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/property.h>
15 #include <linux/gpio/consumer.h>
16 #include <linux/mod_devicetable.h>
17 #include <linux/module.h>
18 
19 #define DEFAULT_TIMEOUT_MS 3000
20 /*
21  * Hold configuration here, cannot be more than one instance of the driver
22  * since pm_power_off itself is global.
23  */
24 static struct gpio_desc *reset_gpio;
25 static u32 timeout = DEFAULT_TIMEOUT_MS;
26 static u32 active_delay = 100;
27 static u32 inactive_delay = 100;
28 
29 static void gpio_poweroff_do_poweroff(void)
30 {
31 	BUG_ON(!reset_gpio);
32 
33 	/* drive it active, also inactive->active edge */
34 	gpiod_direction_output(reset_gpio, 1);
35 	mdelay(active_delay);
36 
37 	/* drive inactive, also active->inactive edge */
38 	gpiod_set_value_cansleep(reset_gpio, 0);
39 	mdelay(inactive_delay);
40 
41 	/* drive it active, also inactive->active edge */
42 	gpiod_set_value_cansleep(reset_gpio, 1);
43 
44 	/* give it some time */
45 	mdelay(timeout);
46 
47 	WARN_ON(1);
48 }
49 
50 static int gpio_poweroff_probe(struct platform_device *pdev)
51 {
52 	bool input = false;
53 	enum gpiod_flags flags;
54 
55 	/* If a pm_power_off function has already been added, leave it alone */
56 	if (pm_power_off != NULL) {
57 		dev_err(&pdev->dev,
58 			"%s: pm_power_off function already registered\n",
59 		       __func__);
60 		return -EBUSY;
61 	}
62 
63 	input = device_property_read_bool(&pdev->dev, "input");
64 	if (input)
65 		flags = GPIOD_IN;
66 	else
67 		flags = GPIOD_OUT_LOW;
68 
69 	device_property_read_u32(&pdev->dev, "active-delay-ms", &active_delay);
70 	device_property_read_u32(&pdev->dev, "inactive-delay-ms",
71 				 &inactive_delay);
72 	device_property_read_u32(&pdev->dev, "timeout-ms", &timeout);
73 
74 	reset_gpio = devm_gpiod_get(&pdev->dev, NULL, flags);
75 	if (IS_ERR(reset_gpio))
76 		return PTR_ERR(reset_gpio);
77 
78 	pm_power_off = &gpio_poweroff_do_poweroff;
79 	return 0;
80 }
81 
82 static int gpio_poweroff_remove(struct platform_device *pdev)
83 {
84 	if (pm_power_off == &gpio_poweroff_do_poweroff)
85 		pm_power_off = NULL;
86 
87 	return 0;
88 }
89 
90 static const struct of_device_id of_gpio_poweroff_match[] = {
91 	{ .compatible = "gpio-poweroff", },
92 	{},
93 };
94 MODULE_DEVICE_TABLE(of, of_gpio_poweroff_match);
95 
96 static struct platform_driver gpio_poweroff_driver = {
97 	.probe = gpio_poweroff_probe,
98 	.remove = gpio_poweroff_remove,
99 	.driver = {
100 		.name = "poweroff-gpio",
101 		.of_match_table = of_gpio_poweroff_match,
102 	},
103 };
104 
105 module_platform_driver(gpio_poweroff_driver);
106 
107 MODULE_AUTHOR("Jamie Lentin <jm@lentin.co.uk>");
108 MODULE_DESCRIPTION("GPIO poweroff driver");
109 MODULE_ALIAS("platform:poweroff-gpio");
110