uc_stm32_clock.cpp

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/*
 * Copyright (C) 2014 Pavel Kirienko <pavel.kirienko@gmail.com>
 */

#include <uavcan_stm32/clock.hpp>
#include <uavcan_stm32/thread.hpp>
#include "internal.hpp"

#if UAVCAN_STM32_TIMER_NUMBER

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

/*
 * Timer instance
 */
# if UAVCAN_STM32_NUTTX
#  define TIMX                    UAVCAN_STM32_GLUE3(STM32_TIM, UAVCAN_STM32_TIMER_NUMBER, _BASE)
#  define  TMR_REG(o)              (TIMX + (o))
#  define TIMX_INPUT_CLOCK         UAVCAN_STM32_GLUE3(STM32_APB1_TIM, UAVCAN_STM32_TIMER_NUMBER, _CLKIN)

#  define TIMX_IRQn                UAVCAN_STM32_GLUE2(STM32_IRQ_TIM, UAVCAN_STM32_TIMER_NUMBER)
# endif

# if UAVCAN_STM32_TIMER_NUMBER >= 2 && UAVCAN_STM32_TIMER_NUMBER <= 7
#  define TIMX_RCC_ENR           RCC->APB1ENR
#  define TIMX_RCC_RSTR          RCC->APB1RSTR
#  define TIMX_RCC_ENR_MASK      UAVCAN_STM32_GLUE3(RCC_APB1ENR_TIM,  UAVCAN_STM32_TIMER_NUMBER, EN)
#  define TIMX_RCC_RSTR_MASK     UAVCAN_STM32_GLUE3(RCC_APB1RSTR_TIM, UAVCAN_STM32_TIMER_NUMBER, RST)
# else
#  error "This UAVCAN_STM32_TIMER_NUMBER is not supported yet"
# endif

/**
 * UAVCAN_STM32_TIMX_INPUT_CLOCK can be used to manually override the auto-detected timer clock speed.
 * This is useful at least with certain versions of ChibiOS which do not support the bit
 * RCC_DKCFGR.TIMPRE that is available in newer models of STM32. In that case, if TIMPRE is active,
 * the auto-detected value of TIMX_INPUT_CLOCK will be twice lower than the actual clock speed.
 * Read this for additional context: http://www.chibios.com/forum/viewtopic.php?f=35&t=3870
 * A normal way to use the override feature is to provide an alternative macro, e.g.:
 *
 *      -DUAVCAN_STM32_TIMX_INPUT_CLOCK=STM32_HCLK
 *
 * Alternatively, the new clock rate can be specified directly.
 */
# ifdef UAVCAN_STM32_TIMX_INPUT_CLOCK
#  undef TIMX_INPUT_CLOCK
#  define TIMX_INPUT_CLOCK      UAVCAN_STM32_TIMX_INPUT_CLOCK
# endif

extern "C" UAVCAN_STM32_IRQ_HANDLER(TIMX_IRQHandler);

namespace uavcan_stm32
{
namespace clock
{
namespace
{

const uavcan::uint32_t USecPerOverflow = 65536;

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;


# if UAVCAN_STM32_NUTTX

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

    // Power-on and reset
    modifyreg32(STM32_RCC_APB1ENR, 0, TIMX_RCC_ENR_MASK);
    modifyreg32(STM32_RCC_APB1RSTR, 0, TIMX_RCC_RSTR_MASK);
    modifyreg32(STM32_RCC_APB1RSTR, TIMX_RCC_RSTR_MASK, 0);


    // Start the timer
    putreg32(0xFFFF, TMR_REG(STM32_BTIM_ARR_OFFSET));
    putreg16(((TIMX_INPUT_CLOCK / 1000000) - 1), TMR_REG(STM32_BTIM_PSC_OFFSET));
    putreg16(BTIM_CR1_URS, TMR_REG(STM32_BTIM_CR1_OFFSET));
    putreg16(0, TMR_REG(STM32_BTIM_SR_OFFSET));
    putreg16(BTIM_EGR_UG, TMR_REG(STM32_BTIM_EGR_OFFSET)); // Reload immediately
    putreg16(BTIM_DIER_UIE, TMR_REG(STM32_BTIM_DIER_OFFSET));
    putreg16(BTIM_CR1_CEN, TMR_REG(STM32_BTIM_CR1_OFFSET)); // Start

    // Prioritize and Enable  IRQ
// todo: Currently changing the NVIC_SYSH_HIGH_PRIORITY is HARD faulting
// need to investigate
//    up_prioritize_irq(TIMX_IRQn, NVIC_SYSH_HIGH_PRIORITY);
    up_enable_irq(TIMX_IRQn);

# endif
}

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()
{
# if UAVCAN_STM32_NUTTX

    UAVCAN_ASSERT(initialized);
    UAVCAN_ASSERT(getreg16(TMR_REG(STM32_BTIM_DIER_OFFSET)) & BTIM_DIER_UIE);

    volatile uavcan::uint64_t time = time_utc;
    volatile uavcan::uint32_t cnt = getreg16(TMR_REG(STM32_BTIM_CNT_OFFSET));

    if (getreg16(TMR_REG(STM32_BTIM_SR_OFFSET)) & BTIM_SR_UIF) {
        cnt = getreg16(TMR_REG(STM32_BTIM_CNT_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;
# endif
}

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;

# if UAVCAN_STM32_NUTTX

        volatile uavcan::uint32_t cnt = getreg16(TMR_REG(STM32_BTIM_CNT_OFFSET));

        if (getreg16(TMR_REG(STM32_BTIM_SR_OFFSET)) & BTIM_SR_UIF) {
            cnt = getreg16(TMR_REG(STM32_BTIM_CNT_OFFSET));
# endif
            time += USecPerOverflow;
        }

        usec = time + cnt;

# ifndef NDEBUG
        static uavcan::uint64_t prev_usec = 0;      // Self-test
        UAVCAN_ASSERT(prev_usec <= usec);
        (void)prev_usec;
        prev_usec = usec;
# endif
    } // 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_stm32


/**
 * Timer interrupt handler
 */

extern "C"
UAVCAN_STM32_IRQ_HANDLER(TIMX_IRQHandler)
{
    UAVCAN_STM32_IRQ_PROLOGUE();

# if UAVCAN_STM32_NUTTX
    putreg16(0, TMR_REG(STM32_BTIM_SR_OFFSET));
# endif

    using namespace uavcan_stm32::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
        }
    }

    UAVCAN_STM32_IRQ_EPILOGUE();
}

#endif