summaryrefslogtreecommitdiffstats
path: root/drivers/gpio/gpio-pisosr.c
blob: cb14b8d1d5120e1535dcef462c1cc041c8a50f2a (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
179
180
181
182
183
/*
 * Copyright (C) 2015 Texas Instruments Incorporated - http://www.ti.com/
 *	Andrew F. Davis <afd@ti.com>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * This program is distributed "as is" WITHOUT ANY WARRANTY of any
 * kind, whether expressed or implied; without even the implied warranty
 * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License version 2 for more details.
 */

#include <linux/delay.h>
#include <linux/gpio/consumer.h>
#include <linux/gpio/driver.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/spi/spi.h>

#define DEFAULT_NGPIO 8

/**
 * struct pisosr_gpio - GPIO driver data
 * @chip: GPIO controller chip
 * @spi: SPI device pointer
 * @buffer: Buffer for device reads
 * @buffer_size: Size of buffer
 * @load_gpio: GPIO pin used to load input into device
 * @lock: Protects read sequences
 */
struct pisosr_gpio {
	struct gpio_chip chip;
	struct spi_device *spi;
	u8 *buffer;
	size_t buffer_size;
	struct gpio_desc *load_gpio;
	struct mutex lock;
};

static int pisosr_gpio_refresh(struct pisosr_gpio *gpio)
{
	int ret;

	mutex_lock(&gpio->lock);

	if (gpio->load_gpio) {
		gpiod_set_value_cansleep(gpio->load_gpio, 1);
		udelay(1); /* registers load time (~10ns) */
		gpiod_set_value_cansleep(gpio->load_gpio, 0);
		udelay(1); /* registers recovery time (~5ns) */
	}

	ret = spi_read(gpio->spi, gpio->buffer, gpio->buffer_size);

	mutex_unlock(&gpio->lock);

	return ret;
}

static int pisosr_gpio_get_direction(struct gpio_chip *chip,
				     unsigned offset)
{
	/* This device always input */
	return 1;
}

static int pisosr_gpio_direction_input(struct gpio_chip *chip,
				       unsigned offset)
{
	/* This device always input */
	return 0;
}

static int pisosr_gpio_direction_output(struct gpio_chip *chip,
					unsigned offset, int value)
{
	/* This device is input only */
	return -EINVAL;
}

static int pisosr_gpio_get(struct gpio_chip *chip, unsigned offset)
{
	struct pisosr_gpio *gpio = gpiochip_get_data(chip);

	/* Refresh may not always be needed */
	pisosr_gpio_refresh(gpio);

	return (gpio->buffer[offset / 8] >> (offset % 8)) & 0x1;
}

static struct gpio_chip template_chip = {
	.label			= "pisosr-gpio",
	.owner			= THIS_MODULE,
	.get_direction		= pisosr_gpio_get_direction,
	.direction_input	= pisosr_gpio_direction_input,
	.direction_output	= pisosr_gpio_direction_output,
	.get			= pisosr_gpio_get,
	.base			= -1,
	.ngpio			= DEFAULT_NGPIO,
	.can_sleep		= true,
};

static int pisosr_gpio_probe(struct spi_device *spi)
{
	struct device *dev = &spi->dev;
	struct pisosr_gpio *gpio;
	int ret;

	gpio = devm_kzalloc(dev, sizeof(*gpio), GFP_KERNEL);
	if (!gpio)
		return -ENOMEM;

	spi_set_drvdata(spi, gpio);

	gpio->chip = template_chip;
	gpio->chip.parent = dev;
	of_property_read_u16(dev->of_node, "ngpios", &gpio->chip.ngpio);

	gpio->spi = spi;

	gpio->buffer_size = DIV_ROUND_UP(gpio->chip.ngpio, 8);
	gpio->buffer = devm_kzalloc(dev, gpio->buffer_size, GFP_KERNEL);
	if (!gpio->buffer)
		return -ENOMEM;

	gpio->load_gpio = devm_gpiod_get_optional(dev, "load", GPIOD_OUT_LOW);
	if (IS_ERR(gpio->load_gpio)) {
		ret = PTR_ERR(gpio->load_gpio);
		if (ret != -EPROBE_DEFER)
			dev_err(dev, "Unable to allocate load GPIO\n");
		return ret;
	}

	mutex_init(&gpio->lock);

	ret = gpiochip_add_data(&gpio->chip, gpio);
	if (ret < 0) {
		dev_err(dev, "Unable to register gpiochip\n");
		return ret;
	}

	return 0;
}

static int pisosr_gpio_remove(struct spi_device *spi)
{
	struct pisosr_gpio *gpio = spi_get_drvdata(spi);

	gpiochip_remove(&gpio->chip);

	mutex_destroy(&gpio->lock);

	return 0;
}

static const struct spi_device_id pisosr_gpio_id_table[] = {
	{ "pisosr-gpio", },
	{ /* sentinel */ }
};
MODULE_DEVICE_TABLE(spi, pisosr_gpio_id_table);

static const struct of_device_id pisosr_gpio_of_match_table[] = {
	{ .compatible = "pisosr-gpio", },
	{ /* sentinel */ }
};
MODULE_DEVICE_TABLE(of, pisosr_gpio_of_match_table);

static struct spi_driver pisosr_gpio_driver = {
	.driver = {
		.name = "pisosr-gpio",
		.of_match_table = pisosr_gpio_of_match_table,
	},
	.probe = pisosr_gpio_probe,
	.remove = pisosr_gpio_remove,
	.id_table = pisosr_gpio_id_table,
};
module_spi_driver(pisosr_gpio_driver);

MODULE_AUTHOR("Andrew F. Davis <afd@ti.com>");
MODULE_DESCRIPTION("SPI Compatible PISO Shift Register GPIO Driver");
MODULE_LICENSE("GPL v2");
OpenPOWER on IntegriCloud