linux-imx

/*

 * Toggles a GPIO pin to power down a device

 *

 * Jamie Lentin <jm@lentin.co.uk>

 * Andrew Lunn <andrew@lunn.ch>

 *

 * Copyright (C) 2012 Jamie Lentin

 *

 * This program is free software; you can redistribute it and/or modify

 * it under the terms of the GNU General Public License version 2 as

 * published by the Free Software Foundation.

 *

 */

#include <linux/kernel.h>

#include <linux/init.h>

#include <linux/delay.h>

#include <linux/platform_device.h>

#include <linux/gpio/consumer.h>

#include <linux/of_platform.h>

#include <linux/module.h>

​

#define DEFAULT_TIMEOUT_MS 3000

/*

 * Hold configuration here, cannot be more than one instance of the driver

 * since pm_power_off itself is global.

 */

static struct gpio_desc *reset_gpio;

static u32 timeout = DEFAULT_TIMEOUT_MS;

static u32 active_delay = 100;

static u32 inactive_delay = 100;

​

static void gpio_poweroff_do_poweroff(void)

{

    BUG_ON(!reset_gpio);

​

    /* drive it active, also inactive->active edge */

    gpiod_direction_output(reset_gpio, 1);

    mdelay(active_delay);

​

    /* drive inactive, also active->inactive edge */

    gpiod_set_value_cansleep(reset_gpio, 0);

    mdelay(inactive_delay);

​

    /* drive it active, also inactive->active edge */

    gpiod_set_value_cansleep(reset_gpio, 1);

​

    /* give it some time */

    mdelay(timeout);

​

    WARN_ON(1);

}

​

static int gpio_poweroff_probe(struct platform_device *pdev)

{

    bool input = false;

    enum gpiod_flags flags;

​

    /* If a pm_power_off function has already been added, leave it alone */

    if (pm_power_off != NULL) {

        dev_err(&pdev->dev,

            "%s: pm_power_off function already registered",

               __func__);

        return -EBUSY;

    }

​

    input = device_property_read_bool(&pdev->dev, "input");

    if (input)

        flags = GPIOD_IN;

    else

        flags = GPIOD_OUT_LOW;

​

    device_property_read_u32(&pdev->dev, "active-delay-ms", &active_delay);

    device_property_read_u32(&pdev->dev, "inactive-delay-ms",

                 &inactive_delay);

    device_property_read_u32(&pdev->dev, "timeout-ms", &timeout);

​

    reset_gpio = devm_gpiod_get(&pdev->dev, NULL, flags);

    if (IS_ERR(reset_gpio))

        return PTR_ERR(reset_gpio);

​

    pm_power_off = &gpio_poweroff_do_poweroff;

    return 0;

}

​

static int gpio_poweroff_remove(struct platform_device *pdev)

{

    if (pm_power_off == &gpio_poweroff_do_poweroff)

        pm_power_off = NULL;

​

    return 0;

}

​