/**
 * @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 "global.h"
#include "os_access.h"
#include "microsecond_timer.h"
#include "scheduler.h"
#include "os_util.h"

// https://my.st.com/public/STe2ecommunities/mcu/Lists/cortex_mx_stm32/Flat.aspx?RootFolder=https%3a%2f%2fmy.st.com%2fpublic%2fSTe2ecommunities%2fmcu%2fLists%2fcortex_mx_stm32%2fInterrupt%20on%20CEN%20bit%20setting%20in%20TIM7&FolderCTID=0x01200200770978C69A1141439FE559EB459D7580009C4E14902C3CDE46A77F0FFD06506F5B&currentviews=474

#if EFI_PROD_CODE && HAL_USE_GPT

#include "periodic_task.h"
#include "engine.h"
EXTERN_ENGINE;

// 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 30
// if hardware timer is 20% off we throw a fatal 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;

// must be one of 32 bit times
#ifndef GPTDEVICE
#define GPTDEVICE GPTD5
#endif /* GPTDEVICE */

static volatile efitick_t lastSetTimerTimeNt;
static int lastSetTimerValue;
static volatile bool isTimerPending = FALSE;

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

schfunc_t globalTimerCallback;

static const char * msg;

static char buff[32];

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

extern bool hasFirmwareErrorFlag;

/**
 * sets the alarm to the specified number of microseconds from now.
 * This function should be invoked under kernel lock which would disable interrupts.
 */
void setHardwareUsTimer(int32_t deltaTimeUs) {
	enginePins.debugSetTimer.setValue(1);
	efiAssertVoid(OBD_PCM_Processor_Fault, hwStarted, "HW.started");
	setHwTimerCounter++;
	/**
	 * #259 BUG error: not positive deltaTimeUs
	 * Once in a while we night get an interrupt where we do not expect it
	 */
	if (deltaTimeUs <= 0) {
		timerFreezeCounter++;
		warning(CUSTOM_OBD_LOCAL_FREEZE, "local freeze cnt=%d", timerFreezeCounter);
	}
	if (deltaTimeUs < 2)
		deltaTimeUs = 2; // for some reason '1' does not really work
	efiAssertVoid(CUSTOM_ERR_6681, deltaTimeUs > 0, "not positive deltaTimeUs");
	if (deltaTimeUs >= TOO_FAR_INTO_FUTURE_US) {
		// we are trying to set callback for too far into the future. This does not look right at all
		firmwareError(CUSTOM_ERR_TIMER_OVERFLOW, "setHardwareUsTimer() too far: %d", deltaTimeUs);
		// let's make this look special and NOT toggle enginePins.debugSetTimer
		return;
	}

	if (GPTDEVICE.state == GPT_ONESHOT) {
		gptStopTimerI(&GPTDEVICE);
	}
	if (GPTDEVICE.state != GPT_READY) {
		firmwareError(CUSTOM_HW_TIMER, "HW timer state %d/%d", GPTDEVICE.state, setHwTimerCounter);
		// let's make this look special and NOT toggle enginePins.debugSetTimer
		return;
	}
	if (hasFirmwareError()) {
		// let's make this look special and NOT toggle enginePins.debugSetTimer
		return;
	}
	gptStartOneShotI(&GPTDEVICE, deltaTimeUs);

	lastSetTimerTimeNt = getTimeNowNt();
	lastSetTimerValue = deltaTimeUs;
	isTimerPending = TRUE;
	timerRestartCounter++;
	enginePins.debugSetTimer.setValue(0);
}

static void hwTimerCallback(GPTDriver *gptp) {
	(void)gptp;
	enginePins.debugTimerCallback.setValue(1);
	timerCallbackCounter++;
	if (globalTimerCallback == NULL) {
		firmwareError(CUSTOM_ERR_NULL_TIMER_CALLBACK, "NULL globalTimerCallback");
		return;
	}
	isTimerPending = false;

	uint32_t before = getTimeNowLowerNt();
	globalTimerCallback(NULL);
	uint32_t precisionCallbackDuration = getTimeNowLowerNt() - before;
	if (precisionCallbackDuration > maxPrecisionCallbackDuration) {
		maxPrecisionCallbackDuration = precisionCallbackDuration;
	}
	enginePins.debugTimerCallback.setValue(0);
}

class MicrosecondTimerWatchdogController : public PeriodicTimerController {
	void PeriodicTask() override {
		efitick_t nowNt = getTimeNowNt();
		if (nowNt >= lastSetTimerTimeNt + 2 * CORE_CLOCK) {
			strcpy(buff, "no_event");
			itoa10(&buff[8], lastSetTimerValue);
			firmwareError(CUSTOM_ERR_SCHEDULING_ERROR, buff);
			return;
		}

		msg = isTimerPending ? "No_cb too long" : "Timer not awhile";
		// 2 seconds of inactivity would not look right
		efiAssertVoid(CUSTOM_ERR_6682, nowNt < lastSetTimerTimeNt + 2 * CORE_CLOCK, msg);
	}

	int getPeriodMs() override {
		return 500;
	}
};

static MicrosecondTimerWatchdogController watchdogControllerInstance;

/*
 * The specific 1MHz frequency is important here since 'setHardwareUsTimer' method takes microsecond parameter
 * For any arbitrary frequency to work we would need an additional layer of conversion.
 */
static constexpr GPTConfig gpt5cfg = { 1000000, /* 1 MHz timer clock.*/
		hwTimerCallback, /* Timer callback.*/
0, 0 };

static scheduling_s watchDogBuddy;

static void watchDogBuddyCallback(void *arg) {
	(void)arg;
	/**
	 * 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->executor.scheduleForLater(&watchDogBuddy, MS2US(1000), watchDogBuddyCallback);
}

static volatile bool testSchedulingHappened = false;
static efitimems_t testSchedulingStart;

static void timerValidationCallback(void *arg) {
	(void)arg;

	testSchedulingHappened = true;
	efitimems_t actualTimeSinceScheduling = (currentTimeMillis() - testSchedulingStart);

	if (absI(actualTimeSinceScheduling - TEST_CALLBACK_DELAY) > TEST_CALLBACK_DELAY * TIMER_PRECISION_THRESHOLD) {
		firmwareError(CUSTOM_ERR_TIMER_TEST_CALLBACK_WRONG_TIME, "hwTimer broken precision");
	}
}

/**
 * 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;
	}
	testSchedulingStart = currentTimeMillis();

	// to save RAM let's use 'watchDogBuddy' here once before we enable watchdog
	engine->executor.scheduleForLater(&watchDogBuddy, MS2US(TEST_CALLBACK_DELAY), timerValidationCallback);

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

void initMicrosecondTimer(void) {

	gptStart(&GPTDEVICE, &gpt5cfg);
	efiAssertVoid(CUSTOM_ERR_TIMER_STATE, GPTDEVICE.state == GPT_READY, "hw state");
	hwStarted = true;

	lastSetTimerTimeNt = getTimeNowNt();

	validateHardwareTimer();

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

#endif /* EFI_PROD_CODE */