microsecond_timer.cpp

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/**
 * @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_task.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_MS 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) {
    criticalAssertVoid(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;
    }
}
 
class MicrosecondTimerWatchdogController : public PeriodicTimerController {
    void PeriodicTask() override {
        efitick_t nowNt = getTimeNowNt();
 
        // 2 seconds of inactivity would not look right
        efiAssertVoid(ObdCode::CUSTOM_TIMER_WATCHDOG, nowNt < lastSetTimerTimeNt + 2 * CORE_CLOCK, "Watchdog: no events for 2 seconds!");
    }
 
    int getPeriodMs() override {
        return 500;
    }
};
 
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->executor.scheduleByTimestampNt("watch", &watchDogBuddy, getTimeNowNt() + MS2NT(1000), watchDogBuddyCallback);
}
 
static volatile bool testSchedulingHappened = false;
static Timer testScheduling;
 
static void timerValidationCallback(void*) {
    testSchedulingHappened = true;
    efitimems_t actualTimeSinceSchedulingMs = 1e3 * testScheduling.getElapsedSeconds();
 
    if (absI(actualTimeSinceSchedulingMs - TEST_CALLBACK_DELAY_MS) > TEST_CALLBACK_DELAY_MS * TIMER_PRECISION_THRESHOLD) {
        firmwareError(ObdCode::CUSTOM_ERR_TIMER_TEST_CALLBACK_WRONG_TIME, "hwTimer broken precision: %ld ms", actualTimeSinceSchedulingMs);
    }
}
 
/**
 * 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->executor.scheduleByTimestampNt(
            "hw-validate",
            &watchDogBuddy,
            getTimeNowNt() + MS2NT(TEST_CALLBACK_DELAY_MS),
            timerValidationCallback);
 
    chThdSleepMilliseconds(TEST_CALLBACK_DELAY_MS + 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 */