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,
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
gpio_poweroff_remove(struct platform_device * pdev)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");
109
