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
gpio_poweroff_do_poweroff(void)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
gpio_poweroff_probe(struct platform_device * pdev)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
gpio_poweroff_remove(struct platform_device * pdev)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