/*
 * TI tlc4541 ADC Driver
 *
 * Copyright (C) 2017 Phil Reid
 *
 * Datasheets can be found here:
 * http://www.ti.com/lit/gpn/tlc3541
 * http://www.ti.com/lit/gpn/tlc4541
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * The tlc4541 requires 24 clock cycles to start a transfer.
 * Conversion then takes 2.94us to complete before data is ready
 * Data is returned MSB first.
 */

#include <linux/delay.h>
#include <linux/device.h>
#include <linux/err.h>
#include <linux/interrupt.h>
#include <linux/iio/iio.h>
#include <linux/iio/sysfs.h>
#include <linux/iio/buffer.h>
#include <linux/iio/trigger_consumer.h>
#include <linux/iio/triggered_buffer.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/regulator/consumer.h>
#include <linux/slab.h>
#include <linux/spi/spi.h>
#include <linux/sysfs.h>

struct tlc4541_state {
	struct spi_device               *spi;
	struct regulator                *reg;
	struct spi_transfer             scan_single_xfer[3];
	struct spi_message              scan_single_msg;

	/*
	 * DMA (thus cache coherency maintenance) requires the
	 * transfer buffers to live in their own cache lines.
	 * 2 bytes data + 6 bytes padding + 8 bytes timestamp when
	 * call iio_push_to_buffers_with_timestamp.
	 */
	__be16                          rx_buf[8] ____cacheline_aligned;
};

struct tlc4541_chip_info {
	const struct iio_chan_spec *channels;
	unsigned int num_channels;
};

enum tlc4541_id {
	TLC3541,
	TLC4541,
};

#define TLC4541_V_CHAN(bits, bitshift) {                              \
		.type = IIO_VOLTAGE,                                  \
		.info_mask_separate       = BIT(IIO_CHAN_INFO_RAW),   \
		.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE), \
		.scan_type = {                                        \
			.sign = 'u',                                  \
			.realbits = (bits),                           \
			.storagebits = 16,                            \
			.shift = (bitshift),                          \
			.endianness = IIO_BE,                         \
		},                                                    \
	}

#define DECLARE_TLC4541_CHANNELS(name, bits, bitshift) \
const struct iio_chan_spec name ## _channels[] = { \
	TLC4541_V_CHAN(bits, bitshift), \
	IIO_CHAN_SOFT_TIMESTAMP(1), \
}

static DECLARE_TLC4541_CHANNELS(tlc3541, 14, 2);
static DECLARE_TLC4541_CHANNELS(tlc4541, 16, 0);

static const struct tlc4541_chip_info tlc4541_chip_info[] = {
	[TLC3541] = {
		.channels = tlc3541_channels,
		.num_channels = ARRAY_SIZE(tlc3541_channels),
	},
	[TLC4541] = {
		.channels = tlc4541_channels,
		.num_channels = ARRAY_SIZE(tlc4541_channels),
	},
};

static irqreturn_t tlc4541_trigger_handler(int irq, void *p)
{
	struct iio_poll_func *pf = p;
	struct iio_dev *indio_dev = pf->indio_dev;
	struct tlc4541_state *st = iio_priv(indio_dev);
	int ret;

	ret = spi_sync(st->spi, &st->scan_single_msg);
	if (ret < 0)
		goto done;

	iio_push_to_buffers_with_timestamp(indio_dev, st->rx_buf,
					   iio_get_time_ns(indio_dev));

done:
	iio_trigger_notify_done(indio_dev->trig);
	return IRQ_HANDLED;
}

static int tlc4541_get_range(struct tlc4541_state *st)
{
	int vref;

	vref = regulator_get_voltage(st->reg);
	if (vref < 0)
		return vref;

	vref /= 1000;

	return vref;
}

static int tlc4541_read_raw(struct iio_dev *indio_dev,
			    struct iio_chan_spec const *chan,
			    int *val,
			    int *val2,
			    long m)
{
	int ret = 0;
	struct tlc4541_state *st = iio_priv(indio_dev);

	switch (m) {
	case IIO_CHAN_INFO_RAW:
		ret = iio_device_claim_direct_mode(indio_dev);
		if (ret)
			return ret;
		ret = spi_sync(st->spi, &st->scan_single_msg);
		iio_device_release_direct_mode(indio_dev);
		if (ret < 0)
			return ret;
		*val = be16_to_cpu(st->rx_buf[0]);
		*val = *val >> chan->scan_type.shift;
		*val &= GENMASK(chan->scan_type.realbits - 1, 0);
		return IIO_VAL_INT;
	case IIO_CHAN_INFO_SCALE:
		ret = tlc4541_get_range(st);
		if (ret < 0)
			return ret;
		*val = ret;
		*val2 = chan->scan_type.realbits;
		return IIO_VAL_FRACTIONAL_LOG2;
	}
	return -EINVAL;
}

static const struct iio_info tlc4541_info = {
	.read_raw = &tlc4541_read_raw,
};

static int tlc4541_probe(struct spi_device *spi)
{
	struct tlc4541_state *st;
	struct iio_dev *indio_dev;
	const struct tlc4541_chip_info *info;
	int ret;
	int8_t device_init = 0;

	indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*st));
	if (indio_dev == NULL)
		return -ENOMEM;

	st = iio_priv(indio_dev);

	spi_set_drvdata(spi, indio_dev);

	st->spi = spi;

	info = &tlc4541_chip_info[spi_get_device_id(spi)->driver_data];

	indio_dev->name = spi_get_device_id(spi)->name;
	indio_dev->dev.parent = &spi->dev;
	indio_dev->modes = INDIO_DIRECT_MODE;
	indio_dev->channels = info->channels;
	indio_dev->num_channels = info->num_channels;
	indio_dev->info = &tlc4541_info;

	/* perform reset */
	spi_write(spi, &device_init, 1);

	/* Setup default message */
	st->scan_single_xfer[0].rx_buf = &st->rx_buf[0];
	st->scan_single_xfer[0].len = 3;
	st->scan_single_xfer[1].delay_usecs = 3;
	st->scan_single_xfer[2].rx_buf = &st->rx_buf[0];
	st->scan_single_xfer[2].len = 2;

	spi_message_init_with_transfers(&st->scan_single_msg,
					st->scan_single_xfer, 3);

	st->reg = devm_regulator_get(&spi->dev, "vref");
	if (IS_ERR(st->reg))
		return PTR_ERR(st->reg);

	ret = regulator_enable(st->reg);
	if (ret)
		return ret;

	ret = iio_triggered_buffer_setup(indio_dev, NULL,
			&tlc4541_trigger_handler, NULL);
	if (ret)
		goto error_disable_reg;

	ret = iio_device_register(indio_dev);
	if (ret)
		goto error_cleanup_buffer;

	return 0;

error_cleanup_buffer:
	iio_triggered_buffer_cleanup(indio_dev);
error_disable_reg:
	regulator_disable(st->reg);

	return ret;
}

static int tlc4541_remove(struct spi_device *spi)
{
	struct iio_dev *indio_dev = spi_get_drvdata(spi);
	struct tlc4541_state *st = iio_priv(indio_dev);

	iio_device_unregister(indio_dev);
	iio_triggered_buffer_cleanup(indio_dev);
	regulator_disable(st->reg);

	return 0;
}

#ifdef CONFIG_OF
static const struct of_device_id tlc4541_dt_ids[] = {
	{ .compatible = "ti,tlc3541", },
	{ .compatible = "ti,tlc4541", },
	{}
};
MODULE_DEVICE_TABLE(of, tlc4541_dt_ids);
#endif

static const struct spi_device_id tlc4541_id[] = {
	{"tlc3541", TLC3541},
	{"tlc4541", TLC4541},
	{}
};
MODULE_DEVICE_TABLE(spi, tlc4541_id);

static struct spi_driver tlc4541_driver = {
	.driver = {
		.name   = "tlc4541",
		.of_match_table = of_match_ptr(tlc4541_dt_ids),
	},
	.probe          = tlc4541_probe,
	.remove         = tlc4541_remove,
	.id_table       = tlc4541_id,
};
module_spi_driver(tlc4541_driver);

MODULE_AUTHOR("Phil Reid <preid@electromag.com.au>");
MODULE_DESCRIPTION("Texas Instruments TLC4541 ADC");
MODULE_LICENSE("GPL v2");