I2C.cpp

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/**
 * @file i2c.cpp
 *
 * Base class for devices attached via the I2C bus.
 *
 * @todo Bus frequency changes; currently we do nothing with the value
 *       that is supplied.  Should we just depend on the bus knowing?
 */

#include "I2C.hpp"

namespace device
{
/*
 *  N.B. By defaulting the value of _bus_clocks to non Zero
 *  All calls to init() will NOT set the buss frequency
 */

unsigned int I2C::_bus_clocks[BOARD_NUMBER_I2C_BUSES] = BOARD_I2C_BUS_CLOCK_INIT;

I2C::I2C(const char *name, const char *devname, const int bus, const uint16_t address, const uint32_t frequency) :
    CDev(name, devname),
    _frequency(frequency)
{
    DEVICE_DEBUG("I2C::I2C name = %s devname = %s", name, devname);
    // fill in _device_id fields for a I2C device
    _device_id.devid_s.bus_type = DeviceBusType_I2C;
    _device_id.devid_s.bus = bus;
    _device_id.devid_s.address = address;
    // devtype needs to be filled in by the driver
    _device_id.devid_s.devtype = 0;
}

I2C::~I2C()
{
    if (_dev) {
        px4_i2cbus_uninitialize(_dev);
        _dev = nullptr;
    }
}

int
I2C::set_bus_clock(unsigned bus, unsigned clock_hz)
{
    int index = bus - 1;

    if (index < 0 || index >= static_cast<int>(sizeof(_bus_clocks) / sizeof(_bus_clocks[0]))) {
        return -EINVAL;
    }

    if (_bus_clocks[index] > 0) {
        // DEVICE_DEBUG("overriding clock of %u with %u Hz\n", _bus_clocks[index], clock_hz);
    }

    _bus_clocks[index] = clock_hz;

    return OK;
}

int
I2C::init()
{
    int ret = PX4_ERROR;
    unsigned bus_index;

    // attach to the i2c bus
    _dev = px4_i2cbus_initialize(get_device_bus());

    if (_dev == nullptr) {
        DEVICE_DEBUG("failed to init I2C");
        ret = -ENOENT;
        goto out;
    }

    // the above call fails for a non-existing bus index,
    // so the index math here is safe.
    bus_index = get_device_bus() - 1;

    // abort if the max frequency we allow (the frequency we ask)
    // is smaller than the bus frequency
    if (_bus_clocks[bus_index] > _frequency) {
        (void)px4_i2cbus_uninitialize(_dev);
        _dev = nullptr;
        DEVICE_LOG("FAIL: too slow for bus #%u: %u KHz, device max: %u KHz)",
               get_device_bus(), _bus_clocks[bus_index] / 1000, _frequency / 1000);
        ret = -EINVAL;
        goto out;
    }

    // set frequency for this instance once to the bus speed
    // the bus speed is the maximum supported by all devices on the bus,
    // as we have to prioritize performance over compatibility.
    // If a new device requires a lower clock speed, this has to be
    // manually set via "fmu i2c <bus> <clock>" before starting any
    // drivers.
    // This is necessary as automatically lowering the bus speed
    // for maximum compatibility could induce timing issues on
    // critical sensors the adopter might be unaware of.

    // set the bus frequency on the first access if it has
    // not been set yet
    if (_bus_clocks[bus_index] == 0) {
        _bus_clocks[bus_index] = _frequency;
    }

    // call the probe function to check whether the device is present
    ret = probe();

    if (ret != OK) {
        DEVICE_DEBUG("probe failed");
        goto out;
    }

    // do base class init, which will create device node, etc
    ret = CDev::init();

    if (ret != OK) {
        DEVICE_DEBUG("cdev init failed");
        goto out;
    }

    // tell the world where we are
    DEVICE_LOG("on I2C bus %d at 0x%02x (bus: %u KHz, max: %u KHz)",
           get_device_bus(), get_device_address(), _bus_clocks[bus_index] / 1000, _frequency / 1000);

out:

    if ((ret != OK) && (_dev != nullptr)) {
        px4_i2cbus_uninitialize(_dev);
        _dev = nullptr;
    }

    return ret;
}

int
I2C::transfer(const uint8_t *send, const unsigned send_len, uint8_t *recv, const unsigned recv_len)
{
    px4_i2c_msg_t msgv[2];
    unsigned msgs;
    int ret = PX4_ERROR;
    unsigned retry_count = 0;

    if (_dev == nullptr) {
        PX4_ERR("I2C device not opened");
        return 1;
    }

    do {
        DEVICE_DEBUG("transfer out %p/%u  in %p/%u", send, send_len, recv, recv_len);
        msgs = 0;

        if (send_len > 0) {
            msgv[msgs].frequency = _bus_clocks[get_device_bus() - 1];
            msgv[msgs].addr = get_device_address();
            msgv[msgs].flags = 0;
            msgv[msgs].buffer = const_cast<uint8_t *>(send);
            msgv[msgs].length = send_len;
            msgs++;
        }

        if (recv_len > 0) {
            msgv[msgs].frequency = _bus_clocks[get_device_bus() - 1];
            msgv[msgs].addr = get_device_address();
            msgv[msgs].flags = I2C_M_READ;
            msgv[msgs].buffer = recv;
            msgv[msgs].length = recv_len;
            msgs++;
        }

        if (msgs == 0) {
            return -EINVAL;
        }

        ret = I2C_TRANSFER(_dev, &msgv[0], msgs);

        /* success */
        if (ret == PX4_OK) {
            break;
        }

        /* if we have already retried once, or we are going to give up, then reset the bus */
        if ((retry_count >= 1) || (retry_count >= _retries)) {
            I2C_RESET(_dev);
        }

    } while (retry_count++ < _retries);

    return ret;
}

} // namespace device