1/*
2 * Copyright (C) 2015 Texas Instruments Incorporated - http://www.ti.com/
3 * Andrew F. Davis <afd@ti.com>
4 *
5 * This program is free software; you can redistribute it and/or
6 * modify it under the terms of the GNU General Public License version 2 as
7 * published by the Free Software Foundation.
8 *
9 * This program is distributed "as is" WITHOUT ANY WARRANTY of any
10 * kind, whether expressed or implied; without even the implied warranty
11 * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 * GNU General Public License version 2 for more details.
13 */
14
15#include <linux/bitmap.h>
16#include <linux/bitops.h>
17#include <linux/delay.h>
18#include <linux/gpio/consumer.h>
19#include <linux/gpio/driver.h>
20#include <linux/module.h>
21#include <linux/mutex.h>
22#include <linux/spi/spi.h>
23
24#define DEFAULT_NGPIO 8
25
26/**
27 * struct pisosr_gpio - GPIO driver data
28 * @chip: GPIO controller chip
29 * @spi: SPI device pointer
30 * @buffer: Buffer for device reads
31 * @buffer_size: Size of buffer
32 * @load_gpio: GPIO pin used to load input into device
33 * @lock: Protects read sequences
34 */
35struct pisosr_gpio {
36 struct gpio_chip chip;
37 struct spi_device *spi;
38 u8 *buffer;
39 size_t buffer_size;
40 struct gpio_desc *load_gpio;
41 struct mutex lock;
42};
43
44static int pisosr_gpio_refresh(struct pisosr_gpio *gpio)
45{
46 int ret;
47
48 mutex_lock(&gpio->lock);
49
50 if (gpio->load_gpio) {
51 gpiod_set_value_cansleep(gpio->load_gpio, 1);
52 udelay(1); /* registers load time (~10ns) */
53 gpiod_set_value_cansleep(gpio->load_gpio, 0);
54 udelay(1); /* registers recovery time (~5ns) */
55 }
56
57 ret = spi_read(gpio->spi, gpio->buffer, gpio->buffer_size);
58
59 mutex_unlock(&gpio->lock);
60
61 return ret;
62}
63
64static int pisosr_gpio_get_direction(struct gpio_chip *chip,
65 unsigned offset)
66{
67 /* This device always input */
68 return 1;
69}
70
71static int pisosr_gpio_direction_input(struct gpio_chip *chip,
72 unsigned offset)
73{
74 /* This device always input */
75 return 0;
76}
77
78static int pisosr_gpio_direction_output(struct gpio_chip *chip,
79 unsigned offset, int value)
80{
81 /* This device is input only */
82 return -EINVAL;
83}
84
85static int pisosr_gpio_get(struct gpio_chip *chip, unsigned offset)
86{
87 struct pisosr_gpio *gpio = gpiochip_get_data(chip);
88
89 /* Refresh may not always be needed */
90 pisosr_gpio_refresh(gpio);
91
92 return (gpio->buffer[offset / 8] >> (offset % 8)) & 0x1;
93}
94
95static int pisosr_gpio_get_multiple(struct gpio_chip *chip,
96 unsigned long *mask, unsigned long *bits)
97{
98 struct pisosr_gpio *gpio = gpiochip_get_data(chip);
99 unsigned int nbytes = DIV_ROUND_UP(chip->ngpio, 8);
100 unsigned int i, j;
101
102 pisosr_gpio_refresh(gpio);
103
104 bitmap_zero(bits, chip->ngpio);
105 for (i = 0; i < nbytes; i++) {
106 j = i / sizeof(unsigned long);
107 bits[j] |= ((unsigned long) gpio->buffer[i])
108 << (8 * (i % sizeof(unsigned long)));
109 }
110
111 return 0;
112}
113
114static const struct gpio_chip template_chip = {
115 .label = "pisosr-gpio",
116 .owner = THIS_MODULE,
117 .get_direction = pisosr_gpio_get_direction,
118 .direction_input = pisosr_gpio_direction_input,
119 .direction_output = pisosr_gpio_direction_output,
120 .get = pisosr_gpio_get,
121 .get_multiple = pisosr_gpio_get_multiple,
122 .base = -1,
123 .ngpio = DEFAULT_NGPIO,
124 .can_sleep = true,
125};
126
127static int pisosr_gpio_probe(struct spi_device *spi)
128{
129 struct device *dev = &spi->dev;
130 struct pisosr_gpio *gpio;
131 int ret;
132
133 gpio = devm_kzalloc(dev, sizeof(*gpio), GFP_KERNEL);
134 if (!gpio)
135 return -ENOMEM;
136
137 spi_set_drvdata(spi, gpio);
138
139 gpio->chip = template_chip;
140 gpio->chip.parent = dev;
141 of_property_read_u16(dev->of_node, "ngpios", &gpio->chip.ngpio);
142
143 gpio->spi = spi;
144
145 gpio->buffer_size = DIV_ROUND_UP(gpio->chip.ngpio, 8);
146 gpio->buffer = devm_kzalloc(dev, gpio->buffer_size, GFP_KERNEL);
147 if (!gpio->buffer)
148 return -ENOMEM;
149
150 gpio->load_gpio = devm_gpiod_get_optional(dev, "load", GPIOD_OUT_LOW);
151 if (IS_ERR(gpio->load_gpio)) {
152 ret = PTR_ERR(gpio->load_gpio);
153 if (ret != -EPROBE_DEFER)
154 dev_err(dev, "Unable to allocate load GPIO\n");
155 return ret;
156 }
157
158 mutex_init(&gpio->lock);
159
160 ret = gpiochip_add_data(&gpio->chip, gpio);
161 if (ret < 0) {
162 dev_err(dev, "Unable to register gpiochip\n");
163 return ret;
164 }
165
166 return 0;
167}
168
169static int pisosr_gpio_remove(struct spi_device *spi)
170{
171 struct pisosr_gpio *gpio = spi_get_drvdata(spi);
172
173 gpiochip_remove(&gpio->chip);
174
175 mutex_destroy(&gpio->lock);
176
177 return 0;
178}
179
180static const struct spi_device_id pisosr_gpio_id_table[] = {
181 { "pisosr-gpio", },
182 { /* sentinel */ }
183};
184MODULE_DEVICE_TABLE(spi, pisosr_gpio_id_table);
185
186static const struct of_device_id pisosr_gpio_of_match_table[] = {
187 { .compatible = "pisosr-gpio", },
188 { /* sentinel */ }
189};
190MODULE_DEVICE_TABLE(of, pisosr_gpio_of_match_table);
191
192static struct spi_driver pisosr_gpio_driver = {
193 .driver = {
194 .name = "pisosr-gpio",
195 .of_match_table = pisosr_gpio_of_match_table,
196 },
197 .probe = pisosr_gpio_probe,
198 .remove = pisosr_gpio_remove,
199 .id_table = pisosr_gpio_id_table,
200};
201module_spi_driver(pisosr_gpio_driver);
202
203MODULE_AUTHOR("Andrew F. Davis <afd@ti.com>");
204MODULE_DESCRIPTION("SPI Compatible PISO Shift Register GPIO Driver");
205MODULE_LICENSE("GPL v2");
206