root/drivers/power/reset/gpio-poweroff.c

DEFINITIONS

1. gpio_poweroff_do_poweroff
2. gpio_poweroff_probe
3. gpio_poweroff_remove

   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  */
  23 static struct gpio_desc *reset_gpio;
  24 static u32 timeout = DEFAULT_TIMEOUT_MS;
  25 static u32 active_delay = 100;
  26 static u32 inactive_delay = 100;
  27 
  28 static 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 
  49 static 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 
  81 static 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 
  89 static const struct of_device_id of_gpio_poweroff_match[] = {
  90         { .compatible = "gpio-poweroff", },
  91         {},
  92 };
  93 
  94 static 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 
 103 module_platform_driver(gpio_poweroff_driver);
 104 
 105 MODULE_AUTHOR("Jamie Lentin <jm@lentin.co.uk>");
 106 MODULE_DESCRIPTION("GPIO poweroff driver");
 107 MODULE_LICENSE("GPL v2");
 108 MODULE_ALIAS("platform:poweroff-gpio");