/*
 * GPIO driver for the ACCES 104-DIO-48E
 * 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.
 */
#include <linux/bitops.h>
#include <linux/device.h>
#include <linux/errno.h>
#include <linux/gpio/driver.h>
#include <linux/io.h>
#include <linux/ioport.h>
#include <linux/interrupt.h>
#include <linux/irqdesc.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/platform_device.h>
#include <linux/spinlock.h>

static unsigned dio_48e_base;
module_param(dio_48e_base, uint, 0);
MODULE_PARM_DESC(dio_48e_base, "ACCES 104-DIO-48E base address");
static unsigned dio_48e_irq;
module_param(dio_48e_irq, uint, 0);
MODULE_PARM_DESC(dio_48e_irq, "ACCES 104-DIO-48E interrupt line number");

/**
 * struct dio48e_gpio - GPIO device private data structure
 * @chip:	instance of the gpio_chip
 * @io_state:	bit I/O state (whether bit is set to input or output)
 * @out_state:	output bits state
 * @control:	Control registers state
 * @lock:	synchronization lock to prevent I/O race conditions
 * @base:	base port address of the GPIO device
 * @irq:	Interrupt line number
 * @irq_mask:	I/O bits affected by interrupts
 */
struct dio48e_gpio {
	struct gpio_chip chip;
	unsigned char io_state[6];
	unsigned char out_state[6];
	unsigned char control[2];
	spinlock_t lock;
	unsigned base;
	unsigned irq;
	unsigned char irq_mask;
};

static int dio48e_gpio_get_direction(struct gpio_chip *chip, unsigned offset)
{
	struct dio48e_gpio *const dio48egpio = gpiochip_get_data(chip);
	const unsigned port = offset / 8;
	const unsigned mask = BIT(offset % 8);

	return !!(dio48egpio->io_state[port] & mask);
}

static int dio48e_gpio_direction_input(struct gpio_chip *chip, unsigned offset)
{
	struct dio48e_gpio *const dio48egpio = gpiochip_get_data(chip);
	const unsigned io_port = offset / 8;
	const unsigned control_port = io_port / 2;
	const unsigned control_addr = dio48egpio->base + 3 + control_port*4;
	unsigned long flags;
	unsigned control;

	spin_lock_irqsave(&dio48egpio->lock, flags);

	/* Check if configuring Port C */
	if (io_port == 2 || io_port == 5) {
		/* Port C can be configured by nibble */
		if (offset % 8 > 3) {
			dio48egpio->io_state[io_port] |= 0xF0;
			dio48egpio->control[control_port] |= BIT(3);
		} else {
			dio48egpio->io_state[io_port] |= 0x0F;
			dio48egpio->control[control_port] |= BIT(0);
		}
	} else {
		dio48egpio->io_state[io_port] |= 0xFF;
		if (io_port == 0 || io_port == 3)
			dio48egpio->control[control_port] |= BIT(4);
		else
			dio48egpio->control[control_port] |= BIT(1);
	}

	control = BIT(7) | dio48egpio->control[control_port];
	outb(control, control_addr);
	control &= ~BIT(7);
	outb(control, control_addr);

	spin_unlock_irqrestore(&dio48egpio->lock, flags);

	return 0;
}

static int dio48e_gpio_direction_output(struct gpio_chip *chip, unsigned offset,
	int value)
{
	struct dio48e_gpio *const dio48egpio = gpiochip_get_data(chip);
	const unsigned io_port = offset / 8;
	const unsigned control_port = io_port / 2;
	const unsigned mask = BIT(offset % 8);
	const unsigned control_addr = dio48egpio->base + 3 + control_port*4;
	const unsigned out_port = (io_port > 2) ? io_port + 1 : io_port;
	unsigned long flags;
	unsigned control;

	spin_lock_irqsave(&dio48egpio->lock, flags);

	/* Check if configuring Port C */
	if (io_port == 2 || io_port == 5) {
		/* Port C can be configured by nibble */
		if (offset % 8 > 3) {
			dio48egpio->io_state[io_port] &= 0x0F;
			dio48egpio->control[control_port] &= ~BIT(3);
		} else {
			dio48egpio->io_state[io_port] &= 0xF0;
			dio48egpio->control[control_port] &= ~BIT(0);
		}
	} else {
		dio48egpio->io_state[io_port] &= 0x00;
		if (io_port == 0 || io_port == 3)
			dio48egpio->control[control_port] &= ~BIT(4);
		else
			dio48egpio->control[control_port] &= ~BIT(1);
	}

	if (value)
		dio48egpio->out_state[io_port] |= mask;
	else
		dio48egpio->out_state[io_port] &= ~mask;

	control = BIT(7) | dio48egpio->control[control_port];
	outb(control, control_addr);

	outb(dio48egpio->out_state[io_port], dio48egpio->base + out_port);

	control &= ~BIT(7);
	outb(control, control_addr);

	spin_unlock_irqrestore(&dio48egpio->lock, flags);

	return 0;
}

static int dio48e_gpio_get(struct gpio_chip *chip, unsigned offset)
{
	struct dio48e_gpio *const dio48egpio = gpiochip_get_data(chip);
	const unsigned port = offset / 8;
	const unsigned mask = BIT(offset % 8);
	const unsigned in_port = (port > 2) ? port + 1 : port;
	unsigned long flags;
	unsigned port_state;

	spin_lock_irqsave(&dio48egpio->lock, flags);

	/* ensure that GPIO is set for input */
	if (!(dio48egpio->io_state[port] & mask)) {
		spin_unlock_irqrestore(&dio48egpio->lock, flags);
		return -EINVAL;
	}

	port_state = inb(dio48egpio->base + in_port);

	spin_unlock_irqrestore(&dio48egpio->lock, flags);

	return !!(port_state & mask);
}

static void dio48e_gpio_set(struct gpio_chip *chip, unsigned offset, int value)
{
	struct dio48e_gpio *const dio48egpio = gpiochip_get_data(chip);
	const unsigned port = offset / 8;
	const unsigned mask = BIT(offset % 8);
	const unsigned out_port = (port > 2) ? port + 1 : port;
	unsigned long flags;

	spin_lock_irqsave(&dio48egpio->lock, flags);

	if (value)
		dio48egpio->out_state[port] |= mask;
	else
		dio48egpio->out_state[port] &= ~mask;

	outb(dio48egpio->out_state[port], dio48egpio->base + out_port);

	spin_unlock_irqrestore(&dio48egpio->lock, flags);
}

static void dio48e_irq_ack(struct irq_data *data)
{
}

static void dio48e_irq_mask(struct irq_data *data)
{
	struct gpio_chip *chip = irq_data_get_irq_chip_data(data);
	struct dio48e_gpio *const dio48egpio = gpiochip_get_data(chip);
	const unsigned long offset = irqd_to_hwirq(data);
	unsigned long flags;

	/* only bit 3 on each respective Port C supports interrupts */
	if (offset != 19 && offset != 43)
		return;

	spin_lock_irqsave(&dio48egpio->lock, flags);

	if (offset == 19)
		dio48egpio->irq_mask &= ~BIT(0);
	else
		dio48egpio->irq_mask &= ~BIT(1);

	if (!dio48egpio->irq_mask)
		/* disable interrupts */
		inb(dio48egpio->base + 0xB);

	spin_unlock_irqrestore(&dio48egpio->lock, flags);
}

static void dio48e_irq_unmask(struct irq_data *data)
{
	struct gpio_chip *chip = irq_data_get_irq_chip_data(data);
	struct dio48e_gpio *const dio48egpio = gpiochip_get_data(chip);
	const unsigned long offset = irqd_to_hwirq(data);
	unsigned long flags;

	/* only bit 3 on each respective Port C supports interrupts */
	if (offset != 19 && offset != 43)
		return;

	spin_lock_irqsave(&dio48egpio->lock, flags);

	if (!dio48egpio->irq_mask) {
		/* enable interrupts */
		outb(0x00, dio48egpio->base + 0xF);
		outb(0x00, dio48egpio->base + 0xB);
	}

	if (offset == 19)
		dio48egpio->irq_mask |= BIT(0);
	else
		dio48egpio->irq_mask |= BIT(1);

	spin_unlock_irqrestore(&dio48egpio->lock, flags);
}

static int dio48e_irq_set_type(struct irq_data *data, unsigned flow_type)
{
	const unsigned long offset = irqd_to_hwirq(data);

	/* only bit 3 on each respective Port C supports interrupts */
	if (offset != 19 && offset != 43)
		return -EINVAL;

	if (flow_type != IRQ_TYPE_NONE && flow_type != IRQ_TYPE_EDGE_RISING)
		return -EINVAL;

	return 0;
}

static struct irq_chip dio48e_irqchip = {
	.name = "104-dio-48e",
	.irq_ack = dio48e_irq_ack,
	.irq_mask = dio48e_irq_mask,
	.irq_unmask = dio48e_irq_unmask,
	.irq_set_type = dio48e_irq_set_type
};

static irqreturn_t dio48e_irq_handler(int irq, void *dev_id)
{
	struct dio48e_gpio *const dio48egpio = dev_id;
	struct gpio_chip *const chip = &dio48egpio->chip;
	const unsigned long irq_mask = dio48egpio->irq_mask;
	unsigned long gpio;

	for_each_set_bit(gpio, &irq_mask, 2)
		generic_handle_irq(irq_find_mapping(chip->irqdomain,
			19 + gpio*24));

	spin_lock(&dio48egpio->lock);

	outb(0x00, dio48egpio->base + 0xF);

	spin_unlock(&dio48egpio->lock);

	return IRQ_HANDLED;
}

static int __init dio48e_probe(struct platform_device *pdev)
{
	struct device *dev = &pdev->dev;
	struct dio48e_gpio *dio48egpio;
	const unsigned base = dio_48e_base;
	const unsigned extent = 16;
	const char *const name = dev_name(dev);
	int err;
	const unsigned irq = dio_48e_irq;

	dio48egpio = devm_kzalloc(dev, sizeof(*dio48egpio), GFP_KERNEL);
	if (!dio48egpio)
		return -ENOMEM;

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

	dio48egpio->chip.label = name;
	dio48egpio->chip.parent = dev;
	dio48egpio->chip.owner = THIS_MODULE;
	dio48egpio->chip.base = -1;
	dio48egpio->chip.ngpio = 48;
	dio48egpio->chip.get_direction = dio48e_gpio_get_direction;
	dio48egpio->chip.direction_input = dio48e_gpio_direction_input;
	dio48egpio->chip.direction_output = dio48e_gpio_direction_output;
	dio48egpio->chip.get = dio48e_gpio_get;
	dio48egpio->chip.set = dio48e_gpio_set;
	dio48egpio->base = base;
	dio48egpio->irq = irq;

	spin_lock_init(&dio48egpio->lock);

	dev_set_drvdata(dev, dio48egpio);

	err = gpiochip_add_data(&dio48egpio->chip, dio48egpio);
	if (err) {
		dev_err(dev, "GPIO registering failed (%d)\n", err);
		return err;
	}

	/* initialize all GPIO as output */
	outb(0x80, base + 3);
	outb(0x00, base);
	outb(0x00, base + 1);
	outb(0x00, base + 2);
	outb(0x00, base + 3);
	outb(0x80, base + 7);
	outb(0x00, base + 4);
	outb(0x00, base + 5);
	outb(0x00, base + 6);
	outb(0x00, base + 7);

	/* disable IRQ by default */
	inb(base + 0xB);

	err = gpiochip_irqchip_add(&dio48egpio->chip, &dio48e_irqchip, 0,
		handle_edge_irq, IRQ_TYPE_NONE);
	if (err) {
		dev_err(dev, "Could not add irqchip (%d)\n", err);
		goto err_gpiochip_remove;
	}

	err = request_irq(irq, dio48e_irq_handler, 0, name, dio48egpio);
	if (err) {
		dev_err(dev, "IRQ handler registering failed (%d)\n", err);
		goto err_gpiochip_remove;
	}

	return 0;

err_gpiochip_remove:
	gpiochip_remove(&dio48egpio->chip);
	return err;
}

static int dio48e_remove(struct platform_device *pdev)
{
	struct dio48e_gpio *const dio48egpio = platform_get_drvdata(pdev);

	free_irq(dio48egpio->irq, dio48egpio);
	gpiochip_remove(&dio48egpio->chip);

	return 0;
}

static struct platform_device *dio48e_device;

static struct platform_driver dio48e_driver = {
	.driver = {
		.name = "104-dio-48e"
	},
	.remove = dio48e_remove
};

static void __exit dio48e_exit(void)
{
	platform_device_unregister(dio48e_device);
	platform_driver_unregister(&dio48e_driver);
}

static int __init dio48e_init(void)
{
	int err;

	dio48e_device = platform_device_alloc(dio48e_driver.driver.name, -1);
	if (!dio48e_device)
		return -ENOMEM;

	err = platform_device_add(dio48e_device);
	if (err)
		goto err_platform_device;

	err = platform_driver_probe(&dio48e_driver, dio48e_probe);
	if (err)
		goto err_platform_driver;

	return 0;

err_platform_driver:
	platform_device_del(dio48e_device);
err_platform_device:
	platform_device_put(dio48e_device);
	return err;
}

module_init(dio48e_init);
module_exit(dio48e_exit);

MODULE_AUTHOR("William Breathitt Gray <vilhelm.gray@gmail.com>");
MODULE_DESCRIPTION("ACCES 104-DIO-48E GPIO driver");
MODULE_LICENSE("GPL v2");