/*
 * Digital I/O driver for Technologic Systems I2C FPGA Core
 *
 * Copyright (C) 2015 Technologic Systems
 * Copyright (C) 2016 Savoir-Faire Linux
 *
 * 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 "as is" WITHOUT ANY WARRANTY of any
 * kind, whether expressed or implied; without even the implied warranty
 * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License version 2 for more details.
 */

#include <linux/gpio/driver.h>
#include <linux/i2c.h>
#include <linux/of_device.h>
#include <linux/module.h>
#include <linux/regmap.h>

#define DEFAULT_PIN_NUMBER      32
/*
 * Register bits used by the GPIO device
 * Some boards, such as TS-7970 do not have a separate input bit
 */
#define TS4900_GPIO_OE          0x01
#define TS4900_GPIO_OUT         0x02
#define TS4900_GPIO_IN          0x04
#define TS7970_GPIO_IN          0x02

struct ts4900_gpio_priv {
        struct regmap *regmap;
        struct gpio_chip gpio_chip;
        unsigned int input_bit;
};

static int ts4900_gpio_get_direction(struct gpio_chip *chip,
                                     unsigned int offset)
{
        struct ts4900_gpio_priv *priv = gpiochip_get_data(chip);
        unsigned int reg;

        regmap_read(priv->regmap, offset, &reg);

        if (reg & TS4900_GPIO_OE)
                return GPIO_LINE_DIRECTION_OUT;

        return GPIO_LINE_DIRECTION_IN;
}

static int ts4900_gpio_direction_input(struct gpio_chip *chip,
                                       unsigned int offset)
{
        struct ts4900_gpio_priv *priv = gpiochip_get_data(chip);

        /*
         * This will clear the output enable bit, the other bits are
         * dontcare when this is cleared
         */
        return regmap_write(priv->regmap, offset, 0);
}

static int ts4900_gpio_direction_output(struct gpio_chip *chip,
                                        unsigned int offset, int value)
{
        struct ts4900_gpio_priv *priv = gpiochip_get_data(chip);
        int ret;

        if (value)
                ret = regmap_write(priv->regmap, offset, TS4900_GPIO_OE |
                                                         TS4900_GPIO_OUT);
        else
                ret = regmap_write(priv->regmap, offset, TS4900_GPIO_OE);

        return ret;
}

static int ts4900_gpio_get(struct gpio_chip *chip, unsigned int offset)
{
        struct ts4900_gpio_priv *priv = gpiochip_get_data(chip);
        unsigned int reg;

        regmap_read(priv->regmap, offset, &reg);

        return !!(reg & priv->input_bit);
}

static void ts4900_gpio_set(struct gpio_chip *chip, unsigned int offset,
                            int value)
{
        struct ts4900_gpio_priv *priv = gpiochip_get_data(chip);

        if (value)
                regmap_update_bits(priv->regmap, offset, TS4900_GPIO_OUT,
                                   TS4900_GPIO_OUT);
        else
                regmap_update_bits(priv->regmap, offset, TS4900_GPIO_OUT, 0);
}

static const struct regmap_config ts4900_regmap_config = {
        .reg_bits = 16,
        .val_bits = 8,
};

static const struct gpio_chip template_chip = {
        .label                  = "ts4900-gpio",
        .owner                  = THIS_MODULE,
        .get_direction          = ts4900_gpio_get_direction,
        .direction_input        = ts4900_gpio_direction_input,
        .direction_output       = ts4900_gpio_direction_output,
        .get                    = ts4900_gpio_get,
        .set                    = ts4900_gpio_set,
        .base                   = -1,
        .can_sleep              = true,
};

static const struct of_device_id ts4900_gpio_of_match_table[] = {
        {
                .compatible = "technologic,ts4900-gpio",
                .data = (void *)TS4900_GPIO_IN,
        }, {
                .compatible = "technologic,ts7970-gpio",
                .data = (void *)TS7970_GPIO_IN,
        },
        { /* sentinel */ },
};
MODULE_DEVICE_TABLE(of, ts4900_gpio_of_match_table);

static int ts4900_gpio_probe(struct i2c_client *client,
                        const struct i2c_device_id *id)
{
        struct ts4900_gpio_priv *priv;
        u32 ngpio;
        int ret;

        if (of_property_read_u32(client->dev.of_node, "ngpios", &ngpio))
                ngpio = DEFAULT_PIN_NUMBER;

        priv = devm_kzalloc(&client->dev, sizeof(*priv), GFP_KERNEL);
        if (!priv)
                return -ENOMEM;

        priv->gpio_chip = template_chip;
        priv->gpio_chip.label = "ts4900-gpio";
        priv->gpio_chip.ngpio = ngpio;
        priv->gpio_chip.parent = &client->dev;
        priv->input_bit = (uintptr_t)of_device_get_match_data(&client->dev);

        priv->regmap = devm_regmap_init_i2c(client, &ts4900_regmap_config);
        if (IS_ERR(priv->regmap)) {
                ret = PTR_ERR(priv->regmap);
                dev_err(&client->dev, "Failed to allocate register map: %d\n",
                        ret);
                return ret;
        }

        ret = devm_gpiochip_add_data(&client->dev, &priv->gpio_chip, priv);
        if (ret < 0) {
                dev_err(&client->dev, "Unable to register gpiochip\n");
                return ret;
        }

        i2c_set_clientdata(client, priv);

        return 0;
}

static const struct i2c_device_id ts4900_gpio_id_table[] = {
        { "ts4900-gpio", },
        { /* sentinel */ }
};
MODULE_DEVICE_TABLE(i2c, ts4900_gpio_id_table);

static struct i2c_driver ts4900_gpio_driver = {
        .driver = {
                .name = "ts4900-gpio",
                .of_match_table = ts4900_gpio_of_match_table,
        },
        .probe = ts4900_gpio_probe,
        .id_table = ts4900_gpio_id_table,
};
module_i2c_driver(ts4900_gpio_driver);

MODULE_AUTHOR("Technologic Systems");
MODULE_DESCRIPTION("GPIO interface for Technologic Systems I2C-FPGA core");
MODULE_LICENSE("GPL");