fome-fw/firmware/hw_layer/microsecond_timer/microsecond_timer.cpp

/**
 * @file	microsecond_timer.cpp
 *
 * Here we have a 1MHz timer dedicated to event scheduling. We are using one of the 32-bit timers here,
 * so this timer can schedule events up to 4B/100M ~ 4000 seconds ~ 1 hour from current time.
 *
 * GPT5 timer clock: 84000000Hz
 * If only it was a better multiplier of 2 (84000000 = 328125 * 256)
 *
 * @date Apr 14, 2014
 * @author Andrey Belomutskiy, (c) 2012-2020
 */

#include "pch.h"
#include "microsecond_timer.h"
#include "port_microsecond_timer.h"

#if EFI_PROD_CODE

#include "periodic_thread_controller.h"

// Just in case we have a mechanism to validate that hardware timer is clocked right and all the
// conversions between wall clock and hardware frequencies are done right
// delay in milliseconds
#define TEST_CALLBACK_DELAY 10
// if hardware timer is 20% off we throw a critical error and call it a day
// maybe this threshold should be 5%? 10%?
#define TIMER_PRECISION_THRESHOLD 0.2

/**
 * Maximum duration of complete timer callback, all pending events together
 * See also 'maxEventCallbackDuration' for maximum duration of one event
 */
uint32_t maxPrecisionCallbackDuration = 0;

static efitick_t lastSetTimerTimeNt;
static bool isTimerPending = false;

static int timerCallbackCounter = 0;
static int timerRestartCounter = 0;

static int timerFreezeCounter = 0;
static int setHwTimerCounter = 0;
static bool hwStarted = false;

/**
 * sets the alarm to the specified number of microseconds from now.
 * This function should be invoked under kernel lock which would disable interrupts.
 */
void setHardwareSchedulerTimer(efitick_t nowNt, efitick_t setTimeNt) {
	efiAssertVoid(ObdCode::OBD_PCM_Processor_Fault, hwStarted, "HW.started");

	setHwTimerCounter++;

	// How many ticks in the future is this event?
	const auto timeDeltaNt = setTimeNt - nowNt;

	/**
	 * #259 BUG error: not positive deltaTimeNt
	 * Once in a while we night get an interrupt where we do not expect it
	 */
	if (timeDeltaNt <= 0) {
		timerFreezeCounter++;
		warning(ObdCode::CUSTOM_OBD_LOCAL_FREEZE, "local freeze cnt=%d", timerFreezeCounter);
	}

	// We need the timer to fire after we return - too close to now may actually schedule in the past
	if (timeDeltaNt < US2NT(2)) {
		setTimeNt = nowNt + US2NT(2);
	} else if (timeDeltaNt >= TOO_FAR_INTO_FUTURE_NT) {
		uint32_t delta32;
		if (timeDeltaNt > UINT32_MAX) {
			delta32 = UINT32_MAX;
		} else {
			delta32 = timeDeltaNt;
		}

		// we are trying to set callback for too far into the future. This does not look right at all
		firmwareError(ObdCode::CUSTOM_ERR_TIMER_OVERFLOW, "setHardwareSchedulerTimer() too far: %lu", delta32);
		return;
	}

	// Skip scheduling if there's a firmware error active
	if (hasFirmwareError()) {
		return;
	}

	// Do the actual hardware-specific timer set operation
	portSetHardwareSchedulerTimer(nowNt, setTimeNt);

	lastSetTimerTimeNt = getTimeNowNt();
	isTimerPending = true;
	timerRestartCounter++;
}

void globalTimerCallback();

void portMicrosecondTimerCallback() {
	timerCallbackCounter++;
	isTimerPending = false;

	uint32_t before = getTimeNowLowerNt();
	globalTimerCallback();
	uint32_t precisionCallbackDuration = getTimeNowLowerNt() - before;
	if (precisionCallbackDuration > maxPrecisionCallbackDuration) {
		maxPrecisionCallbackDuration = precisionCallbackDuration;
	}
}

struct MicrosecondTimerWatchdogController : public PeriodicController<256> {
	MicrosecondTimerWatchdogController()
		: PeriodicController("MstWatchdog", NORMALPRIO, 2)
	{
	}

	void PeriodicTask(efitick_t nowNt) override {
		// 2 seconds of inactivity would not look right
		efiAssertVoid(ObdCode::CUSTOM_TIMER_WATCHDOG, nowNt < lastSetTimerTimeNt + 2 * CORE_CLOCK, "Watchdog: no events for 2 seconds!");
	}
};

static MicrosecondTimerWatchdogController watchdogControllerInstance;

static scheduling_s watchDogBuddy;

static void watchDogBuddyCallback(void*) {
	/**
	 * the purpose of this periodic activity is to make watchdogControllerInstance
	 * watchdog happy by ensuring that we have scheduler activity even in case of very broken configuration
	 * without any PWM or input pins
	 */
	engine->scheduler.schedule("watch", &watchDogBuddy, getTimeNowNt() + MS2NT(1000), watchDogBuddyCallback);
}

static volatile bool testSchedulingHappened = false;
static Timer testScheduling;

static void timerValidationCallback(void*) {
	testSchedulingHappened = true;
	float actualTimeSinceScheduling = 1e3 * testScheduling.getElapsedSeconds();
	
	if (absI(actualTimeSinceScheduling - TEST_CALLBACK_DELAY) > TEST_CALLBACK_DELAY * TIMER_PRECISION_THRESHOLD) {
		firmwareError(ObdCode::CUSTOM_ERR_TIMER_TEST_CALLBACK_WRONG_TIME, "hwTimer broken precision: %.3f ms", actualTimeSinceScheduling);
	}
}

/**
 * This method would validate that hardware timer callbacks happen with some reasonable precision
 * helps to make sure our GPT hardware settings are somewhat right
 */
static void validateHardwareTimer() {
	if (hasFirmwareError()) {
		return;
	}
	testScheduling.reset();

	// to save RAM let's use 'watchDogBuddy' here once before we enable watchdog
	engine->scheduler.schedule(
			"hw-validate",
			&watchDogBuddy,
			getTimeNowNt() + MS2NT(TEST_CALLBACK_DELAY),
			timerValidationCallback);

	chThdSleepMilliseconds(TEST_CALLBACK_DELAY + 2);
	if (!testSchedulingHappened) {
		firmwareError(ObdCode::CUSTOM_ERR_TIMER_TEST_CALLBACK_NOT_HAPPENED, "hwTimer not alive");
	}
}

void initMicrosecondTimer() {
	portInitMicrosecondTimer();

	hwStarted = true;

	lastSetTimerTimeNt = getTimeNowNt();

	validateHardwareTimer();

	watchDogBuddyCallback(NULL);
#if EFI_EMULATE_POSITION_SENSORS
	watchdogControllerInstance.start();
#endif /* EFI_EMULATE_POSITION_SENSORS */
}

#endif /* EFI_PROD_CODE */