1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * Copyright (C) 2015 Texas Instruments Incorporated - http://www.ti.com/
4 * Andrew F. Davis <afd@ti.com>
5 */
6
7 #include <linux/bitmap.h>
8 #include <linux/bitops.h>
9 #include <linux/delay.h>
10 #include <linux/gpio/consumer.h>
11 #include <linux/gpio/driver.h>
12 #include <linux/module.h>
13 #include <linux/mutex.h>
14 #include <linux/spi/spi.h>
15
16 #define DEFAULT_NGPIO 8
17
18 /**
19 * struct pisosr_gpio - GPIO driver data
20 * @chip: GPIO controller chip
21 * @spi: SPI device pointer
22 * @buffer: Buffer for device reads
23 * @buffer_size: Size of buffer
24 * @load_gpio: GPIO pin used to load input into device
25 * @lock: Protects read sequences
26 */
27 struct pisosr_gpio {
28 struct gpio_chip chip;
29 struct spi_device *spi;
30 u8 *buffer;
31 size_t buffer_size;
32 struct gpio_desc *load_gpio;
33 struct mutex lock;
34 };
35
pisosr_gpio_refresh(struct pisosr_gpio * gpio)36 static int pisosr_gpio_refresh(struct pisosr_gpio *gpio)
37 {
38 int ret;
39
40 mutex_lock(&gpio->lock);
41
42 if (gpio->load_gpio) {
43 gpiod_set_value_cansleep(gpio->load_gpio, 1);
44 udelay(1); /* registers load time (~10ns) */
45 gpiod_set_value_cansleep(gpio->load_gpio, 0);
46 udelay(1); /* registers recovery time (~5ns) */
47 }
48
49 ret = spi_read(gpio->spi, gpio->buffer, gpio->buffer_size);
50
51 mutex_unlock(&gpio->lock);
52
53 return ret;
54 }
55
pisosr_gpio_get_direction(struct gpio_chip * chip,unsigned offset)56 static int pisosr_gpio_get_direction(struct gpio_chip *chip,
57 unsigned offset)
58 {
59 /* This device always input */
60 return GPIO_LINE_DIRECTION_IN;
61 }
62
pisosr_gpio_direction_input(struct gpio_chip * chip,unsigned offset)63 static int pisosr_gpio_direction_input(struct gpio_chip *chip,
64 unsigned offset)
65 {
66 /* This device always input */
67 return 0;
68 }
69
pisosr_gpio_direction_output(struct gpio_chip * chip,unsigned offset,int value)70 static int pisosr_gpio_direction_output(struct gpio_chip *chip,
71 unsigned offset, int value)
72 {
73 /* This device is input only */
74 return -EINVAL;
75 }
76
pisosr_gpio_get(struct gpio_chip * chip,unsigned offset)77 static int pisosr_gpio_get(struct gpio_chip *chip, unsigned offset)
78 {
79 struct pisosr_gpio *gpio = gpiochip_get_data(chip);
80
81 /* Refresh may not always be needed */
82 pisosr_gpio_refresh(gpio);
83
84 return (gpio->buffer[offset / 8] >> (offset % 8)) & 0x1;
85 }
86
pisosr_gpio_get_multiple(struct gpio_chip * chip,unsigned long * mask,unsigned long * bits)87 static int pisosr_gpio_get_multiple(struct gpio_chip *chip,
88 unsigned long *mask, unsigned long *bits)
89 {
90 struct pisosr_gpio *gpio = gpiochip_get_data(chip);
91 unsigned long offset;
92 unsigned long gpio_mask;
93 unsigned long buffer_state;
94
95 pisosr_gpio_refresh(gpio);
96
97 bitmap_zero(bits, chip->ngpio);
98 for_each_set_clump8(offset, gpio_mask, mask, chip->ngpio) {
99 buffer_state = gpio->buffer[offset / 8] & gpio_mask;
100 bitmap_set_value8(bits, buffer_state, offset);
101 }
102
103 return 0;
104 }
105
106 static const struct gpio_chip template_chip = {
107 .label = "pisosr-gpio",
108 .owner = THIS_MODULE,
109 .get_direction = pisosr_gpio_get_direction,
110 .direction_input = pisosr_gpio_direction_input,
111 .direction_output = pisosr_gpio_direction_output,
112 .get = pisosr_gpio_get,
113 .get_multiple = pisosr_gpio_get_multiple,
114 .base = -1,
115 .ngpio = DEFAULT_NGPIO,
116 .can_sleep = true,
117 };
118
pisosr_gpio_probe(struct spi_device * spi)119 static int pisosr_gpio_probe(struct spi_device *spi)
120 {
121 struct device *dev = &spi->dev;
122 struct pisosr_gpio *gpio;
123 int ret;
124
125 gpio = devm_kzalloc(dev, sizeof(*gpio), GFP_KERNEL);
126 if (!gpio)
127 return -ENOMEM;
128
129 spi_set_drvdata(spi, gpio);
130
131 gpio->chip = template_chip;
132 gpio->chip.parent = dev;
133 of_property_read_u16(dev->of_node, "ngpios", &gpio->chip.ngpio);
134
135 gpio->spi = spi;
136
137 gpio->buffer_size = DIV_ROUND_UP(gpio->chip.ngpio, 8);
138 gpio->buffer = devm_kzalloc(dev, gpio->buffer_size, GFP_KERNEL);
139 if (!gpio->buffer)
140 return -ENOMEM;
141
142 gpio->load_gpio = devm_gpiod_get_optional(dev, "load", GPIOD_OUT_LOW);
143 if (IS_ERR(gpio->load_gpio))
144 return dev_err_probe(dev, PTR_ERR(gpio->load_gpio),
145 "Unable to allocate load GPIO\n");
146
147 mutex_init(&gpio->lock);
148
149 ret = gpiochip_add_data(&gpio->chip, gpio);
150 if (ret < 0) {
151 dev_err(dev, "Unable to register gpiochip\n");
152 return ret;
153 }
154
155 return 0;
156 }
157
pisosr_gpio_remove(struct spi_device * spi)158 static void pisosr_gpio_remove(struct spi_device *spi)
159 {
160 struct pisosr_gpio *gpio = spi_get_drvdata(spi);
161
162 gpiochip_remove(&gpio->chip);
163
164 mutex_destroy(&gpio->lock);
165 }
166
167 static const struct spi_device_id pisosr_gpio_id_table[] = {
168 { "pisosr-gpio", },
169 { /* sentinel */ }
170 };
171 MODULE_DEVICE_TABLE(spi, pisosr_gpio_id_table);
172
173 static const struct of_device_id pisosr_gpio_of_match_table[] = {
174 { .compatible = "pisosr-gpio", },
175 { /* sentinel */ }
176 };
177 MODULE_DEVICE_TABLE(of, pisosr_gpio_of_match_table);
178
179 static struct spi_driver pisosr_gpio_driver = {
180 .driver = {
181 .name = "pisosr-gpio",
182 .of_match_table = pisosr_gpio_of_match_table,
183 },
184 .probe = pisosr_gpio_probe,
185 .remove = pisosr_gpio_remove,
186 .id_table = pisosr_gpio_id_table,
187 };
188 module_spi_driver(pisosr_gpio_driver);
189
190 MODULE_AUTHOR("Andrew F. Davis <afd@ti.com>");
191 MODULE_DESCRIPTION("SPI Compatible PISO Shift Register GPIO Driver");
192 MODULE_LICENSE("GPL v2");
193
