe.iteration = 0;
 			safe.periodNt = periodNt;
+
+			forceCycleStart = false;
 #if DEBUG_PWM
 			scheduleMsg(&logger, "state reset start=%d iteration=%d", state->safe.start, state->safe.iteration);
 #endif
@@ -225,10 +227,18 @@ efitick_t PwmConfig::togglePwmState() {
 	scheduleMsg(&logger, "%s: nextSwitchTime %d", state->name, nextSwitchTime);
 #endif /* DEBUG_PWM */
 
+	// If we're very far behind schedule, restart the cycle fresh to avoid scheduling a huge pile of events all at once
+	// This can happen during config write or debugging where CPU is halted for multiple seconds
+	bool isVeryBehindSchedule = nextSwitchTimeNt < getTimeNowNt() - MS2NT(10);
+
 	safe.phaseIndex++;
-	if (safe.phaseIndex == phaseCount || mode != PM_NORMAL) {
+	if (isVeryBehindSchedule || safe.phaseIndex == phaseCount || mode != PM_NORMAL) {
 		safe.phaseIndex = 0; // restart
 		safe.iteration++;
+
+		if (isVeryBehindSchedule) {
+			forceCycleStart = true;
+		}
 	}
 #if EFI_UNIT_TEST
 	printf("PWM: nextSwitchTimeNt=%d phaseIndex=%d iteration=%d\r\n", nextSwitchTimeNt,
diff --git a/firmware/controllers/system/timer/pwm_generator_logic.h b/firmware/controllers/system/timer/pwm_generator_logic.h
index d60f8317de..b7ab616792 100644
--- a/firmware/controllers/system/timer/pwm_generator_logic.h
+++ b/firmware/controllers/system/timer/pwm_generator_logic.h
@@ -110,6 +110,9 @@ private:
 	 * PWM generation is not happening while this value is NAN
 	 */
 	float periodNt;
+
+	// Set if we are very far behind schedule and need to reset back to the beginning of a cycle to find our way
+	bool forceCycleStart = true;
 };
 
 struct hardware_pwm;
diff --git a/firmware/controllers/system/timer/single_timer_executor.cpp b/firmware/controllers/system/timer/single_timer_executor.cpp
index 268217b8b1..a36de7d2c0 100644
--- a/firmware/controllers/system/timer/single_timer_executor.cpp
+++ b/firmware/controllers/system/timer/single_timer_executor.cpp
@@ -123,16 +123,21 @@ void SingleTimerExecutor::executeAllPendingActions() {
 	 * TODO: add a counter & figure out a limit of iterations?
 	 */
 
-	executeCounter = 0;
+	// starts at -1 because do..while will run a minimum of once
+	executeCounter = -1;
+
 	bool didExecute;
 	do {
 		efitick_t nowNt = getTimeNowNt();
 		didExecute = queue.executeOne(nowNt);
-		if (executeCounter++ == 10000) {
-			firmwareError(CUSTOM_ERR_LOCK_ISSUE, "Looks like firmware is really busy");
+
+		// if we're stuck in a loop executing lots of events, panic!
+		if (executeCounter++ == 500) {
+			firmwareError(CUSTOM_ERR_LOCK_ISSUE, "Maximum scheduling run length exceeded - CPU load too high");
 		}
 
 	} while (didExecute);
+
 	maxExecuteCounter = maxI(maxExecuteCounter, executeCounter);
 
 	if (!isLocked()) {
@@ -169,7 +174,7 @@ void initSingleTimerExecutorHardware(void) {
 
 void executorStatistics() {
 	if (engineConfiguration->debugMode == DBG_EXECUTOR) {
-#if EFI_TUNER_STUDIO && EFI_SIGNAL_EXECUTOR_ONE_TIMER
+#if EFI_TUNER_STUDIO
 		tsOutputChannels.debugIntField1 = ___engine.executor.timerCallbackCounter;
 		tsOutputChannels.debugIntField2 = ___engine.executor.executeAllPendingActionsInvocationCounter;
 		tsOutputChannels.debugIntField3 = ___engine.executor.scheduleCounter;