summaryrefslogtreecommitdiffstats
path: root/drivers/w1/w1-gpio.c
blob: 3b0ead6f6dc15d6df2faafc8ecdd53c2d7850a1d (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
/* SPDX-License-Identifier:	GPL-2.0+
 *
 * Copyright (c) 2015 Free Electrons
 * Copyright (c) 2015 NextThing Co
 *
 * Maxime Ripard <maxime.ripard@free-electrons.com>
 *
 */

#include <common.h>
#include <dm.h>
#include <log.h>
#include <w1.h>
#include <linux/delay.h>

#include <asm/gpio.h>

#define W1_TIMING_A	6
#define W1_TIMING_B	64
#define W1_TIMING_C	60
#define W1_TIMING_D	10
#define W1_TIMING_E	9
#define W1_TIMING_F	55
#define W1_TIMING_G	0
#define W1_TIMING_H	480
#define W1_TIMING_I	70
#define W1_TIMING_J	410

struct w1_gpio_pdata {
	struct gpio_desc	gpio;
	u64			search_id;
};

static bool w1_gpio_read_bit(struct udevice *dev)
{
	struct w1_gpio_pdata *pdata = dev_get_plat(dev);
	int val;

	dm_gpio_set_dir_flags(&pdata->gpio, GPIOD_IS_OUT);
	udelay(W1_TIMING_A);

	dm_gpio_set_dir_flags(&pdata->gpio, GPIOD_IS_IN);
	udelay(W1_TIMING_E);

	val = dm_gpio_get_value(&pdata->gpio);
	if (val < 0)
		debug("error in retrieving GPIO value");
	udelay(W1_TIMING_F);

	return val;
}

static u8 w1_gpio_read_byte(struct udevice *dev)
{
	int i;
	u8 ret = 0;

	for (i = 0; i < 8; ++i)
		ret |= (w1_gpio_read_bit(dev) ? 1 : 0) << i;

	return ret;
}

static void w1_gpio_write_bit(struct udevice *dev, bool bit)
{
	struct w1_gpio_pdata *pdata = dev_get_plat(dev);

	dm_gpio_set_dir_flags(&pdata->gpio, GPIOD_IS_OUT);

	bit ? udelay(W1_TIMING_A) : udelay(W1_TIMING_C);

	dm_gpio_set_value(&pdata->gpio, 1);

	bit ? udelay(W1_TIMING_B) : udelay(W1_TIMING_D);
}

static void w1_gpio_write_byte(struct udevice *dev, u8 byte)
{
	int i;

	for (i = 0; i < 8; ++i)
		w1_gpio_write_bit(dev, (byte >> i) & 0x1);
}

static bool w1_gpio_reset(struct udevice *dev)
{
	struct w1_gpio_pdata *pdata = dev_get_plat(dev);
	int val;

	/* initiate the reset pulse. first we must pull the bus to low */
	dm_gpio_set_dir_flags(&pdata->gpio, GPIOD_IS_OUT | GPIOD_IS_OUT_ACTIVE);
	udelay(W1_TIMING_G);

	dm_gpio_set_value(&pdata->gpio, 0);
	/* wait for the specified time with the bus kept low */
	udelay(W1_TIMING_H);

	/* now we must read the presence pulse */
	dm_gpio_set_dir_flags(&pdata->gpio, GPIOD_IS_IN);
	udelay(W1_TIMING_I);

	val = dm_gpio_get_value(&pdata->gpio);
	if (val < 0)
		debug("error in retrieving GPIO value");

	/* if nobody pulled the bus down , it means nobody is on the bus */
	if (val != 0)
		return 1;
	/* we have the bus pulled down, let's wait for the specified presence time */
	udelay(W1_TIMING_J);

	/* read again, the other end should leave the bus free */
	val = dm_gpio_get_value(&pdata->gpio);
	if (val < 0)
		debug("error in retrieving GPIO value");

	/* bus is not going up again, so we have an error */
	if (val != 1)
		return 1;

	/* all good, presence detected */
	return 0;
}

static u8 w1_gpio_triplet(struct udevice *dev, bool bdir)
{
	u8 id_bit   = w1_gpio_read_bit(dev);
	u8 comp_bit = w1_gpio_read_bit(dev);
	u8 retval;

	if (id_bit && comp_bit)
		return 0x03;  /* error */

	if (!id_bit && !comp_bit) {
		/* Both bits are valid, take the direction given */
		retval = bdir ? 0x04 : 0;
	} else {
		/* Only one bit is valid, take that direction */
		bdir = id_bit;
		retval = id_bit ? 0x05 : 0x02;
	}

	w1_gpio_write_bit(dev, bdir);
	return retval;
}

static const struct w1_ops w1_gpio_ops = {
	.read_byte	= w1_gpio_read_byte,
	.reset		= w1_gpio_reset,
	.triplet	= w1_gpio_triplet,
	.write_byte	= w1_gpio_write_byte,
};

static int w1_gpio_of_to_plat(struct udevice *dev)
{
	struct w1_gpio_pdata *pdata = dev_get_plat(dev);
	int ret;

	ret = gpio_request_by_name(dev, "gpios", 0, &pdata->gpio, 0);
	if (ret < 0)
		printf("Error claiming GPIO %d\n", ret);

	return ret;
};

static const struct udevice_id w1_gpio_id[] = {
	{ "w1-gpio", 0 },
	{ },
};

U_BOOT_DRIVER(w1_gpio_drv) = {
	.id				= UCLASS_W1,
	.name				= "w1_gpio_drv",
	.of_match			= w1_gpio_id,
	.of_to_plat		= w1_gpio_of_to_plat,
	.ops				= &w1_gpio_ops,
	.plat_auto	= sizeof(struct w1_gpio_pdata),
};