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
20struct w1_gpio_ddata {
21 struct gpio_desc *gpiod;
22 struct gpio_desc *pullup_gpiod;
23 unsigned int pullup_duration;
24};
25
26static 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(desc: ddata->gpiod, value: 1);
39 msleep(msecs: 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(desc: ddata->gpiod, value: 1);
45 }
46 ddata->pullup_duration = 0;
47 }
48
49 return 0;
50}
51
52static void w1_gpio_write_bit(void *data, u8 bit)
53{
54 struct w1_gpio_ddata *ddata = data;
55
56 gpiod_set_value(desc: ddata->gpiod, value: bit);
57}
58
59static u8 w1_gpio_read_bit(void *data)
60{
61 struct w1_gpio_ddata *ddata = data;
62
63 return gpiod_get_value(desc: ddata->gpiod) ? 1 : 0;
64}
65
66#if defined(CONFIG_OF)
67static const struct of_device_id w1_gpio_dt_ids[] = {
68 { .compatible = "w1-gpio" },
69 {}
70};
71MODULE_DEVICE_TABLE(of, w1_gpio_dt_ids);
72#endif
73
74static 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(dev: &pdev->dev, size: 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, propname: "linux,open-drain"))
95 gflags = GPIOD_OUT_LOW;
96
97 master = devm_kzalloc(dev, size: sizeof(struct w1_bus_master),
98 GFP_KERNEL);
99 if (!master)
100 return -ENOMEM;
101
102 ddata->gpiod = devm_gpiod_get_index(dev, NULL, idx: 0, flags: gflags);
103 if (IS_ERR(ptr: ddata->gpiod)) {
104 dev_err(dev, "gpio_request (pin) failed\n");
105 return PTR_ERR(ptr: ddata->gpiod);
106 }
107
108 ddata->pullup_gpiod =
109 devm_gpiod_get_index_optional(dev, NULL, index: 1, flags: GPIOD_OUT_LOW);
110 if (IS_ERR(ptr: ddata->pullup_gpiod)) {
111 dev_err(dev, "gpio_request_one "
112 "(ext_pullup_enable_pin) failed\n");
113 return PTR_ERR(ptr: ddata->pullup_gpiod);
114 }
115
116 master->data = ddata;
117 master->read_bit = w1_gpio_read_bit;
118 gpiod_direction_output(desc: ddata->gpiod, value: 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(desc: ddata->pullup_gpiod, value: 1);
138
139 platform_set_drvdata(pdev, data: master);
140
141 return 0;
142}
143
144static 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(desc: ddata->pullup_gpiod, value: 0);
151
152 w1_remove_master_device(master);
153}
154
155static 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
164module_platform_driver(w1_gpio_driver);
165
166MODULE_DESCRIPTION("GPIO w1 bus master driver");
167MODULE_AUTHOR("Ville Syrjala <syrjala@sci.fi>");
168MODULE_LICENSE("GPL");
169

source code of linux/drivers/w1/masters/w1-gpio.c