mcu_mpc8349emitx.c

// 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 <[email protected]>
 */

#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));
	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(sizeof(*mcu), GFP_KERNEL);
	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 <[email protected]>");
MODULE_LICENSE("GPL");