/*
 * IIO driver for the ACCES 104-QUAD-8
 * Copyright (C) 2016 William Breathitt Gray
 *
 * 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.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * This driver supports the ACCES 104-QUAD-8 and ACCES 104-QUAD-4.
 */
#include <linux/bitops.h>
#include <linux/device.h>
#include <linux/errno.h>
#include <linux/iio/iio.h>
#include <linux/iio/types.h>
#include <linux/io.h>
#include <linux/ioport.h>
#include <linux/isa.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/types.h>

#define QUAD8_EXTENT 32

static unsigned int base[max_num_isa_dev(QUAD8_EXTENT)];
static unsigned int num_quad8;
module_param_array(base, uint, &num_quad8, 0);
MODULE_PARM_DESC(base, "ACCES 104-QUAD-8 base addresses");

#define QUAD8_NUM_COUNTERS 8

/**
 * struct quad8_iio - IIO device private data structure
 * @preset:		array of preset values
 * @count_mode:		array of count mode configurations
 * @quadrature_mode:	array of quadrature mode configurations
 * @quadrature_scale:	array of quadrature mode scale configurations
 * @ab_enable:		array of A and B inputs enable configurations
 * @preset_enable:	array of set_to_preset_on_index attribute configurations
 * @synchronous_mode:	array of index function synchronous mode configurations
 * @index_polarity:	array of index function polarity configurations
 * @base:		base port address of the IIO device
 */
struct quad8_iio {
	unsigned int preset[QUAD8_NUM_COUNTERS];
	unsigned int count_mode[QUAD8_NUM_COUNTERS];
	unsigned int quadrature_mode[QUAD8_NUM_COUNTERS];
	unsigned int quadrature_scale[QUAD8_NUM_COUNTERS];
	unsigned int ab_enable[QUAD8_NUM_COUNTERS];
	unsigned int preset_enable[QUAD8_NUM_COUNTERS];
	unsigned int synchronous_mode[QUAD8_NUM_COUNTERS];
	unsigned int index_polarity[QUAD8_NUM_COUNTERS];
	unsigned int base;
};

#define QUAD8_REG_CHAN_OP 0x11
#define QUAD8_REG_INDEX_INPUT_LEVELS 0x16
/* Borrow Toggle flip-flop */
#define QUAD8_FLAG_BT BIT(0)
/* Carry Toggle flip-flop */
#define QUAD8_FLAG_CT BIT(1)
/* Error flag */
#define QUAD8_FLAG_E BIT(4)
/* Up/Down flag */
#define QUAD8_FLAG_UD BIT(5)
/* Reset and Load Signal Decoders */
#define QUAD8_CTR_RLD 0x00
/* Counter Mode Register */
#define QUAD8_CTR_CMR 0x20
/* Input / Output Control Register */
#define QUAD8_CTR_IOR 0x40
/* Index Control Register */
#define QUAD8_CTR_IDR 0x60
/* Reset Byte Pointer (three byte data pointer) */
#define QUAD8_RLD_RESET_BP 0x01
/* Reset Counter */
#define QUAD8_RLD_RESET_CNTR 0x02
/* Reset Borrow Toggle, Carry Toggle, Compare Toggle, and Sign flags */
#define QUAD8_RLD_RESET_FLAGS 0x04
/* Reset Error flag */
#define QUAD8_RLD_RESET_E 0x06
/* Preset Register to Counter */
#define QUAD8_RLD_PRESET_CNTR 0x08
/* Transfer Counter to Output Latch */
#define QUAD8_RLD_CNTR_OUT 0x10
#define QUAD8_CHAN_OP_ENABLE_COUNTERS 0x00
#define QUAD8_CHAN_OP_RESET_COUNTERS 0x01

static int quad8_read_raw(struct iio_dev *indio_dev,
	struct iio_chan_spec const *chan, int *val, int *val2, long mask)
{
	struct quad8_iio *const priv = iio_priv(indio_dev);
	const int base_offset = priv->base + 2 * chan->channel;
	unsigned int flags;
	unsigned int borrow;
	unsigned int carry;
	int i;

	switch (mask) {
	case IIO_CHAN_INFO_RAW:
		if (chan->type == IIO_INDEX) {
			*val = !!(inb(priv->base + QUAD8_REG_INDEX_INPUT_LEVELS)
				& BIT(chan->channel));
			return IIO_VAL_INT;
		}

		flags = inb(base_offset + 1);
		borrow = flags & QUAD8_FLAG_BT;
		carry = !!(flags & QUAD8_FLAG_CT);

		/* Borrow XOR Carry effectively doubles count range */
		*val = (borrow ^ carry) << 24;

		/* Reset Byte Pointer; transfer Counter to Output Latch */
		outb(QUAD8_CTR_RLD | QUAD8_RLD_RESET_BP | QUAD8_RLD_CNTR_OUT,
		     base_offset + 1);

		for (i = 0; i < 3; i++)
			*val |= (unsigned int)inb(base_offset) << (8 * i);

		return IIO_VAL_INT;
	case IIO_CHAN_INFO_ENABLE:
		*val = priv->ab_enable[chan->channel];
		return IIO_VAL_INT;
	case IIO_CHAN_INFO_SCALE:
		*val = 1;
		*val2 = priv->quadrature_scale[chan->channel];
		return IIO_VAL_FRACTIONAL_LOG2;
	}

	return -EINVAL;
}

static int quad8_write_raw(struct iio_dev *indio_dev,
	struct iio_chan_spec const *chan, int val, int val2, long mask)
{
	struct quad8_iio *const priv = iio_priv(indio_dev);
	const int base_offset = priv->base + 2 * chan->channel;
	int i;
	unsigned int ior_cfg;

	switch (mask) {
	case IIO_CHAN_INFO_RAW:
		if (chan->type == IIO_INDEX)
			return -EINVAL;

		/* Only 24-bit values are supported */
		if ((unsigned int)val > 0xFFFFFF)
			return -EINVAL;

		/* Reset Byte Pointer */
		outb(QUAD8_CTR_RLD | QUAD8_RLD_RESET_BP, base_offset + 1);

		/* Counter can only be set via Preset Register */
		for (i = 0; i < 3; i++)
			outb(val >> (8 * i), base_offset);

		/* Transfer Preset Register to Counter */
		outb(QUAD8_CTR_RLD | QUAD8_RLD_PRESET_CNTR, base_offset + 1);

		/* Reset Byte Pointer */
		outb(QUAD8_CTR_RLD | QUAD8_RLD_RESET_BP, base_offset + 1);

		/* Set Preset Register back to original value */
		val = priv->preset[chan->channel];
		for (i = 0; i < 3; i++)
			outb(val >> (8 * i), base_offset);

		/* Reset Borrow, Carry, Compare, and Sign flags */
		outb(QUAD8_CTR_RLD | QUAD8_RLD_RESET_FLAGS, base_offset + 1);
		/* Reset Error flag */
		outb(QUAD8_CTR_RLD | QUAD8_RLD_RESET_E, base_offset + 1);

		return 0;
	case IIO_CHAN_INFO_ENABLE:
		/* only boolean values accepted */
		if (val < 0 || val > 1)
			return -EINVAL;

		priv->ab_enable[chan->channel] = val;

		ior_cfg = val | priv->preset_enable[chan->channel] << 1;

		/* Load I/O control configuration */
		outb(QUAD8_CTR_IOR | ior_cfg, base_offset + 1);

		return 0;
	case IIO_CHAN_INFO_SCALE:
		/* Quadrature scaling only available in quadrature mode */
		if (!priv->quadrature_mode[chan->channel] && (val2 || val != 1))
			return -EINVAL;

		/* Only three gain states (1, 0.5, 0.25) */
		if (val == 1 && !val2)
			priv->quadrature_scale[chan->channel] = 0;
		else if (!val)
			switch (val2) {
			case 500000:
				priv->quadrature_scale[chan->channel] = 1;
				break;
			case 250000:
				priv->quadrature_scale[chan->channel] = 2;
				break;
			default:
				return -EINVAL;
			}
		else
			return -EINVAL;

		return 0;
	}

	return -EINVAL;
}

static const struct iio_info quad8_info = {
	.read_raw = quad8_read_raw,
	.write_raw = quad8_write_raw
};

static ssize_t quad8_read_preset(struct iio_dev *indio_dev, uintptr_t private,
	const struct iio_chan_spec *chan, char *buf)
{
	const struct quad8_iio *const priv = iio_priv(indio_dev);

	return snprintf(buf, PAGE_SIZE, "%u\n", priv->preset[chan->channel]);
}

static ssize_t quad8_write_preset(struct iio_dev *indio_dev, uintptr_t private,
	const struct iio_chan_spec *chan, const char *buf, size_t len)
{
	struct quad8_iio *const priv = iio_priv(indio_dev);
	const int base_offset = priv->base + 2 * chan->channel;
	unsigned int preset;
	int ret;
	int i;

	ret = kstrtouint(buf, 0, &preset);
	if (ret)
		return ret;

	/* Only 24-bit values are supported */
	if (preset > 0xFFFFFF)
		return -EINVAL;

	priv->preset[chan->channel] = preset;

	/* Reset Byte Pointer */
	outb(QUAD8_CTR_RLD | QUAD8_RLD_RESET_BP, base_offset + 1);

	/* Set Preset Register */
	for (i = 0; i < 3; i++)
		outb(preset >> (8 * i), base_offset);

	return len;
}

static ssize_t quad8_read_set_to_preset_on_index(struct iio_dev *indio_dev,
	uintptr_t private, const struct iio_chan_spec *chan, char *buf)
{
	const struct quad8_iio *const priv = iio_priv(indio_dev);

	return snprintf(buf, PAGE_SIZE, "%u\n",
		!priv->preset_enable[chan->channel]);
}

static ssize_t quad8_write_set_to_preset_on_index(struct iio_dev *indio_dev,
	uintptr_t private, const struct iio_chan_spec *chan, const char *buf,
	size_t len)
{
	struct quad8_iio *const priv = iio_priv(indio_dev);
	const int base_offset = priv->base + 2 * chan->channel + 1;
	bool preset_enable;
	int ret;
	unsigned int ior_cfg;

	ret = kstrtobool(buf, &preset_enable);
	if (ret)
		return ret;

	/* Preset enable is active low in Input/Output Control register */
	preset_enable = !preset_enable;

	priv->preset_enable[chan->channel] = preset_enable;

	ior_cfg = priv->ab_enable[chan->channel] |
		(unsigned int)preset_enable << 1;

	/* Load I/O control configuration to Input / Output Control Register */
	outb(QUAD8_CTR_IOR | ior_cfg, base_offset);

	return len;
}

static const char *const quad8_noise_error_states[] = {
	"No excessive noise is present at the count inputs",
	"Excessive noise is present at the count inputs"
};

static int quad8_get_noise_error(struct iio_dev *indio_dev,
	const struct iio_chan_spec *chan)
{
	struct quad8_iio *const priv = iio_priv(indio_dev);
	const int base_offset = priv->base + 2 * chan->channel + 1;

	return !!(inb(base_offset) & QUAD8_FLAG_E);
}

static const struct iio_enum quad8_noise_error_enum = {
	.items = quad8_noise_error_states,
	.num_items = ARRAY_SIZE(quad8_noise_error_states),
	.get = quad8_get_noise_error
};

static const char *const quad8_count_direction_states[] = {
	"down",
	"up"
};

static int quad8_get_count_direction(struct iio_dev *indio_dev,
	const struct iio_chan_spec *chan)
{
	struct quad8_iio *const priv = iio_priv(indio_dev);
	const int base_offset = priv->base + 2 * chan->channel + 1;

	return !!(inb(base_offset) & QUAD8_FLAG_UD);
}

static const struct iio_enum quad8_count_direction_enum = {
	.items = quad8_count_direction_states,
	.num_items = ARRAY_SIZE(quad8_count_direction_states),
	.get = quad8_get_count_direction
};

static const char *const quad8_count_modes[] = {
	"normal",
	"range limit",
	"non-recycle",
	"modulo-n"
};

static int quad8_set_count_mode(struct iio_dev *indio_dev,
	const struct iio_chan_spec *chan, unsigned int count_mode)
{
	struct quad8_iio *const priv = iio_priv(indio_dev);
	unsigned int mode_cfg = count_mode << 1;
	const int base_offset = priv->base + 2 * chan->channel + 1;

	priv->count_mode[chan->channel] = count_mode;

	/* Add quadrature mode configuration */
	if (priv->quadrature_mode[chan->channel])
		mode_cfg |= (priv->quadrature_scale[chan->channel] + 1) << 3;

	/* Load mode configuration to Counter Mode Register */
	outb(QUAD8_CTR_CMR | mode_cfg, base_offset);

	return 0;
}

static int quad8_get_count_mode(struct iio_dev *indio_dev,
	const struct iio_chan_spec *chan)
{
	const struct quad8_iio *const priv = iio_priv(indio_dev);

	return priv->count_mode[chan->channel];
}

static const struct iio_enum quad8_count_mode_enum = {
	.items = quad8_count_modes,
	.num_items = ARRAY_SIZE(quad8_count_modes),
	.set = quad8_set_count_mode,
	.get = quad8_get_count_mode
};

static const char *const quad8_synchronous_modes[] = {
	"non-synchronous",
	"synchronous"
};

static int quad8_set_synchronous_mode(struct iio_dev *indio_dev,
	const struct iio_chan_spec *chan, unsigned int synchronous_mode)
{
	struct quad8_iio *const priv = iio_priv(indio_dev);
	const unsigned int idr_cfg = synchronous_mode |
		priv->index_polarity[chan->channel] << 1;
	const int base_offset = priv->base + 2 * chan->channel + 1;

	/* Index function must be non-synchronous in non-quadrature mode */
	if (synchronous_mode && !priv->quadrature_mode[chan->channel])
		return -EINVAL;

	priv->synchronous_mode[chan->channel] = synchronous_mode;

	/* Load Index Control configuration to Index Control Register */
	outb(QUAD8_CTR_IDR | idr_cfg, base_offset);

	return 0;
}

static int quad8_get_synchronous_mode(struct iio_dev *indio_dev,
	const struct iio_chan_spec *chan)
{
	const struct quad8_iio *const priv = iio_priv(indio_dev);

	return priv->synchronous_mode[chan->channel];
}

static const struct iio_enum quad8_synchronous_mode_enum = {
	.items = quad8_synchronous_modes,
	.num_items = ARRAY_SIZE(quad8_synchronous_modes),
	.set = quad8_set_synchronous_mode,
	.get = quad8_get_synchronous_mode
};

static const char *const quad8_quadrature_modes[] = {
	"non-quadrature",
	"quadrature"
};

static int quad8_set_quadrature_mode(struct iio_dev *indio_dev,
	const struct iio_chan_spec *chan, unsigned int quadrature_mode)
{
	struct quad8_iio *const priv = iio_priv(indio_dev);
	unsigned int mode_cfg = priv->count_mode[chan->channel] << 1;
	const int base_offset = priv->base + 2 * chan->channel + 1;

	if (quadrature_mode)
		mode_cfg |= (priv->quadrature_scale[chan->channel] + 1) << 3;
	else {
		/* Quadrature scaling only available in quadrature mode */
		priv->quadrature_scale[chan->channel] = 0;

		/* Synchronous function not supported in non-quadrature mode */
		if (priv->synchronous_mode[chan->channel])
			quad8_set_synchronous_mode(indio_dev, chan, 0);
	}

	priv->quadrature_mode[chan->channel] = quadrature_mode;

	/* Load mode configuration to Counter Mode Register */
	outb(QUAD8_CTR_CMR | mode_cfg, base_offset);

	return 0;
}

static int quad8_get_quadrature_mode(struct iio_dev *indio_dev,
	const struct iio_chan_spec *chan)
{
	const struct quad8_iio *const priv = iio_priv(indio_dev);

	return priv->quadrature_mode[chan->channel];
}

static const struct iio_enum quad8_quadrature_mode_enum = {
	.items = quad8_quadrature_modes,
	.num_items = ARRAY_SIZE(quad8_quadrature_modes),
	.set = quad8_set_quadrature_mode,
	.get = quad8_get_quadrature_mode
};

static const char *const quad8_index_polarity_modes[] = {
	"negative",
	"positive"
};

static int quad8_set_index_polarity(struct iio_dev *indio_dev,
	const struct iio_chan_spec *chan, unsigned int index_polarity)
{
	struct quad8_iio *const priv = iio_priv(indio_dev);
	const unsigned int idr_cfg = priv->synchronous_mode[chan->channel] |
		index_polarity << 1;
	const int base_offset = priv->base + 2 * chan->channel + 1;

	priv->index_polarity[chan->channel] = index_polarity;

	/* Load Index Control configuration to Index Control Register */
	outb(QUAD8_CTR_IDR | idr_cfg, base_offset);

	return 0;
}

static int quad8_get_index_polarity(struct iio_dev *indio_dev,
	const struct iio_chan_spec *chan)
{
	const struct quad8_iio *const priv = iio_priv(indio_dev);

	return priv->index_polarity[chan->channel];
}

static const struct iio_enum quad8_index_polarity_enum = {
	.items = quad8_index_polarity_modes,
	.num_items = ARRAY_SIZE(quad8_index_polarity_modes),
	.set = quad8_set_index_polarity,
	.get = quad8_get_index_polarity
};

static const struct iio_chan_spec_ext_info quad8_count_ext_info[] = {
	{
		.name = "preset",
		.shared = IIO_SEPARATE,
		.read = quad8_read_preset,
		.write = quad8_write_preset
	},
	{
		.name = "set_to_preset_on_index",
		.shared = IIO_SEPARATE,
		.read = quad8_read_set_to_preset_on_index,
		.write = quad8_write_set_to_preset_on_index
	},
	IIO_ENUM("noise_error", IIO_SEPARATE, &quad8_noise_error_enum),
	IIO_ENUM_AVAILABLE("noise_error", &quad8_noise_error_enum),
	IIO_ENUM("count_direction", IIO_SEPARATE, &quad8_count_direction_enum),
	IIO_ENUM_AVAILABLE("count_direction", &quad8_count_direction_enum),
	IIO_ENUM("count_mode", IIO_SEPARATE, &quad8_count_mode_enum),
	IIO_ENUM_AVAILABLE("count_mode", &quad8_count_mode_enum),
	IIO_ENUM("quadrature_mode", IIO_SEPARATE, &quad8_quadrature_mode_enum),
	IIO_ENUM_AVAILABLE("quadrature_mode", &quad8_quadrature_mode_enum),
	{}
};

static const struct iio_chan_spec_ext_info quad8_index_ext_info[] = {
	IIO_ENUM("synchronous_mode", IIO_SEPARATE,
		&quad8_synchronous_mode_enum),
	IIO_ENUM_AVAILABLE("synchronous_mode", &quad8_synchronous_mode_enum),
	IIO_ENUM("index_polarity", IIO_SEPARATE, &quad8_index_polarity_enum),
	IIO_ENUM_AVAILABLE("index_polarity", &quad8_index_polarity_enum),
	{}
};

#define QUAD8_COUNT_CHAN(_chan) {					\
	.type = IIO_COUNT,						\
	.channel = (_chan),						\
	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |			\
		BIT(IIO_CHAN_INFO_ENABLE) | BIT(IIO_CHAN_INFO_SCALE),	\
	.ext_info = quad8_count_ext_info,				\
	.indexed = 1							\
}

#define QUAD8_INDEX_CHAN(_chan) {			\
	.type = IIO_INDEX,				\
	.channel = (_chan),				\
	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),	\
	.ext_info = quad8_index_ext_info,		\
	.indexed = 1					\
}

static const struct iio_chan_spec quad8_channels[] = {
	QUAD8_COUNT_CHAN(0), QUAD8_INDEX_CHAN(0),
	QUAD8_COUNT_CHAN(1), QUAD8_INDEX_CHAN(1),
	QUAD8_COUNT_CHAN(2), QUAD8_INDEX_CHAN(2),
	QUAD8_COUNT_CHAN(3), QUAD8_INDEX_CHAN(3),
	QUAD8_COUNT_CHAN(4), QUAD8_INDEX_CHAN(4),
	QUAD8_COUNT_CHAN(5), QUAD8_INDEX_CHAN(5),
	QUAD8_COUNT_CHAN(6), QUAD8_INDEX_CHAN(6),
	QUAD8_COUNT_CHAN(7), QUAD8_INDEX_CHAN(7)
};

static int quad8_probe(struct device *dev, unsigned int id)
{
	struct iio_dev *indio_dev;
	struct quad8_iio *priv;
	int i, j;
	unsigned int base_offset;

	indio_dev = devm_iio_device_alloc(dev, sizeof(*priv));
	if (!indio_dev)
		return -ENOMEM;

	if (!devm_request_region(dev, base[id], QUAD8_EXTENT,
		dev_name(dev))) {
		dev_err(dev, "Unable to lock port addresses (0x%X-0x%X)\n",
			base[id], base[id] + QUAD8_EXTENT);
		return -EBUSY;
	}

	indio_dev->info = &quad8_info;
	indio_dev->modes = INDIO_DIRECT_MODE;
	indio_dev->num_channels = ARRAY_SIZE(quad8_channels);
	indio_dev->channels = quad8_channels;
	indio_dev->name = dev_name(dev);
	indio_dev->dev.parent = dev;

	priv = iio_priv(indio_dev);
	priv->base = base[id];

	/* Reset all counters and disable interrupt function */
	outb(QUAD8_CHAN_OP_RESET_COUNTERS, base[id] + QUAD8_REG_CHAN_OP);
	/* Set initial configuration for all counters */
	for (i = 0; i < QUAD8_NUM_COUNTERS; i++) {
		base_offset = base[id] + 2 * i;
		/* Reset Byte Pointer */
		outb(QUAD8_CTR_RLD | QUAD8_RLD_RESET_BP, base_offset + 1);
		/* Reset Preset Register */
		for (j = 0; j < 3; j++)
			outb(0x00, base_offset);
		/* Reset Borrow, Carry, Compare, and Sign flags */
		outb(QUAD8_CTR_RLD | QUAD8_RLD_RESET_FLAGS, base_offset + 1);
		/* Reset Error flag */
		outb(QUAD8_CTR_RLD | QUAD8_RLD_RESET_E, base_offset + 1);
		/* Binary encoding; Normal count; non-quadrature mode */
		outb(QUAD8_CTR_CMR, base_offset + 1);
		/* Disable A and B inputs; preset on index; FLG1 as Carry */
		outb(QUAD8_CTR_IOR, base_offset + 1);
		/* Disable index function; negative index polarity */
		outb(QUAD8_CTR_IDR, base_offset + 1);
	}
	/* Enable all counters */
	outb(QUAD8_CHAN_OP_ENABLE_COUNTERS, base[id] + QUAD8_REG_CHAN_OP);

	return devm_iio_device_register(dev, indio_dev);
}

static struct isa_driver quad8_driver = {
	.probe = quad8_probe,
	.driver = {
		.name = "104-quad-8"
	}
};

module_isa_driver(quad8_driver, num_quad8);

MODULE_AUTHOR("William Breathitt Gray <vilhelm.gray@gmail.com>");
MODULE_DESCRIPTION("ACCES 104-QUAD-8 IIO driver");
MODULE_LICENSE("GPL v2");