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
gpio_poweroff_do_poweroff(void)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
gpio_poweroff_probe(struct platform_device *pdev)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, "%s: pm_power_off function already registered\n", __func__);
57 return -EBUSY;
58 }
59
60 input = device_property_read_bool(&pdev->dev, "input");
61 if (input) {
62 flags = GPIOD_IN;
63 } else {
64 flags = GPIOD_OUT_LOW;
65 }
66
67 device_property_read_u32(&pdev->dev, "active-delay-ms", &active_delay);
68 device_property_read_u32(&pdev->dev, "inactive-delay-ms", &inactive_delay);
69 device_property_read_u32(&pdev->dev, "timeout-ms", &timeout);
70
71 reset_gpio = devm_gpiod_get(&pdev->dev, NULL, flags);
72 if (IS_ERR(reset_gpio)) {
73 return PTR_ERR(reset_gpio);
74 }
75
76 pm_power_off = &gpio_poweroff_do_poweroff;
77 return 0;
78 }
79
gpio_poweroff_remove(struct platform_device *pdev)80 static int gpio_poweroff_remove(struct platform_device *pdev)
81 {
82 if (pm_power_off == &gpio_poweroff_do_poweroff) {
83 pm_power_off = NULL;
84 }
85
86 return 0;
87 }
88
89 static const struct of_device_id of_gpio_poweroff_match[] = {
90 {
91 .compatible = "gpio-poweroff",
92 },
93 {},
94 };
95
96 static struct platform_driver gpio_poweroff_driver = {
97 .probe = gpio_poweroff_probe,
98 .remove = gpio_poweroff_remove,
99 .driver =
100 {
101 .name = "poweroff-gpio",
102 .of_match_table = of_gpio_poweroff_match,
103 },
104 };
105
106 module_platform_driver(gpio_poweroff_driver);
107
108 MODULE_AUTHOR("Jamie Lentin <jm@lentin.co.uk>");
109 MODULE_DESCRIPTION("GPIO poweroff driver");
110 MODULE_LICENSE("GPL v2");
111 MODULE_ALIAS("platform:poweroff-gpio");
112