mcu_mpc8349emitx.c

Go to the documentation of this file.

/*
 * Power Management and GPIO expander driver for MPC8349E-mITX-compatible MCU
 *
 * Copyright (c) 2008  MontaVista Software, Inc.
 *
 * Author: Anton Vorontsov <[email protected]>
 *
 * 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 <linux/kthread.h>
#include <linux/reboot.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_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, S_IRUGO, 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 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");
    }

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

    kthread_stop(shutdown_thread);

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

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

static struct i2c_driver mcu_driver = {
    .driver = {
        .name = "mcu-mpc8349emitx",
        .owner = THIS_MODULE,
        .of_match_table = mcu_of_match_table,
    },
    .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 <[email protected]>");
MODULE_LICENSE("GPL");