// SPDX-License-Identifier: GPL-2.0-only
/*
 * FXL6408 GPIO driver
 *
 * Copyright 2023 Toradex
 *
 * Author: Emanuele Ghidoli <emanuele.ghidoli@toradex.com>
 */

#include <linux/err.h>
#include <linux/gpio/regmap.h>
#include <linux/i2c.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/regmap.h>

#define FXL6408_REG_DEVICE_ID           0x01
#define FXL6408_MF_FAIRCHILD            0b101
#define FXL6408_MF_SHIFT                5

/* Bits set here indicate that the GPIO is an output. */
#define FXL6408_REG_IO_DIR              0x03

/*
 * Bits set here, when the corresponding bit of IO_DIR is set, drive
 * the output high instead of low.
 */
#define FXL6408_REG_OUTPUT              0x05

/* Bits here make the output High-Z, instead of the OUTPUT value. */
#define FXL6408_REG_OUTPUT_HIGH_Z       0x07

/* Returns the current status (1 = HIGH) of the input pins. */
#define FXL6408_REG_INPUT_STATUS        0x0f

/*
 * Return the current interrupt status
 * This bit is HIGH if input GPIO != default state (register 09h).
 * The flag is cleared after being read (bit returns to 0).
 * The input must go back to default state and change again before this flag is raised again.
 */
#define FXL6408_REG_INT_STS             0x13

#define FXL6408_NGPIO                   8

static const struct regmap_range rd_range[] = {
        { FXL6408_REG_DEVICE_ID, FXL6408_REG_DEVICE_ID },
        { FXL6408_REG_IO_DIR, FXL6408_REG_OUTPUT },
        { FXL6408_REG_INPUT_STATUS, FXL6408_REG_INPUT_STATUS },
};

static const struct regmap_range wr_range[] = {
        { FXL6408_REG_DEVICE_ID, FXL6408_REG_DEVICE_ID },
        { FXL6408_REG_IO_DIR, FXL6408_REG_OUTPUT },
        { FXL6408_REG_OUTPUT_HIGH_Z, FXL6408_REG_OUTPUT_HIGH_Z },
};

static const struct regmap_range volatile_range[] = {
        { FXL6408_REG_DEVICE_ID, FXL6408_REG_DEVICE_ID },
        { FXL6408_REG_INPUT_STATUS, FXL6408_REG_INPUT_STATUS },
};

static const struct regmap_access_table rd_table = {
        .yes_ranges = rd_range,
        .n_yes_ranges = ARRAY_SIZE(rd_range),
};

static const struct regmap_access_table wr_table = {
        .yes_ranges = wr_range,
        .n_yes_ranges = ARRAY_SIZE(wr_range),
};

static const struct regmap_access_table volatile_table = {
        .yes_ranges = volatile_range,
        .n_yes_ranges = ARRAY_SIZE(volatile_range),
};

static const struct regmap_config regmap = {
        .reg_bits = 8,
        .val_bits = 8,

        .max_register = FXL6408_REG_INT_STS,
        .wr_table = &wr_table,
        .rd_table = &rd_table,
        .volatile_table = &volatile_table,

        .cache_type = REGCACHE_MAPLE,
        .num_reg_defaults_raw = FXL6408_REG_INT_STS + 1,
};

static int fxl6408_identify(struct device *dev, struct regmap *regmap)
{
        int val, ret;

        ret = regmap_read(regmap, FXL6408_REG_DEVICE_ID, &val);
        if (ret)
                return dev_err_probe(dev, ret, "error reading DEVICE_ID\n");
        if (val >> FXL6408_MF_SHIFT != FXL6408_MF_FAIRCHILD)
                return dev_err_probe(dev, -ENODEV, "invalid device id 0x%02x\n", val);

        return 0;
}

static int fxl6408_probe(struct i2c_client *client)
{
        struct device *dev = &client->dev;
        int ret;
        struct gpio_regmap_config gpio_config = {
                .parent = dev,
                .ngpio = FXL6408_NGPIO,
                .reg_dat_base = GPIO_REGMAP_ADDR(FXL6408_REG_INPUT_STATUS),
                .reg_set_base = GPIO_REGMAP_ADDR(FXL6408_REG_OUTPUT),
                .reg_dir_out_base = GPIO_REGMAP_ADDR(FXL6408_REG_IO_DIR),
                .ngpio_per_reg = FXL6408_NGPIO,
        };

        gpio_config.regmap = devm_regmap_init_i2c(client, &regmap);
        if (IS_ERR(gpio_config.regmap))
                return dev_err_probe(dev, PTR_ERR(gpio_config.regmap),
                                     "failed to allocate register map\n");

        ret = fxl6408_identify(dev, gpio_config.regmap);
        if (ret)
                return ret;

        i2c_set_clientdata(client, gpio_config.regmap);

        /* Disable High-Z of outputs, so that our OUTPUT updates actually take effect. */
        ret = regmap_write(gpio_config.regmap, FXL6408_REG_OUTPUT_HIGH_Z, 0);
        if (ret)
                return dev_err_probe(dev, ret, "failed to write 'output high Z' register\n");

        return PTR_ERR_OR_ZERO(devm_gpio_regmap_register(dev, &gpio_config));
}

static int fxl6408_resume(struct device *dev)
{
        struct regmap *regmap = dev_get_drvdata(dev);

        regcache_mark_dirty(regmap);
        return regcache_sync(regmap);
}

static DEFINE_SIMPLE_DEV_PM_OPS(fxl6408_pm_ops, NULL, fxl6408_resume);

static const __maybe_unused struct of_device_id fxl6408_dt_ids[] = {
        { .compatible = "fcs,fxl6408" },
        { }
};
MODULE_DEVICE_TABLE(of, fxl6408_dt_ids);

static const struct i2c_device_id fxl6408_id[] = {
        { "fxl6408" },
        { }
};
MODULE_DEVICE_TABLE(i2c, fxl6408_id);

static struct i2c_driver fxl6408_driver = {
        .driver = {
                .name   = "fxl6408",
                .pm     = pm_sleep_ptr(&fxl6408_pm_ops),
                .of_match_table = fxl6408_dt_ids,
        },
        .probe          = fxl6408_probe,
        .id_table       = fxl6408_id,
};
module_i2c_driver(fxl6408_driver);

MODULE_AUTHOR("Emanuele Ghidoli <emanuele.ghidoli@toradex.com>");
MODULE_DESCRIPTION("FXL6408 GPIO driver");
MODULE_LICENSE("GPL");