// SPDX-License-Identifier: GPL-2.0+
/*
 * Acer Iconia Tab A500 Embedded Controller Driver
 *
 * Copyright 2020 GRATE-driver project
 */

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

#define A500_EC_I2C_ERR_TIMEOUT         500
#define A500_EC_POWER_CMD_TIMEOUT       1000

/*
 * Controller's firmware expects specific command opcodes to be used for the
 * corresponding registers. Unsupported commands are skipped by the firmware.
 */
#define CMD_SHUTDOWN                    0x0
#define CMD_WARM_REBOOT                 0x0
#define CMD_COLD_REBOOT                 0x1

enum {
        REG_CURRENT_NOW = 0x03,
        REG_SHUTDOWN = 0x52,
        REG_WARM_REBOOT = 0x54,
        REG_COLD_REBOOT = 0x55,
};

static struct i2c_client *a500_ec_client_pm_off;

static int a500_ec_read(void *context, const void *reg_buf, size_t reg_size,
                        void *val_buf, size_t val_sizel)
{
        struct i2c_client *client = context;
        unsigned int reg, retries = 5;
        u16 *ret_val = val_buf;
        s32 ret = 0;

        reg = *(u8 *)reg_buf;

        while (retries-- > 0) {
                ret = i2c_smbus_read_word_data(client, reg);
                if (ret >= 0)
                        break;

                msleep(A500_EC_I2C_ERR_TIMEOUT);
        }

        if (ret < 0) {
                dev_err(&client->dev, "read 0x%x failed: %d\n", reg, ret);
                return ret;
        }

        *ret_val = ret;

        if (reg == REG_CURRENT_NOW)
                fsleep(10000);

        return 0;
}

static int a500_ec_write(void *context, const void *data, size_t count)
{
        struct i2c_client *client = context;
        unsigned int reg, val, retries = 5;
        s32 ret = 0;

        reg = *(u8  *)(data + 0);
        val = *(u16 *)(data + 1);

        while (retries-- > 0) {
                ret = i2c_smbus_write_word_data(client, reg, val);
                if (ret >= 0)
                        break;

                msleep(A500_EC_I2C_ERR_TIMEOUT);
        }

        if (ret < 0) {
                dev_err(&client->dev, "write 0x%x failed: %d\n", reg, ret);
                return ret;
        }

        return 0;
}

static const struct regmap_config a500_ec_regmap_config = {
        .name = "KB930",
        .reg_bits = 8,
        .val_bits = 16,
        .max_register = 0xff,
};

static const struct regmap_bus a500_ec_regmap_bus = {
        .reg_format_endian_default = REGMAP_ENDIAN_NATIVE,
        .val_format_endian_default = REGMAP_ENDIAN_LITTLE,
        .write = a500_ec_write,
        .read = a500_ec_read,
        .max_raw_read = 2,
};

static void a500_ec_poweroff(void)
{
        i2c_smbus_write_word_data(a500_ec_client_pm_off,
                                  REG_SHUTDOWN, CMD_SHUTDOWN);

        mdelay(A500_EC_POWER_CMD_TIMEOUT);
}

static int a500_ec_restart_notify(struct notifier_block *this,
                                  unsigned long reboot_mode, void *data)
{
        if (reboot_mode == REBOOT_WARM)
                i2c_smbus_write_word_data(a500_ec_client_pm_off,
                                          REG_WARM_REBOOT, CMD_WARM_REBOOT);
        else
                i2c_smbus_write_word_data(a500_ec_client_pm_off,
                                          REG_COLD_REBOOT, CMD_COLD_REBOOT);

        mdelay(A500_EC_POWER_CMD_TIMEOUT);

        return NOTIFY_DONE;
}

static struct notifier_block a500_ec_restart_handler = {
        .notifier_call = a500_ec_restart_notify,
        .priority = 200,
};

static const struct mfd_cell a500_ec_cells[] = {
        { .name = "acer-a500-iconia-battery", },
        { .name = "acer-a500-iconia-leds", },
};

static int a500_ec_probe(struct i2c_client *client)
{
        struct regmap *regmap;
        int err;

        regmap = devm_regmap_init(&client->dev, &a500_ec_regmap_bus,
                                  client, &a500_ec_regmap_config);
        if (IS_ERR(regmap))
                return PTR_ERR(regmap);

        err = devm_mfd_add_devices(&client->dev, PLATFORM_DEVID_AUTO,
                                   a500_ec_cells, ARRAY_SIZE(a500_ec_cells),
                                   NULL, 0, NULL);
        if (err) {
                dev_err(&client->dev, "failed to add sub-devices: %d\n", err);
                return err;
        }

        if (of_device_is_system_power_controller(client->dev.of_node)) {
                a500_ec_client_pm_off = client;

                err = register_restart_handler(&a500_ec_restart_handler);
                if (err)
                        return err;

                if (!pm_power_off)
                        pm_power_off = a500_ec_poweroff;
        }

        return 0;
}

static void a500_ec_remove(struct i2c_client *client)
{
        if (of_device_is_system_power_controller(client->dev.of_node)) {
                if (pm_power_off == a500_ec_poweroff)
                        pm_power_off = NULL;

                unregister_restart_handler(&a500_ec_restart_handler);
        }
}

static const struct of_device_id a500_ec_match[] = {
        { .compatible = "acer,a500-iconia-ec" },
        { }
};
MODULE_DEVICE_TABLE(of, a500_ec_match);

static struct i2c_driver a500_ec_driver = {
        .driver = {
                .name = "acer-a500-embedded-controller",
                .of_match_table = a500_ec_match,
        },
        .probe = a500_ec_probe,
        .remove = a500_ec_remove,
};
module_i2c_driver(a500_ec_driver);

MODULE_DESCRIPTION("Acer Iconia Tab A500 Embedded Controller driver");
MODULE_AUTHOR("Dmitry Osipenko <digetx@gmail.com>");
MODULE_LICENSE("GPL");