gpio-pcf857x.c

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/*
 * Driver for pcf857x, pca857x, and pca967x I2C GPIO expanders
 *
 * Copyright (C) 2007 David Brownell
 *
 * 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.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/gpio.h>
#include <linux/i2c.h>
#include <linux/i2c/pcf857x.h>
#include <linux/interrupt.h>
#include <linux/irq.h>
#include <linux/irqdomain.h>
#include <linux/module.h>
#include <linux/spinlock.h>
#include <linux/workqueue.h>


static const struct i2c_device_id pcf857x_id[] = {
    { "pcf8574", 8 },
    { "pcf8574a", 8 },
    { "pca8574", 8 },
    { "pca9670", 8 },
    { "pca9672", 8 },
    { "pca9674", 8 },
    { "pcf8575", 16 },
    { "pca8575", 16 },
    { "pca9671", 16 },
    { "pca9673", 16 },
    { "pca9675", 16 },
    { "max7328", 8 },
    { "max7329", 8 },
    { }
};
MODULE_DEVICE_TABLE(i2c, pcf857x_id);

/*
 * The pcf857x, pca857x, and pca967x chips only expose one read and one
 * write register.  Writing a "one" bit (to match the reset state) lets
 * that pin be used as an input; it's not an open-drain model, but acts
 * a bit like one.  This is described as "quasi-bidirectional"; read the
 * chip documentation for details.
 *
 * Many other I2C GPIO expander chips (like the pca953x models) have
 * more complex register models and more conventional circuitry using
 * push/pull drivers.  They often use the same 0x20..0x27 addresses as
 * pcf857x parts, making the "legacy" I2C driver model problematic.
 */
struct pcf857x {
    struct gpio_chip    chip;
    struct i2c_client   *client;
    struct mutex        lock;       /* protect 'out' */
    struct work_struct  work;       /* irq demux work */
    struct irq_domain   *irq_domain;    /* for irq demux  */
    spinlock_t      slock;      /* protect irq demux */
    unsigned        out;        /* software latch */
    unsigned        status;     /* current status */
    int         irq;        /* real irq number */

    int (*write)(struct i2c_client *client, unsigned data);
    int (*read)(struct i2c_client *client);
};

/*-------------------------------------------------------------------------*/

/* Talk to 8-bit I/O expander */

static int i2c_write_le8(struct i2c_client *client, unsigned data)
{
    return i2c_smbus_write_byte(client, data);
}

static int i2c_read_le8(struct i2c_client *client)
{
    return (int)i2c_smbus_read_byte(client);
}

/* Talk to 16-bit I/O expander */

static int i2c_write_le16(struct i2c_client *client, unsigned word)
{
    u8 buf[2] = { word & 0xff, word >> 8, };
    int status;

    status = i2c_master_send(client, buf, 2);
    return (status < 0) ? status : 0;
}

static int i2c_read_le16(struct i2c_client *client)
{
    u8 buf[2];
    int status;

    status = i2c_master_recv(client, buf, 2);
    if (status < 0)
        return status;
    return (buf[1] << 8) | buf[0];
}

/*-------------------------------------------------------------------------*/

static int pcf857x_input(struct gpio_chip *chip, unsigned offset)
{
    struct pcf857x  *gpio = container_of(chip, struct pcf857x, chip);
    int     status;

    mutex_lock(&gpio->lock);
    gpio->out |= (1 << offset);
    status = gpio->write(gpio->client, gpio->out);
    mutex_unlock(&gpio->lock);

    return status;
}

static int pcf857x_get(struct gpio_chip *chip, unsigned offset)
{
    struct pcf857x  *gpio = container_of(chip, struct pcf857x, chip);
    int     value;

    value = gpio->read(gpio->client);
    return (value < 0) ? 0 : (value & (1 << offset));
}

static int pcf857x_output(struct gpio_chip *chip, unsigned offset, int value)
{
    struct pcf857x  *gpio = container_of(chip, struct pcf857x, chip);
    unsigned    bit = 1 << offset;
    int     status;

    mutex_lock(&gpio->lock);
    if (value)
        gpio->out |= bit;
    else
        gpio->out &= ~bit;
    status = gpio->write(gpio->client, gpio->out);
    mutex_unlock(&gpio->lock);

    return status;
}

static void pcf857x_set(struct gpio_chip *chip, unsigned offset, int value)
{
    pcf857x_output(chip, offset, value);
}

/*-------------------------------------------------------------------------*/

static int pcf857x_to_irq(struct gpio_chip *chip, unsigned offset)
{
    struct pcf857x *gpio = container_of(chip, struct pcf857x, chip);

    return irq_create_mapping(gpio->irq_domain, offset);
}

static void pcf857x_irq_demux_work(struct work_struct *work)
{
    struct pcf857x *gpio = container_of(work,
                           struct pcf857x,
                           work);
    unsigned long change, i, status, flags;

    status = gpio->read(gpio->client);

    spin_lock_irqsave(&gpio->slock, flags);

    change = gpio->status ^ status;
    for_each_set_bit(i, &change, gpio->chip.ngpio)
        generic_handle_irq(irq_find_mapping(gpio->irq_domain, i));
    gpio->status = status;

    spin_unlock_irqrestore(&gpio->slock, flags);
}

static irqreturn_t pcf857x_irq_demux(int irq, void *data)
{
    struct pcf857x  *gpio = data;

    /*
     * pcf857x can't read/write data here,
     * since i2c data access might go to sleep.
     */
    schedule_work(&gpio->work);

    return IRQ_HANDLED;
}

static int pcf857x_irq_domain_map(struct irq_domain *domain, unsigned int virq,
                 irq_hw_number_t hw)
{
    irq_set_chip_and_handler(virq,
                 &dummy_irq_chip,
                 handle_level_irq);
    return 0;
}

static struct irq_domain_ops pcf857x_irq_domain_ops = {
    .map    = pcf857x_irq_domain_map,
};

static void pcf857x_irq_domain_cleanup(struct pcf857x *gpio)
{
    if (gpio->irq_domain)
        irq_domain_remove(gpio->irq_domain);

    if (gpio->irq)
        free_irq(gpio->irq, gpio);
}

static int pcf857x_irq_domain_init(struct pcf857x *gpio,
                   struct pcf857x_platform_data *pdata,
                   struct device *dev)
{
    int status;

    gpio->irq_domain = irq_domain_add_linear(dev->of_node,
                         gpio->chip.ngpio,
                         &pcf857x_irq_domain_ops,
                         NULL);
    if (!gpio->irq_domain)
        goto fail;

    /* enable real irq */
    status = request_irq(pdata->irq, pcf857x_irq_demux, 0,
                 dev_name(dev), gpio);
    if (status)
        goto fail;

    /* enable gpio_to_irq() */
    INIT_WORK(&gpio->work, pcf857x_irq_demux_work);
    gpio->chip.to_irq   = pcf857x_to_irq;
    gpio->irq       = pdata->irq;

    return 0;

fail:
    pcf857x_irq_domain_cleanup(gpio);
    return -EINVAL;
}

/*-------------------------------------------------------------------------*/

static int pcf857x_probe(struct i2c_client *client,
             const struct i2c_device_id *id)
{
    struct pcf857x_platform_data    *pdata;
    struct pcf857x          *gpio;
    int             status;

    pdata = client->dev.platform_data;
    if (!pdata) {
        dev_dbg(&client->dev, "no platform data\n");
    }

    /* Allocate, initialize, and register this gpio_chip. */
    gpio = kzalloc(sizeof *gpio, GFP_KERNEL);
    if (!gpio)
        return -ENOMEM;

    mutex_init(&gpio->lock);
    spin_lock_init(&gpio->slock);

    gpio->chip.base         = pdata ? pdata->gpio_base : -1;
    gpio->chip.can_sleep        = 1;
    gpio->chip.dev          = &client->dev;
    gpio->chip.owner        = THIS_MODULE;
    gpio->chip.get          = pcf857x_get;
    gpio->chip.set          = pcf857x_set;
    gpio->chip.direction_input  = pcf857x_input;
    gpio->chip.direction_output = pcf857x_output;
    gpio->chip.ngpio        = id->driver_data;

    /* enable gpio_to_irq() if platform has settings */
    if (pdata && pdata->irq) {
        status = pcf857x_irq_domain_init(gpio, pdata, &client->dev);
        if (status < 0) {
            dev_err(&client->dev, "irq_domain init failed\n");
            goto fail;
        }
    }

    /* NOTE:  the OnSemi jlc1562b is also largely compatible with
     * these parts, notably for output.  It has a low-resolution
     * DAC instead of pin change IRQs; and its inputs can be the
     * result of comparators.
     */

    /* 8574 addresses are 0x20..0x27; 8574a uses 0x38..0x3f;
     * 9670, 9672, 9764, and 9764a use quite a variety.
     *
     * NOTE: we don't distinguish here between *4 and *4a parts.
     */
    if (gpio->chip.ngpio == 8) {
        gpio->write = i2c_write_le8;
        gpio->read  = i2c_read_le8;

        if (!i2c_check_functionality(client->adapter,
                I2C_FUNC_SMBUS_BYTE))
            status = -EIO;

        /* fail if there's no chip present */
        else
            status = i2c_smbus_read_byte(client);

    /* '75/'75c addresses are 0x20..0x27, just like the '74;
     * the '75c doesn't have a current source pulling high.
     * 9671, 9673, and 9765 use quite a variety of addresses.
     *
     * NOTE: we don't distinguish here between '75 and '75c parts.
     */
    } else if (gpio->chip.ngpio == 16) {
        gpio->write = i2c_write_le16;
        gpio->read  = i2c_read_le16;

        if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
            status = -EIO;

        /* fail if there's no chip present */
        else
            status = i2c_read_le16(client);

    } else {
        dev_dbg(&client->dev, "unsupported number of gpios\n");
        status = -EINVAL;
    }

    if (status < 0)
        goto fail;

    gpio->chip.label = client->name;

    gpio->client = client;
    i2c_set_clientdata(client, gpio);

    /* NOTE:  these chips have strange "quasi-bidirectional" I/O pins.
     * We can't actually know whether a pin is configured (a) as output
     * and driving the signal low, or (b) as input and reporting a low
     * value ... without knowing the last value written since the chip
     * came out of reset (if any).  We can't read the latched output.
     *
     * In short, the only reliable solution for setting up pin direction
     * is to do it explicitly.  The setup() method can do that, but it
     * may cause transient glitching since it can't know the last value
     * written (some pins may need to be driven low).
     *
     * Using pdata->n_latch avoids that trouble.  When left initialized
     * to zero, our software copy of the "latch" then matches the chip's
     * all-ones reset state.  Otherwise it flags pins to be driven low.
     */
    gpio->out = pdata ? ~pdata->n_latch : ~0;
    gpio->status = gpio->out;

    status = gpiochip_add(&gpio->chip);
    if (status < 0)
        goto fail;

    /* NOTE: these chips can issue "some pin-changed" IRQs, which we
     * don't yet even try to use.  Among other issues, the relevant
     * genirq state isn't available to modular drivers; and most irq
     * methods can't be called from sleeping contexts.
     */

    dev_info(&client->dev, "%s\n",
            client->irq ? " (irq ignored)" : "");

    /* Let platform code set up the GPIOs and their users.
     * Now is the first time anyone could use them.
     */
    if (pdata && pdata->setup) {
        status = pdata->setup(client,
                gpio->chip.base, gpio->chip.ngpio,
                pdata->context);
        if (status < 0)
            dev_warn(&client->dev, "setup --> %d\n", status);
    }

    return 0;

fail:
    dev_dbg(&client->dev, "probe error %d for '%s'\n",
            status, client->name);

    if (pdata && pdata->irq)
        pcf857x_irq_domain_cleanup(gpio);

    kfree(gpio);
    return status;
}

static int pcf857x_remove(struct i2c_client *client)
{
    struct pcf857x_platform_data    *pdata = client->dev.platform_data;
    struct pcf857x          *gpio = i2c_get_clientdata(client);
    int             status = 0;

    if (pdata && pdata->teardown) {
        status = pdata->teardown(client,
                gpio->chip.base, gpio->chip.ngpio,
                pdata->context);
        if (status < 0) {
            dev_err(&client->dev, "%s --> %d\n",
                    "teardown", status);
            return status;
        }
    }

    if (pdata && pdata->irq)
        pcf857x_irq_domain_cleanup(gpio);

    status = gpiochip_remove(&gpio->chip);
    if (status == 0)
        kfree(gpio);
    else
        dev_err(&client->dev, "%s --> %d\n", "remove", status);
    return status;
}

static struct i2c_driver pcf857x_driver = {
    .driver = {
        .name   = "pcf857x",
        .owner  = THIS_MODULE,
    },
    .probe  = pcf857x_probe,
    .remove = pcf857x_remove,
    .id_table = pcf857x_id,
};

static int __init pcf857x_init(void)
{
    return i2c_add_driver(&pcf857x_driver);
}
/* register after i2c postcore initcall and before
 * subsys initcalls that may rely on these GPIOs
 */
subsys_initcall(pcf857x_init);

static void __exit pcf857x_exit(void)
{
    i2c_del_driver(&pcf857x_driver);
}
module_exit(pcf857x_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("David Brownell");