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(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
52static 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
59static 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)
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(&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
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(ddata->pullup_gpiod, 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