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\n",
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 MODULE_DEVICE_TABLE(of, of_gpio_poweroff_match);
94 
95 static struct platform_driver gpio_poweroff_driver = {
96 	.probe = gpio_poweroff_probe,
97 	.remove = gpio_poweroff_remove,
98 	.driver = {
99 		.name = "poweroff-gpio",
100 		.of_match_table = of_gpio_poweroff_match,
101 	},
102 };
103 
104 module_platform_driver(gpio_poweroff_driver);
105 
106 MODULE_AUTHOR("Jamie Lentin <jm@lentin.co.uk>");
107 MODULE_DESCRIPTION("GPIO poweroff driver");
108 MODULE_ALIAS("platform:poweroff-gpio");
109