/*
 * GPIO driver for the Diamond Systems GPIO-MM
 * 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 following Diamond Systems devices: GPIO-MM and
 * GPIO-MM-12.
 */
#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/isa.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/spinlock.h>

#define GPIOMM_EXTENT 8
#define MAX_NUM_GPIOMM max_num_isa_dev(GPIOMM_EXTENT)

static unsigned int base[MAX_NUM_GPIOMM];
static unsigned int num_gpiomm;
module_param_array(base, uint, &num_gpiomm, 0);
MODULE_PARM_DESC(base, "Diamond Systems GPIO-MM base addresses");

/**
 * struct gpiomm_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
 */
struct gpiomm_gpio {
	struct gpio_chip chip;
	unsigned char io_state[6];
	unsigned char out_state[6];
	unsigned char control[2];
	spinlock_t lock;
	unsigned int base;
};

static int gpiomm_gpio_get_direction(struct gpio_chip *chip,
	unsigned int offset)
{
	struct gpiomm_gpio *const gpiommgpio = gpiochip_get_data(chip);
	const unsigned int port = offset / 8;
	const unsigned int mask = BIT(offset % 8);

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

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

	spin_lock_irqsave(&gpiommgpio->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) {
			gpiommgpio->io_state[io_port] |= 0xF0;
			gpiommgpio->control[control_port] |= BIT(3);
		} else {
			gpiommgpio->io_state[io_port] |= 0x0F;
			gpiommgpio->control[control_port] |= BIT(0);
		}
	} else {
		gpiommgpio->io_state[io_port] |= 0xFF;
		if (io_port == 0 || io_port == 3)
			gpiommgpio->control[control_port] |= BIT(4);
		else
			gpiommgpio->control[control_port] |= BIT(1);
	}

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

	spin_unlock_irqrestore(&gpiommgpio->lock, flags);

	return 0;
}

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

	spin_lock_irqsave(&gpiommgpio->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) {
			gpiommgpio->io_state[io_port] &= 0x0F;
			gpiommgpio->control[control_port] &= ~BIT(3);
		} else {
			gpiommgpio->io_state[io_port] &= 0xF0;
			gpiommgpio->control[control_port] &= ~BIT(0);
		}
	} else {
		gpiommgpio->io_state[io_port] &= 0x00;
		if (io_port == 0 || io_port == 3)
			gpiommgpio->control[control_port] &= ~BIT(4);
		else
			gpiommgpio->control[control_port] &= ~BIT(1);
	}

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

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

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

	spin_unlock_irqrestore(&gpiommgpio->lock, flags);

	return 0;
}

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

	spin_lock_irqsave(&gpiommgpio->lock, flags);

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

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

	spin_unlock_irqrestore(&gpiommgpio->lock, flags);

	return !!(port_state & mask);
}

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

	spin_lock_irqsave(&gpiommgpio->lock, flags);

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

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

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

static int gpiomm_probe(struct device *dev, unsigned int id)
{
	struct gpiomm_gpio *gpiommgpio;
	const char *const name = dev_name(dev);
	int err;

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

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

	gpiommgpio->chip.label = name;
	gpiommgpio->chip.parent = dev;
	gpiommgpio->chip.owner = THIS_MODULE;
	gpiommgpio->chip.base = -1;
	gpiommgpio->chip.ngpio = 48;
	gpiommgpio->chip.get_direction = gpiomm_gpio_get_direction;
	gpiommgpio->chip.direction_input = gpiomm_gpio_direction_input;
	gpiommgpio->chip.direction_output = gpiomm_gpio_direction_output;
	gpiommgpio->chip.get = gpiomm_gpio_get;
	gpiommgpio->chip.set = gpiomm_gpio_set;
	gpiommgpio->base = base[id];

	spin_lock_init(&gpiommgpio->lock);

	dev_set_drvdata(dev, gpiommgpio);

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

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

	return 0;
}

static int gpiomm_remove(struct device *dev, unsigned int id)
{
	struct gpiomm_gpio *const gpiommgpio = dev_get_drvdata(dev);

	gpiochip_remove(&gpiommgpio->chip);

	return 0;
}

static struct isa_driver gpiomm_driver = {
	.probe = gpiomm_probe,
	.driver = {
		.name = "gpio-mm"
	},
	.remove = gpiomm_remove
};

module_isa_driver(gpiomm_driver, num_gpiomm);

MODULE_AUTHOR("William Breathitt Gray <vilhelm.gray@gmail.com>");
MODULE_DESCRIPTION("Diamond Systems GPIO-MM GPIO driver");
MODULE_LICENSE("GPL v2");