xref: /linux/drivers/w1/masters/w1-gpio.c (revision 6d9b262afe0ec1d6e0ef99321ca9d6b921310471)
1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * w1-gpio - GPIO w1 bus master driver
4  *
5  * Copyright (C) 2007 Ville Syrjala <syrjala@sci.fi>
6  */
7 
8 #include <linux/init.h>
9 #include <linux/module.h>
10 #include <linux/platform_device.h>
11 #include <linux/slab.h>
12 #include <linux/gpio/consumer.h>
13 #include <linux/of_platform.h>
14 #include <linux/err.h>
15 #include <linux/of.h>
16 #include <linux/delay.h>
17 
18 #include <linux/w1.h>
19 
20 struct w1_gpio_ddata {
21 	struct gpio_desc *gpiod;
22 	struct gpio_desc *pullup_gpiod;
23 	unsigned int pullup_duration;
24 };
25 
26 static u8 w1_gpio_set_pullup(void *data, int delay)
27 {
28 	struct w1_gpio_ddata *ddata = data;
29 
30 	if (delay) {
31 		ddata->pullup_duration = delay;
32 	} else {
33 		if (ddata->pullup_duration) {
34 			/*
35 			 * This will OVERRIDE open drain emulation and force-pull
36 			 * the line high for some time.
37 			 */
38 			gpiod_set_raw_value(ddata->gpiod, 1);
39 			msleep(ddata->pullup_duration);
40 			/*
41 			 * This will simply set the line as input since we are doing
42 			 * open drain emulation in the GPIO library.
43 			 */
44 			gpiod_set_value(ddata->gpiod, 1);
45 		}
46 		ddata->pullup_duration = 0;
47 	}
48 
49 	return 0;
50 }
51 
52 static void w1_gpio_write_bit(void *data, u8 bit)
53 {
54 	struct w1_gpio_ddata *ddata = data;
55 
56 	gpiod_set_value(ddata->gpiod, bit);
57 }
58 
59 static u8 w1_gpio_read_bit(void *data)
60 {
61 	struct w1_gpio_ddata *ddata = data;
62 
63 	return gpiod_get_value(ddata->gpiod) ? 1 : 0;
64 }
65 
66 #if defined(CONFIG_OF)
67 static const struct of_device_id w1_gpio_dt_ids[] = {
68 	{ .compatible = "w1-gpio" },
69 	{}
70 };
71 MODULE_DEVICE_TABLE(of, w1_gpio_dt_ids);
72 #endif
73 
74 static int w1_gpio_probe(struct platform_device *pdev)
75 {
76 	struct w1_bus_master *master;
77 	struct w1_gpio_ddata *ddata;
78 	struct device *dev = &pdev->dev;
79 	struct device_node *np = dev->of_node;
80 	/* Enforce open drain mode by default */
81 	enum gpiod_flags gflags = GPIOD_OUT_LOW_OPEN_DRAIN;
82 	int err;
83 
84 	ddata = devm_kzalloc(&pdev->dev, sizeof(*ddata), GFP_KERNEL);
85 	if (!ddata)
86 		return -ENOMEM;
87 
88 	/*
89 	 * This parameter means that something else than the gpiolib has
90 	 * already set the line into open drain mode, so we should just
91 	 * driver it high/low like we are in full control of the line and
92 	 * open drain will happen transparently.
93 	 */
94 	if (of_property_present(np, "linux,open-drain"))
95 		gflags = GPIOD_OUT_LOW;
96 
97 	master = devm_kzalloc(dev, sizeof(struct w1_bus_master),
98 			GFP_KERNEL);
99 	if (!master)
100 		return -ENOMEM;
101 
102 	ddata->gpiod = devm_gpiod_get_index(dev, NULL, 0, gflags);
103 	if (IS_ERR(ddata->gpiod)) {
104 		dev_err(dev, "gpio_request (pin) failed\n");
105 		return PTR_ERR(ddata->gpiod);
106 	}
107 
108 	ddata->pullup_gpiod =
109 		devm_gpiod_get_index_optional(dev, NULL, 1, GPIOD_OUT_LOW);
110 	if (IS_ERR(ddata->pullup_gpiod)) {
111 		dev_err(dev, "gpio_request_one "
112 			"(ext_pullup_enable_pin) failed\n");
113 		return PTR_ERR(ddata->pullup_gpiod);
114 	}
115 
116 	master->data = ddata;
117 	master->read_bit = w1_gpio_read_bit;
118 	gpiod_direction_output(ddata->gpiod, 1);
119 	master->write_bit = w1_gpio_write_bit;
120 
121 	/*
122 	 * If we are using open drain emulation from the GPIO library,
123 	 * we need to use this pullup function that hammers the line
124 	 * high using a raw accessor to provide pull-up for the w1
125 	 * line.
126 	 */
127 	if (gflags == GPIOD_OUT_LOW_OPEN_DRAIN)
128 		master->set_pullup = w1_gpio_set_pullup;
129 
130 	err = w1_add_master_device(master);
131 	if (err) {
132 		dev_err(dev, "w1_add_master device failed\n");
133 		return err;
134 	}
135 
136 	if (ddata->pullup_gpiod)
137 		gpiod_set_value(ddata->pullup_gpiod, 1);
138 
139 	platform_set_drvdata(pdev, master);
140 
141 	return 0;
142 }
143 
144 static void w1_gpio_remove(struct platform_device *pdev)
145 {
146 	struct w1_bus_master *master = platform_get_drvdata(pdev);
147 	struct w1_gpio_ddata *ddata = master->data;
148 
149 	if (ddata->pullup_gpiod)
150 		gpiod_set_value(ddata->pullup_gpiod, 0);
151 
152 	w1_remove_master_device(master);
153 }
154 
155 static struct platform_driver w1_gpio_driver = {
156 	.driver = {
157 		.name	= "w1-gpio",
158 		.of_match_table = of_match_ptr(w1_gpio_dt_ids),
159 	},
160 	.probe = w1_gpio_probe,
161 	.remove_new = w1_gpio_remove,
162 };
163 
164 module_platform_driver(w1_gpio_driver);
165 
166 MODULE_DESCRIPTION("GPIO w1 bus master driver");
167 MODULE_AUTHOR("Ville Syrjala <syrjala@sci.fi>");
168 MODULE_LICENSE("GPL");
169