// SPDX-License-Identifier: BSD-2-Clause OR GPL-2.0-or-later
/*
 * ENE KB3930 Embedded Controller Driver
 *
 * Copyright (C) 2020 Lubomir Rintel
 */

#include <linux/delay.h>
#include <linux/gpio/consumer.h>
#include <linux/i2c.h>
#include <linux/mfd/core.h>
#include <linux/module.h>
#include <linux/reboot.h>
#include <linux/regmap.h>

/* I2C registers that are multiplexing access to the EC RAM. */
enum {
        EC_DATA_IN      = 0x00,
        EC_RAM_OUT      = 0x80,
        EC_RAM_IN       = 0x81,
};

/* EC RAM registers. */
enum {
        EC_MODEL        = 0x30,
        EC_VERSION_MAJ  = 0x31,
        EC_VERSION_MIN  = 0x32,
};

struct kb3930 {
        struct i2c_client *client;
        struct regmap *ram_regmap;
        struct gpio_descs *off_gpios;
};

static struct kb3930 *kb3930_power_off;

#define EC_GPIO_WAVE            0
#define EC_GPIO_OFF_MODE        1

#define EC_OFF_MODE_REBOOT      0
#define EC_OFF_MODE_POWER       1

static void kb3930_off(struct kb3930 *ddata, int off_mode)
{
        gpiod_direction_output(ddata->off_gpios->desc[EC_GPIO_OFF_MODE],
                               off_mode);

        /*
         * This creates a 10 Hz wave on EC_GPIO_WAVE that signals a
         * shutdown request to the EC. Once the EC detects it, it will
         * proceed to turn the power off or reset the board depending on
         * the value of EC_GPIO_OFF_MODE.
         */
        while (1) {
                mdelay(50);
                gpiod_direction_output(ddata->off_gpios->desc[EC_GPIO_WAVE], 0);
                mdelay(50);
                gpiod_direction_output(ddata->off_gpios->desc[EC_GPIO_WAVE], 1);
        }
}

static int kb3930_restart(struct notifier_block *this,
                          unsigned long mode, void *cmd)
{
        kb3930_off(kb3930_power_off, EC_OFF_MODE_REBOOT);
        return NOTIFY_DONE;
}

static void kb3930_pm_power_off(void)
{
        kb3930_off(kb3930_power_off, EC_OFF_MODE_POWER);
}

static struct notifier_block kb3930_restart_nb = {
        .notifier_call = kb3930_restart,
};

static const struct mfd_cell ariel_ec_cells[] = {
        { .name = "dell-wyse-ariel-led", },
        { .name = "dell-wyse-ariel-power", },
};

static int kb3930_ec_ram_reg_write(void *context, unsigned int reg,
                                   unsigned int val)
{
        struct kb3930 *ddata = context;

        return i2c_smbus_write_word_data(ddata->client, EC_RAM_OUT,
                                         (val << 8) | reg);
}

static int kb3930_ec_ram_reg_read(void *context, unsigned int reg,
                                  unsigned int *val)
{
        struct kb3930 *ddata = context;
        int ret;

        ret = i2c_smbus_write_word_data(ddata->client, EC_RAM_IN, reg);
        if (ret < 0)
                return ret;

        ret = i2c_smbus_read_word_data(ddata->client, EC_DATA_IN);
        if (ret < 0)
                return ret;

        *val = ret >> 8;
        return 0;
}

static const struct regmap_config kb3930_ram_regmap_config = {
        .name = "ec_ram",
        .reg_bits = 8,
        .val_bits = 8,
        .reg_stride = 1,
        .max_register = 0xff,
        .reg_write = kb3930_ec_ram_reg_write,
        .reg_read = kb3930_ec_ram_reg_read,
        .fast_io = false,
};

static int kb3930_probe(struct i2c_client *client)
{
        struct device *dev = &client->dev;
        struct device_node *np = dev->of_node;
        struct kb3930 *ddata;
        unsigned int model;
        int ret;

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

        kb3930_power_off = ddata;
        ddata->client = client;
        i2c_set_clientdata(client, ddata);

        ddata->ram_regmap = devm_regmap_init(dev, NULL, ddata,
                                             &kb3930_ram_regmap_config);
        if (IS_ERR(ddata->ram_regmap))
                return PTR_ERR(ddata->ram_regmap);

        ret = regmap_read(ddata->ram_regmap, EC_MODEL, &model);
        if (ret < 0)
                return ret;

        /* Currently we only support the cells present on Dell Ariel model. */
        if (model != 'J') {
                dev_err(dev, "unknown board model: %02x\n", model);
                return -ENODEV;
        }

        ret = devm_mfd_add_devices(dev, PLATFORM_DEVID_AUTO,
                                   ariel_ec_cells,
                                   ARRAY_SIZE(ariel_ec_cells),
                                   NULL, 0, NULL);
        if (ret)
                return ret;

        if (of_property_read_bool(np, "system-power-controller")) {
                ddata->off_gpios =
                        devm_gpiod_get_array_optional(dev, "off", GPIOD_IN);
                if (IS_ERR(ddata->off_gpios))
                        return PTR_ERR(ddata->off_gpios);
                if (ddata->off_gpios && ddata->off_gpios->ndescs < 2) {
                        dev_err(dev, "invalid off-gpios property\n");
                        return -EINVAL;
                }
        }

        if (ddata->off_gpios) {
                register_restart_handler(&kb3930_restart_nb);
                if (!pm_power_off)
                        pm_power_off = kb3930_pm_power_off;
        }

        return 0;
}

static void kb3930_remove(struct i2c_client *client)
{
        struct kb3930 *ddata = i2c_get_clientdata(client);

        if (ddata->off_gpios) {
                if (pm_power_off == kb3930_pm_power_off)
                        pm_power_off = NULL;
                unregister_restart_handler(&kb3930_restart_nb);
        }
        kb3930_power_off = NULL;
}

static const struct of_device_id kb3930_dt_ids[] = {
        { .compatible = "ene,kb3930" },
        { }
};
MODULE_DEVICE_TABLE(of, kb3930_dt_ids);

static struct i2c_driver kb3930_driver = {
        .probe = kb3930_probe,
        .remove = kb3930_remove,
        .driver = {
                .name = "ene-kb3930",
                .of_match_table = kb3930_dt_ids,
        },
};
module_i2c_driver(kb3930_driver);

MODULE_AUTHOR("Lubomir Rintel <lkundrak@v3.sk>");
MODULE_DESCRIPTION("ENE KB3930 Embedded Controller Driver");
MODULE_LICENSE("Dual BSD/GPL");