w1-gpio.c

  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
 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
 66static 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
127static 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
137static const struct of_device_id w1_gpio_dt_ids[] = {
138	{ .compatible = "w1-gpio" },
139	{}
140};
141MODULE_DEVICE_TABLE(of, w1_gpio_dt_ids);
142
143static 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
152module_platform_driver(w1_gpio_driver);
153
154MODULE_DESCRIPTION("GPIO w1 bus master driver");
155MODULE_AUTHOR("Ville Syrjala <syrjala@sci.fi>");
156MODULE_LICENSE("GPL");