mcu_mpc8349emitx.c

/*
 * Power Management and GPIO expander driver for MPC8349E-mITX-compatible MCU
 *
 * Copyright (c) 2008  MontaVista Software, Inc.
 *
 * Author: Anton Vorontsov <avorontsov@ru.mvista.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 */

#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/device.h>
#include <linux/mutex.h>
#include <linux/i2c.h>
#include <linux/gpio.h>
#include <linux/of.h>
#include <linux/of_gpio.h>
#include <linux/slab.h>
#include <asm/prom.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_NUM_GPIO	2

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

static struct mcu *glob_mcu;

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(glob_mcu->client, MCU_REG_CTRL,
				  mcu->reg_ctrl | MCU_CTRL_POFF);
	mutex_unlock(&mcu->lock);
}

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

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

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

static int mcu_gpio_dir_out(struct gpio_chip *gc, unsigned int gpio, int val)
{
	mcu_gpio_set(gc, gpio, val);
	return 0;
}

static int mcu_gpiochip_add(struct mcu *mcu)
{
	struct device_node *np;
	struct gpio_chip *gc = &mcu->gc;

	np = of_find_compatible_node(NULL, NULL, "fsl,mcu-mpc8349emitx");
	if (!np)
		return -ENODEV;

	gc->owner = THIS_MODULE;
	gc->label = np->full_name;
	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->of_node = np;

	return gpiochip_add(gc);
}

static int mcu_gpiochip_remove(struct mcu *mcu)
{
	return gpiochip_remove(&mcu->gc);
}

static int __devinit mcu_probe(struct i2c_client *client,
			       const struct i2c_device_id *id)
{
	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 ppc_md */
	if (!ppc_md.power_off) {
		glob_mcu = mcu;
		ppc_md.power_off = mcu_power_off;
		dev_info(&client->dev, "will provide power-off service\n");
	}

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

static int __devexit mcu_remove(struct i2c_client *client)
{
	struct mcu *mcu = i2c_get_clientdata(client);
	int ret;

	if (glob_mcu == mcu) {
		ppc_md.power_off = NULL;
		glob_mcu = NULL;
	}

	ret = mcu_gpiochip_remove(mcu);
	if (ret)
		return ret;
	i2c_set_clientdata(client, NULL);
	kfree(mcu);
	return 0;
}

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

static struct i2c_driver mcu_driver = {
	.driver = {
		.name = "mcu-mpc8349emitx",
		.owner = THIS_MODULE,
	},
	.probe = mcu_probe,
	.remove	= __devexit_p(mcu_remove),
	.id_table = mcu_ids,
};

static int __init mcu_init(void)
{
	return i2c_add_driver(&mcu_driver);
}
module_init(mcu_init);

static void __exit mcu_exit(void)
{
	i2c_del_driver(&mcu_driver);
}
module_exit(mcu_exit);

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