xref: /openbmc/linux/drivers/w1/masters/w1-gpio.c (revision 6da07bdd)
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/w1-gpio.h>
13 #include <linux/gpio/consumer.h>
14 #include <linux/of_platform.h>
15 #include <linux/err.h>
16 #include <linux/of.h>
17 #include <linux/delay.h>
18 
19 #include <linux/w1.h>
20 
w1_gpio_set_pullup(void * data,int delay)21 static u8 w1_gpio_set_pullup(void *data, int delay)
22 {
23 	struct w1_gpio_platform_data *pdata = data;
24 
25 	if (delay) {
26 		pdata->pullup_duration = delay;
27 	} else {
28 		if (pdata->pullup_duration) {
29 			/*
30 			 * This will OVERRIDE open drain emulation and force-pull
31 			 * the line high for some time.
32 			 */
33 			gpiod_set_raw_value(pdata->gpiod, 1);
34 			msleep(pdata->pullup_duration);
35 			/*
36 			 * This will simply set the line as input since we are doing
37 			 * open drain emulation in the GPIO library.
38 			 */
39 			gpiod_set_value(pdata->gpiod, 1);
40 		}
41 		pdata->pullup_duration = 0;
42 	}
43 
44 	return 0;
45 }
46 
w1_gpio_write_bit(void * data,u8 bit)47 static void w1_gpio_write_bit(void *data, u8 bit)
48 {
49 	struct w1_gpio_platform_data *pdata = data;
50 
51 	gpiod_set_value(pdata->gpiod, bit);
52 }
53 
w1_gpio_read_bit(void * data)54 static u8 w1_gpio_read_bit(void *data)
55 {
56 	struct w1_gpio_platform_data *pdata = data;
57 
58 	return gpiod_get_value(pdata->gpiod) ? 1 : 0;
59 }
60 
61 #if defined(CONFIG_OF)
62 static const struct of_device_id w1_gpio_dt_ids[] = {
63 	{ .compatible = "w1-gpio" },
64 	{}
65 };
66 MODULE_DEVICE_TABLE(of, w1_gpio_dt_ids);
67 #endif
68 
w1_gpio_probe(struct platform_device * pdev)69 static int w1_gpio_probe(struct platform_device *pdev)
70 {
71 	struct w1_bus_master *master;
72 	struct w1_gpio_platform_data *pdata;
73 	struct device *dev = &pdev->dev;
74 	struct device_node *np = dev->of_node;
75 	/* Enforce open drain mode by default */
76 	enum gpiod_flags gflags = GPIOD_OUT_LOW_OPEN_DRAIN;
77 	int err;
78 
79 	if (of_have_populated_dt()) {
80 		pdata = devm_kzalloc(&pdev->dev, sizeof(*pdata), GFP_KERNEL);
81 		if (!pdata)
82 			return -ENOMEM;
83 
84 		/*
85 		 * This parameter means that something else than the gpiolib has
86 		 * already set the line into open drain mode, so we should just
87 		 * driver it high/low like we are in full control of the line and
88 		 * open drain will happen transparently.
89 		 */
90 		if (of_property_present(np, "linux,open-drain"))
91 			gflags = GPIOD_OUT_LOW;
92 
93 		pdev->dev.platform_data = pdata;
94 	}
95 	pdata = dev_get_platdata(dev);
96 
97 	if (!pdata) {
98 		dev_err(dev, "No configuration data\n");
99 		return -ENXIO;
100 	}
101 
102 	master = devm_kzalloc(dev, sizeof(struct w1_bus_master),
103 			GFP_KERNEL);
104 	if (!master)
105 		return -ENOMEM;
106 
107 	pdata->gpiod = devm_gpiod_get_index(dev, NULL, 0, gflags);
108 	if (IS_ERR(pdata->gpiod)) {
109 		dev_err(dev, "gpio_request (pin) failed\n");
110 		return PTR_ERR(pdata->gpiod);
111 	}
112 
113 	pdata->pullup_gpiod =
114 		devm_gpiod_get_index_optional(dev, NULL, 1, GPIOD_OUT_LOW);
115 	if (IS_ERR(pdata->pullup_gpiod)) {
116 		dev_err(dev, "gpio_request_one "
117 			"(ext_pullup_enable_pin) failed\n");
118 		return PTR_ERR(pdata->pullup_gpiod);
119 	}
120 
121 	master->data = pdata;
122 	master->read_bit = w1_gpio_read_bit;
123 	gpiod_direction_output(pdata->gpiod, 1);
124 	master->write_bit = w1_gpio_write_bit;
125 
126 	/*
127 	 * If we are using open drain emulation from the GPIO library,
128 	 * we need to use this pullup function that hammers the line
129 	 * high using a raw accessor to provide pull-up for the w1
130 	 * line.
131 	 */
132 	if (gflags == GPIOD_OUT_LOW_OPEN_DRAIN)
133 		master->set_pullup = w1_gpio_set_pullup;
134 
135 	err = w1_add_master_device(master);
136 	if (err) {
137 		dev_err(dev, "w1_add_master device failed\n");
138 		return err;
139 	}
140 
141 	if (pdata->enable_external_pullup)
142 		pdata->enable_external_pullup(1);
143 
144 	if (pdata->pullup_gpiod)
145 		gpiod_set_value(pdata->pullup_gpiod, 1);
146 
147 	platform_set_drvdata(pdev, master);
148 
149 	return 0;
150 }
151 
w1_gpio_remove(struct platform_device * pdev)152 static int w1_gpio_remove(struct platform_device *pdev)
153 {
154 	struct w1_bus_master *master = platform_get_drvdata(pdev);
155 	struct w1_gpio_platform_data *pdata = dev_get_platdata(&pdev->dev);
156 
157 	if (pdata->enable_external_pullup)
158 		pdata->enable_external_pullup(0);
159 
160 	if (pdata->pullup_gpiod)
161 		gpiod_set_value(pdata->pullup_gpiod, 0);
162 
163 	w1_remove_master_device(master);
164 
165 	return 0;
166 }
167 
w1_gpio_suspend(struct device * dev)168 static int __maybe_unused w1_gpio_suspend(struct device *dev)
169 {
170 	struct w1_gpio_platform_data *pdata = dev_get_platdata(dev);
171 
172 	if (pdata->enable_external_pullup)
173 		pdata->enable_external_pullup(0);
174 
175 	return 0;
176 }
177 
w1_gpio_resume(struct device * dev)178 static int __maybe_unused w1_gpio_resume(struct device *dev)
179 {
180 	struct w1_gpio_platform_data *pdata = dev_get_platdata(dev);
181 
182 	if (pdata->enable_external_pullup)
183 		pdata->enable_external_pullup(1);
184 
185 	return 0;
186 }
187 
188 static SIMPLE_DEV_PM_OPS(w1_gpio_pm_ops, w1_gpio_suspend, w1_gpio_resume);
189 
190 static struct platform_driver w1_gpio_driver = {
191 	.driver = {
192 		.name	= "w1-gpio",
193 		.pm	= &w1_gpio_pm_ops,
194 		.of_match_table = of_match_ptr(w1_gpio_dt_ids),
195 	},
196 	.probe = w1_gpio_probe,
197 	.remove = w1_gpio_remove,
198 };
199 
200 module_platform_driver(w1_gpio_driver);
201 
202 MODULE_DESCRIPTION("GPIO w1 bus master driver");
203 MODULE_AUTHOR("Ville Syrjala <syrjala@sci.fi>");
204 MODULE_LICENSE("GPL");
205