// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Power Management and GPIO expander driver for MPC8349E-mITX-compatible MCU
 *
 * Copyright (c) 2008  MontaVista Software, Inc.
 *
 * Author: Anton Vorontsov <avorontsov@ru.mvista.com>
 */

#include <linux/kernel.h>
#include <linux/mod_devicetable.h>
#include <linux/module.h>
#include <linux/device.h>
#include <linux/mutex.h>
#include <linux/i2c.h>
#include <linux/gpio/driver.h>
#include <linux/slab.h>
#include <linux/kthread.h>
#include <linux/property.h>
#include <linux/reboot.h>
#include <asm/machdep.h>

/*
 * I don't have specifications for the MCU firmware, I found this register
 * and bits positions by the trial&error method.
 */
#define MCU_REG_CTRL    0x20
#define MCU_CTRL_POFF   0x40
#define MCU_CTRL_BTN    0x80

#define MCU_NUM_GPIO    2

struct mcu {
        struct mutex lock;
        struct i2c_client *client;
        struct gpio_chip gc;
        u8 reg_ctrl;
};

static struct mcu *glob_mcu;

struct task_struct *shutdown_thread;
static int shutdown_thread_fn(void *data)
{
        int ret;
        struct mcu *mcu = glob_mcu;

        while (!kthread_should_stop()) {
                ret = i2c_smbus_read_byte_data(mcu->client, MCU_REG_CTRL);
                if (ret < 0)
                        pr_err("MCU status reg read failed.\n");
                mcu->reg_ctrl = ret;


                if (mcu->reg_ctrl & MCU_CTRL_BTN) {
                        i2c_smbus_write_byte_data(mcu->client, MCU_REG_CTRL,
                                                  mcu->reg_ctrl & ~MCU_CTRL_BTN);

                        ctrl_alt_del();
                }

                set_current_state(TASK_INTERRUPTIBLE);
                schedule_timeout(HZ);
        }

        return 0;
}

static ssize_t show_status(struct device *d,
                           struct device_attribute *attr, char *buf)
{
        int ret;
        struct mcu *mcu = glob_mcu;

        ret = i2c_smbus_read_byte_data(mcu->client, MCU_REG_CTRL);
        if (ret < 0)
                return -ENODEV;
        mcu->reg_ctrl = ret;

        return sprintf(buf, "%02x\n", ret);
}
static DEVICE_ATTR(status, 0444, show_status, NULL);

static void mcu_power_off(void)
{
        struct mcu *mcu = glob_mcu;

        pr_info("Sending power-off request to the MCU...\n");
        mutex_lock(&mcu->lock);
        i2c_smbus_write_byte_data(mcu->client, MCU_REG_CTRL,
                                  mcu->reg_ctrl | MCU_CTRL_POFF);
        mutex_unlock(&mcu->lock);
}

static int mcu_gpio_set(struct gpio_chip *gc, unsigned int gpio, int val)
{
        struct mcu *mcu = gpiochip_get_data(gc);
        u8 bit = 1 << (4 + gpio);
        int ret;

        mutex_lock(&mcu->lock);
        if (val)
                mcu->reg_ctrl &= ~bit;
        else
                mcu->reg_ctrl |= bit;

        ret = i2c_smbus_write_byte_data(mcu->client, MCU_REG_CTRL,
                                        mcu->reg_ctrl);
        mutex_unlock(&mcu->lock);

        return ret;
}

static int mcu_gpio_dir_out(struct gpio_chip *gc, unsigned int gpio, int val)
{
        return mcu_gpio_set(gc, gpio, val);
}

static int mcu_gpiochip_add(struct mcu *mcu)
{
        struct device *dev = &mcu->client->dev;
        struct gpio_chip *gc = &mcu->gc;

        gc->owner = THIS_MODULE;
        gc->label = kasprintf(GFP_KERNEL, "%pfw", dev_fwnode(dev));
        if (!gc->label)
                return -ENOMEM;
        gc->can_sleep = 1;
        gc->ngpio = MCU_NUM_GPIO;
        gc->base = -1;
        gc->set = mcu_gpio_set;
        gc->direction_output = mcu_gpio_dir_out;
        gc->parent = dev;

        return gpiochip_add_data(gc, mcu);
}

static void mcu_gpiochip_remove(struct mcu *mcu)
{
        kfree(mcu->gc.label);
        gpiochip_remove(&mcu->gc);
}

static int mcu_probe(struct i2c_client *client)
{
        struct mcu *mcu;
        int ret;

        mcu = kzalloc_obj(*mcu);
        if (!mcu)
                return -ENOMEM;

        mutex_init(&mcu->lock);
        mcu->client = client;
        i2c_set_clientdata(client, mcu);

        ret = i2c_smbus_read_byte_data(mcu->client, MCU_REG_CTRL);
        if (ret < 0)
                goto err;
        mcu->reg_ctrl = ret;

        ret = mcu_gpiochip_add(mcu);
        if (ret)
                goto err;

        /* XXX: this is potentially racy, but there is no lock for pm_power_off */
        if (!pm_power_off) {
                glob_mcu = mcu;
                pm_power_off = mcu_power_off;
                dev_info(&client->dev, "will provide power-off service\n");
        }

        if (device_create_file(&client->dev, &dev_attr_status))
                dev_err(&client->dev,
                        "couldn't create device file for status\n");

        shutdown_thread = kthread_run(shutdown_thread_fn, NULL,
                                      "mcu-i2c-shdn");

        return 0;
err:
        kfree(mcu);
        return ret;
}

static void mcu_remove(struct i2c_client *client)
{
        struct mcu *mcu = i2c_get_clientdata(client);

        kthread_stop(shutdown_thread);

        device_remove_file(&client->dev, &dev_attr_status);

        if (glob_mcu == mcu) {
                pm_power_off = NULL;
                glob_mcu = NULL;
        }

        mcu_gpiochip_remove(mcu);
        kfree(mcu);
}

static const struct i2c_device_id mcu_ids[] = {
        { "mcu-mpc8349emitx", },
        {},
};
MODULE_DEVICE_TABLE(i2c, mcu_ids);

static const struct of_device_id mcu_of_match_table[] = {
        { .compatible = "fsl,mcu-mpc8349emitx", },
        { },
};

static struct i2c_driver mcu_driver = {
        .driver = {
                .name = "mcu-mpc8349emitx",
                .of_match_table = mcu_of_match_table,
        },
        .probe = mcu_probe,
        .remove = mcu_remove,
        .id_table = mcu_ids,
};

module_i2c_driver(mcu_driver);

MODULE_DESCRIPTION("Power Management and GPIO expander driver for "
                   "MPC8349E-mITX-compatible MCU");
MODULE_AUTHOR("Anton Vorontsov <avorontsov@ru.mvista.com>");
MODULE_LICENSE("GPL");