uc_kinetis_clock.cpp

Go to the documentation of this file.

/*
 * Copyright (C) 2014, 2018 Pavel Kirienko <pavel.kirienko@gmail.com>
 * Kinetis Port Author David Sidrane <david_s5@nscdg.com>
 */

#include <uavcan_kinetis/clock.hpp>
#include <uavcan_kinetis/thread.hpp>
#include "internal.hpp"

#if UAVCAN_KINETIS_TIMER_NUMBER
# include <cassert>
# include <math.h>

/*
 * Timer instance
 * todo:Consider using Lifetime Timer support
 */
# define TIMX_IRQHandler         UAVCAN_KINETIS_GLUE3(PIT, UAVCAN_KINETIS_TIMER_NUMBER, _IRQHandler)
# define TIMX                    (KINETIS_PIT_BASE + (UAVCAN_KINETIS_TIMER_NUMBER << 4))
# define TMR_REG(o)              (TIMX + (o))
# define TIMX_INPUT_CLOCK        BOARD_BUS_FREQ
# define TIMX_INTERRUPT_FREQ     16
# define TIMX_IRQn               UAVCAN_KINETIS_GLUE2(KINETIS_IRQ_PITCH, UAVCAN_KINETIS_TIMER_NUMBER)

# if UAVCAN_KINETIS_TIMER_NUMBER >= 0 && UAVCAN_KINETIS_TIMER_NUMBER <= 3
#  define KINETIS_PIT_LDVAL_OFFSET KINETIS_PIT_LDVAL0_OFFSET
#  define KINETIS_PIT_CVAL_OFFSET  KINETIS_PIT_CVAL0_OFFSET
#  define KINETIS_PIT_TCTRL_OFFSET KINETIS_PIT_TCTRL0_OFFSET
#  define KINETIS_PIT_TFLG_OFFSET  KINETIS_PIT_TFLG0_OFFSET
# else
#  error "This UAVCAN_KINETIS_TIMER_NUMBER is not supported yet"
# endif

extern "C" UAVCAN_KINETIS_IRQ_HANDLER(TIMX_IRQHandler);

namespace uavcan_kinetis
{
namespace clock
{
namespace
{

const uavcan::uint32_t CountsPerPeriod = (TIMX_INPUT_CLOCK / TIMX_INTERRUPT_FREQ);
const uavcan::uint32_t CountsPerUs = (TIMX_INPUT_CLOCK / 1000000);
const uavcan::uint32_t USecPerOverflow = (1000000 / TIMX_INTERRUPT_FREQ);

Mutex mutex;

bool initialized = false;

bool utc_set = false;
bool utc_locked = false;
uavcan::uint32_t utc_jump_cnt = 0;
UtcSyncParams utc_sync_params;
float utc_prev_adj = 0;
float utc_rel_rate_ppm = 0;
float utc_rel_rate_error_integral = 0;
uavcan::int32_t utc_accumulated_correction_nsec = 0;
uavcan::int32_t utc_correction_nsec_per_overflow = 0;
uavcan::MonotonicTime prev_utc_adj_at;

uavcan::uint64_t time_mono = 0;
uavcan::uint64_t time_utc = 0;

}

void init()
{
    CriticalSectionLocker lock;

    if (initialized) {
        return;
    }

    initialized = true;

    // Attach IRQ
    irq_attach(TIMX_IRQn, &TIMX_IRQHandler, NULL);

    // Power-on Clock
    modifyreg32(KINETIS_SIM_SCGC6, 0, SIM_SCGC6_PIT);

    // Enable module
    putreg32(0, KINETIS_PIT_MCR);

    // Start the timer

    putreg32(CountsPerPeriod - 1, TMR_REG(KINETIS_PIT_LDVAL_OFFSET));
    putreg32(PIT_TCTRL_TEN | PIT_TCTRL_TIE, TMR_REG(KINETIS_PIT_TCTRL_OFFSET));     // Start

    // Prioritize and Enable  IRQ

#if 0
    // This has to be off or uses the default priority
    // Without the ability to point the vector
    // Directly to this ISR this will reenter the
    // exception_common and cause the interrupt
    // Stack pointer to be reset
    up_prioritize_irq(TIMX_IRQn, NVIC_SYSH_HIGH_PRIORITY);
#endif
    up_enable_irq(TIMX_IRQn);
}

void setUtc(uavcan::UtcTime time)
{
    MutexLocker mlocker(mutex);
    UAVCAN_ASSERT(initialized);

    {
        CriticalSectionLocker locker;
        time_utc = time.toUSec();
    }

    utc_set = true;
    utc_locked = false;
    utc_jump_cnt++;
    utc_prev_adj = 0;
    utc_rel_rate_ppm = 0;
}

static uavcan::uint64_t sampleUtcFromCriticalSection()
{
    UAVCAN_ASSERT(initialized);
    UAVCAN_ASSERT(getreg32(TMR_REG(KINETIS_PIT_TCTRL_OFFSET)) & PIT_TCTRL_TIE);

    volatile uavcan::uint64_t time = time_utc;
    volatile uavcan::uint32_t cnt = CountsPerPeriod - getreg32(TMR_REG(KINETIS_PIT_CVAL_OFFSET));

    if (getreg32(TMR_REG(KINETIS_PIT_TFLG_OFFSET)) & PIT_TFLG_TIF) {
        cnt = CountsPerPeriod - getreg32(TMR_REG(KINETIS_PIT_CVAL_OFFSET));
        const uavcan::int32_t add = uavcan::int32_t(USecPerOverflow) +
                        (utc_accumulated_correction_nsec + utc_correction_nsec_per_overflow) / 1000;
        time = uavcan::uint64_t(uavcan::int64_t(time) + add);
    }

    return time + (cnt / CountsPerUs);
}

uavcan::uint64_t getUtcUSecFromCanInterrupt()
{
    return utc_set ? sampleUtcFromCriticalSection() : 0;
}

uavcan::MonotonicTime getMonotonic()
{
    uavcan::uint64_t usec = 0;
    // Scope Critical section
    {
        CriticalSectionLocker locker;

        volatile uavcan::uint64_t time = time_mono;
        volatile uavcan::uint32_t cnt = CountsPerPeriod - getreg32(TMR_REG(KINETIS_PIT_CVAL_OFFSET));

        if (getreg32(TMR_REG(KINETIS_PIT_TFLG_OFFSET)) & PIT_TFLG_TIF) {
            cnt = CountsPerPeriod - getreg32(TMR_REG(KINETIS_PIT_CVAL_OFFSET));
            time += USecPerOverflow;
        }

        usec = time + (cnt / CountsPerUs);

    }     // End Scope Critical section

    return uavcan::MonotonicTime::fromUSec(usec);
}


uavcan::UtcTime getUtc()
{
    if (utc_set) {
        uavcan::uint64_t usec = 0;
        {
            CriticalSectionLocker locker;
            usec = sampleUtcFromCriticalSection();
        }
        return uavcan::UtcTime::fromUSec(usec);
    }

    return uavcan::UtcTime();
}

static float lowpass(float xold, float xnew, float corner, float dt)
{
    const float tau = 1.F / corner;
    return (dt * xnew + tau * xold) / (dt + tau);
}

static void updateRatePID(uavcan::UtcDuration adjustment)
{
    const uavcan::MonotonicTime ts = getMonotonic();
    const float dt = float((ts - prev_utc_adj_at).toUSec()) / 1e6F;
    prev_utc_adj_at = ts;
    const float adj_usec = float(adjustment.toUSec());

    /*
     * Target relative rate in PPM
     * Positive to go faster
     */
    const float target_rel_rate_ppm = adj_usec * utc_sync_params.offset_p;

    /*
     * Current relative rate in PPM
     * Positive if the local clock is faster
     */
    const float new_rel_rate_ppm = (utc_prev_adj - adj_usec) / dt;     // rate error in [usec/sec], which is PPM
    utc_prev_adj = adj_usec;
    utc_rel_rate_ppm = lowpass(utc_rel_rate_ppm, new_rel_rate_ppm, utc_sync_params.rate_error_corner_freq, dt);

    const float rel_rate_error = target_rel_rate_ppm - utc_rel_rate_ppm;

    if (dt > 10) {
        utc_rel_rate_error_integral = 0;

    } else {
        utc_rel_rate_error_integral += rel_rate_error * dt * utc_sync_params.rate_i;
        utc_rel_rate_error_integral =
            uavcan::max(utc_rel_rate_error_integral, -utc_sync_params.max_rate_correction_ppm);
        utc_rel_rate_error_integral =
            uavcan::min(utc_rel_rate_error_integral, utc_sync_params.max_rate_correction_ppm);
    }

    /*
     * Rate controller
     */
    float total_rate_correction_ppm = rel_rate_error + utc_rel_rate_error_integral;
    total_rate_correction_ppm = uavcan::max(total_rate_correction_ppm, -utc_sync_params.max_rate_correction_ppm);
    total_rate_correction_ppm = uavcan::min(total_rate_correction_ppm, utc_sync_params.max_rate_correction_ppm);

    utc_correction_nsec_per_overflow = uavcan::int32_t((USecPerOverflow * 1000) * (total_rate_correction_ppm / 1e6F));

//    syslog("$ adj=%f   rel_rate=%f   rel_rate_eint=%f   tgt_rel_rate=%f   ppm=%f\n",
//              adj_usec, utc_rel_rate_ppm, utc_rel_rate_error_integral, target_rel_rate_ppm,
// total_rate_correction_ppm);
}

void adjustUtc(uavcan::UtcDuration adjustment)
{
    MutexLocker mlocker(mutex);
    UAVCAN_ASSERT(initialized);

    if (adjustment.getAbs() > utc_sync_params.min_jump || !utc_set) {
        const uavcan::int64_t adj_usec = adjustment.toUSec();

        {
            CriticalSectionLocker locker;

            if ((adj_usec < 0) && uavcan::uint64_t(-adj_usec) > time_utc) {
                time_utc = 1;

            } else {
                time_utc = uavcan::uint64_t(uavcan::int64_t(time_utc) + adj_usec);
            }
        }

        utc_set = true;
        utc_locked = false;
        utc_jump_cnt++;
        utc_prev_adj = 0;
        utc_rel_rate_ppm = 0;

    } else {
        updateRatePID(adjustment);

        if (!utc_locked) {
            utc_locked =
                (std::abs(utc_rel_rate_ppm) < utc_sync_params.lock_thres_rate_ppm) &&
                (std::abs(utc_prev_adj) < float(utc_sync_params.lock_thres_offset.toUSec()));
        }
    }
}

float getUtcRateCorrectionPPM()
{
    MutexLocker mlocker(mutex);
    const float rate_correction_mult = float(utc_correction_nsec_per_overflow) / float(USecPerOverflow * 1000);
    return 1e6F * rate_correction_mult;
}

uavcan::uint32_t getUtcJumpCount()
{
    MutexLocker mlocker(mutex);
    return utc_jump_cnt;
}

bool isUtcLocked()
{
    MutexLocker mlocker(mutex);
    return utc_locked;
}

UtcSyncParams getUtcSyncParams()
{
    MutexLocker mlocker(mutex);
    return utc_sync_params;
}

void setUtcSyncParams(const UtcSyncParams &params)
{
    MutexLocker mlocker(mutex);
    // Add some sanity check
    utc_sync_params = params;
}

} // namespace clock

SystemClock &SystemClock::instance()
{
    static union SystemClockStorage {
        uavcan::uint8_t buffer[sizeof(SystemClock)];
        long long _aligner_1;
        long double _aligner_2;
    } storage;

    SystemClock *const ptr = reinterpret_cast<SystemClock *>(storage.buffer);

    if (!clock::initialized) {
        MutexLocker mlocker(clock::mutex);
        clock::init();
        new (ptr)SystemClock();
    }

    return *ptr;
}

} // namespace uavcan_kinetis


/**
 * Timer interrupt handler
 */

extern "C"
UAVCAN_KINETIS_IRQ_HANDLER(TIMX_IRQHandler)
{
    putreg32(PIT_TFLG_TIF, TMR_REG(KINETIS_PIT_TFLG_OFFSET));

    using namespace uavcan_kinetis::clock;
    UAVCAN_ASSERT(initialized);

    time_mono += USecPerOverflow;

    if (utc_set) {
        time_utc += USecPerOverflow;
        utc_accumulated_correction_nsec += utc_correction_nsec_per_overflow;

        if (std::abs(utc_accumulated_correction_nsec) >= 1000) {
            time_utc = uavcan::uint64_t(uavcan::int64_t(time_utc) + utc_accumulated_correction_nsec / 1000);
            utc_accumulated_correction_nsec %= 1000;
        }

        // Correction decay - 1 nsec per 65536 usec
        if (utc_correction_nsec_per_overflow > 0) {
            utc_correction_nsec_per_overflow--;

        } else if (utc_correction_nsec_per_overflow < 0) {
            utc_correction_nsec_per_overflow++;

        } else {
            ;             // Zero
        }
    }

    return 0;
}

#endif