1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * Copyright (C) 2015-2023 Texas Instruments Incorporated - https://www.ti.com/
4 * Andrew 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_get(struct gpio_chip * chip,unsigned offset)70 static int pisosr_gpio_get(struct gpio_chip *chip, unsigned offset)
71 {
72 struct pisosr_gpio *gpio = gpiochip_get_data(chip);
73
74 /* Refresh may not always be needed */
75 pisosr_gpio_refresh(gpio);
76
77 return (gpio->buffer[offset / 8] >> (offset % 8)) & 0x1;
78 }
79
pisosr_gpio_get_multiple(struct gpio_chip * chip,unsigned long * mask,unsigned long * bits)80 static int pisosr_gpio_get_multiple(struct gpio_chip *chip,
81 unsigned long *mask, unsigned long *bits)
82 {
83 struct pisosr_gpio *gpio = gpiochip_get_data(chip);
84 unsigned long offset;
85 unsigned long gpio_mask;
86 unsigned long buffer_state;
87
88 pisosr_gpio_refresh(gpio);
89
90 bitmap_zero(bits, chip->ngpio);
91 for_each_set_clump8(offset, gpio_mask, mask, chip->ngpio) {
92 buffer_state = gpio->buffer[offset / 8] & gpio_mask;
93 bitmap_set_value8(bits, buffer_state, offset);
94 }
95
96 return 0;
97 }
98
99 static const struct gpio_chip template_chip = {
100 .label = "pisosr-gpio",
101 .owner = THIS_MODULE,
102 .get_direction = pisosr_gpio_get_direction,
103 .direction_input = pisosr_gpio_direction_input,
104 .get = pisosr_gpio_get,
105 .get_multiple = pisosr_gpio_get_multiple,
106 .base = -1,
107 .ngpio = DEFAULT_NGPIO,
108 .can_sleep = true,
109 };
110
pisosr_mutex_destroy(void * lock)111 static void pisosr_mutex_destroy(void *lock)
112 {
113 mutex_destroy(lock);
114 }
115
pisosr_gpio_probe(struct spi_device * spi)116 static int pisosr_gpio_probe(struct spi_device *spi)
117 {
118 struct device *dev = &spi->dev;
119 struct pisosr_gpio *gpio;
120 int ret;
121
122 gpio = devm_kzalloc(dev, sizeof(*gpio), GFP_KERNEL);
123 if (!gpio)
124 return -ENOMEM;
125
126 gpio->chip = template_chip;
127 gpio->chip.parent = dev;
128 of_property_read_u16(dev->of_node, "ngpios", &gpio->chip.ngpio);
129
130 gpio->spi = spi;
131
132 gpio->buffer_size = DIV_ROUND_UP(gpio->chip.ngpio, 8);
133 gpio->buffer = devm_kzalloc(dev, gpio->buffer_size, GFP_KERNEL);
134 if (!gpio->buffer)
135 return -ENOMEM;
136
137 gpio->load_gpio = devm_gpiod_get_optional(dev, "load", GPIOD_OUT_LOW);
138 if (IS_ERR(gpio->load_gpio))
139 return dev_err_probe(dev, PTR_ERR(gpio->load_gpio),
140 "Unable to allocate load GPIO\n");
141
142 mutex_init(&gpio->lock);
143 ret = devm_add_action_or_reset(dev, pisosr_mutex_destroy, &gpio->lock);
144 if (ret)
145 return ret;
146
147 ret = devm_gpiochip_add_data(dev, &gpio->chip, gpio);
148 if (ret < 0) {
149 dev_err(dev, "Unable to register gpiochip\n");
150 return ret;
151 }
152
153 return 0;
154 }
155
156 static const struct spi_device_id pisosr_gpio_id_table[] = {
157 { "pisosr-gpio", },
158 { /* sentinel */ }
159 };
160 MODULE_DEVICE_TABLE(spi, pisosr_gpio_id_table);
161
162 static const struct of_device_id pisosr_gpio_of_match_table[] = {
163 { .compatible = "pisosr-gpio", },
164 { /* sentinel */ }
165 };
166 MODULE_DEVICE_TABLE(of, pisosr_gpio_of_match_table);
167
168 static struct spi_driver pisosr_gpio_driver = {
169 .driver = {
170 .name = "pisosr-gpio",
171 .of_match_table = pisosr_gpio_of_match_table,
172 },
173 .probe = pisosr_gpio_probe,
174 .id_table = pisosr_gpio_id_table,
175 };
176 module_spi_driver(pisosr_gpio_driver);
177
178 MODULE_AUTHOR("Andrew Davis <afd@ti.com>");
179 MODULE_DESCRIPTION("SPI Compatible PISO Shift Register GPIO Driver");
180 MODULE_LICENSE("GPL v2");
181