/*
 * Texas Instruments ADS7950 SPI ADC driver
 *
 * Copyright 2016 David Lechner <david@lechnology.com>
 *
 * Based on iio/ad7923.c:
 * Copyright 2011 Analog Devices Inc
 * Copyright 2012 CS Systemes d'Information
 *
 * And also on hwmon/ads79xx.c
 * Copyright (C) 2013 Texas Instruments Incorporated - http://www.ti.com/
 *	Nishanth Menon
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation version 2.
 *
 * This program is distributed "as is" WITHOUT ANY WARRANTY of any
 * kind, whether express or implied; without even the implied warranty
 * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 */

#include <linux/bitops.h>
#include <linux/device.h>
#include <linux/err.h>
#include <linux/interrupt.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/iio/buffer.h>
#include <linux/iio/iio.h>
#include <linux/iio/sysfs.h>
#include <linux/iio/trigger_consumer.h>
#include <linux/iio/triggered_buffer.h>

#define TI_ADS7950_CR_MANUAL	BIT(12)
#define TI_ADS7950_CR_WRITE	BIT(11)
#define TI_ADS7950_CR_CHAN(ch)	((ch) << 7)
#define TI_ADS7950_CR_RANGE_5V	BIT(6)

#define TI_ADS7950_MAX_CHAN	16

#define TI_ADS7950_TIMESTAMP_SIZE (sizeof(int64_t) / sizeof(__be16))

/* val = value, dec = left shift, bits = number of bits of the mask */
#define TI_ADS7950_EXTRACT(val, dec, bits) \
	(((val) >> (dec)) & ((1 << (bits)) - 1))

struct ti_ads7950_state {
	struct spi_device	*spi;
	struct spi_transfer	ring_xfer[TI_ADS7950_MAX_CHAN + 2];
	struct spi_transfer	scan_single_xfer[3];
	struct spi_message	ring_msg;
	struct spi_message	scan_single_msg;

	struct regulator	*reg;

	unsigned int		settings;

	/*
	 * DMA (thus cache coherency maintenance) requires the
	 * transfer buffers to live in their own cache lines.
	 */
	__be16	rx_buf[TI_ADS7950_MAX_CHAN + TI_ADS7950_TIMESTAMP_SIZE]
							____cacheline_aligned;
	__be16	tx_buf[TI_ADS7950_MAX_CHAN];
};

struct ti_ads7950_chip_info {
	const struct iio_chan_spec *channels;
	unsigned int num_channels;
};

enum ti_ads7950_id {
	TI_ADS7950,
	TI_ADS7951,
	TI_ADS7952,
	TI_ADS7953,
	TI_ADS7954,
	TI_ADS7955,
	TI_ADS7956,
	TI_ADS7957,
	TI_ADS7958,
	TI_ADS7959,
	TI_ADS7960,
	TI_ADS7961,
};

#define TI_ADS7950_V_CHAN(index, bits)				\
{								\
	.type = IIO_VOLTAGE,					\
	.indexed = 1,						\
	.channel = index,					\
	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),		\
	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),	\
	.address = index,					\
	.datasheet_name = "CH##index",				\
	.scan_index = index,					\
	.scan_type = {						\
		.sign = 'u',					\
		.realbits = bits,				\
		.storagebits = 16,				\
		.shift = 12 - (bits),				\
		.endianness = IIO_BE,				\
	},							\
}

#define DECLARE_TI_ADS7950_4_CHANNELS(name, bits) \
const struct iio_chan_spec name ## _channels[] = { \
	TI_ADS7950_V_CHAN(0, bits), \
	TI_ADS7950_V_CHAN(1, bits), \
	TI_ADS7950_V_CHAN(2, bits), \
	TI_ADS7950_V_CHAN(3, bits), \
	IIO_CHAN_SOFT_TIMESTAMP(4), \
}

#define DECLARE_TI_ADS7950_8_CHANNELS(name, bits) \
const struct iio_chan_spec name ## _channels[] = { \
	TI_ADS7950_V_CHAN(0, bits), \
	TI_ADS7950_V_CHAN(1, bits), \
	TI_ADS7950_V_CHAN(2, bits), \
	TI_ADS7950_V_CHAN(3, bits), \
	TI_ADS7950_V_CHAN(4, bits), \
	TI_ADS7950_V_CHAN(5, bits), \
	TI_ADS7950_V_CHAN(6, bits), \
	TI_ADS7950_V_CHAN(7, bits), \
	IIO_CHAN_SOFT_TIMESTAMP(8), \
}

#define DECLARE_TI_ADS7950_12_CHANNELS(name, bits) \
const struct iio_chan_spec name ## _channels[] = { \
	TI_ADS7950_V_CHAN(0, bits), \
	TI_ADS7950_V_CHAN(1, bits), \
	TI_ADS7950_V_CHAN(2, bits), \
	TI_ADS7950_V_CHAN(3, bits), \
	TI_ADS7950_V_CHAN(4, bits), \
	TI_ADS7950_V_CHAN(5, bits), \
	TI_ADS7950_V_CHAN(6, bits), \
	TI_ADS7950_V_CHAN(7, bits), \
	TI_ADS7950_V_CHAN(8, bits), \
	TI_ADS7950_V_CHAN(9, bits), \
	TI_ADS7950_V_CHAN(10, bits), \
	TI_ADS7950_V_CHAN(11, bits), \
	IIO_CHAN_SOFT_TIMESTAMP(12), \
}

#define DECLARE_TI_ADS7950_16_CHANNELS(name, bits) \
const struct iio_chan_spec name ## _channels[] = { \
	TI_ADS7950_V_CHAN(0, bits), \
	TI_ADS7950_V_CHAN(1, bits), \
	TI_ADS7950_V_CHAN(2, bits), \
	TI_ADS7950_V_CHAN(3, bits), \
	TI_ADS7950_V_CHAN(4, bits), \
	TI_ADS7950_V_CHAN(5, bits), \
	TI_ADS7950_V_CHAN(6, bits), \
	TI_ADS7950_V_CHAN(7, bits), \
	TI_ADS7950_V_CHAN(8, bits), \
	TI_ADS7950_V_CHAN(9, bits), \
	TI_ADS7950_V_CHAN(10, bits), \
	TI_ADS7950_V_CHAN(11, bits), \
	TI_ADS7950_V_CHAN(12, bits), \
	TI_ADS7950_V_CHAN(13, bits), \
	TI_ADS7950_V_CHAN(14, bits), \
	TI_ADS7950_V_CHAN(15, bits), \
	IIO_CHAN_SOFT_TIMESTAMP(16), \
}

static DECLARE_TI_ADS7950_4_CHANNELS(ti_ads7950, 12);
static DECLARE_TI_ADS7950_8_CHANNELS(ti_ads7951, 12);
static DECLARE_TI_ADS7950_12_CHANNELS(ti_ads7952, 12);
static DECLARE_TI_ADS7950_16_CHANNELS(ti_ads7953, 12);
static DECLARE_TI_ADS7950_4_CHANNELS(ti_ads7954, 10);
static DECLARE_TI_ADS7950_8_CHANNELS(ti_ads7955, 10);
static DECLARE_TI_ADS7950_12_CHANNELS(ti_ads7956, 10);
static DECLARE_TI_ADS7950_16_CHANNELS(ti_ads7957, 10);
static DECLARE_TI_ADS7950_4_CHANNELS(ti_ads7958, 8);
static DECLARE_TI_ADS7950_8_CHANNELS(ti_ads7959, 8);
static DECLARE_TI_ADS7950_12_CHANNELS(ti_ads7960, 8);
static DECLARE_TI_ADS7950_16_CHANNELS(ti_ads7961, 8);

static const struct ti_ads7950_chip_info ti_ads7950_chip_info[] = {
	[TI_ADS7950] = {
		.channels	= ti_ads7950_channels,
		.num_channels	= ARRAY_SIZE(ti_ads7950_channels),
	},
	[TI_ADS7951] = {
		.channels	= ti_ads7951_channels,
		.num_channels	= ARRAY_SIZE(ti_ads7951_channels),
	},
	[TI_ADS7952] = {
		.channels	= ti_ads7952_channels,
		.num_channels	= ARRAY_SIZE(ti_ads7952_channels),
	},
	[TI_ADS7953] = {
		.channels	= ti_ads7953_channels,
		.num_channels	= ARRAY_SIZE(ti_ads7953_channels),
	},
	[TI_ADS7954] = {
		.channels	= ti_ads7954_channels,
		.num_channels	= ARRAY_SIZE(ti_ads7954_channels),
	},
	[TI_ADS7955] = {
		.channels	= ti_ads7955_channels,
		.num_channels	= ARRAY_SIZE(ti_ads7955_channels),
	},
	[TI_ADS7956] = {
		.channels	= ti_ads7956_channels,
		.num_channels	= ARRAY_SIZE(ti_ads7956_channels),
	},
	[TI_ADS7957] = {
		.channels	= ti_ads7957_channels,
		.num_channels	= ARRAY_SIZE(ti_ads7957_channels),
	},
	[TI_ADS7958] = {
		.channels	= ti_ads7958_channels,
		.num_channels	= ARRAY_SIZE(ti_ads7958_channels),
	},
	[TI_ADS7959] = {
		.channels	= ti_ads7959_channels,
		.num_channels	= ARRAY_SIZE(ti_ads7959_channels),
	},
	[TI_ADS7960] = {
		.channels	= ti_ads7960_channels,
		.num_channels	= ARRAY_SIZE(ti_ads7960_channels),
	},
	[TI_ADS7961] = {
		.channels	= ti_ads7961_channels,
		.num_channels	= ARRAY_SIZE(ti_ads7961_channels),
	},
};

/*
 * ti_ads7950_update_scan_mode() setup the spi transfer buffer for the new
 * scan mask
 */
static int ti_ads7950_update_scan_mode(struct iio_dev *indio_dev,
				       const unsigned long *active_scan_mask)
{
	struct ti_ads7950_state *st = iio_priv(indio_dev);
	int i, cmd, len;

	len = 0;
	for_each_set_bit(i, active_scan_mask, indio_dev->num_channels) {
		cmd = TI_ADS7950_CR_WRITE | TI_ADS7950_CR_CHAN(i) | st->settings;
		st->tx_buf[len++] = cpu_to_be16(cmd);
	}

	/* Data for the 1st channel is not returned until the 3rd transfer */
	len += 2;
	for (i = 0; i < len; i++) {
		if ((i + 2) < len)
			st->ring_xfer[i].tx_buf = &st->tx_buf[i];
		if (i >= 2)
			st->ring_xfer[i].rx_buf = &st->rx_buf[i - 2];
		st->ring_xfer[i].len = 2;
		st->ring_xfer[i].cs_change = 1;
	}
	/* make sure last transfer's cs_change is not set */
	st->ring_xfer[len - 1].cs_change = 0;

	spi_message_init_with_transfers(&st->ring_msg, st->ring_xfer, len);

	return 0;
}

static irqreturn_t ti_ads7950_trigger_handler(int irq, void *p)
{
	struct iio_poll_func *pf = p;
	struct iio_dev *indio_dev = pf->indio_dev;
	struct ti_ads7950_state *st = iio_priv(indio_dev);
	int ret;

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

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

out:
	iio_trigger_notify_done(indio_dev->trig);

	return IRQ_HANDLED;
}

static int ti_ads7950_scan_direct(struct ti_ads7950_state *st, unsigned int ch)
{
	int ret, cmd;

	cmd = TI_ADS7950_CR_WRITE | TI_ADS7950_CR_CHAN(ch) | st->settings;
	st->tx_buf[0] = cpu_to_be16(cmd);

	ret = spi_sync(st->spi, &st->scan_single_msg);
	if (ret)
		return ret;

	return be16_to_cpu(st->rx_buf[0]);
}

static int ti_ads7950_get_range(struct ti_ads7950_state *st)
{
	int vref;

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

	vref /= 1000;

	if (st->settings & TI_ADS7950_CR_RANGE_5V)
		vref *= 2;

	return vref;
}

static int ti_ads7950_read_raw(struct iio_dev *indio_dev,
			       struct iio_chan_spec const *chan,
			       int *val, int *val2, long m)
{
	struct ti_ads7950_state *st = iio_priv(indio_dev);
	int ret;

	switch (m) {
	case IIO_CHAN_INFO_RAW:

		ret = iio_device_claim_direct_mode(indio_dev);
		if (ret < 0)
			return ret;

		ret = ti_ads7950_scan_direct(st, chan->address);
		iio_device_release_direct_mode(indio_dev);
		if (ret < 0)
			return ret;

		if (chan->address != TI_ADS7950_EXTRACT(ret, 12, 4))
			return -EIO;

		*val = TI_ADS7950_EXTRACT(ret, chan->scan_type.shift,
					  chan->scan_type.realbits);

		return IIO_VAL_INT;
	case IIO_CHAN_INFO_SCALE:
		ret = ti_ads7950_get_range(st);
		if (ret < 0)
			return ret;

		*val = ret;
		*val2 = (1 << chan->scan_type.realbits) - 1;

		return IIO_VAL_FRACTIONAL;
	}

	return -EINVAL;
}

static const struct iio_info ti_ads7950_info = {
	.read_raw		= &ti_ads7950_read_raw,
	.update_scan_mode	= ti_ads7950_update_scan_mode,
	.driver_module		= THIS_MODULE,
};

static int ti_ads7950_probe(struct spi_device *spi)
{
	struct ti_ads7950_state *st;
	struct iio_dev *indio_dev;
	const struct ti_ads7950_chip_info *info;
	int ret;

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

	st = iio_priv(indio_dev);

	spi_set_drvdata(spi, indio_dev);

	st->spi = spi;
	st->settings = TI_ADS7950_CR_MANUAL | TI_ADS7950_CR_RANGE_5V;

	info = &ti_ads7950_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 = &ti_ads7950_info;

	/*
	 * Setup default message. The sample is read at the end of the first
	 * transfer, then it takes one full cycle to convert the sample and one
	 * more cycle to send the value. The conversion process is driven by
	 * the SPI clock, which is why we have 3 transfers. The middle one is
	 * just dummy data sent while the chip is converting the sample that
	 * was read at the end of the first transfer.
	 */

	st->scan_single_xfer[0].tx_buf = &st->tx_buf[0];
	st->scan_single_xfer[0].len = 2;
	st->scan_single_xfer[0].cs_change = 1;
	st->scan_single_xfer[1].tx_buf = &st->tx_buf[0];
	st->scan_single_xfer[1].len = 2;
	st->scan_single_xfer[1].cs_change = 1;
	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)) {
		dev_err(&spi->dev, "Failed get get regulator \"vref\"\n");
		return PTR_ERR(st->reg);
	}

	ret = regulator_enable(st->reg);
	if (ret) {
		dev_err(&spi->dev, "Failed to enable regulator \"vref\"\n");
		return ret;
	}

	ret = iio_triggered_buffer_setup(indio_dev, NULL,
					 &ti_ads7950_trigger_handler, NULL);
	if (ret) {
		dev_err(&spi->dev, "Failed to setup triggered buffer\n");
		goto error_disable_reg;
	}

	ret = iio_device_register(indio_dev);
	if (ret) {
		dev_err(&spi->dev, "Failed to register iio device\n");
		goto error_cleanup_ring;
	}

	return 0;

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

	return ret;
}

static int ti_ads7950_remove(struct spi_device *spi)
{
	struct iio_dev *indio_dev = spi_get_drvdata(spi);
	struct ti_ads7950_state *st = iio_priv(indio_dev);

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

	return 0;
}

static const struct spi_device_id ti_ads7950_id[] = {
	{ "ads7950", TI_ADS7950 },
	{ "ads7951", TI_ADS7951 },
	{ "ads7952", TI_ADS7952 },
	{ "ads7953", TI_ADS7953 },
	{ "ads7954", TI_ADS7954 },
	{ "ads7955", TI_ADS7955 },
	{ "ads7956", TI_ADS7956 },
	{ "ads7957", TI_ADS7957 },
	{ "ads7958", TI_ADS7958 },
	{ "ads7959", TI_ADS7959 },
	{ "ads7960", TI_ADS7960 },
	{ "ads7961", TI_ADS7961 },
	{ }
};
MODULE_DEVICE_TABLE(spi, ti_ads7950_id);

static struct spi_driver ti_ads7950_driver = {
	.driver = {
		.name	= "ads7950",
	},
	.probe		= ti_ads7950_probe,
	.remove		= ti_ads7950_remove,
	.id_table	= ti_ads7950_id,
};
module_spi_driver(ti_ads7950_driver);

MODULE_AUTHOR("David Lechner <david@lechnology.com>");
MODULE_DESCRIPTION("TI TI_ADS7950 ADC");
MODULE_LICENSE("GPL v2");