/*
 * GPIO driver for EXAR XRA1403 16-bit GPIO expander
 *
 * Copyright (c) 2017, General Electric Company
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms and conditions of the GNU General Public License,
 * version 2, as published by the Free Software Foundation.
 *
 * This program is distributed in the hope 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.  If not, see <http://www.gnu.org/licenses/>.
 */

#include <linux/bitops.h>
#include <linux/gpio/driver.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/of_device.h>
#include <linux/of_gpio.h>
#include <linux/seq_file.h>
#include <linux/spi/spi.h>
#include <linux/regmap.h>

/* XRA1403 registers */
#define XRA_GSR   0x00 /* GPIO State */
#define XRA_OCR   0x02 /* Output Control */
#define XRA_PIR   0x04 /* Input Polarity Inversion */
#define XRA_GCR   0x06 /* GPIO Configuration */
#define XRA_PUR   0x08 /* Input Internal Pull-up Resistor Enable/Disable */
#define XRA_IER   0x0A /* Input Interrupt Enable */
#define XRA_TSCR  0x0C /* Output Three-State Control */
#define XRA_ISR   0x0E /* Input Interrupt Status */
#define XRA_REIR  0x10 /* Input Rising Edge Interrupt Enable */
#define XRA_FEIR  0x12 /* Input Falling Edge Interrupt Enable */
#define XRA_IFR   0x14 /* Input Filter Enable/Disable */

struct xra1403 {
        struct gpio_chip  chip;
        struct regmap     *regmap;
};

static const struct regmap_config xra1403_regmap_cfg = {
                .reg_bits = 7,
                .pad_bits = 1,
                .val_bits = 8,

                .max_register = XRA_IFR | 0x01,
};

static unsigned int to_reg(unsigned int reg, unsigned int offset)
{
        return reg + (offset > 7);
}

static int xra1403_direction_input(struct gpio_chip *chip, unsigned int offset)
{
        struct xra1403 *xra = gpiochip_get_data(chip);

        return regmap_update_bits(xra->regmap, to_reg(XRA_GCR, offset),
                        BIT(offset % 8), BIT(offset % 8));
}

static int xra1403_direction_output(struct gpio_chip *chip, unsigned int offset,
                                    int value)
{
        int ret;
        struct xra1403 *xra = gpiochip_get_data(chip);

        ret = regmap_update_bits(xra->regmap, to_reg(XRA_GCR, offset),
                        BIT(offset % 8), 0);
        if (ret)
                return ret;

        ret = regmap_update_bits(xra->regmap, to_reg(XRA_OCR, offset),
                        BIT(offset % 8), value ? BIT(offset % 8) : 0);

        return ret;
}

static int xra1403_get_direction(struct gpio_chip *chip, unsigned int offset)
{
        int ret;
        unsigned int val;
        struct xra1403 *xra = gpiochip_get_data(chip);

        ret = regmap_read(xra->regmap, to_reg(XRA_GCR, offset), &val);
        if (ret)
                return ret;

        return !!(val & BIT(offset % 8));
}

static int xra1403_get(struct gpio_chip *chip, unsigned int offset)
{
        int ret;
        unsigned int val;
        struct xra1403 *xra = gpiochip_get_data(chip);

        ret = regmap_read(xra->regmap, to_reg(XRA_GSR, offset), &val);
        if (ret)
                return ret;

        return !!(val & BIT(offset % 8));
}

static void xra1403_set(struct gpio_chip *chip, unsigned int offset, int value)
{
        int ret;
        struct xra1403 *xra = gpiochip_get_data(chip);

        ret = regmap_update_bits(xra->regmap, to_reg(XRA_OCR, offset),
                        BIT(offset % 8), value ? BIT(offset % 8) : 0);
        if (ret)
                dev_err(chip->parent, "Failed to set pin: %d, ret: %d\n",
                                offset, ret);
}

#ifdef CONFIG_DEBUG_FS
static void xra1403_dbg_show(struct seq_file *s, struct gpio_chip *chip)
{
        int reg;
        struct xra1403 *xra = gpiochip_get_data(chip);
        int value[xra1403_regmap_cfg.max_register];
        int i;
        unsigned int gcr;
        unsigned int gsr;

        seq_puts(s, "xra reg:");
        for (reg = 0; reg <= xra1403_regmap_cfg.max_register; reg++)
                seq_printf(s, " %2.2x", reg);
        seq_puts(s, "\n  value:");
        for (reg = 0; reg < xra1403_regmap_cfg.max_register; reg++) {
                regmap_read(xra->regmap, reg, &value[reg]);
                seq_printf(s, " %2.2x", value[reg]);
        }
        seq_puts(s, "\n");

        gcr = value[XRA_GCR + 1] << 8 | value[XRA_GCR];
        gsr = value[XRA_GSR + 1] << 8 | value[XRA_GSR];
        for (i = 0; i < chip->ngpio; i++) {
                const char *label = gpiochip_is_requested(chip, i);

                if (!label)
                        continue;

                seq_printf(s, " gpio-%-3d (%-12s) %s %s\n",
                           chip->base + i, label,
                           (gcr & BIT(i)) ? "in" : "out",
                           (gsr & BIT(i)) ? "hi" : "lo");
        }
}
#else
#define xra1403_dbg_show NULL
#endif

static int xra1403_probe(struct spi_device *spi)
{
        struct xra1403 *xra;
        struct gpio_desc *reset_gpio;
        int ret;

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

        /* bring the chip out of reset if reset pin is provided*/
        reset_gpio = devm_gpiod_get_optional(&spi->dev, "reset", GPIOD_OUT_LOW);
        if (IS_ERR(reset_gpio))
                dev_warn(&spi->dev, "Could not get reset-gpios\n");

        xra->chip.direction_input = xra1403_direction_input;
        xra->chip.direction_output = xra1403_direction_output;
        xra->chip.get_direction = xra1403_get_direction;
        xra->chip.get = xra1403_get;
        xra->chip.set = xra1403_set;

        xra->chip.dbg_show = xra1403_dbg_show;

        xra->chip.ngpio = 16;
        xra->chip.label = "xra1403";

        xra->chip.base = -1;
        xra->chip.can_sleep = true;
        xra->chip.parent = &spi->dev;
        xra->chip.owner = THIS_MODULE;

        xra->regmap = devm_regmap_init_spi(spi, &xra1403_regmap_cfg);
        if (IS_ERR(xra->regmap)) {
                ret = PTR_ERR(xra->regmap);
                dev_err(&spi->dev, "Failed to allocate regmap: %d\n", ret);
                return ret;
        }

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

        spi_set_drvdata(spi, xra);

        return 0;
}

static const struct spi_device_id xra1403_ids[] = {
        { "xra1403" },
        {},
};
MODULE_DEVICE_TABLE(spi, xra1403_ids);

static const struct of_device_id xra1403_spi_of_match[] = {
        { .compatible = "exar,xra1403" },
        {},
};
MODULE_DEVICE_TABLE(of, xra1403_spi_of_match);

static struct spi_driver xra1403_driver = {
        .probe    = xra1403_probe,
        .id_table = xra1403_ids,
        .driver   = {
                .name           = "xra1403",
                .of_match_table = of_match_ptr(xra1403_spi_of_match),
        },
};

module_spi_driver(xra1403_driver);

MODULE_AUTHOR("Nandor Han <nandor.han@ge.com>");
MODULE_AUTHOR("Semi Malinen <semi.malinen@ge.com>");
MODULE_DESCRIPTION("GPIO expander driver for EXAR XRA1403");
MODULE_LICENSE("GPL v2");