LXR linux/drivers/power/reset/gpio-poweroff.c

   1// SPDX-License-Identifier: GPL-2.0-only
   2/*
   3 * Toggles a GPIO pin to power down a device
   4 *
   5 * Jamie Lentin <jm@lentin.co.uk>
   6 * Andrew Lunn <andrew@lunn.ch>
   7 *
   8 * Copyright (C) 2012 Jamie Lentin
   9 */
  10#include <linux/kernel.h>
  11#include <linux/init.h>
  12#include <linux/delay.h>
  13#include <linux/platform_device.h>
  14#include <linux/gpio/consumer.h>
  15#include <linux/of_platform.h>
  16#include <linux/module.h>
  17
  18#define DEFAULT_TIMEOUT_MS 3000
  19/*
  20 * Hold configuration here, cannot be more than one instance of the driver
  21 * since pm_power_off itself is global.
  22 */
  23static struct gpio_desc *reset_gpio;
  24static u32 timeout = DEFAULT_TIMEOUT_MS;
  25static u32 active_delay = 100;
  26static u32 inactive_delay = 100;
  27
  28static void gpio_poweroff_do_poweroff(void)
  29{
  30        BUG_ON(!reset_gpio);
  31
  32        /* drive it active, also inactive->active edge */
  33        gpiod_direction_output(reset_gpio, 1);
  34        mdelay(active_delay);
  35
  36        /* drive inactive, also active->inactive edge */
  37        gpiod_set_value_cansleep(reset_gpio, 0);
  38        mdelay(inactive_delay);
  39
  40        /* drive it active, also inactive->active edge */
  41        gpiod_set_value_cansleep(reset_gpio, 1);
  42
  43        /* give it some time */
  44        mdelay(timeout);
  45
  46        WARN_ON(1);
  47}
  48
  49static int gpio_poweroff_probe(struct platform_device *pdev)
  50{
  51        bool input = false;
  52        enum gpiod_flags flags;
  53
  54        /* If a pm_power_off function has already been added, leave it alone */
  55        if (pm_power_off != NULL) {
  56                dev_err(&pdev->dev,
  57                        "%s: pm_power_off function already registered",
  58                       __func__);
  59                return -EBUSY;
  60        }
  61
  62        input = device_property_read_bool(&pdev->dev, "input");
  63        if (input)
  64                flags = GPIOD_IN;
  65        else
  66                flags = GPIOD_OUT_LOW;
  67
  68        device_property_read_u32(&pdev->dev, "active-delay-ms", &active_delay);
  69        device_property_read_u32(&pdev->dev, "inactive-delay-ms",
  70                                 &inactive_delay);
  71        device_property_read_u32(&pdev->dev, "timeout-ms", &timeout);
  72
  73        reset_gpio = devm_gpiod_get(&pdev->dev, NULL, flags);
  74        if (IS_ERR(reset_gpio))
  75                return PTR_ERR(reset_gpio);
  76
  77        pm_power_off = &gpio_poweroff_do_poweroff;
  78        return 0;
  79}
  80
  81static int gpio_poweroff_remove(struct platform_device *pdev)
  82{
  83        if (pm_power_off == &gpio_poweroff_do_poweroff)
  84                pm_power_off = NULL;
  85
  86        return 0;
  87}
  88
  89static const struct of_device_id of_gpio_poweroff_match[] = {
  90        { .compatible = "gpio-poweroff", },
  91        {},
  92};
  93
  94static struct platform_driver gpio_poweroff_driver = {
  95        .probe = gpio_poweroff_probe,
  96        .remove = gpio_poweroff_remove,
  97        .driver = {
  98                .name = "poweroff-gpio",
  99                .of_match_table = of_gpio_poweroff_match,
 100        },
 101};
 102
 103module_platform_driver(gpio_poweroff_driver);
 104
 105MODULE_AUTHOR("Jamie Lentin <jm@lentin.co.uk>");
 106MODULE_DESCRIPTION("GPIO poweroff driver");
 107MODULE_LICENSE("GPL v2");
 108MODULE_ALIAS("platform:poweroff-gpio");
 109