/*
 * STMicroelectronics st_lsm6dsx FIFO buffer library driver
 *
 * LSM6DS3/LSM6DS3H/LSM6DSL/LSM6DSM: The FIFO buffer can be configured
 * to store data from gyroscope and accelerometer. Samples are queued
 * without any tag according to a specific pattern based on 'FIFO data sets'
 * (6 bytes each):
 *  - 1st data set is reserved for gyroscope data
 *  - 2nd data set is reserved for accelerometer data
 * The FIFO pattern changes depending on the ODRs and decimation factors
 * assigned to the FIFO data sets. The first sequence of data stored in FIFO
 * buffer contains the data of all the enabled FIFO data sets
 * (e.g. Gx, Gy, Gz, Ax, Ay, Az), then data are repeated depending on the
 * value of the decimation factor and ODR set for each FIFO data set.
 * FIFO supported modes:
 *  - BYPASS: FIFO disabled
 *  - CONTINUOUS: FIFO enabled. When the buffer is full, the FIFO index
 *    restarts from the beginning and the oldest sample is overwritten
 *
 * Copyright 2016 STMicroelectronics Inc.
 *
 * Lorenzo Bianconi <lorenzo.bianconi@st.com>
 * Denis Ciocca <denis.ciocca@st.com>
 *
 * Licensed under the GPL-2.
 */
#include <linux/module.h>
#include <linux/interrupt.h>
#include <linux/irq.h>
#include <linux/iio/kfifo_buf.h>
#include <linux/iio/iio.h>
#include <linux/iio/buffer.h>

#include "st_lsm6dsx.h"

#define ST_LSM6DSX_REG_FIFO_THL_ADDR		0x06
#define ST_LSM6DSX_REG_FIFO_THH_ADDR		0x07
#define ST_LSM6DSX_FIFO_TH_MASK			GENMASK(11, 0)
#define ST_LSM6DSX_REG_FIFO_DEC_GXL_ADDR	0x08
#define ST_LSM6DSX_REG_FIFO_MODE_ADDR		0x0a
#define ST_LSM6DSX_FIFO_MODE_MASK		GENMASK(2, 0)
#define ST_LSM6DSX_FIFO_ODR_MASK		GENMASK(6, 3)
#define ST_LSM6DSX_REG_FIFO_DIFFL_ADDR		0x3a
#define ST_LSM6DSX_FIFO_DIFF_MASK		GENMASK(11, 0)
#define ST_LSM6DSX_FIFO_EMPTY_MASK		BIT(12)
#define ST_LSM6DSX_REG_FIFO_OUTL_ADDR		0x3e

#define ST_LSM6DSX_MAX_FIFO_ODR_VAL		0x08

struct st_lsm6dsx_decimator_entry {
	u8 decimator;
	u8 val;
};

static const
struct st_lsm6dsx_decimator_entry st_lsm6dsx_decimator_table[] = {
	{  0, 0x0 },
	{  1, 0x1 },
	{  2, 0x2 },
	{  3, 0x3 },
	{  4, 0x4 },
	{  8, 0x5 },
	{ 16, 0x6 },
	{ 32, 0x7 },
};

static int st_lsm6dsx_get_decimator_val(u8 val)
{
	const int max_size = ARRAY_SIZE(st_lsm6dsx_decimator_table);
	int i;

	for (i = 0; i < max_size; i++)
		if (st_lsm6dsx_decimator_table[i].decimator == val)
			break;

	return i == max_size ? 0 : st_lsm6dsx_decimator_table[i].val;
}

static void st_lsm6dsx_get_max_min_odr(struct st_lsm6dsx_hw *hw,
				       u16 *max_odr, u16 *min_odr)
{
	struct st_lsm6dsx_sensor *sensor;
	int i;

	*max_odr = 0, *min_odr = ~0;
	for (i = 0; i < ST_LSM6DSX_ID_MAX; i++) {
		sensor = iio_priv(hw->iio_devs[i]);

		if (!(hw->enable_mask & BIT(sensor->id)))
			continue;

		*max_odr = max_t(u16, *max_odr, sensor->odr);
		*min_odr = min_t(u16, *min_odr, sensor->odr);
	}
}

static int st_lsm6dsx_update_decimators(struct st_lsm6dsx_hw *hw)
{
	struct st_lsm6dsx_sensor *sensor;
	u16 max_odr, min_odr, sip = 0;
	int err, i;
	u8 data;

	st_lsm6dsx_get_max_min_odr(hw, &max_odr, &min_odr);

	for (i = 0; i < ST_LSM6DSX_ID_MAX; i++) {
		sensor = iio_priv(hw->iio_devs[i]);

		/* update fifo decimators and sample in pattern */
		if (hw->enable_mask & BIT(sensor->id)) {
			sensor->sip = sensor->odr / min_odr;
			sensor->decimator = max_odr / sensor->odr;
			data = st_lsm6dsx_get_decimator_val(sensor->decimator);
		} else {
			sensor->sip = 0;
			sensor->decimator = 0;
			data = 0;
		}

		err = st_lsm6dsx_write_with_mask(hw,
					ST_LSM6DSX_REG_FIFO_DEC_GXL_ADDR,
					sensor->decimator_mask, data);
		if (err < 0)
			return err;

		sip += sensor->sip;
	}
	hw->sip = sip;

	return 0;
}

static int st_lsm6dsx_set_fifo_mode(struct st_lsm6dsx_hw *hw,
				    enum st_lsm6dsx_fifo_mode fifo_mode)
{
	u8 data;
	int err;

	switch (fifo_mode) {
	case ST_LSM6DSX_FIFO_BYPASS:
		data = fifo_mode;
		break;
	case ST_LSM6DSX_FIFO_CONT:
		data = (ST_LSM6DSX_MAX_FIFO_ODR_VAL <<
			__ffs(ST_LSM6DSX_FIFO_ODR_MASK)) | fifo_mode;
		break;
	default:
		return -EINVAL;
	}

	err = hw->tf->write(hw->dev, ST_LSM6DSX_REG_FIFO_MODE_ADDR,
			    sizeof(data), &data);
	if (err < 0)
		return err;

	hw->fifo_mode = fifo_mode;

	return 0;
}

int st_lsm6dsx_update_watermark(struct st_lsm6dsx_sensor *sensor, u16 watermark)
{
	u16 fifo_watermark = ~0, cur_watermark, sip = 0;
	struct st_lsm6dsx_hw *hw = sensor->hw;
	struct st_lsm6dsx_sensor *cur_sensor;
	__le16 wdata;
	int i, err;
	u8 data;

	for (i = 0; i < ST_LSM6DSX_ID_MAX; i++) {
		cur_sensor = iio_priv(hw->iio_devs[i]);

		if (!(hw->enable_mask & BIT(cur_sensor->id)))
			continue;

		cur_watermark = (cur_sensor == sensor) ? watermark
						       : cur_sensor->watermark;

		fifo_watermark = min_t(u16, fifo_watermark, cur_watermark);
		sip += cur_sensor->sip;
	}

	if (!sip)
		return 0;

	fifo_watermark = max_t(u16, fifo_watermark, sip);
	fifo_watermark = (fifo_watermark / sip) * sip;
	fifo_watermark = fifo_watermark * ST_LSM6DSX_SAMPLE_DEPTH;

	mutex_lock(&hw->lock);

	err = hw->tf->read(hw->dev, ST_LSM6DSX_REG_FIFO_THH_ADDR,
			   sizeof(data), &data);
	if (err < 0)
		goto out;

	fifo_watermark = ((data << 8) & ~ST_LSM6DSX_FIFO_TH_MASK) |
			 (fifo_watermark & ST_LSM6DSX_FIFO_TH_MASK);

	wdata = cpu_to_le16(fifo_watermark);
	err = hw->tf->write(hw->dev, ST_LSM6DSX_REG_FIFO_THL_ADDR,
			    sizeof(wdata), (u8 *)&wdata);
out:
	mutex_unlock(&hw->lock);

	return err < 0 ? err : 0;
}

/**
 * st_lsm6dsx_read_fifo() - LSM6DS3-LSM6DS3H-LSM6DSL-LSM6DSM read FIFO routine
 * @hw: Pointer to instance of struct st_lsm6dsx_hw.
 *
 * Read samples from the hw FIFO and push them to IIO buffers.
 *
 * Return: Number of bytes read from the FIFO
 */
static int st_lsm6dsx_read_fifo(struct st_lsm6dsx_hw *hw)
{
	u16 fifo_len, pattern_len = hw->sip * ST_LSM6DSX_SAMPLE_SIZE;
	int err, acc_sip, gyro_sip, read_len, samples, offset;
	struct st_lsm6dsx_sensor *acc_sensor, *gyro_sensor;
	s64 acc_ts, acc_delta_ts, gyro_ts, gyro_delta_ts;
	u8 iio_buff[ALIGN(ST_LSM6DSX_SAMPLE_SIZE, sizeof(s64)) + sizeof(s64)];
	u8 buff[pattern_len];
	__le16 fifo_status;

	err = hw->tf->read(hw->dev, ST_LSM6DSX_REG_FIFO_DIFFL_ADDR,
			   sizeof(fifo_status), (u8 *)&fifo_status);
	if (err < 0)
		return err;

	if (fifo_status & cpu_to_le16(ST_LSM6DSX_FIFO_EMPTY_MASK))
		return 0;

	fifo_len = (le16_to_cpu(fifo_status) & ST_LSM6DSX_FIFO_DIFF_MASK) *
		   ST_LSM6DSX_CHAN_SIZE;
	samples = fifo_len / ST_LSM6DSX_SAMPLE_SIZE;
	fifo_len = (fifo_len / pattern_len) * pattern_len;

	/*
	 * compute delta timestamp between two consecutive samples
	 * in order to estimate queueing time of data generated
	 * by the sensor
	 */
	acc_sensor = iio_priv(hw->iio_devs[ST_LSM6DSX_ID_ACC]);
	acc_ts = acc_sensor->ts - acc_sensor->delta_ts;
	acc_delta_ts = div_s64(acc_sensor->delta_ts * acc_sensor->decimator,
			       samples);

	gyro_sensor = iio_priv(hw->iio_devs[ST_LSM6DSX_ID_GYRO]);
	gyro_ts = gyro_sensor->ts - gyro_sensor->delta_ts;
	gyro_delta_ts = div_s64(gyro_sensor->delta_ts * gyro_sensor->decimator,
				samples);

	for (read_len = 0; read_len < fifo_len; read_len += pattern_len) {
		err = hw->tf->read(hw->dev, ST_LSM6DSX_REG_FIFO_OUTL_ADDR,
				   sizeof(buff), buff);
		if (err < 0)
			return err;

		/*
		 * Data are written to the FIFO with a specific pattern
		 * depending on the configured ODRs. The first sequence of data
		 * stored in FIFO contains the data of all enabled sensors
		 * (e.g. Gx, Gy, Gz, Ax, Ay, Az), then data are repeated
		 * depending on the value of the decimation factor set for each
		 * sensor.
		 *
		 * Supposing the FIFO is storing data from gyroscope and
		 * accelerometer at different ODRs:
		 *   - gyroscope ODR = 208Hz, accelerometer ODR = 104Hz
		 * Since the gyroscope ODR is twice the accelerometer one, the
		 * following pattern is repeated every 9 samples:
		 *   - Gx, Gy, Gz, Ax, Ay, Az, Gx, Gy, Gz
		 */
		gyro_sip = gyro_sensor->sip;
		acc_sip = acc_sensor->sip;
		offset = 0;

		while (acc_sip > 0 || gyro_sip > 0) {
			if (gyro_sip-- > 0) {
				memcpy(iio_buff, &buff[offset],
				       ST_LSM6DSX_SAMPLE_SIZE);
				iio_push_to_buffers_with_timestamp(
					hw->iio_devs[ST_LSM6DSX_ID_GYRO],
					iio_buff, gyro_ts);
				offset += ST_LSM6DSX_SAMPLE_SIZE;
				gyro_ts += gyro_delta_ts;
			}

			if (acc_sip-- > 0) {
				memcpy(iio_buff, &buff[offset],
				       ST_LSM6DSX_SAMPLE_SIZE);
				iio_push_to_buffers_with_timestamp(
					hw->iio_devs[ST_LSM6DSX_ID_ACC],
					iio_buff, acc_ts);
				offset += ST_LSM6DSX_SAMPLE_SIZE;
				acc_ts += acc_delta_ts;
			}
		}
	}

	return read_len;
}

static int st_lsm6dsx_flush_fifo(struct st_lsm6dsx_hw *hw)
{
	int err;

	mutex_lock(&hw->fifo_lock);

	st_lsm6dsx_read_fifo(hw);
	err = st_lsm6dsx_set_fifo_mode(hw, ST_LSM6DSX_FIFO_BYPASS);

	mutex_unlock(&hw->fifo_lock);

	return err;
}

static int st_lsm6dsx_update_fifo(struct iio_dev *iio_dev, bool enable)
{
	struct st_lsm6dsx_sensor *sensor = iio_priv(iio_dev);
	struct st_lsm6dsx_hw *hw = sensor->hw;
	int err;

	if (hw->fifo_mode != ST_LSM6DSX_FIFO_BYPASS) {
		err = st_lsm6dsx_flush_fifo(hw);
		if (err < 0)
			return err;
	}

	if (enable) {
		err = st_lsm6dsx_sensor_enable(sensor);
		if (err < 0)
			return err;
	} else {
		err = st_lsm6dsx_sensor_disable(sensor);
		if (err < 0)
			return err;
	}

	err = st_lsm6dsx_update_decimators(hw);
	if (err < 0)
		return err;

	err = st_lsm6dsx_update_watermark(sensor, sensor->watermark);
	if (err < 0)
		return err;

	if (hw->enable_mask) {
		err = st_lsm6dsx_set_fifo_mode(hw, ST_LSM6DSX_FIFO_CONT);
		if (err < 0)
			return err;

		/*
		 * store enable buffer timestamp as reference to compute
		 * first delta timestamp
		 */
		sensor->ts = iio_get_time_ns(iio_dev);
	}

	return 0;
}

static irqreturn_t st_lsm6dsx_handler_irq(int irq, void *private)
{
	struct st_lsm6dsx_hw *hw = private;
	struct st_lsm6dsx_sensor *sensor;
	int i;

	if (!hw->sip)
		return IRQ_NONE;

	for (i = 0; i < ST_LSM6DSX_ID_MAX; i++) {
		sensor = iio_priv(hw->iio_devs[i]);

		if (sensor->sip > 0) {
			s64 timestamp;

			timestamp = iio_get_time_ns(hw->iio_devs[i]);
			sensor->delta_ts = timestamp - sensor->ts;
			sensor->ts = timestamp;
		}
	}

	return IRQ_WAKE_THREAD;
}

static irqreturn_t st_lsm6dsx_handler_thread(int irq, void *private)
{
	struct st_lsm6dsx_hw *hw = private;
	int count;

	mutex_lock(&hw->fifo_lock);
	count = st_lsm6dsx_read_fifo(hw);
	mutex_unlock(&hw->fifo_lock);

	return !count ? IRQ_NONE : IRQ_HANDLED;
}

static int st_lsm6dsx_buffer_preenable(struct iio_dev *iio_dev)
{
	return st_lsm6dsx_update_fifo(iio_dev, true);
}

static int st_lsm6dsx_buffer_postdisable(struct iio_dev *iio_dev)
{
	return st_lsm6dsx_update_fifo(iio_dev, false);
}

static const struct iio_buffer_setup_ops st_lsm6dsx_buffer_ops = {
	.preenable = st_lsm6dsx_buffer_preenable,
	.postdisable = st_lsm6dsx_buffer_postdisable,
};

int st_lsm6dsx_fifo_setup(struct st_lsm6dsx_hw *hw)
{
	struct iio_buffer *buffer;
	unsigned long irq_type;
	int i, err;

	irq_type = irqd_get_trigger_type(irq_get_irq_data(hw->irq));

	switch (irq_type) {
	case IRQF_TRIGGER_HIGH:
	case IRQF_TRIGGER_RISING:
		break;
	default:
		dev_info(hw->dev, "mode %lx unsupported\n", irq_type);
		return -EINVAL;
	}

	err = devm_request_threaded_irq(hw->dev, hw->irq,
					st_lsm6dsx_handler_irq,
					st_lsm6dsx_handler_thread,
					irq_type | IRQF_ONESHOT,
					"lsm6dsx", hw);
	if (err) {
		dev_err(hw->dev, "failed to request trigger irq %d\n",
			hw->irq);
		return err;
	}

	for (i = 0; i < ST_LSM6DSX_ID_MAX; i++) {
		buffer = devm_iio_kfifo_allocate(hw->dev);
		if (!buffer)
			return -ENOMEM;

		iio_device_attach_buffer(hw->iio_devs[i], buffer);
		hw->iio_devs[i]->modes |= INDIO_BUFFER_SOFTWARE;
		hw->iio_devs[i]->setup_ops = &st_lsm6dsx_buffer_ops;
	}

	return 0;
}