PX4-Autopilot/src/lib/drivers/device/nuttx/SPI.cpp

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/**
 * @file spi.cpp
 *
 * Base class for devices connected via SPI.
 *
 * @todo Work out if caching the mode/frequency would save any time.
 *
 * @todo A separate bus/device abstraction would allow for mixed interrupt-mode
 * and non-interrupt-mode clients to arbitrate for the bus.  As things stand,
 * a bus shared between clients of both kinds is vulnerable to races between
 * the two, where an interrupt-mode client will ignore the lock held by the
 * non-interrupt-mode client.
 */

#include "SPI.hpp"

#include <px4_platform_common/px4_config.h>
#include <nuttx/arch.h>

#ifndef CONFIG_SPI_EXCHANGE
# error This driver requires CONFIG_SPI_EXCHANGE
#endif

namespace device
{

SPI::SPI(uint8_t device_type, const char *name, int bus, uint32_t device, enum spi_mode_e mode, uint32_t frequency) :
	CDev(name, nullptr),
	_device(device),
	_mode(mode),
	_frequency(frequency)
{
	_device_id.devid_s.devtype = device_type;
	// fill in _device_id fields for a SPI device
	_device_id.devid_s.bus_type = DeviceBusType_SPI;
	_device_id.devid_s.bus = bus;
	// Use the 2. LSB byte as SPI address. This is currently 0, but will allow to extend
	// for multiple instances of the same device on a bus, should that ever be required.
	_device_id.devid_s.address = (uint8_t)(device >> 8);

	if (!px4_spi_bus_requires_locking(bus)) {
		_locking_mode = LOCK_NONE;
	}
}

SPI::~SPI()
{
	// XXX no way to let go of the bus...
}

int
SPI::init()
{
	/* attach to the spi bus */
	if (_dev == nullptr) {
		int bus = get_device_bus();

		if (!board_has_bus(BOARD_SPI_BUS, bus)) {
			return -ENOENT;
		}

		_dev = px4_spibus_initialize(bus);
	}

	if (_dev == nullptr) {
		DEVICE_DEBUG("failed to init SPI");
		return -ENOENT;
	}

	/* deselect device to ensure high to low transition of pin select */
	SPI_SELECT(_dev, _device, false);

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

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

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

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

	/* tell the world where we are */
	DEVICE_DEBUG("on SPI bus %d at %"  PRId32 " (%"  PRId32 " KHz)", get_device_bus(), PX4_SPI_DEV_ID(_device),
		     _frequency / 1000);

	return PX4_OK;
}

int
SPI::transfer(uint8_t *send, uint8_t *recv, unsigned len)
{
	int result;

	if ((send == nullptr) && (recv == nullptr)) {
		return -EINVAL;
	}

	LockMode mode = up_interrupt_context() ? LOCK_NONE : _locking_mode;

	/* lock the bus as required */
	switch (mode) {
	default:
	case LOCK_PREEMPTION: {
			irqstate_t state = px4_enter_critical_section();
			result = _transfer(send, recv, len);
			px4_leave_critical_section(state);
		}
		break;

	case LOCK_THREADS:
		SPI_LOCK(_dev, true);
		result = _transfer(send, recv, len);
		SPI_LOCK(_dev, false);
		break;

	case LOCK_NONE:
		result = _transfer(send, recv, len);
		break;
	}

	return result;
}

int
SPI::_transfer(uint8_t *send, uint8_t *recv, unsigned len)
{
	SPI_SETFREQUENCY(_dev, _frequency);
	SPI_SETMODE(_dev, _mode);
	SPI_SETBITS(_dev, 8);
	SPI_SELECT(_dev, _device, true);

	/* do the transfer */
	SPI_EXCHANGE(_dev, send, recv, len);

	/* and clean up */
	SPI_SELECT(_dev, _device, false);

	return PX4_OK;
}

int
SPI::transferhword(uint16_t *send, uint16_t *recv, unsigned len)
{
	int result;

	if ((send == nullptr) && (recv == nullptr)) {
		return -EINVAL;
	}

	LockMode mode = up_interrupt_context() ? LOCK_NONE : _locking_mode;

	/* lock the bus as required */
	switch (mode) {
	default:
	case LOCK_PREEMPTION: {
			irqstate_t state = px4_enter_critical_section();
			result = _transferhword(send, recv, len);
			px4_leave_critical_section(state);
		}
		break;

	case LOCK_THREADS:
		SPI_LOCK(_dev, true);
		result = _transferhword(send, recv, len);
		SPI_LOCK(_dev, false);
		break;

	case LOCK_NONE:
		result = _transferhword(send, recv, len);
		break;
	}

	return result;
}

int
SPI::_transferhword(uint16_t *send, uint16_t *recv, unsigned len)
{
	SPI_SETFREQUENCY(_dev, _frequency);
	SPI_SETMODE(_dev, _mode);
	SPI_SETBITS(_dev, 16);			/* 16 bit transfer */
	SPI_SELECT(_dev, _device, true);

	/* do the transfer */
	SPI_EXCHANGE(_dev, send, recv, len);

	/* and clean up */
	SPI_SELECT(_dev, _device, false);

	return PX4_OK;
}

} // namespace device