/*
 *  GPIO interface for IT8761E Super I/O chip
 *
 *  Author: Denis Turischev <denis@compulab.co.il>
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License 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.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; see the file COPYING.  If not, write to
 *  the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
 */

#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/io.h>
#include <linux/errno.h>
#include <linux/ioport.h>

#include <linux/gpio.h>

#define SIO_CHIP_ID             0x8761
#define CHIP_ID_HIGH_BYTE       0x20
#define CHIP_ID_LOW_BYTE        0x21

static u8 ports[2] = { 0x2e, 0x4e };
static u8 port;

static DEFINE_SPINLOCK(sio_lock);

#define GPIO_NAME               "it8761-gpio"
#define GPIO_BA_HIGH_BYTE       0x60
#define GPIO_BA_LOW_BYTE        0x61
#define GPIO_IOSIZE             4
#define GPIO1X_IO               0xf0
#define GPIO2X_IO               0xf1

static u16 gpio_ba;

static u8 read_reg(u8 addr, u8 port)
{
        outb(addr, port);
        return inb(port + 1);
}

static void write_reg(u8 data, u8 addr, u8 port)
{
        outb(addr, port);
        outb(data, port + 1);
}

static void enter_conf_mode(u8 port)
{
        outb(0x87, port);
        outb(0x61, port);
        outb(0x55, port);
        outb((port == 0x2e) ? 0x55 : 0xaa, port);
}

static void exit_conf_mode(u8 port)
{
        outb(0x2, port);
        outb(0x2, port + 1);
}

static void enter_gpio_mode(u8 port)
{
        write_reg(0x2, 0x7, port);
}

static int it8761e_gpio_get(struct gpio_chip *gc, unsigned gpio_num)
{
        u16 reg;
        u8 bit;

        bit = gpio_num % 8;
        reg = (gpio_num >= 8) ? gpio_ba + 1 : gpio_ba;

        return !!(inb(reg) & (1 << bit));
}

static int it8761e_gpio_direction_in(struct gpio_chip *gc, unsigned gpio_num)
{
        u8 curr_dirs;
        u8 io_reg, bit;

        bit = gpio_num % 8;
        io_reg = (gpio_num >= 8) ? GPIO2X_IO : GPIO1X_IO;

        spin_lock(&sio_lock);

        enter_conf_mode(port);
        enter_gpio_mode(port);

        curr_dirs = read_reg(io_reg, port);

        if (curr_dirs & (1 << bit))
                write_reg(curr_dirs & ~(1 << bit), io_reg, port);

        exit_conf_mode(port);

        spin_unlock(&sio_lock);
        return 0;
}

static void it8761e_gpio_set(struct gpio_chip *gc,
                                unsigned gpio_num, int val)
{
        u8 curr_vals, bit;
        u16 reg;

        bit = gpio_num % 8;
        reg = (gpio_num >= 8) ? gpio_ba + 1 : gpio_ba;

        spin_lock(&sio_lock);

        curr_vals = inb(reg);
        if (val)
                outb(curr_vals | (1 << bit) , reg);
        else
                outb(curr_vals & ~(1 << bit), reg);

        spin_unlock(&sio_lock);
}

static int it8761e_gpio_direction_out(struct gpio_chip *gc,
                                        unsigned gpio_num, int val)
{
        u8 curr_dirs, io_reg, bit;

        bit = gpio_num % 8;
        io_reg = (gpio_num >= 8) ? GPIO2X_IO : GPIO1X_IO;

        it8761e_gpio_set(gc, gpio_num, val);

        spin_lock(&sio_lock);

        enter_conf_mode(port);
        enter_gpio_mode(port);

        curr_dirs = read_reg(io_reg, port);

        if (!(curr_dirs & (1 << bit)))
                write_reg(curr_dirs | (1 << bit), io_reg, port);

        exit_conf_mode(port);

        spin_unlock(&sio_lock);
        return 0;
}

static struct gpio_chip it8761e_gpio_chip = {
        .label                  = GPIO_NAME,
        .owner                  = THIS_MODULE,
        .get                    = it8761e_gpio_get,
        .direction_input        = it8761e_gpio_direction_in,
        .set                    = it8761e_gpio_set,
        .direction_output       = it8761e_gpio_direction_out,
};

static int __init it8761e_gpio_init(void)
{
        int i, id, err;

        /* chip and port detection */
        for (i = 0; i < ARRAY_SIZE(ports); i++) {
                spin_lock(&sio_lock);
                enter_conf_mode(ports[i]);

                id = (read_reg(CHIP_ID_HIGH_BYTE, ports[i]) << 8) +
                                read_reg(CHIP_ID_LOW_BYTE, ports[i]);

                exit_conf_mode(ports[i]);
                spin_unlock(&sio_lock);

                if (id == SIO_CHIP_ID) {
                        port = ports[i];
                        break;
                }
        }

        if (!port)
                return -ENODEV;

        /* fetch GPIO base address */
        enter_conf_mode(port);
        enter_gpio_mode(port);
        gpio_ba = (read_reg(GPIO_BA_HIGH_BYTE, port) << 8) +
                                read_reg(GPIO_BA_LOW_BYTE, port);
        exit_conf_mode(port);

        if (!request_region(gpio_ba, GPIO_IOSIZE, GPIO_NAME))
                return -EBUSY;

        it8761e_gpio_chip.base = -1;
        it8761e_gpio_chip.ngpio = 16;

        err = gpiochip_add(&it8761e_gpio_chip);
        if (err < 0)
                goto gpiochip_add_err;

        return 0;

gpiochip_add_err:
        release_region(gpio_ba, GPIO_IOSIZE);
        gpio_ba = 0;
        return err;
}

static void __exit it8761e_gpio_exit(void)
{
        if (gpio_ba) {
                int ret = gpiochip_remove(&it8761e_gpio_chip);

                WARN(ret, "%s(): gpiochip_remove() failed, ret=%d\n",
                                __func__, ret);

                release_region(gpio_ba, GPIO_IOSIZE);
                gpio_ba = 0;
        }
}
module_init(it8761e_gpio_init);
module_exit(it8761e_gpio_exit);

MODULE_AUTHOR("Denis Turischev <denis@compulab.co.il>");
MODULE_DESCRIPTION("GPIO interface for IT8761E Super I/O chip");
MODULE_LICENSE("GPL");