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/delay.h>
9 #include <linux/device.h>
10 #include <linux/err.h>
11 #include <linux/gpio/consumer.h>
12 #include <linux/mod_devicetable.h>
13 #include <linux/module.h>
14 #include <linux/platform_device.h>
15 #include <linux/property.h>
16 #include <linux/types.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
w1_gpio_set_pullup(void * data,int delay)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
w1_gpio_write_bit(void * data,u8 bit)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
w1_gpio_read_bit(void * data)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
w1_gpio_probe(struct platform_device * pdev)66 static int w1_gpio_probe(struct platform_device *pdev)
67 {
68 struct w1_bus_master *master;
69 struct w1_gpio_ddata *ddata;
70 struct device *dev = &pdev->dev;
71 /* Enforce open drain mode by default */
72 enum gpiod_flags gflags = GPIOD_OUT_LOW_OPEN_DRAIN;
73 int err;
74
75 ddata = devm_kzalloc(&pdev->dev, sizeof(*ddata), GFP_KERNEL);
76 if (!ddata)
77 return -ENOMEM;
78
79 /*
80 * This parameter means that something else than the gpiolib has
81 * already set the line into open drain mode, so we should just
82 * driver it high/low like we are in full control of the line and
83 * open drain will happen transparently.
84 */
85 if (device_property_present(dev, "linux,open-drain"))
86 gflags = GPIOD_OUT_LOW;
87
88 master = devm_kzalloc(dev, sizeof(*master), GFP_KERNEL);
89 if (!master)
90 return -ENOMEM;
91
92 ddata->gpiod = devm_gpiod_get_index(dev, NULL, 0, gflags);
93 if (IS_ERR(ddata->gpiod))
94 return dev_err_probe(dev, PTR_ERR(ddata->gpiod), "gpio_request (pin) failed\n");
95
96 ddata->pullup_gpiod =
97 devm_gpiod_get_index_optional(dev, NULL, 1, GPIOD_OUT_LOW);
98 if (IS_ERR(ddata->pullup_gpiod))
99 return dev_err_probe(dev, PTR_ERR(ddata->pullup_gpiod),
100 "gpio_request (ext_pullup_enable_pin) failed\n");
101
102 master->data = ddata;
103 master->read_bit = w1_gpio_read_bit;
104 gpiod_direction_output(ddata->gpiod, 1);
105 master->write_bit = w1_gpio_write_bit;
106
107 /*
108 * If we are using open drain emulation from the GPIO library,
109 * we need to use this pullup function that hammers the line
110 * high using a raw accessor to provide pull-up for the w1
111 * line.
112 */
113 if (gflags == GPIOD_OUT_LOW_OPEN_DRAIN)
114 master->set_pullup = w1_gpio_set_pullup;
115
116 err = w1_add_master_device(master);
117 if (err)
118 return dev_err_probe(dev, err, "w1_add_master device failed\n");
119
120 gpiod_set_value(ddata->pullup_gpiod, 1);
121
122 platform_set_drvdata(pdev, master);
123
124 return 0;
125 }
126
w1_gpio_remove(struct platform_device * pdev)127 static void w1_gpio_remove(struct platform_device *pdev)
128 {
129 struct w1_bus_master *master = platform_get_drvdata(pdev);
130 struct w1_gpio_ddata *ddata = master->data;
131
132 gpiod_set_value(ddata->pullup_gpiod, 0);
133
134 w1_remove_master_device(master);
135 }
136
137 static const struct of_device_id w1_gpio_dt_ids[] = {
138 { .compatible = "w1-gpio" },
139 {}
140 };
141 MODULE_DEVICE_TABLE(of, w1_gpio_dt_ids);
142
143 static struct platform_driver w1_gpio_driver = {
144 .driver = {
145 .name = "w1-gpio",
146 .of_match_table = w1_gpio_dt_ids,
147 },
148 .probe = w1_gpio_probe,
149 .remove = w1_gpio_remove,
150 };
151
152 module_platform_driver(w1_gpio_driver);
153
154 MODULE_DESCRIPTION("GPIO w1 bus master driver");
155 MODULE_AUTHOR("Ville Syrjala <syrjala@sci.fi>");
156 MODULE_LICENSE("GPL");
157